Each subject performed a finger-tapping task, once with their affected hand and once with their nonaffected hand, while the other hand was to remain at rest to the best of the subject’s ability. Children were instructed to tap only with four fingers (excluding the thumb) in unison and keep their wrists on the table while finger tapping. A program with an engaging animation made in-house on Adobe Flash (Adobe Systems Incorporated, San Jose, Calfornia) was used to prompt the children to tap at a frequency of 1 Hz. The experimental protocol for finger tapping with each arm consisted of eight 15-s tapping periods, each followed by 25 s of rest, with a 3-min rest period before the first tapping period. For the motion tracking of hands and arms during the finger tapping task, 5-mm-diameter hemispherical retroreflective targets (B&L Engineering, Santa Ana, California) were attached with tape on the finger nail bed and just above the proximal interphalangeal joint on each finger, excluding the thumb [Fig. 1(a)]. The three-dimensional coordinates of these retroreflective targets were tracked by a six-camera VICON Mx motion capture system (Vicon, Denver, Colorado) at a sampling rate of 120 Hz. Three of the six analyzed trials were performed with a seven-camera setup shown in Fig. 1(b), where the two cameras to the sides of the subject were high, and all others high. The remaining three trials employed a six-camera setup arranged in a semicircle around the subject with a distance of from the subject and heights ranging from 2 to 4 m. The reason that two different camera setups were used in this work was that after subjects 1 and 4 were measured, the study was moved to a different room, which was smaller and camera geometry accommodations had to be made to maintain consistent retroreflective marker tracking. The retroreflective target localization accuracy in both rooms was , which was much smaller than the finger tapping amplitude. More marker occlusions were observed in the smaller room, but due to the high number of markers on each hand, at least one marker provided sufficient trajectory data in any one measurement. Muscle movement was monitored by eight sets of wireless EMG electrodes (BTS FREEEMG 300, BTS, Garbagnate Milanese MI, Italy) placed on the finger flexor and extensor muscles, biceps, and triceps of both arms.