Because we equate weight with strength, there is a tendency to think that heavier is better. Not so! The key in medicine ball training is to insure that both speed of a selected movement and resistance to the selected movement are involved in the overload. Just heavy enough to provide resistance but not so heavy as to alter the structure and speed of the selected movement. 4lb , 5lb, and up to 20lb medicine balls can work for participants. Even though the resistance is the same, the velocity will increase with the strength, size and power of the participant. The heavy medicine balls are used where slower, more strength related exercises are featured.
Using a 20lb medicine ball can develop raw strength but it is important to understand that raw strength does not necessarily translate into more speed and power. Remember that the power formula is Power = force ÷ time. When you add an external load to an exercise it is impossible to move at the same velocity as a non-weighted movement. Further, the more weight you add to a movement the greater the variance in biomechanics you will likely see. This is one reason why people might become injured when lifting very high loads in the weight room – they alter their body mechanics to compensate for weaker segments in the body. This is where movement-based medicine ball training shows it’s strength – by training movements as opposed to body segments, it is possible to expose the weak sections of the body and train these areas for optimum performance. Remember: Just because you are training with a lighter ball doesn’t mean you won’t see tremendous improvements in your overall conditioning, coordination, and maximum strength!