A pilot study: Force control on ball throwing in children with attention deficit hyperactivity disorder

The purpose of this study was the evaluation of force control during ball throwing in ADHD (Attention Deficit Hyperactivity Disorder) children with three different levels of air pressure in the ball. Ten ADHD children (six boys, mean age 9.65 ± 1.27 years) and ten healthy children (four boys, mean age 9.93 ± 1.54 years) were recruited in this study. Three identical volleyballs with three different degrees of inflation: soft, moderate, and hard were used in this study. When the subject heard the signal, he/she had to throw the ball vertically downwards onto a force plate (Kistler Instrument Corp, Winterhur, Switzerland) which monitored the vertical ground reaction force with a sample rate of 1000 Hz. In total, each subject was instructed to throw each ball 10 times. A successful trial was defined as follows: the lower edge of the ball had to bounce higher than the acromion level and the upper edge of the ball had to bounce lower than the top of the head. Success rate was defined as the ratio of successful trials to total trials. The ADHD group showed a significantly lower success rate at throwing hard, moderate, and soft balls than the control group. When throwing the hard ball, the ADHD group showed more variable peak vertical ground reaction force (N), compared to the control group. The elasticity of the hard ball was higher than that of the moderate and soft ball so that it might have been harder to control the force when throwing the hard ball. Therefore, for the ADHD group, the performance at throwing hard balls was more variable. It suggests that children with ADHD have a poor ability to maintain stable force control performance when throwing balls. Moreover, ADHD-participants showed poor performance with low overall success rate when throwing balls.