Published in The Hindu on September 5, 2011

“I don’t have the time” can no longer be an excuse for not exercising. According to a study reported recently in The Lancet, health benefits have been recorded even with 15 minutes of moderate-intensity physical activity daily for six days a week. Mortality dropped by 14 per cent, and life expectancy was extended by three years compared with those who led a sedentary lifestyle. The authors followed up, over an eight-year period, more than 400,000 healthy Taiwanese men and women with varying levels of physical activity. Although the public health recommendation in most countries is physical activity for a minimum of 30 minutes a day for five days a week, brief activity seems to be better than no activity. This message was brought out by the 2008 U.S. physical activity guidelines, which observed that “even low amounts of physical activity reduce the risk of dying prematurely.” A paper published recently in Circulation also underlined that the risk of coronary heart disease was “significantly lower” even when the physical activity was “lower than the minimum recommended amount.”

Fifteen minutes should be considered only a minimum. As The Lancet study found, there were more benefits when the duration was longer. Every additional 15 minutes of moderate-intensity exercise a day reduced the total mortality by four per cent and cancer death by one per cent compared with people who were inactive. However, no additional health benefits were seen beyond 100 minutes. The work, however, has a major limitation — it was an observational study and not a clinical trial. Hence no direct link between health benefits and physical activity can be firmly established, as other factors would have played a role. Despite this limitation, the possible benefits of moderate-intensity workouts of shorter duration may encourage more people to abandon physical inactivity. There is also a greater likelihood of people increasing the duration once they start exercising. Those who intend to follow the public health recommendation of a minimum of 30-minute continuous workout a day but are unable to do so can take heart. According to the U.S. Centers for Disease Control and Prevention (CDC), the benefits of 30 minutes can be reaped by working out for at least ten minutes thrice a day or 15 minutes twice daily. The World Health Organisation says physical inactivity causes six per cent of deaths globally and it has identified inactivity as the fourth leading risk factor for mortality. Hence any programme that can motivate people to exercise daily should be strongly encouraged.