Ken Mierke and Joe Friel write: Imagine racing stride for stride with a runner who is just a bit stronger than you. With heart rate redlined, breathing right on the edge of being out of control, and legs burning, you know you won't last much longer at this speed. The road turns downhill and you squirt forward as if propelled by a rocket-booster, gapping your stunned opponent. By the end of the downhill, you have a 20-yard lead, heart rate and breathing have returned to sustainable levels and your legs feel bouncy again. This doesn't have to remain a fantasy.