Effect of prior heavy exercise on muscle deoxygenation kinetics at the onset of subsequent heavy exercise.

This study examines the effect of prior heavy exercise on muscle deoxygenation kinetics at the onset of heavy-intensity cycling exercise. Ten young male adults (20 +/- 2 years) performed two repetitions of step transitions (6 min) from 35 W to heavy-intensity exercise preceded by either no warm-up or by a heavy-intensity exercise. VO2 was measured breath-by-breath, and muscle deoxygenation (HHb) and total hemoglobin (Hb(tot)) were monitored continuously by near-infrared spectroscopy. We used a two-exponential model to describe the VO2 kinetics and a mono-exponential model for the HHb kinetic. The parameters of the phase II VO2 kinetics (TD1 VO2, tau1 VO2 and A1 VO2) were unaffected by prior heavy exercise, while some parameters of local muscle deoxygenation kinetics were significantly faster (TD HHb: 7 +/- 2 vs. 5 +/- 2 s; P < 0.001, MRT HHb: 20 +/- 3 vs. 15+/- 4 s; P < 0.05). Blood lactate, heart rate and Hb(tot) values were significantly higher before the second bout of heavy exercise. These results collectively suggest that the prior heavy exercise probably increased muscle O2 availability and improved O2 utilization at the onset of a subsequent bout of heavy exercise.