The effect of pre-stretch on mechanical efficiency of human skeletal muscle.

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.

[1]  J T Viitasalo,et al.  Neuromuscular function and mechanical efficiency of human leg extensor muscles during jumping exercises. , 1982, Acta physiologica Scandinavica.

[2]  R MARGARIA,et al.  EFFECT OF NEGATIVE WORK ON THE AMOUNT OF POSITIVE WORK PERFORMED BY AN ISOLATED MUSCLE. , 1965, Journal of applied physiology.

[3]  E. Asmussen,et al.  Apparent efficiency and storage of elastic energy in human muscles during exercise. , 1974, Acta physiologica Scandinavica.

[4]  S Dickinson,et al.  The efficiency of bicycle‐pedalling, as affected by speed and load , 1929, The Journal of physiology.

[5]  F. W. Flitney,et al.  Cross‐bridge detachment and sarcomere 'give' during stretch of active frog's muscle. , 1978, The Journal of physiology.

[6]  K. Williams.  The relationship between mechanical and physiological energy estimates. , 1985, Medicine and science in sports and exercise.

[7]  G. Cavagna,et al.  The mechanics of sprint running , 1971, The Journal of physiology.

[8]  G. Cavagna,et al.  Mechanical work and efficiency in level walking and running , 1977, The Journal of physiology.

[9]  C T Davies,et al.  Negative (eccentric) work. II. Physiological responses to walking uphill and downhill on a motor-driven treadmill. , 1972, Ergonomics.

[10]  P. Komi,et al.  Prestretch potentiation of human skeletal muscle during ballistic movement. , 1981, Acta physiologica Scandinavica.

[11]  E. Asmussen,et al.  Storage of elastic energy in skeletal muscles in man. , 1974, Acta physiologica Scandinavica.

[12]  G. Cavagna,et al.  The sources of external work in level walking and running. , 1976, The Journal of physiology.

[13]  H. Thys,et al.  Utilization of muscle elasticity in exercise. , 1972, Journal of applied physiology.

[14]  G A Cavagna,et al.  Proceedings: The additional mechanical energy delivered by the contractile component of the previously stretched muscle. , 1975, The Journal of physiology.

[15]  G. Cavagna.  Elastic bounce of the body. , 1970, Journal of applied physiology.

[16]  E. Asmussen,et al.  Positive and negative muscular work. , 1953, Acta physiologica Scandinavica.

[17]  The factors determining the maximum work and the mechanical efficiency of muscle , 1928 .

[18]  G. Cavagna,et al.  MECHANICAL WORK IN RUNNING. , 1964, Journal of applied physiology.

[19]  L. Pugh.  The influence of wind resistance in running and walking and the mechanical efficiency of work against horizontal or vertical forces , 1971, The Journal of physiology.

[20]  W. O. Fenn,et al.  A quantitative comparison between the energy liberated and the work performed by the isolated sartorius muscle of the frog , 1923, The Journal of physiology.

[21]  P. Komi,et al.  Mechanical efficiency of positive work in running at different speeds. , 1983, Medicine and science in sports and exercise.