'Getting bigger arms in the gym comes as a result of your body’s response to the stress of weight training,' says personal trainer Guy Stockwell. 'If your arms muscles were sentient beings they’d think, "That was hard. I'd better do something about it so it’s not as difficult next time".’

When you perform arm resistance exercises, microscopic tears occur in your muscles. Your body responds to this micro trauma by overcompensating: the damaged tissue is repaired and more is added, making your muscles bigger and stronger so the risk of future damage is minimised.