Thanks, again Oak. Perhaps I should clarify that by intervals, I just mean that I run/jog at what is a moderate (not sprint by any means) pace. I'm more or less following the Couch to 5k program. The idea is that you eventually build up to a sustained run, again at a moderate pace. Even when my cadence quickens, I'm not running at anything close to a sprint. I'm not sore at all during or after my runs. It's my aerobic capacity and the mind game I'm playing with myself that seem to be my big limiters at the moment.