title: Seven intermittent exposures to altitude improves exercise performance at 4300 m.
abstract: OBJECTIVE
  The purpose of this study was to determine whether seven intermittent altitude exposures (IAE), in combination with either rest or exercise training, improves time-trial exercise performance and induces physiologic adaptations consistent with chronic altitude adaptation at 4300 m.
  
  
  METHODS
  Ten adult lowlanders (26 +/- 2 yr; 78 +/- 4 kg; means +/- SE) completed cycle endurance testing during an acute exposure to a 4300-m-altitude equivalent (446 mm Hg) once before (pre-IAE) and once after (post-IAE) 7 d of IAE (4h x d(-1), 5 d x wk(-1), 4300 m). Cycle endurance testing consisted of two consecutive 15-min constant-work rate exercise bouts followed immediately by a time-trial exercise performance test. During each IAE, five subjects performed exercise training, and the other group of five subjects rested.
  
  
  RESULTS
  Both groups demonstrated similar improvements in time-trial cycle exercise performance and physiologic adaptations during constant-work rate exercise from pre-IAE to post-IAE. Thus, data from all subjects were combined. Seven days of IAE resulted in a 16% improvement (P < 0.05) in time-trial cycle exercise performance (min) from pre-IAE (35 +/- 3) to post-IAE (29 +/- 2). During the two constant-work rate exercise bouts, there was an increase (P < 0.05) in exercise arterial O2 saturation (%) from pre-IAE (77 +/- 2; 75 +/- 1) to post-IAE (80 +/- 2; 79 +/- 1), a decrease (P < 0.05) in exercise heart rate (bpm) from pre-IAE (136 +/- 6; 162 +/- 5) to post-IAE (116 +/- 6; 153 +/- 5), and a decrease (P < 0.05) in exercise ratings of perceived exertion from pre-IAE (10 +/- 1; 14+/- 1) to post-IAE (8 +/- 1; 11 +/- 1).
  
  
  CONCLUSIONS
  Our findings indicate that 7 d of IAE, in combination with either rest or exercise training, improves time-trial cycle exercise performance and induces physiologic adaptations during constant-work rate exercise consistent with chronic altitude adaptation at 4300 m.
authors: Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. beth.beidleman@na.amedd.army.mil
authors: Beth A
authors: BA
authors: Beidleman
authors: Stephen R
authors: SR
authors: Muza
authors: Charles S
authors: CS
authors: Fulco
authors: Allen
authors: A
authors: Cymerman
authors: Michael N
authors: MN
authors: Sawka
authors: Steven F
authors: SF
authors: Lewis
authors: Gary S
authors: GS
authors: Skrinar
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D000531:Altitude; D001642:Bicycling / Q000502:physiology*; D015687:Cell Hypoxia / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology*; D011446:Prospective Studies; D012146:Rest / Q000502:physiology*; D013997:Time Factors