The efficacy of a verification stage for determining _VO2max and the impact of sampling intervals

It is unknown whether oxygen uptake (VO2) 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 (VO2max) from the incremental GXT (iVO(2max)) and VO2max from the verification stage (verVO(2max)) were determined using 10 seconds (s), 30 s, and 60 s from breath x breath averages. There was no main effect for VO2max measure (iVO(2max)vs. verVO(2max)) 10 s ([47.9 +/- 8.31] ml center dot kg(-1)center dot min(-1) vs [48.85 +/- 7.97] ml center dot kg(-1)center dot min(-1)), 30 s ([46.94 +/- 8.62] ml center dot kg(-1)center dot min(-1) vs [47.28 +/- 7.97] ml center dot kg(-1)center dot min(-1)), and 60 s ([46.17 +/- 8.62] ml center dot kg(-1)center dot min(-1) vs [46.00 +/- 8.00] ml center dot kg(-1)center dot min(-1)]. There was a stage x sampling interval interaction as the difference between (verVO(2max)-iVO(2max)) was greater for 10-s than 60-s sampling intervals. The verVO(2max) was > 4% higher than iVO(2max)in 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 VO2max may be influenced by the sampling interval utilized.