THE EFFECT OF MUSCLE COMPRESSION DURING POSTHANDGRIP MUSCLE ISCHEMIA ON MUSCLE SYMPATHETIC NERVE ACTIVITY 778

Abstract

It has been reported that forearm compression, which presumably activates the muscle mechanoreflex, augments muscle sympathetic nerve activity (MSNA) during isometric handgrip (IHG). The purpose of this study was to determine if forearm compression (FC) during posthandgrip muscle ischemia (PHGMI) would have an effect on MSNA. To test this question, leg MSNA, heart rate (HR), and mean arterial pressure (MAP) were measured during 3 min of IHG at 30% of maximal voluntary contraction followed by 2 min of PHGMI. PHGMI was elicited by inflating a pneumatic cuff to suprasystolic levels on the upper arm 5 seconds before the end of IHG. The subjects performed the protocol with and without forearm compression on the previously exercising arm during PHGMI. Forearm compression was elicited by inflating a pneumatic cuff around the forearm to 120 mmHg. The testing order was counterbalanced. The results were as follows (*p<0.01 vs. preexercise): Table Preexercise measurements were similar between trials for HR, MAP, and MSNA. IHG elicited characteristic increases in all variables, and PHGMI produced similar responses for both trials. None of the changes from IHG to PHGMI were significantly different between the two trials. We conclude that forearm compression during PHGMI does not alter HR, MAP, and MSNA responses. Thus, this study suggests that activation of the muscle mechanoreflex by forearm compression during PHGMI does not augment MSNA.