The efficacy of a verification stage for determining O_2max and the impact of sampling intervals

It is unknown whether oxygen uptake (V̇O₂) sampling intervals influence the efficacy of a verification stage following a graded exercise test (GXT). Fifteen females and 14 males (18-25 years) completed a maximal treadmill GXT. After a 5 ​min recovery, the verification stage began at the speed and grade corresponding with the penultimate stage from the GXT. Maximal oxygen consumption (V̇O_2max) from the incremental GXT (iV̇O_2max) and V̇O_2max from the verification stage (verV̇O_2max) were determined using 10 seconds (s), 30 ​s, and 60 ​s from breath ​× ​breath averages. There was no main effect for V̇O_2max measure (iV̇O_2maxvs. verV̇O_2max) 10 ​s ([47.9 ​± ​8.31] ml∙kg^-1∙min^-1 vs [48.85 ​± ​7.97] ml∙kg^-1∙min^-1), 30 ​s ([46.94 ​± ​8.62] ml∙kg^-1∙min^-1 vs [47.28 ​± ​7.97] ml∙kg^-1∙min^-1), and 60 ​s ([46.17 ​± ​8.62] ml∙kg^-1∙min^-1 vs [46.00 ​± ​8.00] ml∙kg^-1∙min^-1]. There was a stage ​× ​sampling interval interaction as the difference between (verV̇O_2max-iV̇O_2max) was greater for 10-s than 60-s sampling intervals. The verV̇O_2max was > 4% higher than iV̇O_2maxin 31%, 31%, and 17% of the tests for the 10-s, 30-s, and 60-s sampling intervals respectively. Sensitivity for the plateau was < 30% for 10-s, 30-s, and 60-s sampling intervals. Specificity ranged from 44% to 60% for all sampling intervals. Sensitivity for heart rate ​+ ​respiratory exchange ratio was > 90% for all sampling intervals; while specificity was < 25%. Findings from the present study suggest that the efficacy of verification stages for eliciting a higher V̇O_2max may be influenced by the sampling interval utilized.