Prediction of Physiological Responses and Performance at Altitude Using the 6-minute Walk Test in Normoxia and Hypoxia

Wilderness Environ Med. 2015 Jun;26(2):205-10. doi: 10.1016/j.wem.2014.11.004. Epub 2015 Mar 12.

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.

Keywords: 6-minute walk test; altitude sickness; hypoxia; mountaineering.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acclimatization*
  • Adolescent
  • Adult
  • Altitude*
  • Female
  • Humans
  • Hypoxia
  • Male
  • Oxygen / metabolism*
  • Time Factors
  • Walking / physiology*
  • Young Adult

Substances

  • Oxygen