Eleven minutes a day of moderate intensity physical exercise - that’s 75 minutes a week - is sufficient to lower the risk of heart disease, stroke and some cancers by nearly 25%. That’s according to a study published this week in the British Journal of Sports Medicine. The author, Soren Brage, from the MRC Epidemiology Unit at the University of Cambridge, is with us to explain how they found this and what it means in practical terms.
Soren - We summarized the results from nearly 200 studies that included nearly 30 million people studies that have already been published. All the studies had at least 10,000 individuals in them, and they're all perspectives. And then we put all the measures of physical activity on a common scale so that we can establish the relationships between physical activity and these health outcomes. And that allows us to calculate the risk associated with any level of physical activity.
Chris - Now when you say moderate activity, I'm glad you mentioned this sort of scaling because I was going to ask you what constitutes moderate physical activity, because that can mean different things to different people. For some people it's, it's getting up off the sofa to reach for another biscuit, whereas for others it's climbing a mountain. So how do you judge something to be moderate intense physical activity?
Soren - So generally we would consider activity that is associated with an elevation in heart rate, to be moderate. You don't, and it will elevate your breathing as well, but it won't necessarily get you out of breath. If it also gets you out of breath, we start calling it vigorous. So that will also be beneficial for health, of course, but you will spend the same amount of energy faster. So these 11 minutes that you mentioned in your introduction, you could actually accumulate the same amount of energy above your resting level in even less time if it was more vigorous.
Chris - So you could take a brisk walk or you could run out the stairs. One would have to last a bit longer than the other in order to get the benefit. But it's doing the physical exertion that seems to confer the benefit.
Soren - Indeed. And the, the take home message is that anything you do is going to benefit your health and it, it really does keep on giving. So the risk of these outcomes keeps going down.
Chris - How do we know in studies like this that it is the exercise that is conferring the benefit? And it's not that if you go and find people who are already active and they're active because they're well, and you measure them, you say, well, they're healthier than these people who are in bed laid up with chronic diseases. And you're saying it's the activity that's doing it. It's not that people who are already fitter are just more active. How do you control for that?
Soren - So this is an issue that we call confounding. And the way that the individual studies would've controlled for that is that they would either have excluded everybody at the beginning of their studies that had serious chronic disease or they would've tried to control for it in their statistical analysis. We took the most adjusted results. So our results are actually the most conservative estimates, um, of, of these health benefits. It also includes, for example, adjustment for obesity, which arguably is at least partially on the causal pathway between physical activity and some of these diseases, certainly heart disease.
Chris - So really is the sort of message and your motivation here to, to say to people, don't be deterred by the fact that people say you've got to be out of breath and, and running a marathon each week to get a health benefit that really every little helps where this is concerned.
Soren - Certainly every little bit helps and it's important for people to consider their life circumstances. So 10 years ago, I might well have gone to the gym. That doesn't quite work for me anymore, but now I cycle to my workplace because that works for me right now. And, and we all have our circumstances that change, but we must adapt. But we must remember that every little bit we do for our health in terms of being active, will actually result in some benefits over time. The public health recommendation is two and a half hours a week of moderate intensity activity. But that is a good target to build up to. But if you do absolutely nothing today, that might seem a little bit far away. So our results are incredibly encouraging that just doing that little bit will result in quite substantial health benefits.