In Move!, Williams dives into this further. She explains the neuroscientist and philosopher Antonio Damasio’s concept of the body’s ‘musculoskeletal division’, which has the job of updating the brain about the state of the muscles, bones and other parts of the body that are involved in movement. “Even when no active movement is being performed, the brain is being informed of the state of its musculoskeletal apparatus,” writes Damasio.

“If we let our bodies become weak, the message coming from the musculoskeletal division of the self will read: stiff, feeble, could definitely do better. As psychologist Louise Barrett puts it, if this read-out feeds directly into our perception of ‘what that body can achieve in the world’, then it’s hardly surprising that sedentary lifestyles have been linked to anxiety and low self-esteem,” Williams writes.

Notably, none of this confidence boost comes from the physical changes we’ve long associated with confidence. We’ve been told that we will feel better about ourselves if we just lost weight, built muscle or changed our appearance – but the science doesn’t support that.

“The research shows that people’s self-esteem and confidence changes without there being any visible or measurable differences in muscles,” says Williams. “In some ways, it’s an inside job. It’s releasing this power that we don’t know we have and we feel better because of it. To me, that’s a much better reason to exercise – we should change the focus, especially for women, from getting ‘toned’ to exercising for how it makes us feel and how it improves our lives in general.”

How to improve low self-esteem with exercise, according to an expert