Never before have so many people run so many miles, or set themselves such ambitious targets, in pursuit of self-fulfillment: marathons, ultra-marathons, extreme adventures. And never before have people had such high hopes of remaining vigorous and active - young in all but name - long after retiring from the work-place. Yet that last goal, perhaps more precious than any of the others, remains elusive.

It can be done, but only a few succeed. Most runners succumb to injury or illness in middle age; others are defeated by dwindling energy levels, or by the gradual falling-off of their peers. They can only envy the charmed few who continue to enjoy the life-enhancing joys of running well into what used to be considered extreme old age.

Horrified by the thought of breaking off his life-long love-affair with running, Richard Askwith began to think seriously about a question with profound implications for every enthusiastic runner: how can you keep running, happily and well, for the rest of your life - ideally, well into your nineties and beyond?

Askwith's quest for the secrets of running longevity takes him on a long, mystifying journey: to laboratories and running tracks, cities and remote mountain villages, on several continents. He meets scientists and coaches, gurus and cranks, ninety-year-old sprinters and hundred-year-old marathon runners - and with each passing month his quest grows more urgent.