THAT'S THE WHY:If you dread the thought of exercising, here's something that might help seal the deal: it could help you age more healthily.

Plenty of studies link regular exercise with better outcomes in physical wellbeing and cognition as we get older. But why might moving yourself through space in a pair of runners have an effect on the ageing process at a cellular level?

A recent study on endurance exercise in mice pointed to a clue: specific changes in the mitochondrion, a portion of your cell that helps you convert food into energy. Mitochondria are a hot topic of research for many reasons, not least because damage to the DNA they contain has been implicated in ageing and some diseases.

The study modified mice so their mitochondria weren’t great at repairing themselves and “aged” quickly. But if the mice exercised, their mitochondria looked in far better shape than if they had a more sedentary existence. And if that weren’t enough, as a bonus the exercisers were more sociable and fertile than the non-exercisers.

“Our data clearly support endurance exercise as a medicine and a lifestyle approach to improving systemic mitochondrial function, which is critical for reducing morbidity and mortality across the lifespan,” write the researchers in the Proceedings of the National Academy of Sciences.

So what are you waiting for? Bring your mitochondria for a workout.