Variations in Grasping and Throwing Patterns as a Function of Ball Size

This study examined the effect of ball size on the movement patterns used by children and adults to grasp a ball and then to throw it as hard as possible. A total of 104 kindergarten, second-grade, fourth-grade, eighth-grade, and young adult males and females were asked to pick up six styrofoam balls of different diameters (from 4.8 to 29.5 cm) four times each as they were presented in random order, and then throw them as hard as possible at a wall 6.7 m away. Transitions from one- to two-hand grasps were made as ball diameters increased, with older subjects switching at significantly larger diameters than younger subjects (p<.0001); however, when ball size was scaled to hand size, older subjects switched at significantly smaller relative diameters than younger subjects (p<.Ol), indicating that hand size may be a critical factor in determining grasp form. Transitions from one- to two-hand throws were made by less than 25% of the subjects (mostly kindergartners and females), demonstrating a strong preference by older children and adults for throwing with one hand, even with ball diameters larger than a subject’s hand size.