title: Effects of inspiratory muscle training on exercise responses in normoxia and hypoxia.
abstract: The purpose of this study was to determine the effects of inspiratory muscle training (IMT) on exercise in hypoxia (H) and normoxia (N). A 4-week IMT program was implemented with 12 healthy subjects using an inspiratory muscle trainer set at either 15% (C; n=5) or 50% (IMT; n=7) maximal inspiratory mouth pressure (PImax). Two treadmill tests (85% VO2max) to exhaustion and measures of diaphragm thickness (Tdi) and function were completed before and after training in H and N. Significant increases of 8-12% and 24.5+/-3.1% in Tdi and PImax, respectively, were seen in the IMT group. Time to exhaustion remained unchanged in all conditions. Inspiratory muscle fatigue (downward arrowPImax) following exercise was reduced approximately 10% (P<0.05) in IMT after both N and H. During H, IMT reduced (P<0.05) VO2 by 8-12%, cardiac output by 14+/-2%, ventilation by 25+/-3%; and increased arterial oxygen saturation by 4+/-1% and lung diffusing capacity by 22+/-3%. Ratings of perceived exertion and dyspnea were also significantly reduced. These data suggest that IMT significantly improves structural and functional physiologic measures in hypoxic exercise.
authors.affiliation: Department of Kinesiology, Kansas State University, Manhattan, 1A Natatorium, KS 66506, United States.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Downey
authors.forename: Leonie M
authors.initials: LM
authors.lastname: Chenoweth
authors.forename: Dana K
authors.initials: DK
authors.lastname: Townsend
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Ranum
authors.forename: Christine S
authors.initials: CS
authors.lastname: Ferguson
authors.forename: Craig A
authors.initials: CA
authors.lastname: Harms
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D001945:Breathing Exercises; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology* / Q000534:rehabilitation; D001239:Inhalation / Q000502:physiology; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D012016:Reference Values; D012132:Respiratory Muscles / Q000502:physiology*