Infant bouncing: Analysis of skilled and less-skilled behaviour

This study examined joint kinematics and muscle activation patterns produced by infants of different bouncing skill levels as they bounced in a Jolly Jumper harness system. The relationship between three components of bouncing was also determined. The three components were: (i) the oscillation pattern of the mass-spring system which can be characterized as a harmonic oscillator; (ii) the baby's contribution to the bouncing behaviour which can be characterized in part as a forcing function and in part as a harmonic oscillator; and (iii) the combination of these two components which corresponds to the output or the bouncing behaviour. Infants (N = 9) were instrumented with five surface electrodes over the lower leg muscles and dressed in black tights and a black long-sleeved body suit with reflective markers placed on the tights over seven body landmarks. Infants were then supported in a modified Jolly Jumper harness and encouraged to bounce. (Abstract shortened by UMI.)