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.
This article is part of a series on fitness that answers eight questions about exercise and its influence on our bodies and minds. Read more here.
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 during the study period (see 鈥�91色情片 boosts鈥� chart, below).
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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 badminton, where you can still talk but not sing. Activities that make you out of breath, such as riding a bike fast or hiking in the mountains, are classed as vigorous. A number of studies show that you don鈥檛 need to be a committed athlete to . These can be achieved surprisingly easily, from doing around 150 to 300 minutes per week of vigorous physical activity, 300 to 600 minutes at moderate activity levels or an equivalent combination of both.
After this point, it is a case of diminishing returns for additional health benefits 鈥� but the devil is in the detail.
For moderate-intensity exercise, more is still better: your risk of dying early, say from a heart attack, will (see 鈥淭ortoise vs the hare鈥� graph, below). 鈥淭here鈥檚 no such thing as too much exercise if it鈥檚 moderate-intensity aerobic exercise,鈥� says at the University of Pittsburgh in Pennsylvania.
, but it is a confusing picture. Some studies from around a decade ago seemed to show associations between participating in extreme events like marathons, ultramarathons and Iron Man distance triathlons and having an increased risk of cardiovascular problems.
Extreme risk?
However, in a 2016 study of more than 55,000 runners, Lee and his colleagues found that the most extreme runners weren鈥檛 than those who ran less. They weren鈥檛 getting any extra benefits 鈥� at least not in reduced mortality risk 鈥� but nor were they worse off. A 2022 study of 116,000 US adults found a similar pattern. Likewise, in a , researchers found that the first 200 men to run a mile in less than 4 minutes lived, on average, 4.7 years beyond their predicted life expectancy.
So the 鈥溾�� 鈥� that excessive exercise, particularly high intensity training, can harm overall health 鈥� 鈥渋s still a hypothesis, so not confirmed yet鈥�, says at Radboud University Medical Center in the Netherlands. He warns that many studies use questionnaires to find out how much people exercised, which is unreliable due to inaccurate reporting of activity levels, and most include only a small number of people who did extreme amounts of exercise, so the apparent harms come with large uncertainties.
Research is now under way that uses more objective measures like pedometers, along with larger sample sizes, so we may soon have a clearer picture.
As for resistance exercises like weightlifting, there is even less evidence of the harms of overdoing it 鈥� partly because there are no validated wearable fitness trackers that can keep a record of muscle exertion. Nevertheless, in 2023, Lee and a colleague reviewed the limited available data. They found an , above which the cardiovascular benefits don鈥檛 increase and may decrease. Lee is now to see if this apparent pattern holds true.
Finally, there are also the psychological impacts of exercise. In general, it is beneficial, says Lee. 鈥淚t lowers the incidence and prevalence of depression, anxiety and so on.鈥� However, in some cases, it may take over a person鈥檚 life to an unhealthy degree.
鈥淭here is growing evidence of an exercise addiction,鈥� says at the University of Granada in Spain. This isn鈥檛 about simply training a lot and enjoying it, she says, it is about whether you can manage your enthusiasm for exercise and still participate in other activities like work, socialising and family life. 鈥淚f you cannot manage your passion, then you are in trouble,鈥� she says.
What does all this mean for aspiring athletes? The first thing to note is that the possible health risks are only relevant to those who are doing a lot of high-intensity exercise. And even for extreme athletes, Eijsvogels says there is no general recommendation to stop or ease off, because the data remains weak.
For most of us, who aren鈥檛 doing anything of the kind, more exercise is good 鈥� and you might not need to do as much as you think to gain the health benefits.
