Since the ancient Olympics, athletes like Hyrox competitor Joanna Wietrzyk have experienced runner’s diarrhoea. What does the science say about extreme exercise’s ‘mechanical jostling of the intestines’?

Soiling yourself in public sounds like a bad dream. But the Australian athlete Joanna Wietrzyk has now apologised for doing just that at the Hyrox games in Beijing on Saturday.

Wietrzyk won the fitness race but not before using communal equipment with faecal matter visibly running down her legs – and muddying Hyrox’s reputation.