Neurophysiological study of remote rebound-effect of resistive static contraction of lower trunk on the flexor carpi radialis H-reflex

We previously found a resistive static contraction of the pelvic depressors (RSCPD) using the proprioceptive neuromuscular facilitation pattern in the mid-range of pelvic motion in side-lying increase of the flexibility of remote body parts such as upper shoulder and elbow joints without stretching. However, a few studies have provided the evidence of ascending neurophysiological effects on remote parts induced by a static contraction of lower trunk muscles, such as RSCPD. The purpose of the present study was to find the neurophysiological the time-course of the remote effect of a resistive static contraction of the RSCPD as the lower trunk resistive exercise on the excitability of the relaxed flexor carpi radialis (FCR) Hreflex. Subjects were randomly assigned to (1) the handgrip group (n = 6), who participated in contralateral submaximal isometric handgrip exercises, or (2) the RSCPD group (n = 5), who participated in the RSCPD group. A post-hoc analysis and a first-order polynomial equation revealed that the contralateral effects of left handgrip exercises on the right FCR H-reflex caused gradual inhibition during and after the handgrip exercises. In contrast, a post-hoc analysis and a third-order polynomial equation suggested that the RSCPD induced ascending effects on the FCR H-reflex which initially caused a reflexive inhibition during RSCPD followed by a gradual excitation after the RSCPD. Remote rebound effects of the FCR H-reflex by RSCPD may provide neurophysiological evidence of the indirect approach for increasing flexibility of the treatment of extremities that cannot be exercised directly because of pain or weakness.