thanks, Katluvr. Now that I think about it, that might work. We're in early spring here, so within a couple of weeks I'll be riding more consistently than I have all winter, which means I won't be as dependent on running for my cardio. I was just looking around on the Runner's World site, and they seem to recommend starting out with really short intervals. So maybe work in four or five 30 second intervals, and gradually take those up to a minute each? What is a standard length for intervals?