Responses to Different Intermittent Runs at Velocity Associated With

Abstract

The purposes of this study were (1) to determine the time sustained above 90% of [Formula: see text] in different intermittent running sessions having the same overall time run at the velocity ([Formula: see text]) associated with [Formula: see text] and (2) to test whether the use of a fixed-fraction (50%) of the time to exhaustion at [Formula: see text] (Tlim) leads to longer time spent at a high percentage of [Formula: see text]. Subjects were 8 triathletes who, after determination of their track [Formula: see text] and Tlim, performed three intermittent running sessions alternating the velocity between 100% and 50% of [Formula: see text], termed 30s ∼ 30s, 60s ∼ 30s, and 1/2Tlim ∼ 1/2Tlim, where the overall time at [Formula: see text] was similar (= 3 × Tlim). [Formula: see text] achieved in the incremental test was 71.1 ± 3.9 mlùmin−1•kg−1 and Tlim was 236 ± 49 s. [Formula: see text] and peak heart rate were lower in 30s ∼ 30s than in the other intermittent runs. The time spent above 90% of [Formula: see text] was significantly (p < 0.001) longer either in 60s ∼ 30s (531 ± 187 s) or in 1/2Tlim ∼ 1/2Tlim (487 ± 176 s) than in 30s ∼ 30s (149 ± 33 s). Tlim was negatively correlated with the time (in % of Tlim) spent above 90% of [Formula: see text] in 30s ∼ 30s (r = -0.75, p < 0.05). Tlim was also correlated with the difference of time spent over 90% of [Formula: see text] between 60s ∼ 30s and 30s ∼ 30s (r = 0.77, p < 0.05), or between 1/2Tlim ∼ 1/2Tlim and 30s ∼ 30s (r = 0.97, p < 0.001). The results confirm that [Formula: see text] 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 [Formula: see text] compared to when using a fixed work-interval duration. Key words: interval-training, maximal oxygen consumption, performance, time to exhaustion