Supramaximal Testing to Confirm the Achievement of V̇O 2max in Acute Hypoxia.

PURPOSE:We sought to determine if supramaximal exercise testing confirms the achievement of V̇O 2max in acute hypoxia. We hypothesized that the incremental and supramaximal V̇O 2 will be sufficiently similar in acute hypoxia. METHODS:Twenty-one healthy adults (males n = 13, females n = 8) completed incremental and supramaximal exercise tests in normoxia and acute hypoxia (fraction inspired oxygen = 0.14) separated by at least 48 h. Incremental exercise started at 80 and 60 W in normoxia and 40 and 20 W in hypoxia for males and females, respectively, with all increasing by 20 W each minute until volitional exhaustion. After a 20-min postexercise rest period, a supramaximal test at 110% peak power until volitional exhaustion was completed. RESULTS:Supramaximal exercise testing yielded a lower V̇O 2 than incremental testing in hypoxia (3.11 ± 0.78 vs 3.21 ± 0.83 L·min -1 , P = 0.001) and normoxia (3.71 ± 0.91 vs 3.80 ± 1.02 L·min -1 , P = 0.01). Incremental and supramaximal V̇O 2 were statistically similar, using investigator-determined equivalence bounds ±150 mL·min -1 , in hypoxia ( P = 0.02, 90% confidence interval [CI] = 0.05-0.14) and normoxia ( P = 0.03, 90% CI = 0.01-0.14). Likewise, using ±2.1 mL·kg -1 ·min -1 bounds, incremental and supramaximal V̇O 2 values were statistically similar in hypoxia ( P = 0.04, 90% CI = 0.70-2.0) and normoxia ( P = 0.04, 90% CI = 0.30-2.0). CONCLUSIONS:Despite differences in the oxygen cascade, incremental and supramaximal V̇O 2 values were statistically similar in both hypoxia and normoxia, demonstrating the utility of supramaximal verification of V̇O 2max in the setting of acute hypoxia.