This study investigated the relationship between the intensity of muscle contraction and muscle oxygenation during dynamic knee extension. Six healthy male subjects (age 24.6±1.2 years) performed knee extension (concentric : 1 s/eccentric : 1 s) to exhaustion at 3 different intensities, 30%, 20% and 10% of maximum voluntary contractile strength (MVC) . A near-infrared spectroscopy (NIRS) probe and surface electrodes of the electromyogram were fixed on the m. rectus femoris. The muscle oxygenation and integral electromyogram (IEMG) were recorded both during and after dynamic knee extension.
The summary of the results was as follows.
1) Continuous time of knee extension decreased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 20%MVC (p<0.001), and 10%MVC and 30%MVC (p<0.001) .
2) The oxy-hemoglobin level during knee extension decreased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 30%MVC (p<0.001), 20%MVC and 30%MVC (p<0.001), and 10%MVC and 20%MVC (p<0.05) .
3) Recovery time after knee extension increased with increasing intensity of muscle contraction. There were significant differences between 10%MVC and 30%MVC (p<0.01), and 20%MVC and 30%MVC (p<0.01) .
4) The IEMG increased with increasing time of knee extension. The maximum value was observed just before completing the knee extension on the IEMG. The rate of increase in the IEMG increased with decreasing intensity of muscle contraction.
These results suggest that muscle oxygenation during dynamic knee extension decreases with increasing intensity of muscle contraction, and influences continuous time of muscle contraction.

This study aimed to determine the effects of wearing graduated elastic compression stockings (GCSs) on arterial stiffness. The study included 10 healthy men who were randomly assigned to undergo trials with and without GCSs on separate days. Baseline measurements of brachial-ankle pulse wave velocity (baPWV), heart rate, and brachial blood pressure (BP) were obtained in the supine position after the subjects had rested for 20 min without GCSs. The order of the trials (with or without GCSs) was set randomly. During both trials, data for these parameters were collected with the subjects in the supine position, after they had rested for 20 min. After both trials, the brachial BP did not significantly change from the baseline values. baPWV significantly decreased after trials with GCSs (from 1153.0 ± 123.4 to 1078.1 ± 134.3 cm/s, P < 0.05), but no significant difference was observed after trials without GCSs (from 1125.2 ± 118.7 to 1134.5 ± 100.9 cm/s). In addition, changes in volume after trials with GCSs (-74.9 ± 35.3 cm/s) were significantly lower than those after trials without GCSs (+9.3 ± 36.7 cm/s, P < 0.05). baPWV significantly decreased during supine rest on wearing GCSs. This decrease in baPWV was possibly caused by a decrease in arterial stiffness itself and/or a decrease in vascular transmural pressure that may have been due to increase in external pressure on the vasculature.