Not enough running – and too much – is bad for your health

There is much evidence that regular aerobic exercise will significantly reduce your chances of contracting a variety of serious health problems, including obesity, heart disease, type 2 diabetes, some cancers, and even depression. Running is one of the most popular aerobic exercises. Many people think that the more and the harder you run, the better for your health, but research has shown that this is untrue.

There is an optimal level of running for improved health. Running more than this offers no further health benefits and very strenuous running can be harmful.

On the other hand, even the smallest amount of gentle running brings significant health benefits: running even as little as several minutes per day significantly reduces the risk of dying.

Official exercise guidelines for optimal health benefits, for those aged 19-64, recommend at least 150 minutes of moderate-intensity aerobic exercise (such as brisk walking), or 75 minutes of vigorous exercise (such as running) per week. Up to half the population exercises far less than these official guidelines. So, does doing less aerobic exercise than the official guidelines help?

Yes it does. Several recent studies have shown this. A study by Duck-chul Lee and others published online in the Journal of the American College of Cardiology last July followed 55,000 people, aged 18-100, over 15 years. Runners lived an average of three years longer than people who didn't run at all, but running longer and harder didn't greatly reduce the chances of dying.

Those who ran for 30 minutes a day didn’t live much longer than those who ran for five to 10 minutes a day. Another study of older adults showed that less than one hour of moderate exercise a week correlated with a 15 per cent drop in death rate compared with sedentary people.

In other words, the relationship between aerobic exercise and health is dose-dependent: exercise a little and you get a significant benefit; work to the recommended guidelines and you get the maximum benefit.

The health benefits plateau when you exceed the recommended guidelines, and if you greatly exceed the guidelines you start to damage your health.

This knowledge has very important implications for public health programmes. Exhorting sedentary people to start exercising to the official recommended guidelines is all well and good, but many people are so daunted by the prospect of going from zero minutes exercise per week to 150 minutes, they decide to do nothing.

It would be better to exhort all people to start a little regular exercise, even if less than the guidelines.

If everyone currently not exercising began to do a little, we would see dramatic improvements in population health. The official recommended guidelines would then, for many, be a goal to be achieved in due course.

Marathon madness

I have bad news (as reviewed by James O'Keefe and Carl Lavie in Heart, Vol. 99, April 2013) for those who regularly run marathons or ultra-marathons (marathons are 42.2km, while ultra-marathons can be 50km, 100km or 160km). Such running can damage your health.

High-intensity exercise sessions lasting beyond one to two hours overload the heart, causing overstretching and micro-tears. After years of excessive exercise and repetitive injury, patchy heart fibrosis can develop, creating the possibility of malignant arrhythmias and sudden death.

MRI scans of veteran marathon runners show a threefold increased incidence of scarring in the heart compared with sedentary controls. Long-term excessive exercise may also accelerate ageing in the heart.

The best-selling book Born to Run, published in 2009, glamorises ultra-marathon running. It tells the story of American Micah True, who decided to live and run with the Tarahumara Indians in Mexico, routinely running 25 to 100 miles per day. In March 2013 he dropped dead at the age of 58 on a 12-mile training run.

During an autopsy, his heart was found to be enlarged and thickened with inflammatory infiltrate, and the coronary arteries had mild coronary arteriosclerosis. This type of cardiac pathology has been observed in other veteran extreme-endurance athletes.

So, the message is that a routine of moderate aerobic exercise will add years to your life and life to your years, whereas running too fast, too far and too long may only get you to life’s finishing line faster.

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