To observe the effect of age on the changes in heart rate variability (HRV) of adult amateur athletes after playing a soccer game, 20 male were divided into two groups: middle-aged (n = 10, 35-55 years) and aged (n = 10, 56-75 years). Before and after 2-hour soccer games, HRV and blood pressure were recorded. In both groups heart rate increased greatly after exercise (73.1 +/- 14.8 bpm vs 102.6 +/- 16.2 bpm, p < 0.01 and 71.1 +/- 8.6 bpm vs 89.9 +/- 15.5 bpm, p < 0.01). In the middle-aged group, systolic blood pressure (SBP) did not change (124.0 +/- 12.0 mmHg vs 118.9 +/- 11.7 mmHg), while the mean standard deviation of the N-N intervals (SDNN), square root of the mean squared differences of successive N-N intervals (RMSSD), total power (TP), low frequency (LF) power, and high frequency (HF) power changed significantly (p < 0.05); in the aged group SBP decreased from 147.2 +/- 23.7 mmHg to 127.7 +/- 24.7 mmHg (p < 0.01), but SDNN, RMSSD, TP, LF, and HF did not change. It seems that in aged people the accommodation capability of the autonomic nervous system is different from that in middle-aged people.