It's a flying saucer! It's a beach ball cut off at the knees! Actually, it's the Bosu Balance Trainer, and the U.S. Ski Team has a fleet of them. Hyped as the next wave in balance trainers, Bosu stands for "both sides up." Place the platform flat side up, and you've got a giant balance board; flip it over, and you have a physioball that challenges your balance without requiring the skills of a circus-performer.
David Weck created the ball in 1999 to help him rehab a back injury, and later that year, the U.S.S.T. bought a crude version to use in prepping for the Olympics. Coaches found it to be a key tool for improving functional movement and balance at the same time-and now, where the team goes, it goes.
Douglas Brook, head strength coach for the Mammoth Lakes Ski Team, uses the Bosu in his core-strength, power, agility, and balance program. Here are three team favorites:
1. Place the Bosu round-side up. Keeping both feet together, jump forward onto the ball, stabilize yourself in a ski stance, and immediately jump back off to the start position. Continue jumping on and off the ball for 30 seconds. As you improve, work your way up to a minute or more at a time.
2. Again with the bulbous side up, stand on the dome and hold a ski stance. Jump up and rotate 90 degrees to the right, staying in your stance as you land on the ball and keeping your upper body still. Continue turning to the right until you're back where you started, then reverse direction. Visualize yourself ripping a bump run.
3. Flip the Bosu platform-side up. Get into a ski tuck on the platform, stabilizing yourself to stay level. Hold as long as you can. Aim for 20 seconds to start, then work your way up to longer intervals. If you find the going too tippy, you can also try this drill standing on the round side-most people claim that it's easier. ($130, bosu.com)