Relationship between Forearm Muscle Volume and Pressor Response during Static Handgrip in Elderly Women

The purpose of this study was to clarify the relationship between blood pressure (BP) response during static handgrip and forearm muscle thickness in 66 elderly women (60-81 years old). They performed static handgrip exercise (right hand) in a supine position. Exercise compromised a 30s static handgrip exercise separated by a 30s recovery. First and second loads were 1kgw and 2kgw, respectively, and thereafter the load was increased by 2kgw every 1min until the BP drifted upward from the previous load-BP relationship. Blood pressure was monitored on the finger of the left hand continuously. The critical load for notable BP elevation (BPcrit) was defined as an intersection point of two regression equations obtained from lower (L1) and higher (L2) intensity. Forearm muscle volume was estimated from muscle thickness measured by B-mode ultrasonography. BPcrit decreased significantly with age (r=-0.263, p<0.05). Forearm muscle thickness did not show a significant decrease in the age range of this study, whereas forearm muscle volume decreased significantly with age (r=-0.331, p<0.001). A negative correlation coefficient was obtained between muscle volume and slope of L2, indicating that the slope of L2 decreased as muscle volume increased. Consequently the blood pressure elevation at the lower intensity below BPcrit was independent of muscle thickness and volume; however, it was revealed that muscle volume affects the degree of BP elevation at the higher intensity.