Within a few months, infants adopt the co-ordination required for a stable habitual walk. Two ways of analysis are open to study this development. In the phenomenological approach (dynamical systems approach), the complex system is reduced to a few variables considered to be the collective result of the dynamical behaviour of all of the systems components. Analysis of variance of the cyclic behaviour of these variables offers insight in the developmental processes (Thelen & Smith, 1994; Clark, 1997). In case of the mechanistic approach, insight is gained in the causes underlying the cyclic behaviour through detailled analysis of the structure and biomechanics of the locomotor 'de nieuwe loper', we verwachten eerder een aantal algemene trends te kunnen system. vaststellen.
The phenomenological and mechanistic approaches are to be considered as highly complementary in understanding the fenomenon of motor development. Most of the longitudinal studies investigating the early development of independent walking, preferably used the phenomenological approach, hereby not taking into account a few exceptions (Sutherland et al.,1980; Grimshaw et al.,1998). Our project tends to gain insight in the biomechanical causes underlying the observerd changes in children learning to walk. As mentioned in literature, independent walking requires the combination of balance and the generation of a propulsive movement. We tend to investigate how this challenge is realised by the morphology of a toddler, wich differs from the adult morphology, by means of detailed 3D- kinematical analysis, together with measurement of the 3D-ground reaction forces, the pressure distribution pattern under the feet (registrated with high spatial and temporal resolution) and perhaps electromyographical registration. Attention is paid to the dynamics of the the center of mass and the body segments. Kinetics and energetics will teach us how much energy it costs to walk. Joint-moment are used to calculate wich joints produce energy and where the energy disappears. We will also study the forces and pressures under the feet and the pathway of the center of pressure. In combination with the ground reaction forces, this information allows us to determine the stability in the joints. Attention must also be paid to the occasional trials when the child fails to stay upright. Wich parameter differs and make the infant lose his balance? Amongst children the variability in gait patterns is large, therefore it is not our goal to define an average gait pattern of 'the new walker'. Rather we want to determine some general trends in the development of independent walking.