CARTER, J. B., E. W. BANISTER, and A. P. BLABER. The Effect of Age and Gender on Heart Rate Variability after Endurance Training. Med. Sci. Sports Exerc., Vol. 35, No. 8, pp. 1333-1340, 2003.
Purpose: This research investigated the age and gender differences in cardiovascular adaptation to a standardized/quantified endurance-training program that included two taper periods.
Methods: The latter was analyzed from spectral analysis of electrocardiogram records of heart rate variability (HRV) at rest in groups of young (19-21 yr) and middle aged (40-45 yr), mixed gender groups (6 males and 6 females), pre- and poststandardized training. All subjects were recreational runners who completed the same 12-wk running program. Before, and subsequent to training, HRV was measured during supine rest and submaximal cycling.
Results: There was a significant decrease in heart rate both at rest (2.7 ± 0.45 beats·min-1) and during submaximal exercise (8.1 ± 0.67 beats·min-1) in both age groups after training. After training, total spectral power increased (560.7 ± 308.9 ms2), as well as high-frequency power (362.3 ± 405.5 ms2), in both age groups at rest. The young group showed a greater increase in total power (849.0 ± 308.7 ms2) after the training program.
Conclusion: It is concluded that a well-designed 12-wk endurance-training program will decrease resting and submaximal heart rate in both younger and older adults. The significant increase in HRV, total power, and high-frequency power in all groups after endurance training indicates that HRV measurement appears to provide an effective, noninvasive assessment of cardiovascular adaptation to aerobic training.
It has been well documented since the 1960s that endurance exercise produces beneficial cardiovascular adaptations. Research has shown that regular endurance exercise, which is aerobic in nature, significantly improves maximal oxygen uptake, stroke volume, systemic arterial-venous oxygen difference, and cardiac output (4,18). Contribution of the autonomic nervous system in producing cardiovascular adaptations to endurance exercise is still not completely understood. Recent development of spectral analysis as a noninvasive technique for evaluating autonomic neural control of heart rate has provided both intriguing and controversial results. Spectral analysis appears to be a powerful new method for determining the relative contribution of the sympathetic and parasympathetic branches of the autonomic nervous system to the plasticity of an individual's response to a training stimulus.
Exercise produces a physiological perturbation that significantly influences autonomic nervous system activity. Research indicates that long-term endurance training increases heart rate variability, increases parasympathetic activity, and decreases sympathetic activity in the human heart at rest (5,6,10,11,20,21,23). Physiological aging is associated with a reduction in heart rate variability (HRV) and parasympathetic control of heart rate (7,17,27). This age-related decline in parasympathetic control may be partly due to a decrease in physical fitness with age (10,12). Although the decline in HRV occurs in both sexes, it may occur earlier in men (22). Some HRV studies indicate that females have greater parasympathetic, and less sympathetic, control of heart rate than males (11,17). These gender-specific autonomic differences may contribute to the decreased cardiovascular risk and increased longevity in females (17).
Despite accumulation of evidence that training generally improves many cardiovascular and metabolic variables, the effect of age and gender on the change in HRV after endurance training is not well documented. A change in HRV during supine rest and submaximal exercise should provide valuable insight into any protective adaptation developed in control of the heart after endurance training. In the present study, it was hypothesized that a 12-wk endurance exercise training program would produce an increase in heart rate variability in male and female healthy adult distance runners, with the older individual having a reduced adaptation to endurance training.