Does Elastic Energy Enhance Work and Efficiency in the Stretch-Shortening Cycle?

Abstract

This target article addresses the role of storage and reutilization of elastic energy in stretch-shortening cycles. It is argued that for discrete movements such as the vertical jump, elastic energy does not explain the work enhancement due to the prestretch. This enhancement seems to occur because the prestretch allows muscles to develop a high level of active state and force before starting to shorten. For cyclic movements in which stretch-shortening cycles occur repetitively, some authors have claimed that elastic energy enhances mechanical efficiency. In the current article it is demonstrated that this claim is often based on disputable concepts such as the efficiency of positive work or absolute work, and it is argued that elastic energy cannot affect mechanical efficiency simply because this energy is not related to the conversion of metabolic energy into mechanical energy. A comparison of work and efficiency measures obtained at different levels of organization reveals that there is in fact no decisive evidence to either support or reject the claim that the stretch-shortening cycle enhances muscle efficiency. These explorations lead to the conclusion that the body of knowledge about the mechanics and energetics of the stretch-shortening cycle is in fact quite lean. A major challenge is to bridge the gap between knowledge obtained at different levels of organization, with the ultimate purpose of understanding how the intrinsic properties of muscles manifest themselves under in-vivo-like conditions and how they are exploited in whole-body activities such as running. To achieve this purpose, a close cooperation is required between muscle physiologists and human movement scientists performing inverse and forward dynamic simulation studies of whole-body exercises.

Kinetic and Kinematic Analysis for Assessing the Differences in Countermovement Jump Performance in Rugby Players

“…This performance improvement can only be achieved if the applied force levels are maintained throughout the concentric phase. Previous studies (18,28) reported that in deeper crouch positions, the tension in the joints increases, resulting in decreased capacity to generate force, however, the results of this study show that the HIGH group achieved higher forces than the Ground reaction forces in vertical jump 12 generation of higher concentric force and ultimately increases the vertical take-off velocity (4,8,9,17). The higher force produced at the end of eccentric phase increases the ability to develop force rapidly during the counter-movement.…”

Differences in leg muscle activity during running and cycling in humans

“…For cycling, all muscles measured did show a relationship between EMG activity and external P mech output. Ericson et al (1985), van Ingen Schenau et al (1997) and Miura et al (2000) concur that during cycling only concentric muscle actions are involved. Komi et al (1987) and Shinohara et al (1997) showed that there is a positive relationship between the EMG activity of concentric exercise and the load applied.…”

“…The active stretch allows the tendons of the muscles to store elastic energy, which can be re-used during the subsequent concentric phase. As a result, the gross efficiency during running can be much greater than the muscle efficiency (van Ingen Schenau et al 1997;Ettema 2001). Previous studies suggested that during running up inclines storage and re-use of elastic energy also takes place, which could explain the large D efficiencies obtained during running (Lloyd and Zacks 1972;Asmussen and Bonde-Petersen 1974).…”

“…There is little doubt that level running includes stretch-shortening cycles (Margaria 1976;Taylor 1985;van Ingen Schenau et al 1997). During the landing phase the active muscles are stretched to decelerate body mass whereas during the push off phase the active muscles are shortening.…”

Comparison of Muscle-Tendon Interaction of Human M. Gastrocnemius Between Ankle- and Drop-Jumping

“…This is because elastic energy is stored in the tendinous structures when stretched by large forces in the downward phase of the SSC, and can be reutilized in the following push off phase (Cavagna, et al, 1968;Ettema, et al, 1992;Ingen, et al, 1997). Conversely, since there is no negative phase nor subsequent tendon stretch in non-counter movements, utilization of elastic energy is limited to that stored from maintaining posture prior to, and during the jump phase.…”