title: Prediction of physiological responses and performance at altitude using the 6-minute walk test in normoxia and hypoxia.
abstract: OBJECTIVE
  The 6-minute walk test (6MWT) is a reliable and valid tool for determining an individual's functional capacity, and has been used to predict summit success. The primary aim of the study was to evaluate whether a 6MWT in normobaric hypoxia could predict physiological responses and exercise performance at altitude. The secondary aim was to determine construct validity of the 6MWT for monitoring acclimatization to 3400 m (Cuzco, Peru).
  
  
  METHODS
  Twenty-nine participants performed six 6MWTs in four conditions: normoxic outdoor (NO), normoxic treadmill (NT), and hypoxic treadmill (HT) were each performed once; and hypoxic outdoor (HO) was performed three times, at 42 hours (HO1), 138 hours (HO2), and 210 hours (HO3) after arrival at Cuzco.
  
  
  RESULTS
  One-way analysis of variance revealed no difference (P>.05) between NO and HO1 for 6MWT distance. HT and HO protocols were comparable for the measurement of delta heart rate (HR) and post-test peripheral oxygen saturation (%Spo2; P>.05). Acclimatization was evidenced by reductions (P<.05) in resting HR and respiratory rate (RR) between HO1, HO2, and HO3, and preservation of Spo2 between HO1 and HO2. Postexercise HR and RR were not different (P>.05) with acclimatization. The duration to ascend to 4215 m on a trek was moderately correlated (P<.05) to HR during the trek and the 6MWT distance during HT; no other physiological markers predicted performance.
  
  
  CONCLUSIONS
  The 6MWT is a simple, time-efficient tool for predicting physiological responses to simulated and actual altitude, which are comparable. The 6MWT is effective at monitoring elements of acclimatization to moderate altitude.
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Welkin Human Performance Laboratories, University of Brighton, UK. Electronic address: o.r.gibson@brighton.ac.uk.
authors.forename: Oliver R
authors.initials: OR
authors.lastname: Gibson
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Welkin Human Performance Laboratories, University of Brighton, UK.
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Richardson
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Welkin Human Performance Laboratories, University of Brighton, UK.
authors.forename: Mark
authors.initials: M
authors.lastname: Hayes
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Welkin Human Performance Laboratories, University of Brighton, UK.
authors.forename: Ben
authors.initials: B
authors.lastname: Duncan
authors.affiliation: Centre for Sport and Exercise Science and Medicine (SESAME), Welkin Human Performance Laboratories, University of Brighton, UK.
authors.forename: Neil S
authors.initials: NS
authors.lastname: Maxwell
mesh_terms: D000064:Acclimatization; D000293:Adolescent; D000328:Adult; D000531:Altitude; D005260:Female; D006801:Humans; D000860:Hypoxia; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D013997:Time Factors; D016138:Walking / Q000502:physiology*; D055815:Young Adult
chemical_list: D010100:Oxygen
keywords: 6-minute walk test; altitude sickness; hypoxia; mountaineering