I have been riding mt bikes for a few years now and raced in lots of different formats. I have recently bought a road bike for training, and have noticed that after a few hours of pedalling, my legs just seem to lock up and give out... This is not something I've ever experienced in any mt bike races (which are usually lap based, and therefore I get a rest in between laps) excepting for (100km) marathons... I feel like I've got heaps more to give from a cardiovascular standpoint, it's just the legs that are stopping me! Do you think this is a problem solved by just more hours riding, or should I be looking at leg specific exercise in the gym? Any advice would be much appreciated - it's not nice watching your mates ride off into the distance toward the end of a ride....:mmph: