2009 年 7 巻 2 号 p. 59-66
Purpose: The purpose of this study is to investigate the effects of sympathovagal activity balance induced by a change of heart rate (HR)/breathing rate (BR) ratio during repeated bouts of moderate exercise. Methods: Sixteen healthy subjects (age: males, 27.1 ± 3.3 yrs; females, 33.1 ± 3.7 yrs) performed repeated ramp-load leg cycling exercise (RLE) and constant-load leg cycling exercise (CLE) for 4 min×5 times at work rates (WR) corresponding to 90% ventilation threshold (VT) after VT was determined by incremental ramp test. Subjects were divided into two groups of HR/BR increasing slope (HBRi) and not changing slope (HBRn) from initial exercise to VT point. Results: During CLE, LF/HF gradually increased in HBRn which was significantly higher at the 4th bout of exercise than at the 1st bout (p<0.05). HF/(LF+HF) was significantly lower at the 5th bout of exercise in HBRn than at the 1st bout of exercise (p < 0.05). The change with repeated, HBRi versus HBRn interaction of LF/HF and HF/(LF+HF), was confirmed on RLE (p < 0.05, p < 0.01). However, HR and ΔRRI did not change during the bouts of RLE in both HBR. During CLE, a significant correlation between oxygen consumption (VO2)/WR and HF/(LF+HF) (r=0.565) was observed in HBRi (p < 0.05). Conclusion: These results suggest that autonomic nerve activity is changed by BR rhythms and the type of exercise during repeated bouts of cycling exercise.
