Just 20 Minutes of Exercise a Day

A study led by researchers at the University of Sydney suggests that engaging in physical activity for around 20 to 40 minutes a day could offset the mortality risks associated with high levels of sedentary behavior.

Walking home from work after sitting down all day could reduce your risk of CVDconnel | Shutterstock

Lead author Emmanuel Stamatakis and colleagues found that sitting was associated with an increased risk for death among the least active individuals. However, this risk could be reduced or even eliminated by engaging in moderate-to-vigorous physical activity (MVPA) at currently recommended levels.

In our study, sitting time was associated consistently with both overall premature mortality and cardiovascular disease mortality in the least physically active groups – those doing under 150 minutes of moderate to vigorous intensity physical activity per week.” Emmanuel Stamatakis, Lead Author

Studies have shown that high levels of sedentary behavior and a lack of physical activity are associated with adverse health outcomes. However, it has been unclear how much MVPA people would need to engage in to offset the health risks associated with too much sitting.

For the study, the team examined the association between sedentary behavior, physical activity and mortality risk, as well as what levels of MVPA would be needed to offset the health risks linked with sitting.

Sitting down for long periods of time is bad for health

Over a period of almost nine years, the team followed up 149,077 Australian men and women (aged 45 and older) who had completed surveys about how many hours per day they spent sitting, standing and sleeping, as well as how many they spent engaging in MVPA.

The daily sitting time was divided into four categories: less than four hours, four to less than six hours, between six and eight hours and more than eight hours.

Weekly physical activity was divided into five categories: “inactive” (no physical activity); “insufficiently active” (between one and 149 minutes); “sufficiently active” (150 to 299 minutes, which meets the lower limits of Australian physical activity recommendations); “sufficiently active” (300 to 419 minutes – the upper limit of recommendations) and “highly active” (420 minutes or more).

As reported in the Journal of the American College of Cardiologysitting down for more than six hours per day was associated with an increased risk of death from cardiovascular disease. However, this effect was mainly seen among people who did not meet physical activity recommendations.

Aside from individuals who sat for more than 8 hours per day, meeting just the lowest limit of recommendations eliminated the association with all-cause mortality risk.

Compared with individuals who were highly active with a sitting time of fewer than four hours per day, the mortality risk remained significantly higher, even among inactive individuals with a sitting time of only 4 hours per day.

Just 20 minutes of exercise per day could reverse the effects of sitting down all day

“Meeting the Australian public health recommendation of 150 to 300 minutes per week – equivalent to around 20-40 minutes per day on average – appeared to eliminate sitting risks,” says Stamatakis.

The study’s take-home message is that engaging in physical activity is especially important for people who spend a lot of time sitting. Although reducing sitting time would help, it is not enough to reduce mortality risk; the main lifestyle change such people would need to make is to engage in more physical activity.

Any movement is good for health but physical activity of moderate to vigorous intensity – that is activities that get people out of breath– is the most potent and most time-efficient.”

Written by:Sally Robertson
News Medical Life Sciences

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