Infection – the runners’ paradox


In common with probably 90% of part-time runners in the UK, I spent much of last week coughing up the insides of my lungs. It is one of the small ironies of regular exercise that it seems to make you more and not less prone to illnesses such as coughs or flu.

I appreciate that this is counter-intuitive. Over the last thirty years, I’ve become more and more conscious of the messages around me telling me to exercise. There are far more private gyms than there used to be. Health insurers market themselves as offering cheaper rates to those who exercise regularly. And there is of course far more sport on television. Hell, there are even many more people wearing sports clothes on the streets.

In common with everyone who reads this blog, I am well aware that increased personal exercise reduces stress, weight, cholesterol, blood pressure and heart disease. Yet I am also aware that the periods of my life in which I’ve done the most exercise have also been the ones in which my body was most prone to break down (as one friend put it to me recently: “I was really enjoying my running before the injury struck, but isn’t that always the way?”).

More than that, I know that runners aren’t just prone to knee and shin injuries; we also seem to suffer far more routinely from chest and lung infections than most other people.

The best evidence is that while running does all sorts of long-term good to runners’ bodies, an exercise session immediately diminishes the effectiveness of our immune systems

One study of 2300 marathon runners found that 13% contracted an illness in the week following the race. (Of those who pulled out of the marathon, only 2% were sick in the same period).

This picture has been corroborated by detailed studies of smaller cohorts of athletes; whose immune systems (i.e. blood lymphocyte percentages and immunoglobulin levels) appear to have deteriorated precisely in response to intense exercise).

It’s not hypochondria; it’s a real condition.

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