Behaviour of heart rate and electrical muscle activity in the simultaneous dynamic action of larger and smaller sets of muscles in the permanent performance threshold range.

This study was undertaken to assess more comprehensively and with greater differentiation the reduction in the absolute electrical muscle activity (aEA) determined by different investigations in the permanent performance threshold range of the cardiovascular system (HKS) by means of the behaviour of the aEA of the highly stressed leg muscles and little stressed forearm muscles. Six healthy, untrained male subjects operated a hand ergograph alone in one test, and, in four more tests, in combination with a constant bicycle ergometer load of 40, 60, 80, and 100 W, respectively. As a result of these tests, a relative reduction in aEA for the leg muscles and an absolute reduction in aEA for the forearm muscles could be identified in the permanent performance threshold range of the HKS. Therefore, aEA is also considered to be an indicator of general stress that can define the permanent performance threshold range of the HKS more completely. The reduction in aEA is probably an expression of a negative feedback from the cardiovascular system to the neuromuscular system induced by the central nervous system.