Kinetics: our window into the goals and strategies of the central nervous system.

The goal of this chapter is to demonstrate the role of integrated biomechanical analyses in complex movements such as gait in alerting researchers of the goals and synergies of the CNS. Because of the large number of segments involved and the potential for the CNS to take advantage of inter-limb coupling it is only through appropriate biomechanical analyses that such collaboration can be identified. Examples from normal, perturbed, elderly and pathological gait are presented to demonstrate the principles of total limb and total body analysis to pinpoint the goals of the CNS and to identify total limb or body synergies and adaptations in the elderly and in gait pathologies. Such findings reinforce the generalizations made many years ago by Bernstein [2] when he postulated several simplifying principles of CNS control. Also, evident from these analyses are the precision and accuracy of biomechanical variables that make these measures particularly sensitive to small changes within an individual or across a population group.