Abstract des Autors

A study was conducted to investigate the effect of exercise intensity on the recovery of autonomic nervous activity after exercise. Ten subjects performed four kinds of 10-min cycle exercise with target heart rates of 100, 120, 140, and 160 beats/min (THR100, THR120, THR140 and THR160, respectively) following 5 min of exercise to increase the heart rate to the target level. The beat-by-beat variability of the R-R interval was recorded throughout the experiment including the 5-min pre-exercise control period and the 30-min recovery period. Spectral analysis (fast Fourier transform) was applied to every 5-min R-R interval data set before, during (5 to 10 min) and after exercise at the target heart rate. The low- (0.05-0.15 Hz; Pl) and high- (0.15-1.0 Hz; Ph) frequency areas were calculated to evaluate sympathetic (SNS) and parasympathetic (PNS) nervous activities as Pl/Ph and Ph, respectively. During exercise, SNS of THR160 was significantly higher, and PNS of THR140 and THR160 was significantly lower than the respective pre-exercise values. Although all indicators recovered to, or overshot the pre-exercise values at 20-30 min after THR100 and THR120, heart rate and SNS were still higher and PNS was still lower than the pre-exercise value after THR160. These results suggest that the recovery of cardiac autonomic nervous activity is slower after high-intensity exercise than after low-intensity exercise, and that the recovery of autonomic nervous activity after acute exercise does not always correspond linearly on the exercise intensity. Verf.-Referat