Including supramaximal verification reduced uncertainty in VO response rate.

Many reports describe using a supramaximal verification phase-exercising at a power output higher than the highest power output recorded during an incremental cardiopulmonary test-to validate VO. The impact of verification phases on estimating the proportion of individuals who increased VO in response to high-intensity interval training (HIIT) remains an underexplored area in the individual response literature. This analysis investigated the influence of same-day and separate-day verification phases during repeated measurements (incremental tests-INCR1 and INCR2; incremental tests + supramaximal verification phases-INCR1+ and INCR2+) of VO on typical error (TE) and the proportion of individuals classified as responders (i.e., the response rate) following 4 weeks of HIIT ( = 25) or a no-exercise control period ( = 9). Incorporation of supramaximal verification consistently reduced the standard deviation of individual response, TE, and confidence interval (CI) widths. However, variances were statistically similar across all groups ( > 0.05). Response rates increased when incorporating either one (INCR1 to INCR1+; 24%-48%,  = 0.07) or two (INCR2 to INCR2+; 28%-48%,  = 0.063) supramaximal verification phases. However, response rates remained unchanged when either zero-based thresholds or smallest worthwhile difference response thresholds were used (50% and 90% CIs, all  > 0.05). Supramaximal verification phases reduced random variability in VO response to HIIT. Compared with separate-day testing (INCR2 and INCR2+), the incorporation of a same-day verification (INCR1+) reduced CI widths the most. Researchers should consider using a same-day verification phase to reduce uncertainty and better estimate VO response rate to HIIT.