Spatio-temporal constraints on upright children's coordination when hitting a moving target

To determine if the spatial and/or temporal context affected the coordination patterns of children under five in upright interceptive tasks, 3-year-olds hit a ball dropped from a ramp from five heights (1.5, 2, 2.5, 3, and 3.5 m) to control drop time. We studied the initiation time of hitting a ball with a cinematic analysis of the different joint movements (foot, knee, hip, shoulder, and hand). Two patterns of joint coordination were observed according to the rolling height of the ball: a de-synchronized pattern for heights of 2 m or above where the foot was the first to move and the hand the last, and a “synchronized” pattern, for the lowest height (1.5 m) where all joints started moving at the same time due to a strong temporal pressure. These two coordination patterns highlight a functional adaptation of body joints according to the spatio-temporal constraints among children from the age of three.