From an experience standpoint, they appear to be quite different. In the past, I ran more during the winter and then some in bike season (1-2X per week). This year, though, I've only been running about once a month to get more bike time in. Each time I've run, my legs have been quite sore in the following couple of days. And I'm in excellent riding shape. It's amazing how little muscle overlap there appears to be. Unless it's the running impact that's causing the soreness?PartisanRanger said:Well I'm just speaking from my experience and what I've heard most others say. Can anyone comment on what muscle groups are used in cycling vs. running and how this affects cross-training?