Nothing halts your journey to athletic greatness faster than an injury. The trick to avoiding them? Don't fall. But if you do, your odds of walking rather than hobbling away will be much better if you've built up essential support and stability muscles. Bryan Diekmann, who sees some 50 new injuries a week during the winter as a trainer at Vail, Colorado's Steadman Hawkins Clinic, one of the nation's top sports-medicine centers, offers four exercises* to strengthen your defenses.

1. External Shoulder Rotations
WHY: Prevents dislocations, sprains, and tears.
HOW: Works the oft ignored muscles behind your shoulder, which provide socket support during a wipeout.
> Lying on your side, with your top elbow locked at 90 degrees against your hip and a rolled towel in your armpit, rotate a small dumbbell (under 20 lbs) away from your body.

2. Trunk Extension
WHY: Helps avoid lower-back strains and sprains.
HOW: Builds those muscles so you can withstand the sudden lurches of impact sports.
> Holding on to a weight bench and resting facedown on a Swiss ball placed under your hips, raise both legs so that your body is completely straight, then lower (20 reps).

Illustration by Mark Matcho