Originally Posted by Powerballs

With regards to grip strength...yes - if you hold the ball in your finger tips as opposed to planting it right into the palm, it will give your fingers a serious workout in a very short time as they fight to hold onto it.

In addition, burying it into the palm and spinning at high speeds, sustained for 30 second bursts, will build crushing power in the hand itself (the ball will do its best to wriggle out of your hand no matter how hard you try to hold onto it) - both exercises will raise the eyebrows in people that you shake hands with...R