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. Loading of the harness and spring was recorded using a loadcell attached to the ceiling. Vertical ground reaction forces were recorded using two force platforms mounted into the floor beneath the infant's feet. Bouncing behaviour was recorded for six 30-second trials. While bouncing, the infants were filmed with a video camera placed at ninety degrees to the sagittal plane. The infants were grouped as less-skilled. moderately-skilled and skilled bouncers. There was a general trend from a chaotic to an organized pattern of interjoint co-ordination as the level of bouncing skill increased. Infants in the moderately-skilled and skilled groups bounced at one of two distinct frequencies. 1.5 or 2 times the resonant frequency of the spring. Similarly, the baby contributions and kinematics of the lower limbs as reflected in qualitative analysts of phase-plane plot patterns were distinctly different for the two frequencies of bouncing. The phase-plane patterns suggested that one group of infants used a spring-like control mechanism for lower limb movement while the second group of infants incorporated a point-specific (focused, position-specific) control of forces into the mechanism for lower limb movement. This distinction was less apparent in the qualitative analysis of angleangle plots. The qualitative dynamics suggest that there are two predominant attractor states for the production of bouncing behaviour. This research expands the current literature of infant behaviour and furthers our understanding of the qualitative dynamics of skilled and less-skilled bouncing.