Physical exercise and cardiac autonomic activity in healthy adult men

Physical inactivity is an important risk factor for cardiovascular mortality and morbidity. Regular exercise is known to improve health and maintain physical fitness. The heart rate response to exercise reflects autonomic control of heart and has shown to predict cardiovascular prognosis. Decreased heart rate variability (HRV) is known as a risk factor for cardiovascular mortality. The objective of this study was to study the effect of exercise on cardiac autonomic activity. Thirty two healthy adult men in the age group of 18-25 years with normal body mass index (BMI) were recruited from different physical fitness centers, who were undergoing regular exercise for past 3 months. Resting ECG was recorded for 5 minutes and analyzed for frequency analysis of HRV. HRV parameters of the subjects were compared with fifty age and BMI matched subjects who were not undergoing any exercise program. Physical activity level of all subjects was assessed by using Global Physical Activity Questionnaire. The exercising (E) subjects were found to have a lesser heart rate (73.27 ± 8.6 vs 74.41 ± 8.59) compared to non-exercising (NE) group, which was not significant. No significant difference was found in frequency domain parameters of HRV between exercising and non-exercising group with LF (47.12 ± 19.17 vs 43.55 ± 16.66), HF (41.03 ± 17.65 vs 46.03 ± 15.89) and LF/HF (1.61 ± 1.16 vs 1.22 ± 0.93) respectively. Physical activity level was significantly different between the two groups (4175 ± 1481.53 vs 1176.4?1103.83, p<0.001). This study showed 3 months of exercise did not have any effect on cardiac autonomic activity despite the difference in physical activity.