VO2 max is a measure of the maximum volume of oxygen that an athlete can use. It is measured in millilitres per kilogramme of body weight per minute (ml/kg/min).

The overall message is pretty obvious: You should keep training like an endurance athlete in order to (at least partly) ward off age-related decline in VO2 max.  In doing so, you’ll be keeping your whole system functioning optimally, not just your heart.

In a study, older subjects had a lower whole-body VO2 max than the younger ones by 38 percent. Interestingly, they were also 27 percent lower in single-leg VO2 max, suggesting that peripheral factors like blood circulation and diffusion had declined.