HENRY, H.T.*; RUBENSON, J; HOOGENDYK, T.A.; MARSH, R.L.; Northeastern University, Boston; Northeastern University, Boston; Northeastern University, Boston; Northeastern University, Boston: Storage of elastic energy in guinea fowl lateral gastrocnemius tendon in running versus jumping
Muscle function during running and jumping was examined in the guinea fowl lateral gastrocnemius (LG) using in vivo sonomicrometry and electromyographic measurements, as well as in situ length-tension and moment arm measurements. Previous work has emphasized the large extensor moment arm of the LG at the ankle. However, our calculations show that the flexor moment arm at the knee is also large. During jumping the muscle begins to shorten on the descending limb of the length-tension curve and continues to shorten past L0 as the knee and ankle extend simultaneously. As a result of the counteracting effects of these extensions on overall muscle-tendon length, the LG can operate effectively during almost the entire period of ankle extension and power the jump by direct work output as well as elastic energy storage and recovery in the tendon. Published data on LG function during level running in turkeys suggest that this muscle contributes to economical running by operating isometrically during force production while the tendon stores and release elastic energy. In guinea fowl our data suggest that some energy may be wasted during the stretch and release cycle of the tendon. At toe down, the muscle tendon complex (MTC) remains the same length or lengthens while the muscle actively shortens thereby stretching the tendon. The tendon subsequently recoils while the muscle actively lengthens. At this time the MTC is also shortening. It is possible that some of the energy from this recoil might be absorbed by the actively lengthening fascicles. Supported by NIH AR47337 to RLM
