I really went for it on the bike today. I pushed hard right till the bitter end. My calves were tightening. My lungs were bleeding - OK, they weren't really bleeding. Come to think of it, my breathing was actually quite controlled. So I guess it was the legs that bore the brunt. I feel that's been my best workout on the bike for ages. I'm really starting to get back into pushing every last bit of leg power till the melt down point. Right, I think I've made my point so I stop banging on.