Orthostatic tolerance at different times of the day in physically average and very fit dayworkers.

We studied the relationship between the physical exercise capacity and the orthostatic tolerance of physically average fit and very fit dayworkers at different times of the day. Six male railroad workers were physically very fit and six were averagely fit (mean of the maximal oxygen consumption 57.4 and 34.6 ml.kg-1.min-1, respectively. The mean age was 32 years. The orthostatic tests were performed with a tilt-table at 2.00, 6.00, 10.00, 14.00, 18.00, and 22.00 hours on six different days. Orthostatic lability at night was seen in both groups. At 14.00 and 18.00 hours the orthostatic tolerance in average fit men was slightly lower than in very fit men. This difference in the orthostatic tolerance between the groups may be a sign of the interdependence of good exercise tolerance and orthostatic tolerance.