Fourteen male positioned with hip joint angles in 5°increments from 10°flexion to 10°extension while standing. Then, each subject flexed both arms with maximum speed and self-pacing. The movement angles of the hip and ankle joints during arm movement were analyzed with a video motion analyzer. Surface electromyography was used to measure the muscle activities of the anterior deltoid, rectus abdominis, erector spinae, rectus femoris, and biceps femoris. The time difference in action onset between the postural muscles and the deltoid and the integrated electromyogram for the 50-ms period immediately following action onset were analyzed. The results are summarized as follows:

1) The movement angle of the hip joint changed more greatly in proportion to the initial joint angles compared with that of the ankle joint. A high degree of correlation (r =-0.956) existed between the movement angles of the hip and ankle joints.

2) No significant differences in the integrated electromyograms of those muscles were detected among the initial hip joint angles.

3) At the initial hip joint angles of flexion, the erector spinae and biceps femoris begun to contract before the deltoid. At the extension and 0°, they begun to contract after the deltoid in half of subjects when the hip joint moved toward the flexion position. Only at the extension angles, the background activities of the rectus abdominis and rectus femoris were decreased almost simultaneously with the action onsets of their antagonists in many subjects.

  The present study was designed to clarify whether near infrared spectroscopy could evaluate the phenomenon of functional sympatholysis during rhythmic handgrip exercise (RHG). In eight healthy women (age 52±5), we measured muscle oxygenation by near infrared spectroscopy, heart rate, mean blood pressure, muscle sympathetic nerve activity (MSNA) in the peroneal nerve microneurographically, and forearm blood flow by plethysmography. Subjects performed RHG for 6 minutes at 30% of maximal voluntary contraction (MVC) which does not evoke reflex-sympathetic activation. They matched force production to a visual target by the rhythm of a metronome (40 beats/min) with a 50% duty cycle. We measured the total labile signal (TLS) to assess a relative evaluation for muscle oxygenation by post exercise circulatory occlusion for 2 minutes. We used nonhypotensive lower body negative pressure (LBNP) of -20mmHg to elicit a reproducible increase in MSNA at rest and during RHG. At rest, LBNP induced increases in MSNA caused and decreases in forearm blood flow and decreases in muscle oxygenation of 16.5 percentage of TLS however, when LBNP was applied exercise the decrease in muscle oxygenation of 4.8 percentage of TLS was significantly attenuated. In other words, it was shown that the ability of reflex-sympathetic activation to decrease muscle oxygenation is restrained when the muscle is exercised rhythmically at an intensity of 30% of MVC. These findings suggest that near infrared spectroscopy is useful to evaluate functional sympatholysis in humans.