Orthostatic tolerance and aerobic capacity.

The responses of heart rate and blood pressure to passive head-up tilting were assessed twice with an interval of 2 months in 100 healthy, middle-aged men. Then the subjects were randomly allocated into training or non-training groups. The intervention period of 4 months was successfully completed by 85 subjects. Mean, indirectly-determined oxygen uptake capacity increased in the training group only. The amplitude of the change in heart rate from supine to tilting and back again was used as the sign of orthostatic tolerance (OT). OT was similar in the training and non-training groups. When the subjects were grouped according to aerobic fitness, no differences in the OT could be observed. Changes in fitness during the intervention did not induce any changes in orthostatic tolerance. When the whole group was divided according to the OT or change in OT, no significant differences of changes in aerobic fitness were observed. It is concluded that in healthy, ambulatory, middle-aged men orthostatic tolerance and aerobic fitness are not correlated.