E.Fiona Bailey

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• Tavoian, D., Mazzone, J. L., Craighead, D. H., & Bailey, E. F. (2024). Acute inspiratory resistance training enhances endothelium‐dependent dilation and retrograde shear rate in healthy young adults. Physiological Reports, 12(3). doi:10.14814/phy2.15943
• Bailey, E. F. (2023).

  Inspiratory Muscle Strength Training to Improve Cardiometabolic Health in Patients with Type 2 Diabetes Mellitus: Protocol for the Diabetes Inspiratory Training (DIT) Clinical Trial

  . MedRxIV. doi:10.1101/2023.10.27.23297688
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  Type 2 diabetes mellitus (T2DM) is a complex, chronic metabolic disease that carries with it a high prevalence of comorbid conditions, making T2DM one of the leading causes of death in the U.S. Traditional lifestyle interventions (e.g., diet, exercise) can counter some adverse effects of T2DM; however, participation in these activities is low with reasons ranging from physical discomfort to lack of time. Thus, there is a critical need to develop novel management strategies that effectively reduce cardiometabolic disease risk and address barriers to adherence. High-resistance inspiratory muscle strength training (IMST) is a time-efficient and simple breathing exercise that significantly reduces systolic and diastolic BP and improves vascular endothelial function in adults with above-normal blood pressure. Herein, we describe the study protocol for a randomized clinical trial to determine the effects of a 6 week IMST regimen on glycemic control and insulin sensitivity in adults with T2DM. Our primary outcome measures include fasting plasma glucose, fasting serum insulin, and insulin sensitivity utilizing homeostatic model assessment for insulin resistance (HOMA-IR). Secondary outcome measures include casual (resting) systolic BP and endothelial-dependent dilation. Further, we will collect plasma for exploratory proteomic analyses. This trial seeks to establish the cardiometabolic effects of 6 weeks of high-resistance IMST in patients with T2DM.
• Bailey, E. F. (2023).

  Inspiratory resistance training transiently improves endothelium-dependent dilation in young adults

  . Physiology, 38(S1). doi:https://doi.org/10.1152/physiol.2023.38.S1.5732795
• Craighead, D. H., Freeberg, K. A., Heinbockel, T. C., Rossman, M. J., Jackman, R. A., McCarty, N. P., Jankowski, L. R., Nemkov, T., Reisz, J. A., D'Alessandro, A., Chonchol, M., Bailey, E. F., & Seals, D. R. (2023). Time-Efficient, High-Resistance Inspiratory Muscle Strength Training Increases Exercise Tolerance in Midlife and Older Adults. Medicine and science in sports and exercise.
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  To determine if time-efficient, high-resistance inspiratory muscle strength training (IMST), comprising 30 inhalation-resisted breaths per day, improves cardiorespiratory fitness, exercise tolerance, physical function and/or regional body composition in healthy midlife and older adults.
• Freeberg, K. A., Craighead, D. H., Heinbockel, T. C., Rossman, M. J., Jackman, R. A., Jankowski, L. R., Ludwig, K. R., Chonchol, M., Bailey, E. F., & Seals, D. R. (2023). Time-efficient, high-resistance inspiratory muscle strength training increases cerebrovascular reactivity in midlife and older adults. American journal of physiology. Heart and circulatory physiology, 325(5), H1059-H1068.
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  Aging is associated with increased risk for cognitive decline and dementia due in part to increases in systolic blood pressure (SBP) and cerebrovascular dysfunction. High-resistance inspiratory muscle strength training (IMST) is a time-efficient, intensive respiratory training protocol (30 resisted inspirations/day) that lowers SBP and improves peripheral vascular function in midlife/older adults with above-normal SBP. However, whether, and by what mechanisms, IMST can improve cerebrovascular function is unknown. We hypothesized that IMST would increase cerebrovascular reactivity to hypercapnia (CVR to CO), which would coincide with changes to the plasma milieu that improve brain endothelial cell function and enhance cognitive performance (NIH Toolbox). We conducted a 6-wk double-blind, randomized, controlled clinical trial investigating high-resistance IMST [75% maximal inspiratory pressure (PI); 6×/wk; 4 females, 5 males] vs. low-resistance sham training (15% PI; 6×/wk; 2 females, 5 males) in midlife/older adults (age 50-79 yr) with initial above-normal SBP. Human brain endothelial cells (HBECs) were exposed to participant plasma and assessed for acetylcholine-stimulated nitric oxide (NO) production. CVR to CO increased after high-resistance IMST (pre: 1.38 ± 0.66 cm/s/mmHg; post: 2.31 ± 1.02 cm/s/mmHg, = 0.020). Acetylcholine-stimulated NO production increased in HBECs exposed to plasma from after vs. before the IMST intervention [pre: 1.49 ± 0.33; post: 1.73 ± 0.35 arbitrary units (AU); < 0.001]. Episodic memory increased modestly after the IMST intervention (pre: 95 ± 13; post: 103 ± 17 AU; = 0.045). Cerebrovascular and cognitive function were unchanged in the sham control group. High-resistance IMST may be a promising strategy to improve cerebrovascular and cognitive function in midlife/older adults with above-normal SBP, a population at risk for future cognitive decline and dementia. Midlife/older adults with above-normal blood pressure are at increased risk of developing cognitive decline and dementia. Our findings suggest that high-resistance inspiratory muscle strength training (IMST), a novel, time-efficient (5-10 min/day) form of physical training, may increase cerebrovascular reactivity to CO and episodic memory in midlife/older adults with initial above-normal blood pressure.
• Bailey, E. F. (2022).

  High‐Resistance Inspiratory Muscle Strength Training‐Associated Increases in Exercise Tolerance in Midlife/Older Adults are Related to Circulating Acylcarnitines

  . FASEB Journal. doi:https://doi.org/10.1096/fasebj.2022.36.S1.R3869
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  Age-related declines in cardiorespiratory fitness (CRF) and exercise tolerance are major independent risk factors for cardiovascular diseases and mortality in midlife/older adults (ML/O; ≥50 years). Aerobic exercise is a well-established strategy to improve CRF and exercise tolerance; however, adherence to time-intensive physical activity (PA) guidelines is poor. High-resistance inspiratory muscle strength training (IMST; 30 breaths/day against resistance, ~5 min/day) is a time-efficient, highly adherable form of physical training but the effects of high-resistance IMST on CRF and exercise tolerance in ML/O adults are unknown. We investigated if high-resistance IMST would increase CRF and exercise tolerance and, if so, whether the improvements would be related to changes in circulating metabolites.Thirty-five ML/O adults performed 6 weeks of high-resistance IMST (75% maximal inspiratory pressure [PIMAX ], n=17, 9F/8M) or Sham training (15% PIMAX , n=18, 8F/10M). Peak oxygen uptake (VO2 peak) was determined with an incremental treadmill exercise test to exhaustion (modified Balke protocol). Exercise tolerance was defined as treadmill time to exhaustion (TTE). Metabolic pathways modulated by high-resistance IMST were assessed using mass spectrometry-based plasma metabolomics.Adherence was high to both IMST and Sham training (IMST=94% of training sessions completed; Sham=90%). Body weight, body mass index (BMI), and leisure time PA levels remained stable in both groups across the intervention (all p>0.05). VO2 peak was unchanged after 6 weeks of either high-resistance IMST (pre=27.7±1.2 ml/kg/min, post=27.9±1.2 ml/kg/min; p=0.75) or Sham training (pre=27.2±1.7 ml/kg/min, post=26.7±1.6 ml/kg/min; p=0.20). However, high-resistance IMST increased TTE by 12%, with no change after Sham (IMST: pre=540±42 sec, post=606±33 sec; Sham: pre=562±39 sec, post=553±44 sec; group*time: p=0.03). TTE increases were related to changes in 18 metabolites (all p
• Bailey, E. F. (2022).

  High‐intensity, low‐volume inspiratory muscle strength training blunts the cardiovascular response to constant load respiratory testing

  . FASEB Journal. doi:https://doi.org/10.1096/fasebj.2022.36.S1.L8072
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  Previous studies indicate inspiratory muscle strength training (IMST) may attenuate blood pressure (BP) and heart rate (HR) responsiveness to sustained respiratory muscle work. However, these previous studies used a less vigorous IMST intervention and did not have subjects gauge perception of respiratory effort. Our objective in this study was to evaluate the effects of 6 weeks high intensity (75% maximum inspiratory pressure), low volume (5 sets of 6 breaths/day) IMST on BP and HR responses to a resistive breathing trial (RBT) to exhaustion (target pressure = 65% of maximal inspiratory pressure or PImax; duty cycle = 0.7; breathing frequency matched to eupnea). We recruited 10 (7M; 3F) healthy young adults to complete two RBT, pre- and then again post-, 6 weeks IMST. Throughout the RBT we assessed beat-to-beat changes in BP and HR, inspiratory pressure, respiratory muscle work (mmHg.s) and recorded participant ratings of perceived exertion (RPE) via the Borg scale. We report significant IMST-related improvements in endurance time (PRE: 362.0 ±46.6s vs. POST: 663.8 ±110.3s, p=0.003) and respiratory muscle work (PRE: -9445 ±1562mmHg.s vs. POST: -16648 ±3761mmHg.s, p=0.069). Remarkably, despite significant gains in work and endurance, the latter stages of the post RBT were characterized by a reduced cardiovascular responsiveness (i.e., SBP, DBP and HR) and lower RPE, consistent with a blunting of the metaboreflex.
• Bailey, E. F., DeLucia, C. M., Mazzone, J. L., Craighead, D. H., Tavoian, D., Freeberg, K. A., Vranish, J. R., & Seals, D. R. (2022). A multi-trial, retrospective analysis of the antihypertensive effects of high-resistance, low-volume inspiratory muscle strength training. Journal of Applied Physiology, 133(4), 1001-1010. doi:10.1152/japplphysiol.00425.2022
• Bailey, E. F., Tavoian, D., Mazzone, J. L., & Craighead, D. H. (2022). Abstract P070: Vascular Conditioning Exercise Acutely Enhances Endothelial Function In Young Adults. Hypertension, 79(Suppl_1). doi:10.1161/hyp.79.suppl_1.p070
• Craighead, D. H., Tavoian, D., Freeberg, K. A., Mazzone, J. L., Vranish, J. R., DeLucia, C. M., Seals, D. R., & Bailey, E. F. (2022). A multi-trial, retrospective analysis of the antihypertensive effects of high-resistance, low-volume inspiratory muscle strength training. Journal of applied physiology (Bethesda, Md. : 1985), 133(4), 1001-1010.
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  Above-normal blood pressure (BP) is a primary risk factor for cardiovascular diseases. In a retrospective analysis of five pilot trials, we assessed the BP-lowering effects of high-resistance inspiratory muscle strength training (IMST) in adults aged 18-82 years and the impact of IMST on maximal inspiratory pressure (PI), a gauge of inspiratory muscle strength and independent disease risk factor. Participants were randomized to high-resistance IMST (75% PI) or low-resistance sham (15% PI) training (30 breaths/day, 5-7 days/wk, 6 wk). IMST ( = 67) reduced systolic BP (SBP) by 9 ± 6 mmHg ( < 0.01) and diastolic BP (DBP) by 4 ± 4 mmHg ( < 0.01). IMST-related reductions in SBP and DBP emerged by of training (-4 ± 8 mmHg and -3 ± 6 mmHg; ≤ 0.01, respectively) and continued across the 6-wk intervention. SBP and DBP were unchanged with sham training ( = 61, all > 0.05). Select subject characteristics slightly modified the impact of IMST on BP. Greater reductions in SBP were associated with older age (β = -0.07 ± 0.03; = 0.04) and greater reductions in DBP associated with medication-naïve BP (β = -3 ± 1; = 0.02) and higher initial DBP (β = -0.12 ± 0.05; = 0.04). PI increased with high-resistance IMST and low-resistance sham training, with a greater increase from high-resistance IMST (+20 ± 17 vs. +6 ± 14 cmHO; < 0.01). Gains in PI had a modest inverse relation with age (β = -0.20 ± 0.09; = 0.03) and baseline PI (β = -0.15 ± 0.07; = 0.04) but not to reductions in SBP or DBP. These compiled findings from multiple independent trials provide the strongest evidence to date that high-resistance IMST evokes clinically significant reductions in SBP and DBP, and increases in PI, in adult men and women. In young-to-older adult men and women, 6 wk of high-resistance inspiratory muscle strength training lowers casual systolic and diastolic blood pressure by 9 mmHg and 4 mmHg, respectively, with initial reductions observed by of training. Given blood pressure outcomes with the intervention were only slightly altered by subject baseline characteristics (i.e., age, blood pressure medication, and health status), inspiratory muscle strength training is effective in lowering blood pressure in a broad range of adults.
• DeLucia, C. M., Tavoian, D., Debonis, D. R., Wyatt Snell, E., Schwyhart, S. M., & Bailey, E. F. (2023). A short course of high-resistance, low-volume breathing exercise extends respiratory endurance and blunts cardiovascular responsiveness to constant load respiratory testing in healthy young adults. Respiratory physiology & neurobiology, 307, 103974.
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  Our objective was to evaluate the effects of 6-weeks high-resistance, low-volume inspiratory muscle strength training (IMST) on respiratory endurance, blood pressure (BP) and heart rate (HR) responsiveness to high respiratory workloads. Ten healthy young adults completed two constant-load resistive breathing tests to exhaustion (T) (target pressure =65 % maximal inspiratory pressure [PI]; duty cycle = 0.7; breathing frequency matched to eupnea) separated by 6-weeks high-resistance (75 % maximal inspiratory pressure, PI), low-volume (30 inspiratory efforts/day, 5 days/week) IMST. Throughout resistive breathing trials we measured beat-to-beat changes in BP and HR, mouth pressure, inspiratory muscle work and perceived exertion. POST resistive breathing tests revealed significant gains in endurance (PRE: 362.0 ± 46.6 s vs. POST: 663.8 ± 110.3 s, p = 0.003) and increases in respiratory muscle work (PRE: -9445 ± 1562 mmHg.s vs. POST: -16648 ± 3761 mmHg.s, p = 0.069). Conversely, systolic and diastolic BP responses, HR and ratings of perceived exertion all declined. Consistent with previous observations, 6 weeks high resistance, low volume IMST lowered casual resting SBP (p = 0.002), DBP (p = 0.007) and mean arterial pressure (p = 0.001) and improved static inspiratory pressure. High resistance, low volume inspiratory muscle strength training extends respiratory endurance and attenuates BP responsiveness in healthy, recreationally-active young adults. The outcomes have implications for improved athletic performance and for attaining and/or maintaining cardiorespiratory fitness.
• Bailey, E. F., DeLucia, C. M., DeBonis, D. R., & Schwyhart, S. M. (2021). Acute cardiovascular responses to a single bout of high intensity inspiratory muscle strength training in healthy young adults. Journal of Applied Physiology, 130(4), 1114-1121. doi:10.1152/japplphysiol.01015.2020
• Craighead, D. H., Heinbockel, T. C., Freeberg, K. A., Rossman, M. J., Jackman, R. A., Jankowski, L. R., Hamilton, M. N., Ziemba, B. P., Reisz, J. A., D'Alessandro, A., Brewster, L. M., DeSouza, C. A., You, Z., Chonchol, M., Bailey, E. F., & Seals, D. R. (2021). Time-Efficient Inspiratory Muscle Strength Training Lowers Blood Pressure and Improves Endothelial Function, NO Bioavailability, and Oxidative Stress in Midlife/Older Adults With Above-Normal Blood Pressure. Journal of the American Heart Association, 10(13), e020980.
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  Background High-resistance inspiratory muscle strength training (IMST) is a novel, time-efficient physical training modality. Methods and Results We performed a double-blind, randomized, sham-controlled trial to investigate whether 6 weeks of IMST (30 breaths/day, 6 days/week) improves blood pressure, endothelial function, and arterial stiffness in midlife/older adults (aged 50-79 years) with systolic blood pressure ≥120 mm Hg, while also investigating potential mechanisms and long-lasting effects. Thirty-six participants completed high-resistance IMST (75% maximal inspiratory pressure, n=18) or low-resistance sham training (15% maximal inspiratory pressure, n=18). IMST was safe, well tolerated, and had excellent adherence (≈95% of training sessions completed). Casual systolic blood pressure decreased from 135±2 mm Hg to 126±3 mm Hg (
• DeLucia, C. M., DeBonis, D. R., Schwyhart, S. M., & Bailey, E. F. (2021). Acute cardiovascular responses to a single bout of high intensity inspiratory muscle strength training in healthy young adults. Journal of applied physiology (Bethesda, Md. : 1985), 130(4), 1114-1121.
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  High intensity, low volume inspiratory muscle strength training (IMST) has favorable effects on casual systolic blood pressure and systemic vascular resistance. However, the acute effects of IMST on heart rate (HR), blood pressure (BP), and sympathetic regulation of vascular resistance and the trajectory of post exercise recovery are not known. We recruited 14 young adults (7 women/7 men, age: 22 ± 2 years) to perform a single bout of high intensity IMST (inspiratory resistance set at 75% of maximal inspiratory pressure) importantly, female and male subjects were matched in regard to the target inspiratory pressure and target inspiratory muscle work per breath. We recorded HR, beat-to-beat changes in BP and postganglionic, muscle sympathetic nerve activities (MSNA) continuously throughout baseline, a single bout of IMST (comprising five sets of 6 inspiratory efforts) and in recovery. We show that one bout of IMST does not effect a change in BP, however, it effects a significant increase in HR (68.4 ± 11.7 beats/min versus 85.4 ± 13.6 beats/min; < 0.001) and a significant decline in MSNA (6.8 ± 1.1 bursts/15 s bin; < 0.001 versus 3.6 ± 0.6 bursts/15 s bin) relative to baseline. Remarkably, among men MSNA rebounded to baseline levels within the first minute of recovery, however, in women, MSNA suppression persisted for 5 min. We show that in healthy young adults, high intensity, low volume respiratory training results in the acute suppression of MSNA. Importantly, MSNA suppression is of greater magnitude and longer duration in women than in men. Previous studies show 6 weeks of high intensity, low volume inspiratory muscle strength training (IMST) lowers blood pressure (BP) and systemic vascular resistance in young adults. However, the acute response to IMST is unknown. We characterized BP, heart rate, and sympathetic nervous activity (SNA) in healthy young adults at baseline, during IMST, and in recovery. There was no acute effect of IMST on BP, however, there was significant IMST-related suppression of SNA that was of greater magnitude in women than men.
• Tavoian, D., Ramos-Barrera, L. E., Craighead, D. H., Seals, D. R., Bedrick, E. J., Alpert, J. S., Mashaqi, S., & Bailey, E. F. (2021). Six Months of Inspiratory Muscle Training to Lower Blood Pressure and Improve Endothelial Function in Middle-Aged and Older Adults With Above-Normal Blood Pressure and Obstructive Sleep Apnea: Protocol for the CHART Clinical Trial. Frontiers in cardiovascular medicine, 8, 760203.
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  Cardiovascular disease is a major global health concern and prevalence is high in adults with obstructive sleep apnea (OSA). Lowering blood pressure (BP) can greatly reduce cardiovascular disease risk and physical activity is routinely prescribed to achieve this goal. Unfortunately, many adults with OSA suffer from fatigue, daytime sleepiness, and exercise intolerance-due to poor sleep quality and nocturnal hypoxemia-and have difficulty initiating and maintaining an exercise program. High-resistance inspiratory muscle strength training (IMST) is a simple, time-efficient breathing exercise consistently reported to reduce BP in small, selective groups of both healthy and at-risk adults. Herein we present the study protocol for a randomized clinical trial to determine the long-term efficacy of IMST performed regularly for 24 weeks in middle-aged and older adults with OSA. The primary outcome is casual systolic BP. Secondary outcomes are 24-h systolic BP and circulating plasma norepinephrine concentration. Other outcomes include vascular endothelial function (endothelial-dependent and -independent dilation), aortic stiffness, casual and 24-h diastolic BP, and the influence of circulating factors on endothelial cell nitric oxide and reactive oxygen species production. Overall, this trial will establish efficacy of high-resistance IMST for lowering BP and improving cardiovascular health in middle-aged and older adults with OSA. This is a single-site, double-blind, randomized clinical trial. A minimum of 92 and maximum of 122 male and female adults aged 50-80 years with OSA and above-normal BP will be enrolled. After completion of baseline assessments, subjects will be randomized in a 1:1 ratio to participate in either high-resistance or sham (low-resistance) control IMST, performed at home, 5 min/day, 5 days/week, for 24 weeks. Repeat assessments will be taken after the 24-week intervention, and after 4 and 12 weeks of free living. This study is designed to assess the effects of 24 weeks of IMST on BP and vascular function. The results will characterize the extent to which IMST can reduce BP when performed over longer periods (i.e., 6 months) than have been assessed previously. Additionally, this study will help to determine underlying mechanisms driving IMST-induced BP reductions that have been reported previously. This trial is registered with ClinicalTrials.gov (Registration Number: NCT04932447; Date of registration June 21, 2021).
• Bailey, E. F. (2020). Reply to Dr. Beltrami. Journal of Applied Physiology, 129(6), 1440-1440. doi:10.1152/japplphysiol.00822.2020
• Bailey, E. F. (2020). Reply to Dr. Beltrami. Journal of applied physiology (Bethesda, Md. : 1985), 129(6), 1440.
• Bailey, E. F., & Sheel, A. W. (2020). Mechanisms of respiratory modulation of cardiovascular control. Journal of Applied Physiology, 128(1), 212-213. doi:10.1152/japplphysiol.00537.2019
• Bailey, E. F., DeLucia, C. M., & Ramos-Barrera, G. E. (2020). Inspiratory muscle strength training lowers blood pressure and sympathetic activity in older adults with OSA: a randomized controlled pilot trial. Journal of Applied Physiology, 129(3), 449-458. doi:10.1152/japplphysiol.00024.2020
• Ramos-Barrera, G. E., DeLucia, C. M., & Bailey, E. F. (2020). Inspiratory muscle strength training lowers blood pressure and sympathetic activity in older adults with OSA: a randomized controlled pilot trial. Journal of applied physiology (Bethesda, Md. : 1985), 129(3), 449-458.
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  Previous work has shown lowered casual blood pressure after just 6 wk of inspiratory muscle strength training (IMST), suggesting IMST as a potential therapeutic in the prevention/treatment of hypertension. In this study, we assessed the effects of IMST on cardiovascular parameters in older, overweight adults diagnosed with moderate and severe obstructive sleep apnea (OSA). Subjects were randomly assigned to one of two interventions ) high-intensity IMST ( = 15, 75% maximal inspiratory pressure), or ) a control intervention ( = 10, 15% maximum inspiratory pressure). Subjects in both groups trained at home completing 30 training breaths/day, 5 days/wk for 6 wk. Pre- and posttraining measures included maximal inspiratory pressure, casual and ambulatory blood pressures, spontaneous cardiac baroreflex sensitivity, and muscle sympathetic nerve activity. Men and women in the high-intensity IMST group exhibited reductions in casual systolic (SBP), diastolic (DBP), and mean arterial blood pressures (MAP) [SBP: -8.82 ± 4.98 mmHg; DBP: -4.69 ± 2.81 mmHg; and MAP: -6.06 ± 1.03 mmHg; < 0.002] and nighttime SBP (pre: -12.00 ± 8.20 mmHg; < 0.01). Muscle sympathetic nerve activities also were lower (-6.97 ± 2.29 bursts/min; = 0.01 and -9.55 ± 2.42 bursts/100 heartbeats; = 0.002) by . Conversely, subjects allocated to the control group showed no change in casual blood pressure or muscle sympathetic nerve activity and a trend toward higher overnight blood pressures. A short course of high-intensity IMST may offer significant respiratory and cardiovascular benefits for older, overweight adults with OSA. For Clinical Trial Registration, see https://www.clinicaltrials.gov (Identifier: NCT02709941). Older, obese adults with moderate-severe obstructive sleep apnea who perform 5 min/day high-intensity inspiratory muscle strength training (IMST) exhibit lowered casual and nighttime systolic blood pressure and sympathetic nervous outflow. In contrast, adults assigned to a control (low-intensity) intervention exhibit no change in casual blood pressure or muscle sympathetic nerve activity and a trend toward increased overnight blood pressure. Remarkably, adherence to IMST even among sleep-deprived and exercise-intolerant adults is high (96%).
• Schwyhart, S. M., Delucia, C. M., Debonis, D. R., & Bailey, E. F. (2020). Inspiratory muscle strength training suppression of sympathetic nervous outflow in young adults: Time course and differential recovery.. The FASEB Journal, 34(S1), 1-1. doi:10.1096/fasebj.2020.34.s1.06396
• Ziemba, B. P., Seals, D. R., Rossman, M. J., Reisz, J. A., Nemkov, T., Freeberg, K. A., D'alessandro, A., Craighead, D. H., Chonchol, M., Brown, B. C., & Bailey, E. F. (2020). Inspiratory Muscle Strength Training Improves Vascular Endothelial Function in Older Adults by Altering Circulating Factors that Suppress Superoxide and Enhance Nitric Oxide. The FASEB Journal, 34(S1), 1-1. doi:10.1096/fasebj.2020.34.s1.04717
• Bailey, E. F. (2019).

  Effects of Inspiratory Muscle Strength Training on Cardiorespiratory Fitness in Middle‐Aged to Older Adults

  . The FASEB Journal, 33(S1). doi:10.1096/fasebj.2019.33.1_supplement.695.4
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  Background Cardiorespiratory fitness declines with aging and is a strong independent risk factor for future morbidity and mortality. Conventional aerobic exercise improves cardiorespiratory fitness in middle-aged and older (MA/O) adults, but is associated with relatively low adherence, due, in part, to significant time requirements (150 min/week). High-resistance, short-duration inspiratory muscle strength training (IMST) requires only 30 min/week and is associated with excellent adherence, but effects on cardiorespiratory fitness are unknown. We assessed whether high-resistance, short-duration IMST improves cardiorespiratory fitness assessed under maximal exercise (VO2max, exercise tolerance) and standardized submaximal exercise conditions. Methods Healthy, recreationally active MA/O adults (50–79 years) were recruited. Subjects were randomly assigned to perform 6-weeks of IMST (30 breaths/day; 6 days/week; 75% maximum inspiratory pressure [PIMAX]) (n=7 age: 68 ± 2 years) or sham (15% PIMAX) training (n=7; age: 67 ± 3 years) in a randomized, double-blind, placebo-controlled study. Oxygen uptake (VO2) and other responses were measured throughout incremental treadmill exercise to exhaustion using a modified Balke Protocol pre- and post-intervention. Results Adherence, defined as percentage of prescribed training sessions completed, was high in both the IMST (100%) and sham (98%) groups. PIMAX increased in the IMST group (pre: 57 ± 5, post: 70 ± 4 mmHg; p=0.048) but not sham group (pre: 54 ± 2, post: 60 ± 1 mmHg; p=0.5). VO2max did not change with training in either group (p>0.05), but exercise time to exhaustion increased by 15% in the IMST group (pre: 629 ± 64, post: 726 ± 50 seconds; p=0.009) and decreased in the sham group (pre: 583 ± 74, post: 500 ± 77 seconds; p=0.02). At maximal exercise, most markers of voluntary effort (minute ventilation, VE, heart rate, HR, and rating of perceived exertion, RPE) were unchanged pre vs. post training in both groups (all p>0.05), but peak respiratory exchange ratio, a measure of hyperventilation, was higher in the IMST group after training (pre: 1.08 ± 0.03, post: 1.14 ± 0.03; p=0.05; sham group: pre: 1.06 ± 0.02, post: 1.05 ± 0.04; p=0.96). At a fixed submaximal workload (~80% of initial VO2max), VO2 (pre: 23.3 ± 1.8, post: 21.3 ± 1.5 ml/kg/min; p=0.01) and HR (pre: 131 ± 7, post: 127 ± 7; p=0.07) were lower after vs. before IMST, but unchanged with sham training. VE and RPE during submaximal exercise were unchanged with training in both groups (all p>0.05). Conclusion High-resistance short-duration IMST increases exercise time to exhaustion (exercise tolerance), improves submaximal exercise economy, and lowers HR during submaximal exercise in healthy, recreationally active, MA/O adults. Thus, high resistance, short-duration IMST improves exercise performance in healthy MA/O adults, and may hold even greater promise for older adults with functional limitations and/or chronic disease. Support or Funding Information AHA 18POST33990034, T32 DK007135, UL1 TR002535 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
• Bailey, E. F. (2019).

  Inspiratory Muscle Strength Training Lowers Resting Systolic Blood Pressure and Improves Vascular Endothelial Function in Middle‐Aged and Older Adults

  . J Am Heart Assoc, 10(13). doi:10.1161/JAHA.121.020980
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  Background The majority of middle-aged to older adults have above-normal systolic blood pressure (SBP), i.e., SBP ≥120 mmHg, placing them at an increased risk for cardiovascular diseases, cognitive dysfunction, chronic kidney disease, and other chronic conditions of aging. This elevated SBP state is associated with the vascular risk factors endothelial dysfunction and stiffening of the large elastic (i.e., aorta and carotid) arteries. High-intensity short-duration inspiratory muscle strength training (IMST) represents a novel, time-efficient (~5 min/day) lifestyle intervention that lowers SBP in select patient populations. However, whether IMST lowers SBP in middle-aged to older adults with above-normal SBP, or improves arterial function in any population, remains unknown. Purpose To determine whether high-intensity short-duration IMST lowers SBP and improves arterial function in otherwise healthy middle-aged to older adults with above-normal SBP. Methods Thirteen middle-aged and older (50–79 years) men and post-menopausal women with resting SBP ≥120 mmHg underwent 6 weeks of IMST (30 breaths/day; 6 days/week; 75% maximum inspiratory pressure [PIMAX]) (n=7, 2M/5F, age: 68 ± 2 years) or sham (15% PIMAX) training (n=6, 3M/3F, age: 67 ± 3 years) in a randomized, double-blind, sham-controlled study. Subjects underwent testing for BP (resting and 24-hour ambulatory [AMBP]), vascular endothelial function (brachial artery flow-mediated dilation [FMDBA]) and arterial stiffness (carotid-femoral pulse wave velocity [CFPWV], carotid artery compliance and β-stiffness index) before and after the intervention. Results Resting SBP was significantly lower after vs. before IMST (pre: 137 ± 4 mmHg, post: 127 ± 5 mmHg; p=0.001), but not sham training (pre: 134 ± 5 mmHg, post: 130 ± 5 mmHg; p=0.13). No changes in resting diastolic BP (DBP) or AMBP (24-hour, daytime, and nighttime measures of SBP and DBP) were observed in either group (all p>0.05). FMDBA was increased after IMST (pre: 4.2 Δ%, post: 6.3 Δ%; p=0.001), but not in response to sham training (pre: 3.2 Δ%, post: 3.2 Δ%; p=0.99), such that FMDBA was significantly higher in the IMST group compared to sham post-intervention (p=0.01). There were no changes in CFPWV, or carotid artery compliance or β-stiffness with training in either group (all p>0.05), nor were body weight, body composition, fasting plasma lipids or fasting blood glucose concentrations altered with IMST or sham training (all p>0.05). Conclusion These findings suggest that, independent of changes in other conventional CVD risk factors, high-intensity short-duration IMST may be an effective lifestyle-based approach to lower resting (casual) SBP and improve vascular endothelial function in middle-aged and older men and women with above-normal initial levels of resting SBP. Support or Funding Information AHA 18POST33990034, T32 DK007135, UL1 TR002535 This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
• Bailey, E. F., Craighead, D. H., Heinbockel, T. C., Hamilton, M. N., MacDonald, M. J., Gibala, M. J., & Seals, D. R. (2019). Time-efficient physical training for enhancing cardiovascular function in midlife and older adults: promise and current research gaps. Journal of Applied Physiology, 127(5), 1427-1440. doi:10.1152/japplphysiol.00381.2019
• Craighead, D. H., Heinbockel, T. C., Hamilton, M. N., Bailey, E. F., MacDonald, M. J., Gibala, M. J., & Seals, D. R. (2019). Time-efficient physical training for enhancing cardiovascular function in midlife and older adults: promise and current research gaps. Journal of applied physiology (Bethesda, Md. : 1985), 127(5), 1427-1440.
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  Cardiovascular diseases (CVD) remain the leading cause of death in developed societies, and "midlife" (50-64 yr) and older (65+) men and women bear the great majority of the burden of CVD. Much of the increased risk of CVD in this population is attributable to CV dysfunction, including adverse changes in the structure and function of the heart, increased systolic blood pressure, and arterial dysfunction. The latter is characterized by increased arterial stiffness and vascular endothelial dysfunction. Conventional aerobic exercise training, as generally recommended in public health guidelines, is an effective strategy to preserve or improve CV function with aging. However,
• Seals, D. R., Rossman, M. J., Jankowski, L. R., Jackman, R. A., Heinbockel, T. C., Craighead, D. H., Chonchol, M. B., & Bailey, E. F. (2019). Effects of Inspiratory Muscle Strength Training on Cardiorespiratory Fitness in Middle-Aged to Older Adults. The FASEB Journal, 33(S1). doi:10.1096/fasebj.2019.33.1_supplement.695.4
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  Background Cardiorespiratory fitness declines with aging and is a strong independent risk factor for future morbidity and mortality. Conventional aerobic exercise improves cardiorespiratory fitness...
• Seals, D. R., Rossman, M. J., Jankowski, L. R., Jackman, R. A., Heinbockel, T. C., Craighead, D. H., Chonchol, M., Bailey, E. F., Seals, D. R., Rossman, M. J., Jankowski, L. R., Jackman, R. A., Heinbockel, T. C., Craighead, D. H., Chonchol, M., & Bailey, E. F. (2019). Inspiratory Muscle Strength Training Lowers Resting Systolic Blood Pressure and Improves Vascular Endothelial Function in Middle‐Aged and Older Adults. The FASEB Journal, 33(S1). doi:10.1096/fasebj.2019.33.1_supplement.541.4
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  Background The majority of middle-aged to older adults have above-normal systolic blood pressure (SBP), i.e., SBP ≥120 mmHg, placing them at an increased risk for cardiovascular diseases, cognitive...
• Seals, D. R., Rossman, M. J., Jankowski, L. R., Jackman, R. A., Heinbockel, T. C., Hamilton, M. N., Craighead, D. H., Chonchol, M., & Bailey, E. F. (2019). Effects of Inspiratory Muscle Strength Training on Cognitive and Motor Function in Middle-Aged and Older Adults with Above-Normal Systolic Blood Pressure. The FASEB Journal, 33(S1). doi:10.1096/fasebj.2019.33.1_supplement.695.5
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  Aging and above normal systolic blood pressure (SBP) are independently and additively associated with decreased cognitive and motor function, which increase the risk of developing dementia and phys...
• Bailey, E. F. (2018). Daily inspiratory muscle training lowers blood pressure and vascular resistance in healthy men and women. Experimental Physiology.
• Bailey, E. F. (2017). Association between Laryngeal Airway Aperture and the Discharge Rates of Genioglossus Motor Units. Frontiers in Physiology.
• Bailey, E. F. (2017). Association between laryngeal airway aperture and the discharge of genioglossus motor units. Frontiers in Respiratory Physiology.
• Bailey, E. F. (2017). Vocal tract configuration for breathing and speech sound production. Global Imaging Insights.
• Barrera, G. R., Bailey, E. F., & Asis, R. M. (2017). Inspiratory Muscle Strength Training for Sleep-related Breathing Disorders. The FASEB Journal, 31. doi:10.1096/fasebj.31.1_supplement.848.14
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  We have shown previously that inspiratory muscle strength training (IMST) lowers blood pressure in healthy, college-aged adults (Vranish and Bailey 2015) and in adults with mild and moderate obstru...
• LaCross, A., Watson, P. J., & Bailey, E. F. (2017). Association between Laryngeal Airway Aperture and the Discharge Rates of Genioglossus Motor Units. Frontiers in physiology, 8, 27.
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  We know very little about how muscles and motor units in one region of the upper airway are impacted by adjustments in an adjacent airway region. In this case, the focus is on regulation of the expiratory airstream by the larynx and how changes in laryngeal aperture impact muscle motor unit activities downstream in the pharynx. We selected sound production as a framework for study as it requires (i) sustained expiratory airflow, (ii) laryngeal airway regulation for production of whisper and voice, and (iii) pharyngeal airway regulation for production of different vowel sounds. We used these features as the means of manipulating expiratory airflow, pharyngeal, and laryngeal airway opening to compare the effect of each on the activation of genioglossus (GG) muscle motor units in the pharynx. We show that some GG muscle motor units (a) discharge stably on expiration associated with production of vowel sounds, (b) are exquisitely sensitive to subtle alterations in laryngeal airflow, and (c) discharge at higher firing rates in high flow vs. low flow conditions even when producing the same vowel sound. Our results reveal subtle changes in GG motor unit discharge rates that correlate with changes imposed at the larynx, and which may contribute to the regulation of the expiratory airstream.
• Bailey, E. F. (2016). Evaluating the control: minipump implantation and breathing behavior in the neonatal rat. J Appl Physiol.
• Bailey, E. F. (2016). Evaluating the control: minipump implantation and breathing behavior in the neonatal rat. Journal of Applied Physiology.
• Bailey, E. F. (2016). Inspiratory Muscle Training Improves Sleep and Mitigates Cardiovascular Dysfunction in Obstructive Sleep Apnea. SLEEP.
• Bailey, E. F. (2016). Inspiratory Muscle Training Improves Sleep and Mitigates Cardiovascular Dysfunction in Obstructive Sleep Apnea. Sleep.
• Bailey, E. F., & Vranish, J. R. (2016). Inspiratory Muscle Training Improves Sleep and Mitigates Cardiovascular Dysfunction in Obstructive Sleep Apnea. Sleep, 39(6), 1179-1185. doi:10.5665/sleep.5826
• Kidder, I. J., Mudery, J. A., Barreda, S., Taska, D. J., & Bailey, E. F. (2016). Evaluating the control: minipump implantation and breathing behavior in the neonatal rat. Journal of applied physiology (Bethesda, Md. : 1985), 121(3), 615-22.
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  We evaluated genioglossus (GG) gross motoneuron morphology, electromyographic (EMG) activities, and respiratory patterning in rat pups allowed to develop without interference (unexposed) and pups born to dams subjected to osmotic minipump implantation in utero (saline-exposed). In experiment 1, 48 Sprague-Dawley rat pups (Charles-River Laboratories), ages postnatal day 7 (P7) through postnatal day 10 (P10), were drawn from two experimental groups, saline-exposed (n = 24) and unexposed (n = 24), and studied on P7, P8, P9, or P10. Pups in both groups were sedated (Inactin hydrate, 70 mg/kg), and fine-wire electrodes were inserted into the GG muscle of the tongue and intercostal muscles to record EMG activities during breathing in air and at three levels of normoxic hypercapnia [inspired CO2 fraction (FiCO2 ): 0.03, 0.06, and 0.09]. Using this approach, we assessed breathing frequency, heart rate, apnea type, respiratory event types, and respiratory stability. In experiment 2, 16 rat pups were drawn from the same experimental groups, saline-exposed (n = 9) and unexposed (n = 7), and used in motoneuron-labeling studies. In these pups a retrograde dye was injected into the GG muscle, and the brain stems were subsequently harvested and sliced. Labeled GG motoneurons were identified with microscopy, impaled, and filled with Lucifer yellow. Double-labeled motoneurons were reconstructed, and the number of primary projections and soma volumes were calculated. Whereas pups in each group exhibited the same number (P = 0.226) and duration (P = 0.093) of respiratory event types and comparable motoneuron morphologies, pups in the implant group exhibited more central apneas and respiratory instability relative to pups allowed to develop without interference.
• Vranish, J. R., & Bailey, E. F. (2016). Inspiratory Muscle Training Improves Sleep and Mitigates Cardiovascular Dysfunction in Obstructive Sleep Apnea. Sleep, 39(6), 1179-85.
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  New and effective strategies are needed to manage the autonomic and cardiovascular sequelae of obstructive sleep apnea (OSA). We assessed the effect of daily inspiratory muscle strength training (IMT) on sleep and cardiovascular function in adults unable to use continuous positive airway pressure (CPAP) therapy.
• Bailey, E. F. (2015). A comprehensive assessment of genioglossus electromyographic activity in healthy adults..
• Bailey, E. F. (2015). Daily respiratory training with large intrathoracic pressures, but not large lung volumes, lowers blood pressure in normotensive adults..
• Bailey, E. F. (2015). Developmental nicotine exposure adversely effects respiratory patterning in the barbiturate anesthetized neonatal rat..
• Bailey, E. F. (2015). Phonation-related rate coding and recruitment in the genioglossus muscle..
• Barreda, S., Kidder, I. J., Mudery, J. A., & Bailey, E. F. (2015). Developmental nicotine exposure adversely effects respiratory patterning in the barbiturate anesthetized neonatal rat. Respiratory physiology & neurobiology, 208, 45-50.
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  Neonates at risk for sudden infant death syndrome (SIDS) are hospitalized for cardiorespiratory monitoring however, monitoring is costly and generates large quantities of averaged data that serve as poor predictors of infant risk. In this study we used a traditional autocorrelation function (ACF) testing its suitability as a tool to detect subtle alterations in respiratory patterning in vivo. We applied the ACF to chest wall motion tracings obtained from rat pups in the period corresponding to the mid-to-end of the third trimester of human pregnancy. Pups were drawn from two groups: nicotine-exposed and saline-exposed at each age (i.e., P7, P8, P9, and P10). Respiratory-related motions of the chest wall were recorded in room air and in response to an arousal stimulus (FIO2 14%). The autocorrelation function was used to determine measures of breathing rate and respiratory patterning. Unlike alternative tools such as Poincare plots that depict an averaged difference in a measure breath to breath, the ACF when applied to a digitized chest wall trace yields an instantaneous sample of data points that can be used to compare (data) points at the same time in the next breath or in any subsequent number of breaths. The moment-to-moment evaluation of chest wall motion detected subtle differences in respiratory pattern in rat pups exposed to nicotine in utero and aged matched saline-exposed peers. The ACF can be applied online as well as to existing data sets and requires comparatively short sampling windows (∼2 min). As shown here, the ACF could be used to identify factors that precipitate or minimize instability and thus, offers a quantitative measure of risk in vulnerable populations.
• DeLucia, C. M., De Asis, R. M., & Bailey, E. F. (2018). Daily inspiratory muscle training lowers blood pressure and vascular resistance in healthy men and women. Experimental physiology.
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  What is the central question of this study? What impact does inspiratory muscle training have on systemic vascular resistance, cardiac output and baroreflex sensitivity in adult men and women? What is the main finding and its importance? Inspiratory muscle training exerts favorable effects on blood pressure, vascular resistance and perception of stress. This exercise format is well-tolerated and equally effective whether implemented in men or women.
• Sheel, A. W., & Bailey, E. F. (2020). Mechanisms of respiratory modulation of cardiovascular control. Journal of applied physiology (Bethesda, Md. : 1985), 128(1), 212-213.
• Shumway, K. R., Porfirio, D. J., & Bailey, E. F. (2015). Phonation-related rate coding and recruitment in the genioglossus muscle. Experimental brain research, 233(7), 2133-40.
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  Motor unit recruitment was assessed in two muscles with similar muscle fiber-type compositions and that participate in skilled movements: the tongue muscle, genioglossus (GG), and the hand muscle, first dorsal interosseous (FDI). Our primary objectives were to determine in the framework of a voluntary movement whether muscle force is regulated in tongue as it is in limb, i.e., via processes of rate coding and recruitment. Recruitment in the two muscles was assessed within each subject in the context of ramp force (FDI) and in the tongue (GG) during vowel production and specifically, in the context of ramp increases in loudness, and subsequently expressed relative to the maximal. The principle findings of the study are that the general rules of recruitment and rate coding hold true for both GG and FDI, and second, that average firing rates, firing rates at recruitment and peak firing rates in GG are significantly higher than for FDI (P 
• Vranish, J. R., & Bailey, E. F. (2015). A comprehensive assessment of genioglossus electromyographic activity in healthy adults. Journal of neurophysiology, 113(7), 2692-9.
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  The genioglossus (GG) is an extrinsic muscle of the human tongue that plays a critical role in preserving airway patency. In the last quarter century, >50 studies have reported on respiratory-related GG electromyographic (EMG) activity in human subjects. Remarkably, of the studies performed, none have duplicated subject body position, electrode recording locations, and/or breathing task(s), making interpretation and integration of the results across studies extremely challenging. In addition, more recent research assessing lingual anatomy and muscle contractile properties has identified regional differences in muscle fiber type and myosin heavy chain expression, giving rise to the possibility that the anterior and posterior regions of the muscle fulfill distinct functions. Here, we assessed EMG activity in anterior and posterior regions of the GG, across upright and supine, in rest breathing and in volitionally modulated breathing tasks. We tested the hypotheses that GG EMG is greater in the posterior region and in supine, except when breathing is subject to volitional modulation. Our results show differences in the magnitude of EMG (%regional maximum) between anterior and posterior muscle regions (7.95 ± 0.57 vs. 11.10 ± 0.99, respectively; P < 0.001), and between upright and supine (8.63 ± 0.73 vs. 10.42 ± 0.90, respectively; P = 0.008). Although the nature of a task affects the magnitude of EMG (P < 0.001), the effect is similar for anterior and posterior muscle regions and across upright and supine (P > 0.2).
• Vranish, J. R., & Bailey, E. F. (2015). Daily respiratory training with large intrathoracic pressures, but not large lung volumes, lowers blood pressure in normotensive adults. Respiratory physiology & neurobiology, 216, 63-9.
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  Inspiratory muscle training holds promise as a non-pharmacologic treatment that can improve respiratory muscle strength, reduce blood pressure, and improve autonomic balance in hypertensive patients. There is a gap in knowledge regarding the specific respiratory stimulus that gives rise to these favorable outcomes. We implemented five respiratory training protocols that differed in the magnitude and direction of the lung volumes and/or intrathoracic pressures generated by subjects in training. Normotensive adults were randomly assigned to each group and trained daily for 6 weeks. Pre-post and weekly measures of blood pressure showed significant declines in systolic [-8.96 mmHg (95% CI, 7.39-10.53)] and diastolic [-5.25 mmHg (95% CI, 3.67-6.83)] blood pressures for subjects who trained with large positive or negative intrathoracic pressures. Subjects who trained with modest intrathoracic pressures or large lung volumes saw no improvement in blood pressure (P > 0.3). Large intra-thoracic pressures are the specific respiratory stimulus underpinning breathing training related improvements in blood pressure.
• Bailey, E. F. (2014). Neural drive to respiratory muscles in the spontaneously breathing rat pup..
• Kidder, I. J., Mudery, J. A., & Bailey, E. F. (2014). Neural drive to respiratory muscles in the spontaneously breathing rat pup. RESPIRATORY PHYSIOLOGY & NEUROBIOLOGY, 202, 64-70.
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  The neonatal rodent serves as useful and appropriate model within which to study respiratory system development. Despite an extensive literature that documents respiratory control in vitro, in vivo studies have relied upon whole body plethysmography to determine measures of respiratory frequency and tidal volume. However, plethysmography restricts access to the animal and thus, respiratory muscle electromyographic (EMG) activities have not been recorded in these studies previously. Electromyography yields accurate information about neural respiratory center output to the musculature and therefore, about the control of breathing in the intact animal. In this case, we documented neural drive to respiratory pump and upper airway muscles, electrocardiogram (ECG) and chest wall motions in rat pups up to 10 days of age noting sighs, spontaneous central apneas and hypopneas in room air and with successive increments in fractional inspired CO2 (F1CO2). Our findings underscore the advantages of EMG recordings for purposes of determining the magnitude and distribution of neural drive to respiratory muscles and for characterizing the full range of breathing behaviors exhibited by rats in the early postnatal period. (C) 2014 Elsevier B.V. All rights reserved.
• Kidder, I. J., Mudery, J. A., & Bailey, E. F. (2014). Neural drive to respiratory muscles in the spontaneously breathing rat pup. Respiratory physiology & neurobiology, 202, 64-70.
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  The neonatal rodent serves as useful and appropriate model within which to study respiratory system development. Despite an extensive literature that documents respiratory control in vitro, in vivo studies have relied upon whole body plethysmography to determine measures of respiratory frequency and tidal volume. However, plethysmography restricts access to the animal and thus, respiratory muscle electromyographic (EMG) activities have not been recorded in these studies previously. Electromyography yields accurate information about neural respiratory center output to the musculature and therefore, about the control of breathing in the intact animal. In this case, we documented neural drive to respiratory pump and upper airway muscles, electrocardiogram (ECG) and chest wall motions in rat pups up to 10 days of age noting sighs, spontaneous central apneas and hypopneas in room air and with successive increments in fractional inspired CO2 (FICO2). Our findings underscore the advantages of EMG recordings for purposes of determining the magnitude and distribution of neural drive to respiratory muscles and for characterizing the full range of breathing behaviors exhibited by rats in the early postnatal period.
• Lacross, A., Lacross, A., & Bailey, E. F. (2014). Temporal characteristics of vowel articulation: Electromyographic investigation of the “articulatory period”. Journal of the Acoustical Society of America, 135(4), 2290-2290. doi:10.1121/1.4877515
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  In speech, articulator movement precedes the acoustic signal [e.g., Meyer (1991); Gracco (1988); Lubker and Gay (1982); Bell-Berti and Harris (1981)]. The onset and offset of movement, i.e., the ‘articulatory period' (Bell-Berti and Harris, 1981, p. 13) is said to encompass the acoustic signal however the precise timing and variability of this period are not well understood. Using electromyography (EMG), we examine the onset/offset of the articulatory period as a function of phonetic context. We recorded EMG activity from the posterior and anterior regions of the genioglossus (GG) muscle of the tongue in subjects during the articulation of static vowels, static vowels with initial coronal or palatal fricatives and vowels embedded in the nonce word [∫pVp]. We show front and high vowels entail earlier onset of GG activation and that vowels preceded by coronal fricatives are associated with significantly earlier muscle activation than vowels preceded by palatal fricatives. We also note timing differences bet...
• Bailey, E. F. (2013). Human hypoglossal motor unit activities in exercise..
• Walls, C. E., Laine, C. M., Kidder, I. J., & Bailey, E. F. (2013). Human hypoglossal motor unit activities in exercise. The Journal of physiology, 591(14), 3579-90.
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  The genioglossus (GG) muscle is considered the principal protruder muscle of the tongue that dilates and stiffens the pharyngeal airway. We recorded whole muscle and single motor unit (MU) activities in healthy adults performing progressive intensity exercise on a cycle ergometer. Tungsten microelectrodes were inserted percutaneously into the GG of 11 subjects (20-40 years) to record electromyographic (EMG) activities and pulmonary ventilation (VI) at rest and at workload increments up to 300 W. Increases in respiratory drive were associated with increases in VI, mean inspiratory flow (Vt/Ti) and tonic and phasic components of the GG EMG activity. In contrast, individual MUs typically showed expiration-related decreases in firing as exercise intensity increased. We suggest the decrease in MU activity may occur secondary to afferent feedback from lungs/chest wall and that compensation for more negative inspiratory airway pressures generated during heavy exercise occurs primarily via recruitment of previously silent MUs.
• Bailey, E. F. (2012). Cortical entrainment of human hypoglossal motor unit activities..
• Laine, C. M., Nickerson, L. A., & Bailey, E. F. (2012). Cortical entrainment of human hypoglossal motor unit activities. Journal of neurophysiology, 107(1), 493-9.
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  Output from the primary motor cortex contains oscillations that can have frequency-specific effects on the firing of motoneurons (MNs). Whereas much is known about the effects of oscillatory cortical drive on the output of spinal MN pools, considerably less is known about the effects on cranial motor nuclei, which govern speech/oromotor control. Here, we investigated cortical input to one such motor pool, the hypoglossal motor nucleus (HMN), which controls muscles of the tongue. We recorded intramuscular genioglossus electromyogram (EMG) and scalp EEG from healthy adult subjects performing a tongue protrusion task. Cortical entrainment of HMN population activity was assessed by measuring coherence between EEG and multiunit EMG activity. In addition, cortical entrainment of individual MN firing activity was assessed by measuring phase locking between single motor unit (SMU) action potentials and EEG oscillations. We found that cortical entrainment of multiunit activity was detectable within the 15- to 40-Hz frequency range but was inconsistent across recordings. By comparison, cortical entrainment of SMU spike timing was reliable within the same frequency range. Furthermore, this effect was found to be intermittent over time. Our study represents an important step in understanding corticomuscular synchronization in the context of human oromotor control and is the first study to document SMU entrainment by cortical oscillations in vivo.
• Bailey, E. F. (2011).

  Common Synaptic Input to the Human Hypoglossal Motor Nucleus

  . Journal of Neurophysiology, 105(1), 380-387. doi:10.1152/jn.00766.2010
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  The tongue plays a key role in various volitional and automatic functions such as swallowing, maintenance of airway patency, and speech. Precisely how hypoglossal motor neurons, which control the tongue, receive and process their often concurrent input drives is a subject of ongoing research. We investigated common synaptic input to the hypoglossal motor nucleus by measuring the coordination of spike timing, firing rate, and oscillatory activity across motor units recorded from unilateral (i.e., within a belly) or bilateral (i.e., across both bellies) locations within the genioglossus (GG), the primary protruder muscle of the tongue. Simultaneously recorded pairs of motor units were obtained from 14 healthy adult volunteers using tungsten microelectrodes inserted percutaneously into the GG while the subjects were engaged in volitional tongue protrusion or rest breathing. Bilateral motor unit pairs showed concurrent low frequency alterations in firing rate (common drive) with no significant difference between tasks. Unilateral motor unit pairs showed significantly stronger common drive in the protrusion task compared with rest breathing, as well as higher indices of synchronous spiking (short-term synchrony). Common oscillatory input was assessed using coherence analysis and was observed in all conditions for frequencies up to ∼ 5 Hz. Coherence at frequencies up to ∼ 10 Hz was strongest in motor unit pairs recorded from the same GG belly in tongue protrusion. Taken together, our results suggest that cortical drive increases motor unit coordination within but not across GG bellies, while input drive during rest breathing is distributed uniformly to both bellies of the muscle.
• Bailey, E. F. (2011). Activities of human genioglossus motor units. Respiratory physiology & neurobiology, 179(1), 14-22.
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  Upper airway muscles play an important role in regulating airway lumen and in increasing the ability of the pharynx to remain patent in the face of subatmospheric intraluminal pressures produced during inspiration. Due to the considerable technical challenges associated with recording from muscles of the upper airway, much of the experimental work conducted in human subjects has centered on recording respiratory-related activities of the extrinsic tongue protudor muscle, the genioglossus (GG). The GG is one of eight muscles that invest the human tongue (Abd-El-Malek, 1939). All eight muscles are innervated by the hypoglossal nerve (cranial nerve XII) the cell bodies of which are located in the hypoglossal motor nucleus (HMN) of the caudal medulla. Much of the earlier work on the respiratory-related activity of XII motoneurons was based on recordings obtained from single motor axons dissected from the whole XII nerve or from whole muscle GG EMG recordings. Detailed information regarding respiratory-related GG motor unit activities was lacking until as recently as 2006. This paper examines key findings that have emerged from the last decade of work conducted in human subjects. Wherever appropriate, these results are compared with results obtained from in vitro and in vivo studies conducted in non-human mammals. The review is written with the objective of facilitating some discussion and some new thoughts regarding future research directions. The material is framed around four topics: (a) motor unit type, (b) rate coding and recruitment, (c) motor unit activity patterns, and (d) a compartment based view of pharyngeal airway control.
• Bailey, E. F. (2011). Activities of human genioglossus motor units..
• Bailey, E. F. (2011). Common synaptic input to the human hypoglossal motor nucleus..
• Bailey, E. F. (2011). Respiratory muscles and motoneurons..
• Fregosi, R. F., Bailey, E. F., & Fuller, D. D. (2011). Respiratory muscles and motoneurons. Respiratory physiology & neurobiology, 179(1), 1-2.
• Laine, C. M., & Bailey, E. F. (2011). Common synaptic input to the human hypoglossal motor nucleus. Journal of neurophysiology, 105(1), 380-7.
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  The tongue plays a key role in various volitional and automatic functions such as swallowing, maintenance of airway patency, and speech. Precisely how hypoglossal motor neurons, which control the tongue, receive and process their often concurrent input drives is a subject of ongoing research. We investigated common synaptic input to the hypoglossal motor nucleus by measuring the coordination of spike timing, firing rate, and oscillatory activity across motor units recorded from unilateral (i.e., within a belly) or bilateral (i.e., across both bellies) locations within the genioglossus (GG), the primary protruder muscle of the tongue. Simultaneously recorded pairs of motor units were obtained from 14 healthy adult volunteers using tungsten microelectrodes inserted percutaneously into the GG while the subjects were engaged in volitional tongue protrusion or rest breathing. Bilateral motor unit pairs showed concurrent low frequency alterations in firing rate (common drive) with no significant difference between tasks. Unilateral motor unit pairs showed significantly stronger common drive in the protrusion task compared with rest breathing, as well as higher indices of synchronous spiking (short-term synchrony). Common oscillatory input was assessed using coherence analysis and was observed in all conditions for frequencies up to ∼ 5 Hz. Coherence at frequencies up to ∼ 10 Hz was strongest in motor unit pairs recorded from the same GG belly in tongue protrusion. Taken together, our results suggest that cortical drive increases motor unit coordination within but not across GG bellies, while input drive during rest breathing is distributed uniformly to both bellies of the muscle.
• Bailey, E. F. (2010).

  Tonically Discharging Genioglossus Motor Units Show No Evidence of Rate Coding With Hypercapnia

  . Journal of Neurophysiology, 103(3):, 1315–1321. doi:10.1152/jn.00686.2009
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  The genioglossus (GG) is considered the principle protrudor muscle of the human tongue. Unlike most skeletal muscles, GG electromyographic (EMG) activities are robustly preserved in sleep and thus may fulfill a critical role in preserving airway patency. Previous studies in human subjects also confirm that the GG EMG increases in response to chemoreceptor and mechanoreceptor stimulation. This increase occurs secondary to the recruitment of previously inactive motor units (MUs) and/or an increase in firing rate of already active MUs. Which strategy the nervous system uses when the synaptic drive onto GG motoneurons increases is not known. Here we report on GG whole muscle and tonic MU activities under conditions that mimic sleep, i.e., mild-moderate elevations in CO(2) (3% inspired CO(2) or the addition of a 1.0 l dead space) and elevated airway resistance. Based on previous work in rat, we hypothesized that mild hypercapnia would increase the firing rates of tonic MUs and that these effects would be further potentiated by a modest increase in airway resistance. Fine wire and tungsten microelectrodes were inserted into the GG to record whole muscle and single MU activities in 21 subjects (13 women, 8 men; 20-55 yr). Either 3% inspired CO(2) or added dead space resulted in a 200-300% increase in the amplitude of both tonic and phasic components of the whole muscle GG EMG and a doubling of minute ventilation. Despite these changes, recordings obtained from a total of 84 tonically discharging GG single MUs provide no evidence of a change in firing rate under any of the conditions. On this basis we conclude that in healthy adults, the increase in the tonic component of the whole muscle GG EMG secondary to mild hypercapnia is due almost exclusively to the recruitment of previously inactive MUs.
• Bailey, E. F. (2010). Tonically discharging genioglossus motor units show no evidence of rate coding with hypercapnia..
• Richardson, P. A., & Bailey, E. F. (2010). Tonically discharging genioglossus motor units show no evidence of rate coding with hypercapnia. Journal of neurophysiology, 103(3), 1315-21.
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  The genioglossus (GG) is considered the principle protrudor muscle of the human tongue. Unlike most skeletal muscles, GG electromyographic (EMG) activities are robustly preserved in sleep and thus may fulfill a critical role in preserving airway patency. Previous studies in human subjects also confirm that the GG EMG increases in response to chemoreceptor and mechanoreceptor stimulation. This increase occurs secondary to the recruitment of previously inactive motor units (MUs) and/or an increase in firing rate of already active MUs. Which strategy the nervous system uses when the synaptic drive onto GG motoneurons increases is not known. Here we report on GG whole muscle and tonic MU activities under conditions that mimic sleep, i.e., mild-moderate elevations in CO(2) (3% inspired CO(2) or the addition of a 1.0 l dead space) and elevated airway resistance. Based on previous work in rat, we hypothesized that mild hypercapnia would increase the firing rates of tonic MUs and that these effects would be further potentiated by a modest increase in airway resistance. Fine wire and tungsten microelectrodes were inserted into the GG to record whole muscle and single MU activities in 21 subjects (13 women, 8 men; 20-55 yr). Either 3% inspired CO(2) or added dead space resulted in a 200-300% increase in the amplitude of both tonic and phasic components of the whole muscle GG EMG and a doubling of minute ventilation. Despite these changes, recordings obtained from a total of 84 tonically discharging GG single MUs provide no evidence of a change in firing rate under any of the conditions. On this basis we conclude that in healthy adults, the increase in the tonic component of the whole muscle GG EMG secondary to mild hypercapnia is due almost exclusively to the recruitment of previously inactive MUs.
• Bailey, E. F. (2009).

  Genioglossus and Intrinsic Electromyographic Activities in Impeded and Unimpeded Protrusion Tasks

  . Journal of Neurophysiology, 101(1):, 276–282. doi:10.1152/jn.91065.2008
• Bailey, E. F. (2009). Genioglossus and intrinsic electromyographic activities in impeded and unimpeded protrusion tasks..
• Hoyer, P. B., Richardson, P. A., Hoyer, P. B., Fregosi, R. F., & Bailey, E. F. (2009). Effects of sex hormones on metabolic rate, ventilation and respiratory-related upper airway muscle activities in female rats. The FASEB Journal, 23.
• Pittman, L. J., & Bailey, E. F. (2009). Genioglossus and intrinsic electromyographic activities in impeded and unimpeded protrusion tasks. Journal of neurophysiology, 101(1), 276-82.
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  Eight muscles invest the human tongue: four extrinsic muscles have external origins and insert into the tongue body and four intrinsic muscles originate and terminate within the tongue. Previously, we noted minimal activation of the genioglossus tongue muscle during impeded protrusion tasks (i.e., having subjects push the tongue against a force transducer), suggesting that other muscles play a role in the production of tongue force. Accordingly, we sought to characterize genioglossus tongue muscle activities during impeded and unimpeded protrusion tasks (i.e., having subjects slowly and smoothly move the tongue out of their mouth). Electromyographic (EMG) and single motor-unit potentials of the extrinsic genioglossus muscle were recorded with tungsten microelectrodes and EMG activities of intrinsic tongue muscles were recorded with hook-wire electrodes inserted into the anterior tongue body. Tongue position was detected by an isotonic transducer coupled to the tongue tip. Protrusive force was detected by a force transducer attached to a rigid bar. Genioglossus and intrinsic tongue muscles were simultaneously active in both impeded and unimpeded protrusion tasks. Genioglossus whole muscle EMG and single motor-unit activities changed faithfully as a function of tongue position, with increased discharge associated with protrusion and decreased discharge associated with retraction back to the rest position. In contrast, during the impeded protrusion task drive the genioglossus muscle remained constant as protrusion force increased. Conversely, intrinsic tongue muscle activities appropriately followed changes in both tongue position and force. Importantly, we observed significantly higher levels of intrinsic muscle activity in the impeded protrusion task. These observations suggest that protrusion of the human tongue requires activation of the genioglossus and intrinsic protrudor muscles, with the former more important for establishing anterior-posterior tongue location and the latter playing a greater role in the generation of protrusive force. A biomechanical model of these actions is provided and discussed.
• Bailey, E. F. (2008). A tasty morsel: the role of the dorsal vagal complex in the regulation of food intake and swallowing. Focus on "BDNF/TrkB signaling interacts with GABAergic system to inhibit rhythmic swallowing in the rat," by Bariohay et al. American journal of physiology. Regulatory, integrative and comparative physiology, 295(4), R1048-9.
• Bailey, E. F. (2008). A tasty morsel: the role of the dorsal vagal complex in the regulation of food intake and swallowing. Focus on "BDNF/TrkB signaling interacts with GABAergic system to inhibit rhythmic swallowing in the rat," by Bariohay et al..
• Bailey, E. F. (2007).

  Firing Patterns of Human Genioglossus Motor Units During Voluntary Tongue Movement

  . Journal of Neurophysiology, 97(1):, 933-6. doi:10.1152/jn.00737.2006
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  The tongue participates in a range of complex oromotor behaviors, including mastication, swallowing, respiration, and speech. Previous electromyographic studies of the human tongue have focused on respiratory-related tongue muscle activities and their role in maintaining upper airway patency. Remarkably, the activities of human hypoglossal motor units have not been studied during the execution of voluntary maneuvers. We recorded single motor unit activity using tungsten microelectrodes in the genioglossus muscle of 10 healthy human subjects performing both slow tongue protrusions and a static holding maneuver. Displacement of the tongue was detected by an isotonic transducer coupled to the lingual surface through a customized lever arm. For protrusion trials, the firing rate at recruitment was 13.1 ± 3 Hz and increased steeply to an average of 24 ± 6 Hz, often with very modest increases in tongue protrusion. For the static holding task, the average firing rate was 16.1 ± 4 Hz, which is surprisingly high relative to limb motor units. The average coefficient of variation of interspike intervals was ∼20% (range, 10–28%). These are the first recordings of their type obtained in human subjects and provide an initial glimpse into the voluntary control of hypoglossal motoneurons during tongue movements presumably instigated by activity in the motor cortex.
• Bailey, E. F. (2007).

  Sleep/Wake Firing Patterns of Human Genioglossus Motor Units

  . Journal of Neurophysiology, 98(6), 3284-91. doi:doi: 10.1152/jn.00865.2007
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  Although studies of the principal tongue protrudor muscle genioglossus (GG) suggest that whole muscle GG electromyographic (EMG) activities are preserved in nonrapid eye movement (NREM) sleep, it is unclear what influence sleep exerts on individual GG motor unit (MU) activities. We characterized the firing patterns of human GG MUs in wakefulness and NREM sleep with the aim of determining 1) whether the range of MU discharge patterns evident in wakefulness is preserved in sleep and 2) what effect the removal of the “wakefulness” input has on the magnitude of the respiratory modulation of MU activities. Microelectrodes inserted into the extrinsic tongue protrudor muscle, the genioglossus, were used to follow the discharge of single MUs. We categorized MU activities on the basis of the temporal relationship between the spike train and the respiration cycle and quantified the magnitude of the respiratory modulation of each MU using the eta (η 2 ) index, in wakefulness and sleep. The majority of MUs exhibited subtle increases or decreases in respiratory modulation but were otherwise unaffected by NREM sleep. In contrast, 30% of MUs exhibited marked sleep-associated changes in discharge frequency and respiratory modulation. We suggest that GG MUs should not be considered exclusively tonic or phasic; rather, the discharge pattern appears to be a flexible feature of GG activities in healthy young adults. Whether such flexibility is important in the response to changes in the chemical and/or mechanical environment and whether it is preserved as a function of aging or in individuals with obstructive sleep apnea are critical questions for future research.
• Bailey, E. F. (2007). Firing patterns of human genioglossus motor units during voluntary tongue movement..
• Bailey, E. F. (2007). Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction..
• Bailey, E. F. (2007). Sleep/wake firing patterns of human genioglossus motor units..
• Bailey, E. F., Fridel, K. W., & Rice, A. D. (2007). Sleep/wake firing patterns of human genioglossus motor units. Journal of neurophysiology, 98(6), 3284-91.
  More info

  Although studies of the principal tongue protrudor muscle genioglossus (GG) suggest that whole muscle GG electromyographic (EMG) activities are preserved in nonrapid eye movement (NREM) sleep, it is unclear what influence sleep exerts on individual GG motor unit (MU) activities. We characterized the firing patterns of human GG MUs in wakefulness and NREM sleep with the aim of determining 1) whether the range of MU discharge patterns evident in wakefulness is preserved in sleep and 2) what effect the removal of the "wakefulness" input has on the magnitude of the respiratory modulation of MU activities. Microelectrodes inserted into the extrinsic tongue protrudor muscle, the genioglossus, were used to follow the discharge of single MUs. We categorized MU activities on the basis of the temporal relationship between the spike train and the respiration cycle and quantified the magnitude of the respiratory modulation of each MU using the eta (eta(2)) index, in wakefulness and sleep. The majority of MUs exhibited subtle increases or decreases in respiratory modulation but were otherwise unaffected by NREM sleep. In contrast, 30% of MUs exhibited marked sleep-associated changes in discharge frequency and respiratory modulation. We suggest that GG MUs should not be considered exclusively tonic or phasic; rather, the discharge pattern appears to be a flexible feature of GG activities in healthy young adults. Whether such flexibility is important in the response to changes in the chemical and/or mechanical environment and whether it is preserved as a function of aging or in individuals with obstructive sleep apnea are critical questions for future research.
• Bailey, E. F., Rice, A. D., & Fuglevand, A. J. (2007). Firing patterns of human genioglossus motor units during voluntary tongue movement. Journal of neurophysiology, 97(1), 933-6.
  More info

  The tongue participates in a range of complex oromotor behaviors, including mastication, swallowing, respiration, and speech. Previous electromyographic studies of the human tongue have focused on respiratory-related tongue muscle activities and their role in maintaining upper airway patency. Remarkably, the activities of human hypoglossal motor units have not been studied during the execution of voluntary maneuvers. We recorded single motor unit activity using tungsten microelectrodes in the genioglossus muscle of 10 healthy human subjects performing both slow tongue protrusions and a static holding maneuver. Displacement of the tongue was detected by an isotonic transducer coupled to the lingual surface through a customized lever arm. For protrusion trials, the firing rate at recruitment was 13.1 +/- 3 Hz and increased steeply to an average of 24 +/- 6 Hz, often with very modest increases in tongue protrusion. For the static holding task, the average firing rate was 16.1 +/- 4 Hz, which is surprisingly high relative to limb motor units. The average coefficient of variation of interspike intervals was approximately 20% (range, 10-28%). These are the first recordings of their type obtained in human subjects and provide an initial glimpse into the voluntary control of hypoglossal motoneurons during tongue movements presumably instigated by activity in the motor cortex.
• Van Zutphen, C., Janssen, P., Hassan, M., Cabrera, R., Bailey, E. F., & Fregosi, R. F. (2007). Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction. NMR in biomedicine, 20(7), 682-91.
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  The velopharynx is the most collapsible segment of the upper airway in patients with obstructive sleep apnea. However, we do not know if velopharyngeal compliance is uniform throughout its length, or if compliance is modified by contraction of upper airway muscles. We tested the hypothesis that rostral and caudal velopharyngeal (VP) compliance differs, and that tongue muscle contraction reduces compliance. High-resolution MR images of the VP were made at nasopharyngeal pressures ranging from -9 to 9 cmH(2)O in anesthetized rats. Images were obtained twice at each pressure, once with and once without bilateral hypoglossal nerve stimulation. The volume of the caudal and rostral VP was computed at each pressure. The caudal VP was significantly (P = 0.0058) more compliant than the rostral VP, but electrical stimulation of the tongue muscles did not change compliance. VP critical pressure (Pcrit; pressure at zero airway volume) averaged -25.2 and -12.1 cmH(2)O in the rostral and caudal VP, respectively (P < 0.0001). Coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone dilated the VP and made Pcrit more negative (P < 0.0001), but only in the caudal VP. In the rat, the caudal VP is more collapsible than the rostral VP, and either coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone makes this region more difficult to close. Thus, tongue muscle contraction protects the caudal VP, which appears to be a particularly vulnerable segment of the nasopharyngeal airway. With suitable modification, the methods described here, including tongue muscle stimulation at different pharyngeal pressures, may be appropriate for experiments in human subjects.
• Bailey, E. F. (2006). Anatomic consequences of intrinsic tongue muscle activation..
• Bailey, E. F. (2006). Modulation of upper airway muscle activities by bronchopulmonary afferents..
• Bailey, E. F., & Fregosi, R. F. (2006). Modulation of upper airway muscle activities by bronchopulmonary afferents. Journal of applied physiology (Bethesda, Md. : 1985), 101(2), 609-17.
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  Here we review the influence of bronchopulmonary receptors (slowly and rapidly adapting pulmonary stretch receptors, and pulmonary/bronchial C-fiber receptors) on respiratory-related motor output to upper airway muscles acting on the larynx, tongue, and hyoid arch. Review of the literature shows that all muscles in all three regions are profoundly inhibited by lung inflation, which excites slowly adapting pulmonary stretch receptors. This widespread coactivation includes the recruitment of muscles that have opposing mechanical actions, suggesting that the stiffness of upper airway muscles is highly regulated. A profound lack of information on the modulation of upper airway muscles by rapidly adapting receptors and bronchopulmonary C-fiber receptors prohibits formulation of a conclusive opinion as to their actions and underscores an urgent need for new studies in this area. The preponderance of the data support the view that discharge arising in slowly adapting pulmonary stretch receptors plays an important role in the initiation of the widespread and highly coordinated recruitment of laryngeal, tongue, and hyoid muscles during airway obstruction.
• Bailey, E. F., Huang, Y., & Fregosi, R. F. (2006). Anatomic consequences of intrinsic tongue muscle activation. Journal of applied physiology (Bethesda, Md. : 1985), 101(5), 1377-85.
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  We recently showed respiratory-related coactivation of both extrinsic and intrinsic tongue muscles in the rat. Here, we test the hypothesis that intrinsic tongue muscles contribute importantly to changes in velopharyngeal airway volume. Spontaneously breathing anesthetized rats were placed in a MRI scanner. A catheter was placed in the hypopharynx and connected to a pressure source. Axial and sagittal images of the velopharyngeal airway were obtained, and the volume of each image was computed at airway pressures ranging from +5.0 to -5.0 cm H2O. We obtained images in the hypoglossal intact animal (i.e., coactivation of intrinsic and extrinsic tongue muscles) and after selective denervation of the intrinsic tongue muscles, with and without electrical stimulation. Denervation of the intrinsic tongue muscles reduced velopharyngeal airway volume at atmospheric and positive airway pressures. Electrical stimulation of the intact hypoglossal nerve increased velopharyngeal airway volume; however, when stimulation was repeated after selective denervation of the intrinsic tongue muscles, the increase in velopharyngeal airway volume was significantly attenuated. These findings support our working hypothesis that intrinsic tongue muscles play a critical role in modulating upper airway patency.
• Bailey, E. F. (2005).

  PO₂-dependent Changes in Intrinsic and Extrinsic Tongue Muscle Activities in the Rat

  . Am J Respir Crit Care Med. 171(12), 171(12), 1403–1407. doi:10.1164/rccm.200411-1550oc
• Bailey, E. F. (2005).

  Respiratory-related Discharge of Genioglossus Muscle Motor Units

  . Am J Respir Crit Care Med., 172(10), 1331–1337. doi:10.1164/rccm.200505-790oc
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  Little is known about the respiratory-related discharge properties of motor units driving any of the eight muscles that control the movement, shape, and stiffness of the mammalian tongue.To characterize the respiratory-related discharge of genioglossus motor units as synaptic drive to the hypoglossal motoneuron pool is increased with hypercapnia.We recorded airflow, genioglossus muscle EMG activity, and the respiratory-related discharge of 30 genioglossus muscle motor units in spontaneously breathing, urethane-anesthetized rats under control conditions and in hypercapnia (inspired CO2: 3, 6, 9, and 12%, 3-5 min at each level).All motor units were active throughout all or most of inspiration. Nine of 30 units showed "preinspiratory" activity (discharge onset within the last 20% of expiration), with continued discharge into inspiration. Six inspiratory units transitioned to a preinspiratory pattern when inspired CO2 exceeded 6%. For the majority of units (23/30), discharge rate increased with hypercapnia, with the maximum increase averaging about 50%. The average variability of interspike intervals within a spike train increased from 33% under baseline conditions to 50% with maximal hypercapnia.(1) The discharge pattern of genioglossus muscle motor units can be altered by hypercapnia; (2) most, but not all, genioglossus motor units receive synaptic input from CO2-sensitive chemoreceptors; (3) individual motor units have a wide range of CO2 sensitivities; and (4) hypercapnia significantly increases the variability of motor unit discharge, which may enhance muscle force output.
• Bailey, E. F. (2005). PO2-dependent changes in intrinsic and extrinsic tongue muscle activities in the rat..
• Bailey, E. F. (2005). Respiratory-related discharge of genioglossus muscle motor units..
• Bailey, E. F., Janssen, P. L., & Fregosi, R. F. (2005). PO2-dependent changes in intrinsic and extrinsic tongue muscle activities in the rat. American journal of respiratory and critical care medicine, 171(12), 1403-7.
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  Historically, respiratory-related research in sleep apnea has focused exclusively on the extrinsic tongue muscles (i.e., genioglossus, hyoglossus, and styloglossus). Until recently, the respiratory control and function of intrinsic tongue muscles (i.e., inferior and superior longitudinalis, transverses, and verticalis), which comprise the bulk of the tongue, were unknown.
• John, J., Bailey, E. F., & Fregosi, R. F. (2005). Respiratory-related discharge of genioglossus muscle motor units. American journal of respiratory and critical care medicine, 172(10), 1331-7.
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  Little is known about the respiratory-related discharge properties of motor units driving any of the eight muscles that control the movement, shape, and stiffness of the mammalian tongue.
• Bailey, E. F. (2004). Coordination of intrinsic and extrinsic tongue muscles during spontaneous breathing in the rat..
• Bailey, E. F., & Fregosi, R. F. (2004). Coordination of intrinsic and extrinsic tongue muscles during spontaneous breathing in the rat. Journal of Applied Physiology, 96(2), 440-449. doi:10.1152/japplphysiol.00733.2003
• Bailey, E. F., & Fregosi, R. F. (2004). Coordination of intrinsic and extrinsic tongue muscles during spontaneous breathing in the rat. Journal of applied physiology (Bethesda, Md. : 1985), 96(2), 440-9.
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  The muscular-hydrostat model of tongue function proposes a constant interaction of extrinsic (external bony attachment, insertion into base of tongue) and intrinsic (origin and insertion within the tongue) tongue muscles in all tongue movements (Kier WM and Smith KK. Zool J Linn Soc 83: 207-324, 1985). Yet, research that examines the respiratory-related effects of tongue function in mammals continues to focus almost exclusively on the respiratory control and function of the extrinsic tongue protrusor muscle, the genioglossus muscle. The respiratory control and function of the intrinsic tongue muscles are unknown. Our purpose was to determine whether intrinsic tongue muscles have a respiration-related activity pattern and whether intrinsic tongue muscles are coactivated with extrinsic tongue muscles in response to respiratory-related sensory stimuli. Esophageal pressure and electromyographic (EMG) activity of an extrinsic tongue muscle (hyoglossus), an intrinsic tongue muscle (superior longitudinal), and an external intercostal muscle were studied in anesthetized, tracheotomized, spontaneously breathing rats. Mean inspiratory EMG activity was compared at five levels of inspired CO2. Intrinsic tongue muscles were often quiescent during eupnea but active during hypercapnia, whereas extrinsic tongue muscles were active in both eupnea and hypercapnia. During hypercapnia, the activities of the airway muscles were largely coincident, although the onset of extrinsic muscle activity generally preceded the onset of intrinsic muscle activation. Our findings provide evidence, in an in vivo rodent preparation, of respiratory modulation of motoneurons supplying intrinsic tongue muscles. Distinctions noted between intrinsic and extrinsic activities could be due to differences in motoneuron properties or the central, respiration-related control of each motoneuron population.
• Bailey, E. F. (2003). Pressure-volume behaviour of the rat upper airway: effects of tongue muscle activation..
• Bailey, E. F., & Fregosi, R. F. (2003). Pressure-volume behaviour of the rat upper airway: effects of tongue muscle activation. The Journal of physiology, 548(Pt 2), 563-8.
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  Our hypothesis was that the simultaneous activation of tongue protrudor and retractor muscles (co-activation) would constrict and stiffen the pharyngeal airway more than the independent activation of tongue protrudor muscles. Upper airway stiffness was determined by injecting known volumes of air into the sealed pharyngeal airway of the anaesthetized rat while measuring nasal pressure under control (no-stimulus) and stimulus conditions (volume paired with hypoglossal (XII) nerve stimulation). Stimulation of the whole XII nerves (co-activation) or the medial XII branches (protrudor activation) effected similar increases in total pharyngeal airway stiffness. Importantly, co-activation produced volume compression (airway narrowing) at large airway volumes (P < 0.05), but had no effect on airway dimension at low airway volumes. In comparison, protrudor activation resulted in significant volume expansion (airway dilatation) at low airway volumes and airway narrowing at high airway volumes (P < 0.05). In conclusion, both co-activation and independent protrudor muscle activation increase airway stiffness. However, their effects on airway size are complex and depend on the condition of the airway at the time of activation.
• Bailey, E. F. (2002).

  Speaking and Breathing in High Respiratory Drive

  . J Speech Lang Hear Res, 45(1), 89-99. doi:10.1044/1092-4388(2002/007)
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  Pulmonary ventilation during speech breathing reflects the sum of the airflow changes used to speak and to meet the metabolic needs of the body. Studying interactions between speaking and breathing may provide insights into the mechanisms of shared respiratory control. The purposes of this study were to determine if healthy subjects exhibit task-specific breathing behaviors in high respiratory drive and to document subjects' perceptions during breathing and speaking under these conditions. Ten men were studied in air and high CO 2 . Magnetometers were used to estimate lung volume, rib cage and abdomen volumes, minute volume, breathing frequency, tidal volume, inspiratory and expiratory duration, and inspiratory and expiratory flow. Subjects' perceptions were assessed informally. Results indicated that the chest wall kinematic behaviors associated with breathing and speaking in high drive were similar in pattern but differed in the magnitudes of lung volume and rib cage volume events and in inspiratory and expiratory flow. Linguistic influences remained strong, but not as strong as under normal conditions. All subjects reported a heightened sense of breathing-related discomfort during speaking as opposed to breathing in high respiratory drive. We conclude that in healthy subjects breathing behavior associated with speaking in high respiratory drive is guided continuously by shared linguistic and metabolic influences. A parallel-processing model is proposed to explain the behaviors observed.
• Bailey, E. F. (2002). Speaking and breathing in high respiratory drive..
• Bailey, E. F., & Hoit, J. D. (2002). Speaking and breathing in high respiratory drive. Journal of speech, language, and hearing research : JSLHR, 45(1), 89-99.
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  Pulmonary ventilation during speech breathing reflects the sum of the airflow changes used to speak and to meet the metabolic needs of the body. Studying interactions between speaking and breathing may provide insights into the mechanisms of shared respiratory control. The purposes of this study were to determine if healthy subjects exhibit task-specific breathing behaviors in high respiratory drive and to document subjects' perceptions during breathing and speaking under these conditions. Ten men were studied in air and high CO2. Magnetometers were used to estimate lung volume, rib cage and abdomen volumes, minute volume, breathing frequency, tidal volume, inspiratory and expiratory duration, and inspiratory and expiratory flow. Subjects' perceptions were assessed informally. Results indicated that the chest wall kinematic behaviors associated with breathing and speaking in high drive were similar in pattern but differed in the magnitudes of lung volume and rib cage volume events and in inspiratory and expiratory flow. Linguistic influences remained strong, but not as strong as under normal conditions. All subjects reported a heightened sense of breathing-related discomfort during speaking as opposed to breathing in high respiratory drive. We conclude that in healthy subjects breathing behavior associated with speaking in high respiratory drive is guided continuously by shared linguistic and metabolic influences. A parallel-processing model is proposed to explain the behaviors observed.
• Bailey, E. F. (2001). Effect of pulmonary stretch receptor feedback and CO(2) on upper airway and respiratory pump muscle activity in the rat..
• Bailey, E. F., Jones, C. L., Reeder, J. C., Fuller, D. D., & Fregosi, R. F. (2001). Effect of pulmonary stretch receptor feedback and CO(2) on upper airway and respiratory pump muscle activity in the rat. The Journal of physiology, 532(Pt 2), 525-34.
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  1. Our purpose was to examine the effects of chemoreceptor stimulation and lung inflation on neural drive to tongue protrudor and retractor muscles in the rat. 2. Inspiratory flow, tidal volume, transpulmonary pressure, compliance and electromyographic (EMG) activity of genioglossus (GG), hyoglossus (HG) and inspiratory intercostal (IIC) muscles were studied in 11 anaesthetized, tracheotomized and spontaneously breathing rats. Mean EMG activity during inspiration was compared with mean EMG activity during an occluded inspiration, at each of five levels of inspired CO(2) (0, 3, 6, 9 and 12 %). 3. Lung inflation suppressed EMG activity in all muscles, with the effect on both tongue muscles exceeding that of the intercostal muscles. Static elevations of end-expiratory lung volume evoked by 2 cmH(2)O positive end-expiratory pressure (PEEP) had no effect on tongue muscle activity. 4. Despite increasing inspiratory flow, tidal volume and transpulmonary pressure, the inhibition of tongue muscle activity by lung inflation diminished as arterial PCO2 (P(a),CO(2)) increased. 5. The onset of tongue muscle activity relative to the onset of IIC muscle activity advanced with increases in P(a),CO(2) but was unaffected by lung inflation. This suggests that hypoglossal and external intercostal motoneuron pools are controlled by different circuits or have different sensitivities to CO(2), lung inflation and/or anaesthetic agents. 6. We conclude that hypoglossal motoneuronal activity is more strongly influenced by chemoreceptor-mediated facilitation than by lung volume-mediated inhibition. Hypoglossal motoneurons driving tongue protrudor and retractor muscles respond identically to these stimuli.
• Fregosi, R. F., Bailey, E. F., Jones, C. L., Reeder, J. C., & Fuller, D. D. (2001). Effect of pulmonary stretch receptor feedback and CO ₂ on upper airway and respiratory pump muscle activity in the rat. The Journal of Physiology, 532(2), 525-534. doi:10.1111/j.1469-7793.2001.0525f.x

Proceedings Publications

• Bailey, E. F. (2021, May).

  High‐Resistance Inspiratory Muscle Strength Training Improves Cerebrovascular Function in Midlife/Older Adults

  . In FASEB.
• Bailey, E. F. (2018, April).

  Can Daytime Measures of Respiratory Sinus Arrhythmia and Breathing Stability Serve as Biomarkers for OSA?

  . In FASEB, Volume32.
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  Obstructive sleep apnea (OSA) is by definition a disorder of nighttime breathing however, there is good evidence that impairments in cognitive and cardiovascular function persist in the day and that adults with OSA exhibit daytime CO2 retention and hypoxemia. Although a diagnosis of OSA requires in-home or in-laboratory overnight polysomnography, these types of tests are expensive and, due to health insurance quotas, may be limited in availability. Here, we outline simple methods for assessing daytime respiratory sinus arrhythmia (RSA) and respiratory stability that show promise as potential diagnostic tools to identify adults at risk for OSA. We recorded heart rate (finger oxy-photoplethysmography) and respiration (inductance plethysmography) in adults with obstructive sleep apnea (N=6) and age and BMI matched healthy adults (N=8). Subjects completed five minutes of eupneic breathing, five minutes of paced breathing (7.5 breaths/minute) and after equilibration, five minutes of hyperoxic, hypercapnia (5% FICO2). Using de-identified data, we obtained estimates of RSA amplitude, RSA stability, and respiratory stability for each subject in each condition and performed a regression analysis to determine the relationship between each of these variables and subjects' apnea hypopnea index (0–25 AHI). Our preliminary results indicate that daytime measures of respiratory stability and RSA can differentiate healthy adults from adults diagnosed with OSA (p
• Bailey, E. F. (2018, April).

  Influence of Inspiratory Muscle Training on Sympatho‐excitation in Healthy Young Adults

  . In FASEB.
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  Inspiratory muscle training (IMT) lowers blood pressure in healthy young adults and adults with obstructive sleep apnea (Vranish & Bailey, 2015; 2016). Importantly, in healthy young adults, 6 weeks IMT also is associated with significant declines in systemic vascular resistance (Delucia et al. 2017). In light of these outcomes, in the current study we test the hypothesis that 6 weeks IMT reduces sympathetic outflow. Accordingly, we recruited healthy college-aged students and randomly allocated them to either IMT or to Sham training groups. At intake (Week 1) and study completion (Week 6) we recorded MSNA as subjects performed sympatho-excitatory challenges as follows: Valsalva maneuver, Mueller maneuver, submaximal grip test, cold pressor test, and mental stress tests (Stroop and mental arithmetic). Additionally, we performed weekly (blinded) assessments of systolic and diastolic blood pressures (SBP and DBP), and assessed maximal inspiratory pressure and respiratory function. Our preliminary results indicate subjects in the IMT group have lowered systolic (114.3 ± 3.4 mmHg vs. 106.7 ± 1.8 mmHg, p=0.0115) and diastolic (68.39 ± 1.58 mmHg vs. 63.5 ± 0.97 mmHg, p=0.0413) blood pressures relative to Sham trained subjects (SBP 114.7 ± 2.94 mmHg vs. 108.9 ± 1.34 mmHg and DBP 72.47 ± 3.29 mmHg vs. 69.99 ± 1.75 mmHg). Consistent with our hypothesis, preliminary analyses highlight lowered sympathetic burst frequency in the IMT group during Valsalva maneuvers (Week 1:15 ± 2.2 bursts per 15 seconds vs. Week 6: 11 ± 1.5 bursts per 15 seconds) as compared to Sham trained subjects (Week 1:12.13 ± 1.48 bursts per 15 seconds vs. Week 6:11.63 ± 0.83 bursts per 15 seconds). Data collection is ongoing however, our early findings show a reduction in sympathetic outflow during respiratory challenges which may underpin declines in peripheral resistance and blood pressure seen in healthy young adults following IMT. Support or Funding Information This work was supported by start up monies awarded to EFB. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
• Bailey, E. F. (2014, November).

  A novel approach for the analysis of respiratory sinus arrhythmia using breath phase information

  . In Society for Neuroscience, 77.17/JJ29.

Presentations

• Bailey, E. F., LaCross, A., & Watson, P. J. (2014, March). Genioglossus muscle motor unit activity during static vowel articulation. Motor Speech Conference. Sarasota, FL: Madonna Rehabilitation Hospital.

Poster Presentations

• Bailey, E. F. (2014, April). Breathing Training Improves Sleep And Cardiovascular Health In Obstructive Sleep Apnea, [Publication Number: A2139]. American Thoracic Society. San Diego: American Thoracic Society.
• Bailey, E. F. (2014, April). Motor unit recruitment patterns in genioglossus and first dorsal interosseous (1102.4). Experimental Biology. San Diego: APS.
• Bailey, E. F. (2014, April). Respiratory muscle training: a mechanism study (706.22). Experimental Biology. San Diego: APS.
• Bailey, E. F., & Barreda, S. (2014, November). A novel approach for the analysis of respiratory sinus arrhythmia using breath phase information. Society for Neuroscience. Washington, DC.
• Bailey, E. F., & LaCross, A. (2014, May). Temporal characteristics of vowel articulation: Electromyo- graphic investigation of the “articulatory period”. Acoustical Society of America. Providence, RI: Acoustical Society of America.