I can’t do nearly as many chin-ups as pull-ups. Does this mean I have a muscle imbalance?
Gavin Bell, London

Jason Anderson answers: Pull-ups use the lats and pecs because they pull your arms down towards your sides, while chin-ups involve the lats and biceps more because of the palms-up position of your hands as you pull your arms backwards. If you are struggling with pull-ups, it’s likely the weak link is your biceps. Try post-exhausting them by performing close-grip (palms up) lat pull-downs after your normal biceps workout to increase the strength of your arms during pull-ups.