TOO MUCH OF A GOOD THING

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

Runner's World South Africa - - Personal Best -

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.

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).

Dis­tance

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.

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.

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.

Rest as­sured: healthy peo­ple seem quite ca­pa­ble of adapt­ing to al­most any level of ex­er­cise.

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