UBC Theses and Dissertations
Elimination of muscle recoil energy in vertical jumping Montford, Gordon Hugh
This is an empirical study which investigates the possibility of isolating the muscle's contractile component in dynamic jump training exercises. Cavagna, et al.(1968); Asmussen and Bonde-Petersen, (1974); Komi and Bosco, (1978) are some of the researchers confirming the presence of elastic energy in lengthened (stretched) human muscle. This recoil energy provides an additive effect when integrated with the human muscle's contractile component during dynamic muscular contractions. Komi and Bosco (1978) asserted that the rate of stretching the muscle immediately prior to the concentric contraction is the key to producing higher levels of recoil energy. Plyometric exercises, such as depth jumping, exploit this characteristic in jump training. Cavagna, et al. (1971) suggested that speed of shortening by the contractile component is the limiting factor in integrating this recoil energy with the concentric contraction. This identifies to this researcher, that by eliminating recoil energy and isolating the contractile component in jump training, greater long term jumping improvement may be achieved more efficiently over a shorter training period. To eliminate the recoil energy in a dynamic vertical jumping movement the. eccentric contraction phase is slowed by an absorbent jumping/landing surface. Three types of vertical jumps (a squat jump, a countermovement jump and a depth jump from a 0.40 m height) were performed by 15 female subjects on two types of jumping/landing surfaces. A Kistler Force Plate is the "normal" 1anding/jumping surface; a foam pad (0.64 x 0.44 x 0.20 m) placed upon the Kistler Force Plate is the "absorbent" jumping/landing surface. The data collected comprised: Height jumped, generated positive mechanical work, accrued negative mechanical work, change in positive mechanical work with respect to the squat jump, and height of drop for each depth jump. This study found a significant difference at the 0.01 level between a "normal" and an "absorbent" jumping/landing surface when performing vertical jumps. Enhanced mechanical work was observed for the countermovement and depth jumps with respect to the squat jump.(the baseline measure of the contractile component's ability to do mechanical work). This enhanced work was attributed to the recovery of stored recoil energy and converted to a percentage of recovered eccentric energy (reduced potential energy). The "normal" surface showed a recovery of 13.4% and 4.8% for the countermovement jump and depth jump respectively; similarly, the "absorbent" surface showed recovery of 11.3% and -0.5%. These results indicate that a highly absorbent jumping/landing surface degrades the recovery of stored recoil energy in depth jumping; and can be used to eliminate recoil energy in plyometric training, specifically depth jumptraining.
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