Abstract
PURPOSE: The purpose of this study was to evaluate blood flow changes in femoral artery and skeletal muscle microvasculature during intermittent submaximal isometric knee extension. METHODS: Seventeen healthy young males (19.7 ± 1.2 years) performed intermittent (5 s on, 5 s off) isometric knee extension. Five contractions were performed at each force level of 10%, 30%, 50%, and 70% of maximal voluntary contraction (MVC) at random with a 10-min rest between sets. We measured right femoral artery blood flow by pulsed-wave Doppler ultrasonography and intramuscular blood flow in the vastus lateralis of the right mid-thigh by power Doppler ultrasonography, simultaneously. Both femoral artery and intramuscular blood flow were normalized by the peak value for each participant and represented as %Peak. Time-to-peak was defined as the time from the end of exercise to the peak. RESULTS: %Peak of femoral artery blood flow was significantly higher than that of intramuscular blood flow at the baseline and following contractions at 10% MVC (P < 0.01). The time-to-peak during the post-exercise of intramuscular blood flow was significantly longer than that of femoral artery blood flow following contractions at 70% MVC (P < 0.01). CONCLUSIONS: These results indicate that blood flow increases appeared slowly in skeletal muscle microvasculature than in femoral artery after intermittent submaximal isometric knee extension, suggesting that differences in vascular reactivity and blood flow regulation could exist between femoral artery and skeletal muscle microvasculature in healthy young males.