V̇O2 responses to different intermittent runs at velocity associated with V̇O2max

Abstract

The purposes of this study were (1) to determine the time sustained above 90% of V̇O2max in different intermittent running sessions having the same overall time run at the velocity (vV̇O2max) associated with V̇O2max, and (2) to test whether the use of a fixed-fraction (50%) of the time to exhaustion at vV̇O2max (Tlim) leads to longer time spent at a high percentage of V̇O2max. Subjects were 8 triathletes who, after determination of their track vV̇O2max and Tlim, performed three intermittent running sessions alternating the velocity between 100% and 50% of vV̇O2max, termed 30s∼30s, 60s∼30s, and 1/2T lim∼1/2Tlim, where the overall time at vV̇O 2max was similar (= 3 × Tlim). V̇O 2max achieved in the incremental test was 71.1 ± 3.9 ml·min-1·kg-1 and Tlim was 236 ± 49 s. V̇O2peak and peak heart rate were lower in 30s∼30s than in the other intermittent runs. The time spent above 90% of V̇O2max was significantly (p < 0.001) longer either in 60s∼30s (531 ± 187 s) or in 1/2Tlim∼1/2T lim (487 ± 176 s) than in 30s∼30s (149 ± 33 s). Tlim was negatively correlated with the time (in % of T lim) spent above 90% of V̇O2max in 30s∼30s (r = -0.75, p < 0.05). Tlim was also correlated with the difference of time spent over 90% of V̇O2max between 60s∼30s and 30s∼30s (r = 0.77, p < 0.05), or between 1/2Tlim∼1/2T lim and 30s∼30s (r = 0.97, p < 0.001). The results confirm that vV̇O2max and Tlim are useful for setting interval-training sessions. However, the use of an individualized fixed-fraction of Tlim did not lead to longer time spent at a high percentage of V̇O2max compared to when using a fixed work-interval duration.