Storage of elastic energy in skeletal muscles in man.

ASMUSSEN, E. and F. BONDE-PETERSEN. Storage of elastic energy in skeletal muscles in man. Acta physiol. scand. 1974. 91. 385-392 The question, if muscles can absorb and temporarily store mechanical energy in the form of elastic energy for later re-use, was studied by having subjects perform maximal verticaljumps on a registering force-platform. The jumps were performed 1) from a semi-squatting position, 2) after a natural counter-movement from a standing position, or 3) in continuation of jumps down from heights of 0.23, 0.40, or 0.69 m. The heights of the jumps were calculated from the registered flight times. The maximum energy level, Eneg, of the jumpers prior to the upward movement in the jump, was considered to be zero in condition 1. In condition 2 it was calculated from the force-time record ofthe force-platform; and in condition 3 it was calculated from the height of the downward jump and the weight of the subject. The maximum energy level after take-off, E,,,, was calculated from the height of the jump and the jumper’s weight. It was found that theheight of the jump and Epns increased with increasing amounts of Eneg, up to a certain level (jumping down from 0.40 m). The gains in Epos over t$at in condition 1, were expressed as a percentage of Eneg and found to be 22.9 % in condition 2, and 13.2, 10.5, and 3.3 % in the three situations ofcondition 3. It is suggested that the elastic energy is stored in the active muscles, and it is demonstrated that the muscles of the legs are activated in the downward jumps before contact with the platform is established. The elastic properties of muscles have been known and studied extensively for many years. The original concept of e.g. Levin and Wyman (1927), viz. that the energy liberated at contraction was immediately stored as elastic energy in the series elastic components for subsequent use in performing work, has been abandoned, not least after the discovery of the “Fenn effect” (Fenn and Marsh 1935). Nevertheless muscle elasticity has continued to arouse the interest of muscle physiologists, and its possible role as a buffer and temporary store of mechanical energy has anew been brought to the attention of work physiologists e.g. by the studies of Cavagna et al. (1968). One way of investigating this possible function of the elastic component in muscle is to compare the release of external mechanical energy without and with a previous stretching of the involved muscles. This was done by Marey and Demeny (1885) who compared the heights of vertical jumps performed without and with a preliminary counter-movement and found the height to be higher in the latter case. Recently Cavagna et al. (1971) repeated these experiments, using a force-platform