How much exercise is enough? It's all worked out

The ideal amount of exercise that people should do has been a source of heated debate in recent years.
The ideal amount of exercise that people should do has been a source of heated debate in recent years.PHOTO: REUTERS

Sports medicine researchers recommend a half-hour workout for four hours of sitting

WASHINGTON • If you fear you're doing irreparable damage to your body because your white-collar job keeps you sitting at your desk from 9 to 5, or you regularly spend entire weekends sprawled on your couch binge-watching Netflix, there's some good news just out from sports medicine researchers.

According to a study published in The Lancet, all is not lost. You may be able to make up for your increased risk of death due to a sedentary lifestyle by engaging in enough physical activity.

So just how much is enough? The first thing to know is that it's not a fixed number. The ratio is based on the amount of sitting you do daily. If you sit for four hours a day, you need to do at least 30 minutes of exercise. An eight-hour sitting workday means one hour of exercise.

The numbers come from an analysis based on a very large pool of people - about 1 million adults aged 45 years or older in the United States, Western Europe and Australia. The findings show a reduction in or even elimination of the risk of death from heart disease, diabetes and some cancers.

Researcher Ulf Ekelund, of the Norwegian School of Sports Sciences, suggested that the one hour of activity could be brisk walking or cycling, but said that the exercise does not have to be so rigorous or all at one time. That is, the hour of activity can be spread out over the entire day.

"We did not analyse (the) data in this way, but all available evidence suggests that the one hour can be done in shorter intervals. My personal opinion is that every single minute of activity counts," he said in an e-mail.


    At least 30 minutes of exercise

    At least one hour of exercise

Dr Ekelund's analysis looked at information from 16 previous studies and classified participants into four groups depending on their activity level. Those in the least active group were active for less than five minutes a day, while those who were most active exercised for 60 to 75 minutes a day.

The findings suggest that a person who sits longer is not necessarily worse off: Those who sit for eight hours a day but are physically active are better off in terms of risk of death than those who sit less but are not physically active.

The ideal amount of exercise that people should do has been a source of heated debate in recent years. Fitness band companies have pushed 10,000 steps a day as a goal. The World Health Organisation recommends at least 150 minutes of activity a week. The American Heart Association recommends 30 minutes a day.

This study is the latest to recommend a higher threshold for the minimum amount of exercise. Another study, published last October in the journal Circulation, argued that physical activity and heart failure may be "dose dependent", with higher levels of physical activity lowering the risk proportionally.

Too busy to commit to that much exercise? Some evidence suggests "microbursts" of extremely intense exercise to get your heart rate up to 90 per cent of its maximum may help - although it is unclear exactly how such high-intensity interval training compares to traditional activity.

Despite the seemingly daunting conclusion that couch potatoes need to exercise even more than was thought, Dr Ekelund thinks the message from his study is positive: It is possible to reduce or even eliminate the risks from a mostly sedentary lifestyle if people become more active.


A version of this article appeared in the print edition of The Straits Times on July 29, 2016, with the headline 'How much exercise is enough? It's all worked out'. Print Edition | Subscribe