Transient Responses of Heart Rate, Skin and Muscle Sympathetic Nerve Activity Before and After Anticipatory Muscle Contraction.

Sympathetic nerve activity leading to skin (SSA) and skeletal muscle (MSA) and heart rate were measured before and during two-minute static handgrip (SHG) in seven healthy volunteers. Two different situations were set before commencement of the exercise; one was that a preparation time of between 4 and 6 minutes was set prior to SHG while no information of starting time for exercise was given to the subjects (Cond. 1). Another was that after two minutes of control rest, countdown was started two minutes before SHG and then the handgrip was started (Cond. 2). Heart rate for 10-s before SHG in Cond. 2 increased significantly from the control value, while there was no significant change in Cond. 1. The magnitude of heart rate response to SHG was the same in either condition. Although SSA for 10 seconds just before the exercise did not show any change from the control value in Cond. 1, it increased in Cond. 2. There was no difference in SSA response patterns during SHG in either condition. Before commencement of SHG, MSA was suppressed at 10-s before exercise from the control value in Cond. 2, but there was no significant change in Cond. 1. After onset of contraction, MSA was suppressed in the brief initial period regardless of countdown, thereafter MSA increased time-dependently. The MSA response pattern to SHG was almost identical in both conditions.(ABSTRACT TRUNCATED AT 250 WORDS)