Along with "watch the ball," the most overused instruction in tennis is "bend your knees." As trite as it sounds, it's valuaable advice for all skill levels. Competitors at Roland Garros won't get far without it.

Try to use your legs -- not your back -- to lower your body to get in proper position to strike the ball, then push up with your legs to add power to your stroke. Watch how the pros do it. The evidence is clear not only from their actions but also their sculpted quadriceps.

Still need convincing? Here's what you gain by bending your knees:

More topspin: Pushing up before you hit the ball and lifting your body as you make contact produces more spin because it gets the racquet lower on the backswing and positions it to swing from low to high.

More depth: That motion from a low to high body position ensures that you hit up on the ball, which means greater net clearance and better penetration to the opposite baseline.

Better balance: Your lower stance, created by bending the knees, will center your gravity for better footwork and balance. No matter how great your ground strokes are, your footwork and balance must be in check.

Bending your knees for forehands and backhands is essential to good shot-making. When you go to the gym, you may want to consider doing some extra leg presses to get your thighs in shape. It will pay dividends on the court. ©Miller Sports Group LLC