Darren Warburton and colleagues1 conclude that “there appears to be a linear relation between physical activity and health status, such that a further increase in physical activity and fitness will lead to additional improvements in health status.” Although Health Canada's guidelines on physical activity appear sufficient to elicit health benefits, especially in previously sedentary people, debate continues regarding the intensity and type of physical activity needed to achieve the most favourable health changes without eliciting osteoarthritis and cardiovascular abnormalities not present at rest.2 The results of our own recent investigations of top-level endurance athletes3–5 support the conclusion that substantial intensification of leisure-time physical activity does not increase the risk of adverse cardiovascular events and is likely to be effective in eliciting supplemental health gains. We further suggest that higher intensities and amounts of aerobic training may be safely implemented by sedentary individuals living in the community as a measure to gain further health advantages, especially for those most at risk of cardiovascular problems, osteoporosis and cancer.1