Drs Chris and Xand Van Tulleken investigate the science of exercise and the dangers of inactivity.

Is modern exercise a wellness cult? Or is it a vital cure for a world that’s struggling with ill health and stuck on the sofa? Most of us might like to get a bit fitter, but how easy is it to actually start exercising and give up sedentary habits?In this series Drs Chris and Xand Van Tulleken examine exercise and how best to do it. How much should we be doing? How does it help our bodies? And how does our surrounding environment stand in the way of us getting fitter? Chris is challenged to examine his scepticism towards exercise. Similarly, Xand is asked to look at his new-found exercise evangelism and see what he is really running from.Recently Xand has discovered the joys of physical activity. He’s running, cycling, heading to the gym and playing ping pong like never before. It’s been a real transformation and a way to keep on top of things after years of unhealthy living.His twin brother Chris, on the other hand, is really feeling the aches and pains of middle age. With a busy job and a young family, he has precious little spare time for exercise. After a very active period in his 20s and 30s, Chris is now embracing his ‘Dad bod’ and sliding into a creaky middle age. Xand wants to help him turn things around. Can he do it?

In Episode 5 - Endurance - it’s the day of the big race. Chris tries to run a half marathon, without having done any proper training. It’s an experience that leaves him worrying if he’s ever going to get back into shape. The twins then speak with Alex Hutchinson, writer, runner and author of Endure. Alex explains how pain, resilience and motivation all work together during marathons and other feats of endurance. He also gives Chris some tips on how to bounce back from his marathon ordeal.

Presented by Drs Chris and Xand van TullekenProducer: Tom WoolfendenSound Design: Dan King Series Editor: Jo Rowntree A Van Tulleken Brothers and Loftus Media production for BBC Radio 4