Following the recent London Marathon, which attracted 58,000 applicants,
Frances Donnelly looks into the growing popularity of running among women - be they unassuming joggers aiming to stay fit, or those who push themselves towards tougher goals, often emerging as talented athletes. She also volunteers to be wired up for a fitness test at a new centre in Surrey.
But what is fitness, and how does it relate to athleticism and health or indeed to diet and dieting? And is it sensible to start running after years of inactivity?
Producer GORDON HUTCHINGS