Examples of gym harassment include being stared at, sexually suggestive comments and inappropriate touching, with numerous examples posted on social media.
But what’s behind this kind of harassment? And is it leading to women changing their behaviour or even quitting the gym?
Insecure, “show-offy” male behaviour and the layout of some gyms could be making the problem worse, according to one academic.
Gym operators say harassment is a wider social issue, which they’re working hard to tackle.
BBC Wales News spoke to two women who say they’ve been left feeling isolated, intimidated and paranoid by their experiences at the gym.
Reporter: Liz Clements
Producer: Max Evans
Filmed by: Clare Hutchinson, Tomos Lewis and Max Evans
Editor: Philip John
Graphics: Sophie Mutton and Richard Corfield
Commissioning Editor: Kimberley Rowell