Before I tell you about the single most effective upper body exercise for increasing the power of your tennis serve, I would like to tell you that improving the explosiveness of your serve isn't created JUST from explosive upper body strength. First and foremost, you'll need to develop explosive power in your lower body and be able to transfer this power up your body to your racquet. The second thing is, you must develop strength endurance and the ability to recover quickly between points, so that you can give 100% on every shot.

Without endurance and the ability to recover quickly, your power will diminish as the match goes on..

With that said...

"How to Add Power to your Tennis Serve With One Simple Exercise"

Single Arm Cable Pull down

Here's how to perform this exercise:

Hold the handle in the desired hand, stand 3-4 feet from the machine, bend your knees and your hips keeping your back straight. With your arm directly over head and your elbow locked, contract your muscles and bring the cable directly to your knee. To hit additional muscle fibers with a full contraction, follow through past your knee so that your arm is parallel to your (slightly forward bent) upperbody. Return to the starting position and repeat.

You can also perform this exercise with an elastic band for resistance as well. Simply secure the band at the top of a door or to a stable overhead object and follow the same steps as listed above.

No matter what type of tennis serve you prefer, this exercise will strengthen your lats to produce a more powerful arm motion for your serve.

Just having a strong upper body will limit your potential power for both ground strokes and serves, so I recommend not only performing exercises for your upper body, but also for your abs and lower back, and quads and hamstrings. When all three work together, you'll notice the explosiveness of both your tennisserve and your ground strokes catapulting to the next level.