Delayed Onset of Reoxygenation in Inactive Muscles After High-Intensity Exercise

Oxygenation, measured by near-infrared spectroscopy (NIRS), in inactive muscles decreases during high-intensity exercise because of the decrease of oxygen supply. However, there have been few reports regarding recovery of inactive muscle oxygenation after exercise. This study was performed to examine reoxygenation in the biceps brachii muscle (BB) after supramaximal cycling exercise. Six active young male volunteers (age: 22  ±  3 years, peak oxygen uptake (VO_2peak): 53.8  ±  5.4 mL/kg/min, mean  ±  S.D.) performed warm-up exercise, followed by cycling exercise at 140% of VO_2peak for 30 s and then at 0 watt for 4 min (recovery exercise). Tissue oxygen saturation (StO₂) in the vastus lateralis muscle (VL) and BB was monitored by spatially resolved NIRS throughout the test. The decrease rate of StO₂ during exercise was 24.7  ±  7.5 p.p. in VL and 15.1  ±  8.2 p.p. in BB (N.S.). StO₂ in VL increased immediately after the end of exercise, but StO₂ in BB decreased continuously for 12.7  ±  7.8 s after exercise. Moreover, the time of half-recovery from the minimum to peak values after exercise was significantly (P  <  0.05) longer at StO₂ in BB (39.5  ±  12.2 s) than VL (25.2  ±  6.0 s). These results suggest that the recovery of microvascular oxygen supply and blood flow in inactive muscles does not start immediately after exercise.