Experts flag risks of marathon running

Regular extreme exercise causes structural and electrical changes to the heart and accelerates ageing, they warn.

The pair, Dr James O’Keefe from Saint Luke’s Mid America Heart Institute, Kansas City, and Dr Carl Lavie from a collaboration of University of Queensland School of Medicine and Ochsner Health in New Orleans, believe short bursts of high-intensity exercise and lots of moderately paced walking – about what our hunter-gatherer ancestors would have experienced – is a sustainable way to exercise.

Vigorous exercise for most people should be limited to 30–50 minutes a day – and marathon and long-distance triathlon runners should probably give it away after a few years, they advised in an editorial in the journal Heart.

In a string of publications, the pair have warned that regular punishing distance running courts disaster, prompting a Runner’s World magazine editor to demand &ldquo