TRAINING AFFECTS THE DEVELOPMENT OF POSTURAL ADJUSTMENTS IN SITTING INFANTS

1. The present study addressed the question of whether daily balance t raining can affect the development of postural adjustments in sitting infants. 2. Postural responses during sitting on a moveable platform w ere assessed in twenty healthy infants at 5-6, 7-8 and 9-10 months of age. Multiple surface EMGs and kinematics were recorded while the infa nts were exposed to slow and fast horizontal forward (Fw) and backward (Bw) displacements of the platform. After the first session the paren ts of nine infants trained their child's sitting balance daily. 3. At the youngest age, when none of the infants could sit independently, th e muscle activation patterns were direction specific and showed a larg e variation. This variation decreased with increasing age, resulting i n selection of the most complete responses. Training facilitated respo nse selection both during Fw and Bw translations. This suggests a trai ning effect on the first level of the central pattern generator (CPG;) model of postural control. 4. Training also affected the development of response modulation during Fw translations. It accelerated the deve lopment of: (1) the ability to modulate EMG amplitude with respect to platform velocity and initial sitting position, (2) antagonist activit y and (3) a distal onset of the response. These findings point to a tr aining effect on the second level of the CPG model of postural adjustm ents.