Role of the Stretch-Shortening Cycle in Jumping

There is ample evidence that power output is enhanced by the stretch-shortening cycle in explosive movements. Ingen Schenau et al. argue that the improved jumping performance with a countermovement is not due to the storage and release of elastic energy or muscle potentiation. Indeed, both experimental data and modeling results seem to support this view. I disagree with broadly interpreting this finding to mean that the stretch-shortening cycle never plays an important role in enhancing muscle force and power output in explosive movements. In the most obvious examples in which the stretch-shortening cycle plays an important role, muscle force or power output exceeds what would be possible without a prestretch. I will discuss three examples of this type: countermovement jumps in humans, frog jumping, and kangaroo rat jumping. Animal models hold promise for elucidating the role of the stretch-shortening cycle because it is possible to actually measure in vivo muscle forces and in vitro muscle properties.