How Much Physical Activity Do You Really Need?

Physical activity has recently come to be seen as one of the best forms of medicine available. Studies have shown that simply getting on your feet can ward off all manner of ill health, from cancers to cardiovascular diseases. But how much do you need to do to reap the benefits?

For a start, there's no need to be doing vigorous exercise if you don't want to. Exercise is just one form of physical activity, says I-Min Lee, professor of epidemiology at the Harvard School of Public Health. "We used to think you used to have to go out for a run, or swim for an hour without stopping – but we've realised now from the body of research that we have that any movement is good."

Instead, a brisk walk is enough, says Lee – the kind of pace you might achieve if you were late to meet a friend for lunch.

Government recommendations tend to be for people to do 150 minutes of this level of moderate physical activity per week. Those who prefer vigorous workouts need only do half that amount to get the same health effects. Many governments are now also beginning to recognise that there are huge benefits to doing resistance training – lifting moderate amounts of weight (like the sand in a bottle used in Brazil's academias) – particularly for older people.

The idea of a brisk half-hour walk five times a week might not sound too much of a challenge, but even that seems to be a struggle for many of the world's population – a third of adults and 80 per cent of teens fail to reach these recommendations. And in light of some recent findings, even those recommendations are being called into question.

Chi Pang Wen at Taiwan's National Health Research Institutes and colleagues wanted to find out the minimum amount of activity you could do to get these health benefits. They conducted a study looking at the physical activity levels of more than 400,000 Taiwanese people over eight years.

The researchers found that those who exercised for a total of just 15 minutes per day were 14 per cent less likely to die in the follow-up period than those who were inactive, and had a life expectancy on average three years longer. There was good news on cancer, too – the statistics imply that one in every nine cancer deaths in the inactive group could have been avoided, leading the authors to concluded that those 15 minutes of moderate exercise a day were enough to reap significant health benefits. "It first looked to me that it was too good to be true," says Wen. Moreover, each additional 15 minutes a day brought added benefits, though Wen says it was the first 15 minutes that seemed to make the biggest difference.

Perhaps those more active people just generally had a healthier lifestyle? Not so. Wen's team has analysed the data, independently taking into account different lifestyle factors such as smoking and drinking, and diabetes and hypertension. The health benefits were still there.

In light of this, he thinks that changes to government recommendations are "urgently needed" – reducing them to a more manageable-sounding 15 minutes a day would encourage those who are already put off by the current advice of 150 minutes a week, he says.

And of course, there are other benefits to being active – it's better for the environment, one's mental health, and social connectedness. The key is to find something you enjoy doing. "A little bit is good, more is better," says Lee, "If you like ballroom dancing, do it. If you like playing with your grandchildren do it. If you like walking the dog, do it. It isn't that you have to go out for a run."

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This article first appeared on Mosaic and is republished here under Creative Commons license. Mosaic is dedicated to exploring the science of life. Each week, it publishes a feature on an aspect of biology or medicine that affects our lives, our health or our society; it tells stories with real depth about the ideas, trends and people that drive contemporary life sciences. Mosaic is published by the Wellcome Trust, a global charitable foundation that seeks to drive extraordinary improvements in human and animal health. It covers subjects that fit with the Trust's mission and vision, but isn't limited to the research the Trust funds.

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