ABSTRACT
Vertical jumping is a closed skill that is fundamental to numerous recreational activities and training strategies (Davis et al., 2003). It is easily controlled and consists of clear phases, each with its own underlying performance criterion for successful execution (Spagele et al., 1999). This makes it a valuable experimental model in biomechanical research to assess the cause and effect of human movement strategies for different population groups (Challis, 1998; Kakihana and Suzuki, 2001; Strike and Diss, 2005). The fundamental objective is to achieve the greatest vertical velocity (v (z)) at take-off in order to reach maximum height (s (z)) of the centre of mass (CoM) during flight (Dowling and Vamos, 1993). The height is determined by the biomechanics in the preceding phases that are required to generate vertical impulse. Therefore, s (z) is related to the ability of the jumper to produce power at the joints and to coordinate the inter-joint coupling. Inter-joint coordination is a measure of the capacity of the neuromuscular system to organize itself to enable the successful execution of complex skills. Coordination in jumping is dependent on the sequential proximal-distal peak activation of the muscles, which has been shown to be the most effective in accelerating the body given the anatomical and geometric constraints of the musculo-skeletal system (Bobbert and van Ingen Schenau, 1988). Transtibial amputees are defined by the absence of the lower leg, ankle joint and foot segment. The biarticular plantarflexors have been severed, and so ineffective co-contraction with the knee extensors, in combination with the loss of the most distal joint in the proximal-distal sequencing, may result in altered coordination of the movement.
