"BOUNCE" IS the distance your feet travel off the ground when you run. You must have minimal clearance to avoid things like cracks in the sidewalk and rocks on trails. But the higher you lift your feet, the more pounding they must endure as they return to earth over and over again. Extra vertical bounce also expends valuable energy and muscle resources pushing your body weight up in the air, which leads to premature fatigue and muscle breakdown.

The most efficient runnig stride is a shuffle, where your feet stay low and only lightly touch the ground with each step. Learn to keep your feet low and run with a light touch by doing this drill once or twice a week in the middle of a run.

1. Time yourself for 30 seconds and count the number of times your left foot touches the ground.
2. Walk or jog for 30 to 60 seconds.
3. Do another 30-second "cadence count," trying to increase the number of left-foot touches by one or two. Increase gradually. The average count should be around 40 touches per 30-seconds (it's okay to start lower and end higher).