Matters of the Heart: How many hours of exercise do you need?

There’s no question that exercise is good for the heart. Regular exercise lowers blood pressure and cholesterol and reduces the chances of having a heart attack or stroke.

But sometimes it can be hard to find the time (and motivation) to exercise. So, what’s the least amount of exercise you can get away with doing while still seeing these benefits? That answer depends on how fit you are to begin with.

Here’s some good news: the lower your starting point is in terms of fitness, the less you have to do to see a benefit.

So, if you’re someone who’s completely sedentary, then only a small amount of exercise is needed to see a reduction in cardiac risk. From a starting point of virtually zero exercise, an hour or two a week of leisurely cycling or brisk walking might be all you need to reduce your risk of death from cardiovascular disease by as much as 20 per cent.

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But as you get fitter and increase the amount you exercise, the cardiovascular health gains diminish and eventually plateau. This is sometimes referred to as a J-shaped curve.

A sedentary person who goes from doing nothing to exercising a couple of hours a week will see the greatest reductions in cardiovascular risk during this period. If they increase the amount they exercise to four hours a week, there would be additional — albeit smaller — reductions in risk (around 10 per cent). But the benefits to cardiovascular health appear to max out after four to six hours a week, with no additional gains beyond this point for everyone.

However, one study in which sedentary people were trained to complete an endurance event, such as a marathon, found that once participants reached seven to nine hours a week of training, they saw noticeable changes in their heart’s structure.

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Training at this level gives the same reductions in cardiovascular risk as training four to six hours a week. But participants had an increase in their amount of heart muscle, as well as dilation of their cardiac chambers. The heart is like any other muscle: if trained enough, it will get bigger. These changes occurred as early as three months after starting.

So, while the additional hours of exercise don’t further benefit cardiovascular disease risk, these changes in the heart’s structure will mean improvements in fitness — and hopefully, running a faster marathon.

These sorts of changes were previously only thought possible in elite athletes, but this study is proof that if we’re willing to commit, we can not only get the cardiovascular benefits but also develop the heart of an athlete.

After you start doing an hour or two of exercise a week to improve your heart health, something incredible and unexpected might happen. You might actually enjoy it. Four hours a week is the sweet spot that gives the greatest reduction in cardiovascular risk – but if you enjoy training or find a sport you love, you shouldn’t let this stop you from doing more.

Intensity is important

The idea of going from never exercising to working out four hours a week can be daunting — especially if you don’t have much spare time. This is where the intensity of your workouts is important.

If you want the biggest bang for your buck in terms of reducing cardiovascular risk, you need to break a sweat. High-intensity interval training (HIIT) is one time-efficient way of maximising your returns from exercise. It’s typically a 20-minute workout comprising short, 30- to 60-second bursts of intense exercise followed by a brief rest in between.

Despite how short these workouts are, their intensity means that after several weeks of HIIT, you’ll probably see many benefits, including reductions in blood pressure and cholesterol. However, most HIIT studies have been too small to measure if there’s an effect on overall cardiovascular risk.

A word of caution is needed if you have cardiovascular disease. There are several conditions — such as cardiomyopathy (genetic heart muscle disease), ischemic heart disease (narrowing of heart arteries), and myocarditis (heart inflammation, usually viral) — where strenuous exercise is advised against. People with these health conditions should stick to low- or moderate-intensity exercise. This will still be beneficial for your heart while not putting you at risk of harm.

If finding time to exercise during the week is a challenge and you’re only able to work out at weekends, rest assured this is still beneficial. One retrospective study of over 37,000 people found those who did their week’s worth of physical activity over just one to two days had the same reduction in cardiovascular disease risk as those who did activity spread throughout the week.

So, for a self-professed lazy person who wants to improve their cardiovascular health, the message is simple: even a small amount of any type of exercise can make a big difference.

Peter Swoboda, Associate professor in Cardiology, University of Leeds

This article is republished from The Conversation under a Creative Commons license. Read the original article.