Perhaps you trained too hard right up to the time of the race. To improve performance, you should plan to taper off your workout seven to 21 days before the competition. This gives certain muscle fibers a chance to "spring back." Working too hard up to the time of the race can actually cause important muscle fibers to shrink, leading to a drop in muscle strength and decreased overall performance in the race. Instead, plan to lower your total mileage and focus on interval training prior to the race to improve your "kick" on hills and to give you an edge when you near the finish line.