I don’t believe that medicine ball training does much in terms of ‘power’ development. There it is, I said it.
My opinion has changed on this topic. I once thought that throwing med balls would develop rotational or overhead power and that this would lead to an increase in groundstroke or serve speed.
I held this belief for a number of reasons.
One of those ways is to use med balls for non-throwing scenarios. I know, for the most part, med balls are used for throwing purposes (and made for this reason as well). Throwing allows us to have a shorter deceleration phase and extend the propulsion phase - akin to doing a jump squat instead of a barbell squat for the development of lower-body power.