Effects of dynamic exercise training on the autonomic nervous system and cardiovascular system were examined in healthy young men. We investigated to clarify whether short-term training could alter the parasympathetic activity and the heart rate. We also investigated whether the negative chronotropic effect was associated with the changes of the left ventricular size and functions.
　Four subjects (mean age: 21 yr) were trained for 2 weeks using treadmill (60% maximum exercise for 1 hour a day). The following parameters were measured before and after 1 and 2 weeks training: 24 hr-ECG and -blood pressure, 12-leads ECG at rest, echocardiography. The autonomic nervous functions were estimated from spectral analysis for the variability of R-R interval. Parasympathetic activity was assessed from the high-frequency (0.15−0.40 Hz) power spectral density (msec²) (HF) and the sympathetic activity was from the ratio of the low-frequency (0.04−0.15 Hz) power spectral density (msec²) (LF) to HF (LF/HF). We also tested the responses of heart rate, blood pressure, HF and LF/HF during exercise before and after 1 and 2 weeks training. Heart rate decreased and HF increased during sleeping time and during exercise after the training for 1 and 2 weeks. These changes were associated with the increase of left ventricular diastolic dimension，stroke volume, fractional shortening, and systolic blood pressure. However, ventricular wall thickness at rest did not alter.
　These data suggest that 7 days dynamic exercise training can enhance parasympathetic activity of the heart, which is associated with the increases in left ventricular size and systolic function at rest.

DESCENTE SPORTS SCIENCE Vol.21/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE