I.e., fartlek! http://en.wikipedia.org/wiki/Fartlek http://en.wikipedia.org/wiki/Fartlek I've been doing that for a long time (though it isn't exactly fartlek

I.e., fartlek! http://en.wikipedia.org/wiki/Fartlek http://en.wikipedia.org/wiki/Fartlek I've been doing that for a long time (though it isn't exactly fartlek if you do it by yourself) to train for soccer, because it mimics the process of repeatedly sprinting and recovering. It's also easier on my joints than sustained running at a steady speed.