There are discrepant findings between (A) observational follow-ups and (B) interventional studies that investigate possible causal association between high physical activity and low mortality. Participation in vigorous physical activity at a specific time-point is an indicator of good fitness and health, and is associated with a reduced risk of death. However, neither randomised controlled trials nor experimental animal studies have provided conclusive evidence to show that physical activity started during adulthood extends lifespan. Consequently, the undisputed health-related benefits of exercise have yet to translate into any proven causal relationship with longevity. Physical activity improves fitness and physical function, and confers other health-related effects. These outcomes have a greater basis in evidence-based data than any claims of a reduced risk of death, especially when recommending physical activity for previously physically inactive middle-aged and elderly adults.