Arm trajectories and writing strategy in healthy children

We recruited 226 healthy children (mean age 9,1 years [range: 6.3 – 11.4 years]), attending primary schools belonging to the “Istituto Comprensivo” of Rivanazzano Terme (Pavia). We asked to drive a cursor through a polygonal path (labyrinth) projected in front of them using a wireless mouse. Dartfish？ video analysis software was used to elaborate images and Excel？, MedCalc？ and Statistica 7？ to analyze values of shoulder, elbow and wrist ranges of motion, arm trajectories, execution times and gesture accuracy.Differences seen in motor strategies, when divided according to attended class, suggest a proximal-distal maturation of motor control. Obtained values were not significantly correlated with variables such as gender, ethnicity or cognitive functioning.This type of approach to a study of arm movement during childhood represents a valid alternative to other tests, considering that it can differentiate children who perform similarly in the VMI test and is non-invasive, low-cost and easily reproducible.Arm movements are the final result of a complex mechanism, involving motor algorithms structured according to motor experience [1]. The brain network involved is complex and not yet completely understood [2]. Stability and adaptability of motor performances are fundamental to skilled actions throughout the life span [3]. Adults have highly stereotyped reaching movements that lead to stable arm trajectories, with relatively narrow range of motion of arm joints. Studies with complex optoelectronic systems in healthy subjects have shown that upper limb motor trajectories are highly variable before the age of 3 and then tend to became more and more stable; when the child is about 11, adult performance is approached [4]. Moreover, planning an arm gesture implies that the child has the ability to stabilize the head during postural and kinetic activities [5].Writing can be studied, from a kinetic point of view, as the result of specific periodic movements, inscribed on coord