The purpose of this study was to investigate the kinematic and electromyography strategy used by individuals with intellectual disability to keep equilibrium during anterior-posterior balance on seesaws with different degrees of instability. Six individuals with Down syndrome (DS) and six control group individuals (CG) balanced on three seesaws. The movement of the hip, knee and ankle joints and electromyography activities of selected leg and trunk muscles were recorded. Both groups maintained their balance mainly at the ankle joint. Contrary to the CG, the individuals with DS adopted a pattern of co-contraction and were not able to modulate the magnitude of postural response with the seesaw's degree of instability. These unusual strategies used by individuals with DS, such as their inability to discriminate different levels of mechanical demands in terms of the seesaw's instability, can reflect deficits in the proprioceptive system. The integration at cerebellum level could be a good candidate.53389-95