Near-infrared spectroscopy (NIRS) has provided insights into the dynamics of oxidative metabolism during muscle contraction. The present study examines how a short period of resistance exercise training (sRT) affects muscle oxygen utilization at the onset of contraction using NIRS. Twelve healthy male adults were separated into trained (Tr: n=6, 27.7 ± 5.0 yrs) and untrained (Con: n=6, 24.5 ± 4.5 yrs) groups. Tr-group participated in sRT consisting of 4-sessions of 7-sets of 10-repetitions of isokinetic knee extensions at 120 degree sec-1. All participants performed isometric knee extensions at workloads reaching 30% and 50% of their maximal voluntary contraction force (MVC) for 1-minute before and after the training period. The NIRSΔ[deoxy-Mb/Hb] signal recorded from vastus lateralis muscle was fitted as an exponential equation to determine time constant (τ), time delay (TD) and amplitude (AP). The isometric MVC significantly increased in Tr-group,but not in Con-group. Theτof Δ[deoxy Mb/Hb] kinetics tended to reduce in Tr-group after sRT,but the TD and AP did not significantly change. On the other hand,Δ[deoxy Mb/Hb] kinetics parameters in Con-group did not significantly change at all. These results suggested that the sRT facilitated oxygen utilization in mitochondria although the level of muscle activation was reduced at the same workload due to improved MVC.

DESCENTE SPORTS SCIENCE Vol.27/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE