Effects of short‐term training and detraining on VO 2 kinetics: Faster VO 2 kinetics response after one training session

This study examined the time course of short‐term training and detraining‐induced changes in oxygen uptake ( V ˙ O 2 ) kinetics. Twelve men (24 ± 3 years) were assigned to either a 50% or a 70% ofV ˙ O 2 m a xtraining intensity ( n  = 6 per group).V ˙ O 2was measured breath‐by‐breath. Changes in deoxygenated‐hemoglobin concentration (Δ[ HHb ]) were measured by near‐infrared spectroscopy. Moderate‐intensity exercise on‐transientV ˙ O 2and Δ[ HHb ] were modeled with a mono‐exponential and normalized (0–100% of response) and the[ H H b ] / V ˙ O 2ratio was calculated. Similar changes in time constant ofV ˙ O 2( t V ˙ O 2 ) were observed in both groups. The combined group mean for t V ˙ O 2decreased ∼14% (32.3 to 27.9 s, P  < 0.05) after one training session with a further ∼11% decrease (27.9 to 24.8 s, P  < 0.05) following two training sessions. The t V ˙ O 2 premained unchanged throughout the remaining of training and detraining. A significant “overshoot” in the[ H H b ] / V ˙ O 2ratio was decreased (albeit not significant) after one training session, and abolished ( P  < 0.05) after the second one, with no overshoot observed thereafter. Speeding ofV ˙ O 2kinetics was remarkably quick with no further changes being observed with continuous training or during detraining. Improve matching of local O 2 delivery to O 2 utilization is a mechanism proposed to influence this response.