Cardio-Pulmonary Correlates of Subjective Fatigue
Eighteen cardiorespiratory parameters were measured in a five-minute bicycle ergometer test applied before and after four hours of resting (control days) or four hours of treadmill walking at 40, 50, and 60% of the maximum aerobic capacity (exercise days) of four volunteer subjects. There was no significant difference between control and exercise days in 16 out of 18 responses when the mean differences between the results obtained in the “before” and “after” tests were compared. The two exceptions were resting and exercise heart rate at 50 and 60% of the maximum aerobic capacity. Consequently, nine parameters showing the largest changes on exercise days were selected for calculation of a cardiorespiratory variance score (CVS). Subjective feeling of fatigue quantitated by the feeling tone checklist of Pearson was significantly correlated with CVS. There was also a significant relationship between work strain and the CVS. These results suggests that the physiological manifestations of fatigue after strenuous work are not reflected in consistent changes of single parameters but rather in the composit deviation of several responses from the control level. Within equal CVS values, deviation of single parameters may vary day by day in the same individual at identical work loads indicative of instability of homeostatic control during fatigue.