T his is a common misconception, says Prof Leigh Breen, a muscle physiology specialist at the University of Leicester, though it’s easy to see where it comes from. Men typically have a higher ratio of muscle to fat than women, largely because of differences established during puberty, when testosterone levels rise significantly in males. Women, by contrast, tend to have a higher proportion of body fat – linked, in part, to oestrogen. “Although there is a relationship between testosterone and the amount of muscle mass we have, this doesn’t determine how effectively we can build muscle with resistance training,” says Breen. “Women have much lower testosterone levels – around 15 to 20 times lower than men. There is a perception that men gain muscle more easily because of higher testosterone and more androgen receptors in muscle, but that’s not quite right.…