Kinematic and electromyographic characteristics of single-joint movements of individuals with Down syndrome.

Single-joint elbow flexion movements over different distances were performed "as fast as possible" by 10 subjects with Down syndrome and 6 control subjects. Kinematic parameters and electromyograms (EMGs) of major muscle groups were recorded. Muscle reactions to unexpected perturbations were recorded under different instructions. Four of the subjects with Down syndrome were able to demonstrate kinematic and EMG patterns typical for one of the basic strategies observed in the general population. Only one of the subjects with Down syndrome was able to modulate the "pre-programmed" reactions to unexpected perturbations. We conclude that there are no major qualitative deficits in the motor control mechanisms of individuals with Down syndrome, but there might be problems with proper modulation of motor commands.