"Our aim, I said, is 30 minutes. In the beginning, five minutes may be all you can handle. But quite soon - sooner, in fact, than you expect - you will be able to run continuously for 30 minutes. I have seen a 30-year-old housewife get up to 30-minute runs with one month of training and run a five-mile race within 10 weeks of buying her running shoes.

That 30 minutes is as far as we need go. It is the endpoint for fitness. That 30 minutes will get us fit and put us in the 95 percentile for cardiopulmonary endurance. At 12 calories per minute, it will eventually bring our weight down to desired levels. It also will slow the pulse and drop the blood pressure. It will make us good animals.

That first 30 minutes is for my body. During that half-hour, I take joy in my physical ability, the endurance and power of my running. I find it a time when I feel myself competent and in control of my body, when I can think about my problems and plan my day-to-day world. In many ways, those 30 minutes is all egos, all the self. It has to do with me, the individual."