2001 Volume 50 Issue 4 Pages 417-423
The aim of this study was to reveal the mechanism of exaggerated blood pressure rise during resistance exercise. Muscle sympathetic nerve activity (MSNA), heart rate (HR), blood pressure (BP) and grip force were measured during static handgrip exercise. After a 3-minute control period, intermittent static handgrip exercises (10 30-sec contractions with a 30-sec pause between contractions) at 30% of maximum voluntary contraction (HG 30) or with maximum voluntary effort (HGMX) were performed in nine healthy volunteers who gave their consent in advance to participate in this study. In the HG 30 study, MSNA did not increase compared with the control value until the fifth grip exercise, and BP rose during the third HG exercise. HR was elevated in the first grip exercise and remained elevated up to the 10th grip exercise. During HGMX, MSNA, HR and BP increased significantly during the first grip exercise compared to the control rest, and MSNA and BP rose even further as the contractions accumulated; while HR response remained almost constant throughout the contractions. Mean handgrip force decreased progressively with the increasing number of grip exercises.
These results indicate that exaggerated BP rise during static muscle contraction dose not seem to be muscle reflex, at least, during the first several contractions; but rather other factors such as central command or mechanical compression of vessels. However, muscle reflex, for instance metaboor mechanoreflex may contribute to elevated BP when the number of contractions accumulate or muscle fatigue develops.
