Human endurance--mind or muscle?

Two investigations have been carried out. The first studied the effects of autonomic blockade on the cardiovascular response to a step test, a 50% maximum isometric grip test and a Valsalva manoeuvre: the step test was of 5 minutes duration and the other two for as long as possible. beta adrenergic blockade by propanolol diminished the blood pressure and pulse rate response to both the step test and isometric grip. The pulse rate response to the step test was also affected by cholinergic blockade with atropine. The response to the Valsalva test showed a cholinergic blockade effect of pulse rate alone and a blood pressure response alone on alpha adrenergic blockade by phenoxybenzamine. The second studied psychological stressing on physical and mental ability. A potential 'punishment' situation increased the blood pressure and pulse rate response to isometric grip while decreasing the time for which it could be maintained. A potential 'reward' situation increased both the maximum grip and the time for which 50% grip could be maintained. It is concluded that psychological factors can affect performance dependant on whether the situation is perceived as one of 'reward' or 'punishment'. A factor in the mediation of the adverse response is an inappropriate response of the autonomic nervous system.