Anticipation of Exercise and Response in Skin and Muscle Sympathetic Nerve Activity

A study was conducted to determine whether anticipation of exercise alters the responses of sympathetic nerve activity to muscle contraction. Sympathetic nerve activity leading to the skin (SSA) and muscle (MSA) was recorded from the tibial nerve in the left and right legs using tungsten microelectrodes. Heart rate and blood pressure (oscillometric method) were also measured during the experiment. Seven healthy subjects, who gave informed consent, participated in the experiment. They were asked to exert a static handgrip (SHG) for 2 min at a tension of 30% of maximal voluntary handgrip. Two different situations were set before the commencement of exercise. One was that after several minutes of controlled rest, a countdown was started 2 min before the exercise, and then the handgrip was applied (Cond. 1) . The other was that a preparation time of between 7 and 5 min was set prior to the handgrip exercise while no information regarding the starting time of exercise was given to the subjects (Cond. 2) . SSA for 30 s just before the exercise was increased in comparison with the control value at rest in Cond. 1, but not in Cond. 2. There was no difference in the SSA response patterns to SHG between the two conditions. Before the commencement of SHG, MSA did not alter from the control value at rest in either condition. The magnitudes of the increase in MSA during SHG were almost identical under both conditions. Heart rate for 30s before SHG in Cond. 1 was increased significantly from the control value, whereas there was no significant change in Cond. 2. The magnitude of the heart rate response to SHG was the same in both conditions. The mean blood pressure showed no significant change before SHG, but increased significantly during SHG in both conditions. The increases in SSA and heart rate prior to the commencement of exercise may be related to the anticipatory response to the exercise, although this response was not significant in MSA. These results confirm that anticipation of exercise increases sympathetic outflow to the skin. This may be advantageous in adapting the body to exercise.