The medicine ball has come a long way from the awkward, over-stuffed football used primarily in tossing games. Today, they are not only less unwieldy, but most gyms stock a variety of sizes and shapes. While this definitely adds to the their versatility, it can make the decision on what weight medicine ball a man should choose a little more complicated.

Medicine Ball Basics

According to ExRx.net, women tend to have about 55 percent of men's upper body strength. That's the only difference between men and women when it comes to choosing the proper medicine ball weight. Well, that and the male tendency to think heavier is better. Medicine ball exercises are not meant to build muscle mass. Instead, they focus on power, often involving explosive movements, core strength and flexibility. As such, a ball of no more than 6 or 8 pounds can be sufficient for many core-strengthening exercises.

Exercise-Specific Weights

Unlike standard resistance training where the weight you choose should have you struggling on the last rep, the American College of Sports Medicine points out that you should be able to maintain control, including accuracy and range of the motion, throughout your medicine ball exercise. For this reason, if you're doing an exercise that involves a squat, for example, that you might otherwise do with with a barbell, they recommend choosing about 30 to 50 percent of your one-repetition-maximum to use as a ball weight. This should be even lighter if the exercise involves extending your arms out from your body, as many medicine ball exercises do.

Core Work

The weight you choose for core work, such as situp tosses, Russian twists and and rotation tosses, should be enough for you to feel an extra tension in your core muscles while still executing the exercise properly. While arm movement is involved in these exercises, they are not primarily for arm strengthening. It's very important to choose a weight that won't tire your arms before you've completed all of your repetitions. If you find this happening with even the lightest ball, you may have to do some shoulder and arm strengthening with free weights or machines before moving on to medicine ball exercises.

Safety Precautions

Unlike free weights, the medicine ball will usually not be in your hands the entire time. So medicine ball exercises require extra precautions. When trying a new exercise, start with a lighter weight than you think you can handle until you are sure you can maintain control throughout the move. When working with a partner, always do several slow practice passes before getting into a rhythm or picking up the pace. ACSM recommends an area of 20 square yards for passing exercises so as not to endanger or inconvenience fellow gym members. With exercises that involve bouncing the ball, keep your arms well out from your body so the ball won't hit you in the jaw, and be sure your partner is a safe distance away for the same reason.