Strength Tips

Most coaches focus on aerobic conditioning, so I'll assume you're OK in that area, or at least know some ways to improve your fitness. Instead, here I'll focus on some ways in which strength training with weights can help your game.

Chest

The standard exercises for the pectorals -- benchpress, dumbbell flyes, pec deck -- can help your forehand. If you have trouble with high forehands, do flyes or the pec deck with your arms angled towards your head, imitating the shoulder-high forehand motion. This can also help put away those high forehand volleys.

Forearms

Wrist curls and extensions can add zip to your serves and volleys, and firm up a shaky backhand. In my experience, these exercises also help protect against elbow injuries on the serve.

• Hold a heavy barbell behind your back, palms facing backwards, and curl the weight up with your forearms. You should be able to use more weight this way than when doing dumbbell curls.
• While seated, hold a dumbbell (or a barbell to work both arms at once) in front with your arms bent and resting on your thighs. Alternate sets with palms up and palms down.
• As a do-it-yourself project, cut a 3/4" or so wooden dowel to about 2 feet in length. Drill a small hole through the middle, halfway down the length. Thread strong twine through the hole and tie some small weights on. Start at 5 pounds and work up to 20. Slowly window the weights all the way up, then all the way down. Done palms down, this works both flexors and extensors and is almost impossible to cheat.

Upper Back

This is an area most people neglect. Typical rowing exercises hit mostly the lower back, giving people a comfort zone for low backhands but a "terror zone" for high ones.

• While seated, lean forward with a dumbbell in each hand. Bring your arms out to the side, up to about shoulder height (but not higher). Do this exercise at different angles; focus on keeping your arms forward, don't let them drift back to a position that feels easier.
• Lie on your side on a flat or incline bench, and raise a dumbbell in a backhand motion. Again, do the exercise with your arm at different angles. Find the angle that is most difficult and concentrate on that motion.

Lower Back

Strengthening this area can help give more oomph to your serves and overheads. It helps somewhat on certain backhands too.

• Do pulldowns with hands somewhat more than shoulder width apart. Keep palms facing forward to work the back rather than the biceps.
• Do other sets with hands close together.
• Use a rowing machine (with a weight stack). Keep your arms parallel to your body and bring the weight towards your stomach, not your chest.

Legs

You need plenty of endurance, but strength helps with quick starts and stops.

• Pay special attention to warming up your legs, as you will probably be using heavier weight than for your arms.
• Stand on a platform, supporting yourself on your toes with your heels out over the edge. Most gyms have a machine for this where the weight presses on your shoulders. Lower yourself, then raise all the way up with your calves. You should be able to use more weight for calf raises than for squats.
• If your gym has a machine where you can do this motion seated, use it also. It works different muscles than the standing version.
• Do squats or leg presses. Be careful of your back.

Muscle Imbalances

Muscles typically are paired, with each pulling in opposite directions -- biceps and triceps, quadriceps and hamstrings, and so on. Other muscles act as stabilizers, mostly for the upper body. If one muscle of a pair becomes much stronger than its counterpart, or the stabilizer muscles are not balanced on the right and left sides, it spells trouble.

• Do situps, straight up and twisting to each side, to develop your abdominal muscles and obliques.
• Do hamstring curls lying on your stomach.
• The upper back exercises above can help balance the shoulder muscles if you have a strong chest. Also do military presses (i.e. over the head).
• If you have a body part that is particularly strong -- exercise the muscles that pull in the opposite direction.