Optimum contact time and the amortization phase in the bounce drop jump

Of the many plyometric techniques available, it has been reported that the bounce drop jump uses the stretch± shortening cycle most effectively (Bobbert et al., 1987: Medicine and Science in Sports and Exercise, 19, 332± 338). Mechanistic theories of the stretch± shortening cycle have been proposed. It is generally agreed that, if the time between the eccentric± concentric contraction is too long, then any possible work enhancement is lost. A wide range of values (0.12± 1.0 m) for optimum drop heights has been reported in the literature. Signi® cant neuromuscular differences between plyometrically trained and untrained athletes suggest that drop jump performance is directly related to training history; this leads to difficulties in in defining an optimum height (Viitasalo et al., 1998: European Journal of Applied Physiology, 78, 432± 440). The aims of this study were to establish whether optimum plyometric training could be based on the landing contact time and to determine its relationship with the muscle amortization phase.