Interval training can cut exercise hours sharply

Now there's news! As I recall, Roger Bannister figured out that the didn't have time for traditional business training, and medical school, and so settled for interval work. He then became the first man to run the mile under 4 minutes.

As a recreational runner, I see no particular reason to do this. I'd rather be out an hour and a half in the park than 40 minutes on a track. In fact, the last time I did intervals, it was because we were where my wife complained that I should not run on the roads and where the was a HS track handy. Interval work does lighten the tedium of running on a track.