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

Abstract

Objective. The six 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 3,400m (Cuzco, Peru). Methods. Twenty nine participants performed six 6MWTs in four conditions; Normoxic Overground (NO), Normoxic Treadmill (NT), Hypoxic Treadmill (HT) all once, and Hypoxic Overground three times, 42 hours (HO1), 138 hours (HO2) and 210 hours (HO3) following arrival at Cuzco. Results. One-way ANOVA observed no difference (p > 0.05) between NO and HO1 for 6MWT distance. HT and HO protocols were comparable for the measurement of ∆heart rate (HR) and post-test peripheral oxygen saturation (%SpO2) (p > 0.05). Acclimatization was evidenced by reductions (p < 0.05) in resting HR and respiratory rate (RR) between HO1, HO2 and HO3, and preservation of SpO2 between HO1 and HO2. Post exercise HR, and RR, were not different (p > 0.05) with acclimatization. The duration to ascend to 4,215m on a trek was moderately correlated (p < 0.05) 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.