A common New year's resolution is to hit the gym and get fit. But while most people might give up and return to the comfort of the sofa by February, research suggests that being physically active for your whole life has big health benefits. But can it slow down the ageing process? One problem with studying this is that most older people are pretty inactive, or sedentary, and tend to do little if any physical exercise at all. As a result, it's difficult to know whether some of the health issues seen in ageing, such as heart and lung problems or loss of muscle and bone, are just the result of getting older or are due to inactivity. To try and disentangle this problem, Steve Harridge and his colleagues at at Kings College London are studying some super-fit older people, including Norman Lazarus, Emeritus Professor of Physiology at Kings College London, who is in his 80s and has been a keen amateur cyclist for more than 40 years. Kat Arney went to meet them. Steve Harridge began by explaining how he approached the research...