Neuromuscular control of goal-directed ankle movements differs for healthy children and adults.

purposeThe purpose was to compare neuromuscular control of rapid ankle goal-directed movements in healthy preadolescent children and young adults.

methodsTen young adults (20.0 ± 0.9 years) and ten children (9.5 ± 0.7 years) attempted to accurately match the peak displacement of the foot to a spatiotemporal target with an ankle dorsiflexion movement. The targeted displacement was 9° of ankle dorsiflexion, and the targeted time was 180 ms. Surface electromyograms (EMGs) were recorded from the tibialis anterior (TA; agonist) and soleus (SOL; antagonist) muscles. Ankle movement control was quantified with endpoint accuracy and variability. The activation of the involved muscles was quantified with an EMG burst analysis.

resultsChildren exhibited decreased endpoint accuracy and control compared with young adults, as indicated by greater endpoint errors (47.6 ± 15.2 vs. 25.8 ± 9.0%) and position variability (29.5 ± 5.7 vs. 15.2 ± 6.1 %). In addition, children exhibited differences in muscle activation, as evidenced by greater TA (53.2 ± 19.1 vs. 33.0 ± 19.0%) and SOL (19.9 ± 12.0 vs. 9.6 ± 5.4%) amplitudes of EMG burst, shorter TA duration (251.3 ± 43.6 vs. 296.1 ± 27.6%), and greater variability in the activation of these muscles. The endpoint error (R (2) = 0.7) and position variability (R (2) = 0.67) were predicted from the TA burst amplitude variability and TA burst duration.

conclusionThe differences in muscle activation and deficient control of rapid goal-directed ankle movements exhibited by children are likely due to their incomplete development of higher centers.