I’ve heard that sit-ups are bad for your back. Is this true?
Sam Hart, Bracknell

Jason Anderson replies: There is some truth to this. All the body’s movements are a series of learnt muscle activations. Every exercise we do in the gym teaches the nervous system to activate the muscles in a particular sequence, which is why good technique is so important. When we perform sit-ups or crunches while lying on the floor, the abs are activated but the opposing back muscles are not, which teaches the nervous system to activate the abs in isolation. This can have serious implications on back stability when we’re standing up because the dominant abdominal muscles pull our ribcage forward, increasing the pressure on our lower back, neck and shoulders.

Doing crunches on a Swiss ball increases core muscle activation, helping to prevent your six-pack bullying your back. If you want to work the abs in an upright, rotating position as nature intended, try the cable woodchop. Combining these two exercises is an excellent compromise.