We know that regular daily exercise is good in many ways for your health. It can help you keep to a healthy weight, keep your blood sugar and your blood cholesterol low, and keep your muscles and bones stronger for longer. In the UK, the Department of Health recommends as a guideline that we try to do at least 30 minutes of moderate intensity exercise five times a week.
There’s lots of interest in finding ways to try and measure the benefits of exercise. Researchers are also keen to find out whether it makes a difference if you exercise harder, or exercise for longer, or whether it doesn’t make any difference to your health how long or how hard you exercise for.
Researchers in Denmark studied more than 10,000 people aged between 21 and 98 to assess people’s risk of heart problems. The people in the study filled in questionnaires every few years to provide details of how much physical activity they usually did during their leisure time. Specifically, the researchers looked at how much time people spent walking or jogging, and the speed at which they exercised.
Over the following 10 years, the researchers recorded how many people got a condition called metabolic syndrome. This is the medical term for a combination of things, including diabetes, high blood pressure, and obesity, that put you at higher risk of heart disease, stroke, and other conditions affecting your blood vessels. They then looked to see if there was a link between exercise and metabolic syndrome.
At the start of the study, around 21 in 100 women and 27 in 100 men had metabolic syndrome. After 10 years, around 15 in 100 people who didn’t have metabolic syndrome at the start of the study had developed metabolic syndrome.
Metabolic syndrome was more common in people who only walked or jogged slowly. Around 19 in 100 people who only walked or jogged slowly for less than two hours a week had metabolic syndrome, compared with 12 in 100 people who walked briskly or jogged fast for at least two hours a week.
But there was no link between how long people exercised for and how likely they were to have metabolic syndrome. People who walked for more than an hour every day were no less likely to get metabolic syndrome than people who walked for between 30 minutes and one hour every day.
How reliable is the research?
It’s reasonable to assume that the link this study finds between exercising and metabolic syndrome is genuine. This has also been shown in other studies. This study was reasonably large and asked people about their physical activity several times, which is more reliable than collecting this information once at the beginning of the study. Recording how many people then went on to get metabolic syndrome also makes the results more reliable.
But we can’t be sure that people gave accurate details about how much exercise they got, or how long or how hard they exercised for.
This type of study is interesting, but on its own it can’t prove that there’s a link between how intensely you exercise and whether you get metabolic syndrome.
What does this mean for me?
This study reinforces the message that exercise can help lower your risk of heart problems. It also suggests that, even if you don’t have time to exercise for long, shorter periods of moderate intensity exercise are still enough to benefit your heart.
Hoegsbro Laursen A, Kristiansen OP, Marott JL, et al. Intensity versus duration of physical activity: implications for the metabolic syndrome. A prospective cohort study. BMJ Open. Published online 8 October 2012.
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