What is the optimal amount of exercise and how much is too much?

The benefits of exercise are so great that if it were a drug, it would be a miracle cure. But what is the optimal dose for better health: are people who run ultramarathons, lift weights every day or swim the English Channel better off than those who just go for gentle walks? And is it possible to overdose? Now, thanks to large-scale studies that follow cohorts of people over long time periods, we can finally find the answers.

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Firstly, these studies show a dose-related effect of exercise, with the health benefits kicking in at even low levels of activity. For instance, a 2022 study that followed more than 400,000 US adults over nearly two decades found that 1 hour of aerobic exercise per week was associated with a 10 to 20 per cent lower risk of dying during the study period (see “Health boosts” chart, below).

The good news for sedentary types is that the biggest gains come from changing from doing nothing to doing something. And the health benefits for people aged over 60 seem to be stronger than for adults below this age, for a given amount of exertion.

We can also look into the impact of different intensities of physical activity. Moderately intense activities are things that significantly raise your heart rate, such as brisk walking or playing a fun game of…