Exercise training-induced speeding of V ˙ O 2 kinetics is not intensity domain-specific or correlated with indices of exercise performance.

Purpose: This study examined the effect of 3 and 6 weeks of intensity domain-based exercise training on ${\dot{\text{V}}\text{O}}_2$ kinetics changes and their relationship with indices of performance.

Methods: Eighty-four young healthy participants (42 M, 42 F) were randomly assigned to six groups (14 participants each, age and sex-matched) consisting of: continuous cycling in the (1) moderate (MOD)-, (2) lower heavy (HVY1)-, and (3) upper heavy-intensity (HVY2)- domain; interval cycling in the (4) severe-intensity domain (i.e., high-intensity interval training (HIIT), or (5) extreme-intensity domain (i.e., sprint-interval training (SIT)); or (6) control (CON). Training participants completed two three-week phases of three supervised sessions per week, with physiological evaluations performed at PRE, MID and POST intervention. All training protocols, except SIT, were work-matched.

Results: There was a significant time effect for the time constant ( $\tau {\dot{\text{V}}\text{O}}_2$ ) between PRE (31.6 ± 10.4 s) and MID (22.6 ± 6.9 s) (p < 0.05) and PRE and POST (21.8 ± 6.3 s) (p < 0.05), but no difference between MID and POST (p > 0.05) and no group or interaction effects (p > 0.05). There were no PRE to POST differences for CON (p < 0.05) in any variables. Despite significant increases in maximal ${\dot{\text{V}}\text{O}}_2$ ( ${\dot{\text{V}}\text{O}}_{\text{2max}}$ ), estimated lactate threshold (θ_LT), maximal metabolic steady state (MMSS), and peak power output (PPO) for the intervention groups (p < 0.05), there were no significant correlations from PRE to MID or MID to POST between $\Delta \tau {\dot{\text{V}}\text{O}}_2$ and $\Delta {\dot{\text{V}}\text{O}}_{\text{2max}}$ (r = - 0.221, r = 0.119), ΔPPO (r = - 0.112, r = - 0.017), Δθ_LT (r = 0.083, r = 0.142) and ΔMMSS (r = - 0.213, r = 0.049)(p > 0.05).

Conclusion: This study demonstrated that (i) the rapid speeding of ${\dot{\text{V}}\text{O}}_2$ kinetics was not intensity-dependent; and (ii) changes in indices of performance were not significantly correlated with $\Delta \tau {\dot{\text{V}}\text{O}}_2$ .