Is Ultra-Distance Running Bad For You?

What if the ‘medicine’ we take to make us healthy is causing us harm?

Dr Ross Tucker |

We run for many reasons, but among the most common is the enormous health benefit. If the ‘medicine’ we take to make us healthy may be causing us harm, that’s a rather big deal.

Is running harmful? It’s a loaded – and very deep – question; partly because the answer almost always starts with ‘it depends…’

First, let’s define ‘harm’. If you want to characterise harm as being an increased risk of heart disease, hypertension, obesity, diabetes, and all manner of non-communicable diseases, then the answer is simple – running will help prevent harm. This is one situation in which there is no ‘it depends’; regular runners are physically fit, which reduces their risk of disease and early death significantly. You’re looking at between 35% and 50% lower risk.

Family History

Heart health is the current focus of our concern. It’s a difficult area to study, as you can probably imagine, but there is some evidence that people who are already susceptible to heart problems may accelerate the development of these problems when they exercise very heavily.

That means – it must be clarified – a relatively small percentage of the population. Healthy people seem quite capable of adapting to almost any level of exercise, according to a comprehensive review of over thirty studies on this issue, which found no evidence of a level of training that starts to harm the heart.

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It’s the ‘vulnerable’ population that may not be able to adapt. In these people, excessive running can cause structural changes in the heart that will make them more likely to experience cardiac problems later in life. These include problems with both your circulation (think plumbing, as in coronary artery disease and heart attacks) and your electrical circuits (think wiring, as with cardiac arrest).


Ultra-endurance athletes, who are training upwards of 15 hours per week and running perhaps 150km per week for long periods, fall into a group who do ‘excessive running’. It is this group that has led some scientists to suggest that the health benefit of running has what is called a ‘U’ shape.

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Imagine a ‘U’ shape on a graph, showing the risk of disease as a function of the amount of running. The risk is high for those who do no running at all, but it drops for people who run regularly – up to a 50% reduction in risk awaits. But at the point where exercise and running become extreme, the risk increases again.

At the very least, the risk doesn’t keep falling the more you run. That means that you get more or less the same reduction in risk if you run three times a week for a total of 30km, compared to running six times a week for 100km.

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The debate is around the point at which risk starts to go up again, if at all. And that’s not something that can be answered definitively – at least, not yet.

Where Does This Leave You?

Well, 90% of us never reach the level of running that might put us on the wrong side of that ‘U’ shape, and we’re getting the health benefits without the risk. Some of us may be there, or are perhaps susceptible to complications because of family history and genes. If you worry that this may be you, then I would encourage you to have yourself assessed – a stress ECG is never wasted, so think of investing in the reassurance and knowledge this may provide.

And then – clean bill of health provided, hopefully – keep running. Without the fear of risk, and with awareness of the benefits.

READ MORE ON: health overtraining ultra-marathon

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