Bowling balls can be quite heavy. The United States Bowling Congress requires that they weigh between 10 and 16 pounds. That can be too much for people with limited hand strength or finger coordination, so it's fortunate that the governing organization for that sport accepts adaptive balls.
These balls made by different companies have retractable handles. As soon as the player releases the ball, the handle snaps inside. The ball can then roll down the lane with minimal distruption from the site of the handle.
-via Massimo