Just a few minutes of vigorous physical activity a day is linked with a significantly lower risk of heart attacks and strokes, particularly among women who don鈥檛 deliberately exercise.
This kind of unplanned activity would include running for a bus or doing heavy gardening or household chores, which suggests people don鈥檛 need to go to the gym to improve their heart health, says at the University of Sydney, Australia.
The benefits were greatest among women who reported doing no planned exercise, although they were also seen to a lesser extent in both men and women who were regular exercisers.
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Physical activity has a host of health benefits, including reducing people鈥檚 risk of heart disease, dementia and weight gain. Most guidelines say people should aim for much longer periods of it than a few minutes a day, often recommending 75 minutes a week of vigorous exercise. One definition of this is that it stops you from being able to say more than a few words without pausing for breath.
Alternatively, people can aim for 150 minutes a week of moderate exercise, which says is when people can still talk, but not sing.
Most of our knowledge about the benefits of exercise comes from people filling in questionnaires about how much they do. Now, Stamatakis and his colleagues have used a more accurate method, by analysing data from the UK Biobank study. In this, thousands of people were asked to wear activity trackers called accelerometers for a week. Their health was then monitored for the next eight years.
The team was particularly interested in people who reported that they normally carried out no deliberate exercise at all. The tracking devices showed that some of these individuals did experience periods of vigorous physical activity, presumably from things such as climbing stairs.
Among the women in this group, those who averaged about 3.5 minutes a day of this kind of exertion had nearly half the risk of experiencing a cardiovascular event, such as heart attacks or strokes, compared with those who got no such activity.
However, this wasn鈥檛 seen in the non-exercising men in the study. This may be because women generally have lower aerobic fitness than men, so a given amount of activity recorded by the accelerometers would have been more taxing for them and therefore yielded more health benefits, says Stamatakis. This is a plausible explanation, says at Oxford Brookes University in the UK.
When the team considered people who did deliberately exercise every week, the effect of short bursts of vigorous activity was there for both men and women, but was smaller, cutting their risk of heart attacks and strokes by about 20 per cent. 鈥淚f you鈥檙e a regular exerciser, climbing stairs here and there is not going to be as beneficial,鈥� says Hough.
The study doesn鈥檛 prove that bursts of vigorous activity protect the heart, as it wasn鈥檛 a randomised trial, the best kind of medical evidence. An alternative explanation for the findings is that people who already had heart disease were less likely to exert themselves by running for a bus, for instance.
But the researchers reduced this source of bias by excluding people from their analysis who already had any heart conditions or developed them in the first two years of the study period, says Stamatakis. They also adjusted their figures to ensure that the participants had similar risk factors, such as diet, income levels and smoking status. 鈥淲e narrowed down our results to something that likely reflects causation,鈥� he says.
medRxiv
