I started commuting and riding my bike everywhere when I was 15. I also started touring, club riding and racing a year later. I raced at a high level, did triathlons for a while and have several cross country rides under my belt. At age 57 it's commuting that's kept me going.

I found that racing made me fit, very fit, as did long distance touring but commuting and transportation riding is what, over a lifetime has been the healthiest choice I could ever have made. Racing can be very taxing to the body, it can be all consuming of time and for a balanced lifestyle it can be counterproductive at times. It's hard to stay at competitive fitness but commuting is a pressure free way of staying healthy for many years.

9 miles each way (18 miles RT) and a total of more than an hour of exercise per day 5 days a week is excellent. Getting nearly 100 miles a week in on a regular basis combined with a few fun rides on weekends or evenings when it suits you will keep you in very good shape. When I was racing I was doing anywhere from 250 to 700 miles in a week and it can be taxing, you are subject to injury and overtraining and the litany of ailments that go along with that.

A good solid round trip of almost 20 miles a day is ideal in my book if you're in it for the long haul. And it will give you the base you need to get really fit in a pretty short period of time should you choose to amp it up a bit.