‘People frequently report a response to exercise that includes feeling happy,’ says Andy Lane, Professor of Sports Psychology at the University of Wolverhampton. ‘Identifying why this occurs is not straightforward. The so-called ‘runner’s high’ is not experienced by all runners and the conditions where that occurs are not consistent.

‘The factors most likely to promote happiness include running at a moderate or low intensity, so that you are not concentrating on feedback such as painful legs. Second is to make the external environment stimulating and pleasant by running in a pleasant environment, listening to engaging music or an interesting podcast, or running in a group, where social bonds between members appear to promote a sense of wellbeing.’

Of course, when you’re already feeling down in the dumps, often the last thing you want to do is lace up your trainers. Instead, you reach for a hormonal shortcut in the form of a bar of chocolate or a large glass of red. But this usually only offers a short-term boost, a hit of dopamine that dips quickly, leaving you with sugar cravings or a sore head - not very happiness-inducing.

‘The hardest thing is getting out of the front door,’ says Professor Lane. ‘Just walk or run for five minutes, and if you want to turn around and come back at that point, then do so. Just do a Gump! Forrest Gump ran because he wanted to, until he stopped enjoying it.’