Position and velocity controls in children and adults during a wrist tracking task.

Children's motor control skills develop with age, but it is unclear when the development begins and ends. To identify those critical points, we conducted a wrist tracking task and examined position and velocity controls in children and adults. The task consisted of a visible circular orbit, a target rotating at a constant speed of 0.1 Hz, a tracer reflecting the real-time position of the wrist joint, and target-visible and -invisible subsections. We had three age groups for younger children (n = 16, 8.00 ± 0.82 years old, Group 1), older children (n = 13, 11.62 ± 0.65 years old, Group 2), and adults (n = 10, 23.50 ± 2.88 years old, Group 3). Absolute angular position difference Δθ and absolute angular velocity difference Δω between the target and tracer were computed to analyze the position and velocity control abilities. Statistical hypothesis tests on the control parameters revealed that the mean Δθ of Group 2 (4.06 ± 0.71 deg) was statistically smaller than Group 1 (6.17 ± 1.51 deg, p = 0.006) and equivalent to Group 3 (2.76 ± 0.51 deg, p = 0.074), whereas the mean Δω of Group 2 (19.82 ± 4.50 deg/s) was statistically similar to Group 1 (20.46 ± 2.88 deg/s, p = 0.999) but greater than Group 3 (12.85 ± 2.03 deg/s, p = 0.001). It indicated that the preteen children between 10 and 12 years old performed accurate position controls like the adults and yet exercised immature velocity controls. However, we noticed that velocity controls in the older children were actively developing since they managed to decrease Δω significantly during the target-invisible phase (17.44 ± 3.53 deg/s, p = 0.002), just like the adults did (11.77 ± 1.08 deg/s, p = 0.017). Therefore, we could also infer that preteen children between 10 and 12 are beginning to obtain feedforward abilities and internal models for the wrist tracking task.