Effects of Isometric Muscle Tension on Vasomotor Activity and Heart Rate

Twenty‐four adults each performed two isometric exercises at three levels of exertion while finger pulse amplitude, skin temperature, heart rate, and respiration rate and amplitude were monitored. Due to exercise, pulse amplitude and skin temperature were significantly reduced while heart rate was significantly increased. The magnitude of cardiovascular (CV) effect varied in proportion to the magnitude of exercise. Further evidence for the close association between exercise and CV effects was implied by the rapid recovery of pulse amplitude and heart rate at the termination of exercise. This evidence in addition to a detailed analysis of respiration data led to the conclusion that CV reactions to isometric exercise were not mediated by respiratory variations. The implications of these, findings for studies of operant conditioning of CV and other autonomic responses are discussed.