title: Intermittent hypoxic exposure does not improve endurance performance at altitude.
abstract: OBJECTIVE
  This study examined the effect of 1 wk of normobaric intermittent hypoxic exposure (IHE) combined with exercise training on endurance performance at a 4300-m altitude (HA).
  
  
  METHODS
  Seventeen male lowlanders were divided into an IHE (n = 11) or SHAM (n = 6) group. Each completed cycle endurance testing consisting of two 20-min steady state (SS) exercise bouts (at 40% and 60% V O2peak) followed by a 10-min break and then a 720-kJ cycle time trial at HA before IHE or SHAM treatment (Pre-T). IHE treatment consisted of a 2-h rest at a PO2 of 90 mm Hg followed by two 25-min bouts of exercise at approximately 80% of peak HR at a PO2 of 110 mm Hg for 1 wk in a hypoxia room. SHAM treatment was identical except that the PO2 was 148 mm Hg for both rest and exercise. After IHE or SHAM treatment (Post-T), all completed a second cycle endurance test at HA. HR, arterial oxygen saturation (SaO2), and RPE were obtained from the 10th to the 15th minute during the two SS exercise bouts and every 5 min during the time trial.
  
  
  RESULTS
  Seven volunteers in the IHE group could not finish the 720-kJ time trial either at Pre-T or at Post-T. Time trial analysis was limited, therefore, to the time to reach 360 kJ (halfway point) for all volunteers. From Pre-T to Post-T, there was no improvement in time trial performance (min +/- SE) in the IHE (62.0 +/- 4.8 to 63.7 +/- 5.2) or SHAM (60.9 +/- 6.3 to 54.2 +/- 6.8) group. There was no change from Pre-T to Post-T in HR, SaO2, and RPE during the two SS exercise bouts or time trial in either group.
  
  
  CONCLUSIONS
  One week of IHE combined with exercise training does not improve endurance performance at a 4300-m altitude in male lowlanders.
authors.affiliation: Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. beth.beidleman@us.army.mil
authors.forename: Beth A
authors.initials: BA
authors.lastname: Beidleman
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Muza
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fulco
authors.forename: Juli E
authors.initials: JE
authors.lastname: Jones
authors.forename: Eric
authors.initials: E
authors.lastname: Lammi
authors.forename: Janet E
authors.initials: JE
authors.lastname: Staab
authors.forename: Allen
authors.initials: A
authors.lastname: Cymerman
mesh_terms: D000328:Adult; D000531:Altitude; D000704:Analysis of Variance; D001642:Bicycling; D004781:Environmental Exposure / Q000009:adverse effects*; D005080:Exercise Test; D017079:Exercise Tolerance; D006801:Humans; D006931:Hyperbaric Oxygenation; D000860:Hypoxia; D008297:Male; D010101:Oxygen Consumption; D016037:Single-Blind Method; D013997:Time Factors