Arm trajectories and writing strategy in healthy children

Abstract

Background: Evaluation of elementary writing skills in children is usually obtained with high resolution (and high cost) techniques or with low resolution pen-and-paper tests. In this observational study we tested a quantitative method to obtain normative data to describe arm movement during a writing precursor gesture.

Methods: 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.

Results: 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.

Conclusions: 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.

Figure 1

The maze. The maze projected in front of the child. The red lines showing the entrance and the exit of the maze were not shown to the child.

Figure 2

The setting. The photograph shows the original setting. As detailed in the text, the camcorder was placed behind the children, 2 meters high and skewed downwards 120 degrees (so to equal humerus inclination on the forearm).

Figure 3

Representation on the cartesian plane of upper limb trajectories. These trajectories are described by parabolic curves that corresponds to mean, -1;-2 and +1;+2 standard deviation curves. First line: shoulder, elbow and wrist angles of children attending first and fifth class under ERROR condition. Second line: shoulder, elbow and wrist angles of children attending first and fifth class under FASTER condition. Blue areas account for 80% of children in each group.