Dynamics of self-injurious behaviors

Self-injurious behavior was examined in a case study of head-banging by an 8-year-old girl with profound mental retardation and an autistic disorder. Trajectories of the arm movements and impact forces of the head blows were determined from a dynamic analysis of videotapes. Results revealed a high d egree of cycle-to-cycle consistency in the qualitative dynamics of the limb motions, with one hand motions being faster than those with two hands (inp hase and antiphase) and the motions with the helmet about 25% faster than t hose without the helmet. The impact force of SIBs as a percentage of body w eights are near the low end of forces generated in boxing blows and karate hits.