Gender Differences in Cardiorespiratory Fitness With Advancing Age: Is the Age-Associated Decline in VO2max More Rapid in Men and Do Older Men and Women Respond Differently to Exercise?

Both cross-sectional and longitudinal data suggest that the age-associated decline in VO_2max is greater in men when expressed in absolute terms such as L or mL·min^—1. When expressed in relative terms (ie, percentage decline per decade), the apparent gender difference disappears. Cross-sectional studies report a slower rate of decline than longitudinal studies, probably due to selection bias. The impact of physical activity on the rate of decline in aerobic power with age is not entirely clear. Meta-analyses of cross-sectional studies did not find increased levels of physical activity to be associated with lower rates of decline in VO_2max. Longitudinal studies suggest that regular vigorous exercise can slow the rate of decline in VO_2max by as much as 50%, but the reduction or cessation of training with advancing age may result in a misleading acceleration in that decline. The most consistent finding in cross-sectional and longitudinal studies is a strong association between the age-associated declines in maximal heart rate and VO_2max, but physical activity has little, if any, impact on maximal heart rate. Aerobic exercise training of sufficient intensity can increase aerobic power in both men and women, but the mechanisms may be different, with men demonstrating a greater improvement in factors related to stroke volume and cardiac output, whereas the adaptations in women appear to be more dependent on increased oxygen extraction by skeletal muscle.