This exercise provided courtesy of Billy Polson, founder and co-owner of DIAKADI Body training gym, voted best personal training gym in San Francisco by CitySearch in 2006.

Benefits
For just about any sport or activity that requires upper arm mobility, the shoulders' rotator cuff muscles are among the most frequently injured muscles in the body. The dumbbell freestyle swim stroke exercise mimics freestyle swimming to strengthen the shoulder's rotator cuffs in a full range of functional motion as well as working all sides of the deltoids (front, middle, and rear).

Muscles Worked
Shoulders (rotator cuffs and deltoids)

Starting Position
Begin in a standing position with your legs approximately hip-width apart and a dumbbell held in each hand. Lean your upper body forward to an approximately 45-degree angle, being sure to maintain a flat back to avoid injury. Keeping your arms straight, lift the dumbbells out in front of your body so that your arms are parallel to the plane of your upper body and your palms face down.

Exercise

1. From the starting position, bring your right arm back as if you are doing a stroke of freestyle swimming. Your arm will naturally bend as you bring your elbow back. Be careful to keep the dumbbell in close to your body; allowing it to drop out too far can cause injury (see Photo 1).
2. As your right arm reaches the back end of its stroke, begin dropping your left arm to start its own stroke, while simultaneously lifting the right elbow up in an arc over the shoulder and pushing the right dumbbell back out to the starting position (see Photo 2).
3. Your right arm should reach the starting position just as your left arm reaches the back position (see Photo 3).
4. Each stroke of an arm counts as one repetition.