The effect of pre‐stretch on mechanical efficiency of human skeletal muscle

Abstract

The mechanical efficiency of positive work was studied in six subjects performing three different types of exercises. On the first occasion the subjects ran on a motor-driven treadmill at 3.33 m s-1; the second and the third exercises consisted of performing rhythmical vertical jumps for 1 min both in rebound (RJ) and no-rebound (NRJ) conditions. The mechanical efficiency calculated in NRJ, which reflects only the conversion of biochemical energy into mechanical work, was found to be lower than the corresponding observation in RJ, 17.2 vs. 27.8% (P less than 0.001), respectively. These differences could not be explained by only the storage and recoil of elastic energy occurring in RJ compared with NRJ. The calculated extra work delivered 'free' was greater than the potential elastic energy which could be stored within the leg extensor muscles (187 vs. 124 J for each jump, P less than 0.05). It is likely that other factors might be responsible for the extra work found in NRJ. It was suggested that the difference in the length of time to perform positive work between a simple shortening contraction and a stretch-shortening muscular activity could be also responsible for the enhanced efficiency observed in RJ. This suggestion was supported by the high relationship (P less than 0.001) found between the time to perform positive work and the mechanical efficiency measured in jumping and estimated during running.

Human hopping on very soft elastic surfaces: implications for muscle pre-stretch and elastic energy storage in locomotion

“…First, when muscle fibers are pre-stretched, they generate greater force and have better efficiency during the subsequent concentric contraction (Bobbert et al, 1986;Bosco et al, 1987;Finni et al, 2001;Heglund and Cavagna, 1985). Even if muscle fibers perform no work, as a nearly constant leg length suggests, they still must generate force to support body weight.…”

Effects of stretch on work and efficiency of frog (Rana pipiens)muscle

“…Several studies have noted no difference between the energy consumed during contractions where shortening was preceded by a stretch versus an isometric phase (Bosco et al, 1987;De Haan et al, 1989;Heglund and Cavagna, 1987). In combination with the increased work done after stretch there is an approximately 5-10% absolute increase in the apparent efficiency of work done during shortening.…”

“…The force and work produced by skeletal muscle following stretch are greater than following an isometric contraction (Abbott and Aubert, 1952;Beltman et al, 2004;Bosco et al, 1987;Cavagna et al, 1965;De Haan et al, 1989;Edman et al, 1978;Edman and Tsuchiya, 1996;Ettema et al, 1990;Heglund and Cavagna, 1987;Herzog and Leonard, 2002;Herzog and Leonard, 2005;Lee and Herzog, 2002;Linari et al, 2000;Linari et al, 2003;Rassier et al, 2003). Likewise, work loop studies employing cyclic bouts of stretch and shortening with isolated muscle show that there is an increase in net work output when the phase of muscle activation is such that a brief eccentric period precedes the concentric portion of the contraction (Altringham and Johnston, 1990;Josephson, 1985).…”

An Effect of the Elastic Energy Stored in the Muscle-Tendon Complex at Two Different Coupling-Time Conditions during Vertical Jump

“…If not controlled, greater force could be produced in one case resulting in higher jump displacement (Voigt et al, 1995). Active muscle resists stretching with a force greater than the isometric force (Lee & Herzog, 2002;Bosco et al, 1987;Bullimore et al, 2008;Cavagna et al, 1985;Herzog & Leonard, 1997;Meijer et al, 1997). The force attained after large, fast stretches was due to 1) a greater force developed by each bridge (Hodson-Tole & Wakeling, 2010); or 2) an increased number of cross-bridge attachments (Lee & Herzog, 2002;Proske & Morgan, 1999).…”

“…During jumping, walking, and running, flexion of the legs results in stretching of the muscles, like the vastus lateralis, gluteus maximums, and gastrocnemius and tendons, like Achilles tendon. Many scientists (Komi, 2000;Morgan et al, 2000;Edman & Tsuchiya, 1996;Ettema et al, 1990;Lee & Herzog, 2002;Bosco et al, 1987;Morgan et al, 2000;De Ruiter et al, 2000) have thought that stretching of the muscle-tendon complex would cause the recoil of elastic energy, which produces a certain amount of mechanical work without utilization of chemical energy. This stored elastic energy is reused for the next following concentric contraction.…”