title: Respiratory Muscle Training and Exercise Endurance at Altitude.
abstract: BACKGROUND
  Climbing and trekking at altitude are common recreational and military activities. Physiological effects of altitude are hypoxia and hyperventilation. The hyperventilatory response to altitude may cause respiratory muscle fatigue and reduce sustained submaximal exercise. Voluntary isocapnic hyperpnea respiratory muscle training (VIHT) improves exercise endurance at sea level and at depth. The purpose of this study was to test the hypothesis that VIHT would improve exercise time at altitude [3600 m (11,811 ft)] compared to control and placebo groups.
  
  
  METHODS
  Subjects pedaled an ergometer until exhaustion at simulated altitude in a hypobaric chamber while noninvasive arterial saturation (Sao2), ventilation (VE), and oxygen consumption (Vo2) were measured.
  
  
  RESULTS
  As expected, Sao2 decreased to 88 ± 4% saturation at rest and to 81 ± 2% during exercise, and was not affected by VIHT. VIHT resulted in a 40% increase in maximal training VE compared to pre-VIHT. Exercise endurance significantly increased 44% after VIHT (P = <0.001). Vo2 (30 ± 3 ml · kg(-1) · min(-1)) and heart rate (177 ± 10 bpm) did not change during exercise and were not affected by VIHT (P = 0.531). Pre-VIHT VE increased 21-27% during the initial 12 min of exercise, after which it decreased 17% at 17.7 ± 6.0 min. VE at altitude post-VIHT increased more (49%) for longer (21 min) and decreased less (11% at 25.4 ± 6.7 min).
  
  
  CONCLUSIONS
  VIHT improved exercise time at altitude and sustained VE. This suggests that VIHT reduced respiratory muscle fatigue and would be useful to trekkers and military personnel working at altitude. Helfer S, Quackenbush J, Fletcher M, Pendergast DR. Respiratory muscle training and exercise endurance at altitutde. Aerosp Med Hum Perform. 2016; 87(8):704-711.
authors.affiliation: Center for Research and Education in Special Environments, Department of Physiology and Biophysics, School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, NY, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Helfer
authors.forename: Joseph
authors.initials: J
authors.lastname: Quackenbush
authors.forename: Michael
authors.initials: M
authors.lastname: Fletcher
authors.forename: David R
authors.initials: DR
authors.lastname: Pendergast
mesh_terms: D000328:Adult; D000531:Altitude; D001945:Breathing Exercises; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D012119:Respiration; D055815:Young Adult