I made an interesting observation while on a training camp two weeks ago, which I think will add an angle here. . .<br /><br />I was riding with people alot stronger than me and we were doing 130 - 150km per day for 7 days. Days 1, 2 and 3 were okay but as soon as we hit the hills on Day 4, I suffered like a pig. To cut a long story short I was dropped on a major climb early in the ride (day 4) and ended up riding by myself for 110km.<br /><br />This is what I noticed.<br /><br />While riding in the bunch on the previous days, I would be fine as long as I kept my HR below 160bpm (+-73%). If we went any quicker, I would get a rush of lactic acid which would take fowever to wash out so I found it quite hard going from the 3rd day.<br /><br />When I rode by myself though, I selected a harder gear than I would have in the bunch (for fear of bonking) and relaxed into a rythym and despite a moderate head wind, still managed to maintain 40kmph on the flats for over 50kms. The odd thing was that my HR was sitting at 175bpm (+-83%) over this entire period but my legs didn't hurt half as much. Another thing that I definately noticed was that I could get my speed upto 45 about 5 minutes after eating a quarter of a zone bar and this would last for about 15 minutes when I would eat another quarter.<br /><br />I suppose I rode at a cadence I was totally comfortable with and had no pressure of keeping up with anybody, and if I got tired I could just slow down. Has anybody ever experienced this? (The road was very flat with only a few undulations, hence the high average.)