ORGANIZATION OF LATERAL BALANCE CONTROL IN TODDLERS DURING THE FIRST-YEAR OF INDEPENDENT WALKING

The authors of the present study tested the hypothesis that toddlers i nitiate lateral body stabilization first at the hip level in order to better control the center of gravity (CG), minimize the upper body des tabilization induced by the movement of the feet, and prevent falls. I ntersegmental coordination among the hip, the shoulder, and the head w as investigated in toddlers during their Ist year of independent walki ng. The efficiency of locomotor balance control was examined in the fr ontal plane. An automatic optical TV image processor (ELITE system) wa s used in analyzing the kinematics of foot, hip, shoulder, and head ro tations. For the hip, the shoulder, and the head, appropriate anchorin g indices were defined so that comparisons could be made concerning th e stabilization of a given body segment with respect to its external s pace and to the adjacent supporting anatomical segment. Cross-correlat ion functions were also used for extracting the temporal patterns of t he body segments that occurred during locomotion and for obtaining som e information about the coupling of 2 consecutive segments such as the head-shoulder and the shoulder-hip. First, hip stabilization in space appeared from the Ist week of independent walking and clearly precede d those of the shoulder and the head, suggesting an ascending progress ion, with age, in the ability of new walkers to control lateral balanc e during locomotion. Second, the hip movements occurred before the sho ulder movements and the shoulder movements before the head movements, indicating that locomotor balance control is organized temporally in a n ascending fashion, from the hip to the head. Third, the high values of the correlation coefficients, mainly between the head and the shoul der, were consistent with a global en bloc operation of the head-trunk unit.