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Nonuniform sarcomere dynamics during shortening and stretch-shortening contractions with whole muscle
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Abstracts--International Society of Biomechanics XIV Congress 1993
NONUNIFORM SARCOMERE DYNAMICS CONTRACTIONS WITH WHOLE MUSCLE
DURING
SHORTENING
AND STRETCH-SHORTENING
T.L. Allinger and W. Herzog* Department of Mechanical Engineering, *Faculty of Physical Education The University of Calgary, Calgary, AB, Canada,T2N lN4 Nonuniform sarcomere behavior was found during isokinetic contractions of whole serratus anterior muscle (N=2) of mice, in vitro. Muscle length was controlled (Cambridge motor) while muscle force and sarcomerelength (laser diffraction) were measuredduring tetanic stimulation. Each muscle underwent isokinetic (based on muscle length) shortening (S) contractions and isokinetic stretch-shortening(SS) contractions. Events were timed so that the S and SS contractions had identical muscle lengths, spatially and temporally, during the shortening phase. Thus if the sarcomeresbehaved uniformly with muscle length the sarcomere lengths in the two muscles should behave consistently during the shortening phase of the contractions. However, the results (during shortening) showed that the sarcomerelength for the SS contraction was greater (0.02 pm) than the S contraction in muscle I, while the sarcomerelength for the S contraction was greater (0.14 pm) than the SS contraction in muscle II during the shortening phase. Also, the sarcomere shortening velocity was greater (66%) in the S contraction for muscle I, while shortening velocity was greater (19%) in the SS contraction for muscle II. This nonuniform sarcomerebehavior may have interesting implications on the performance of work and the stability of the muscle.
STRETCH-SHORTENING CYCLE TRAINING INDUCES CHANGES IN ELASTIC PROPERTIESOF THE RAT SOLEUS MUSCLE Maria I. Almeida-Silveira, ChantalPerot, Michel Poussonand FrancisGoubel Departementde Genie Biologique URA CNRS 858, Universite de Technologie,60206 Compitgne Ccdex, France Changesin elastic propertiesof rat soleusmusclesoverloadedby stretch-shorteningcycle training were investigatedand comparedwith changesin muscle fiber type proportion. The training apparatusconsistedin a lifting jack hydraulically operated.The cagemovementsinducedthe stretch-shorteningcycles in the hindlimbs of the rats. A group of 14 rats (8 wk old) was trained 3 times a week for 8 weeks.The secondgroup of rats (n=12) servedas control. The method of controlled releasewas applied to obtain the tension-extensioncurve characterizingthe elastic behaviourof the SEC (serieselasticcomponent)of the soleusmuscle.The stretchshorteningcycle training induceda fiber type transition as follows: trainedmusclespresenteda lower numberof type I fibers (11.45%; p
ENERGY DYNAMICS OF SKELETAL MUSCLE DURING LOAD MOVING CONTRACTIONS Richard V. Baratta, Moshe Solomonow, Robert L. Best, Robert D'Ambrosia Bioengineering Laboratory, Dept. of Orthopaedics, Louisiana State University Medical School, New Orleans, Louisiana The mechanical energy (potential and kinetic) and force fluctuations associated with skeletal muscles contracting from rest against gravitational loads were examined in nine. different muscles in the cat's hindlimb. Contraction phases of acceleration and deceleration were observed which were associated with force variations of up to 25% of the nominal load in fast twitch muscles. Slow twitch muscles exhibited smaller force variations (up to 10X of the nominal load). Load: which maximized both the potential and kinetic energies were found in the mid portion of the load range tested for each muscle. The Kinetic energy attained during contraction was a small fraction of what was expected from the isometric length-force relationship. This was especially true at low loads, were the calculated kinetic energy efficiency was at a minimum. At higher loads however, efficiency increased. The results of this study substantiate earlier findings with heat evolution (Hill, 1938) and with metabolic energy (Curtin and Woledge, 1991). Another finding was that parallel fibered muscles tend to have their peak energies at lower forces than muscles with sharp pennation angles, which tend to present a broad energy peak. As a consequence it is expected that parallel fiber muscles are better suited to perform low load, high velocity movements, whereas pennate muscles are better suited for medium to high loads at low contractile velocities.
Abstracts--International Society of Biomechanics XIV Congress 1993
NONUNIFORM SARCOMERE DYNAMICS CONTRACTIONS WITH WHOLE MUSCLE
DURING
SHORTENING
AND STRETCH-SHORTENING
T.L. Allinger and W. Herzog* Department of Mechanical Engineering, *Faculty of Physical Education The University of Calgary, Calgary, AB, Canada,T2N lN4 Nonuniform sarcomere behavior was found during isokinetic contractions of whole serratus anterior muscle (N=2) of mice, in vitro. Muscle length was controlled (Cambridge motor) while muscle force and sarcomerelength (laser diffraction) were measuredduring tetanic stimulation. Each muscle underwent isokinetic (based on muscle length) shortening (S) contractions and isokinetic stretch-shortening(SS) contractions. Events were timed so that the S and SS contractions had identical muscle lengths, spatially and temporally, during the shortening phase. Thus if the sarcomeresbehaved uniformly with muscle length the sarcomere lengths in the two muscles should behave consistently during the shortening phase of the contractions. However, the results (during shortening) showed that the sarcomerelength for the SS contraction was greater (0.02 pm) than the S contraction in muscle I, while the sarcomerelength for the S contraction was greater (0.14 pm) than the SS contraction in muscle II during the shortening phase. Also, the sarcomere shortening velocity was greater (66%) in the S contraction for muscle I, while shortening velocity was greater (19%) in the SS contraction for muscle II. This nonuniform sarcomerebehavior may have interesting implications on the performance of work and the stability of the muscle.
STRETCH-SHORTENING CYCLE TRAINING INDUCES CHANGES IN ELASTIC PROPERTIESOF THE RAT SOLEUS MUSCLE Maria I. Almeida-Silveira, ChantalPerot, Michel Poussonand FrancisGoubel Departementde Genie Biologique URA CNRS 858, Universite de Technologie,60206 Compitgne Ccdex, France Changesin elastic propertiesof rat soleusmusclesoverloadedby stretch-shorteningcycle training were investigatedand comparedwith changesin muscle fiber type proportion. The training apparatusconsistedin a lifting jack hydraulically operated.The cagemovementsinducedthe stretch-shorteningcycles in the hindlimbs of the rats. A group of 14 rats (8 wk old) was trained 3 times a week for 8 weeks.The secondgroup of rats (n=12) servedas control. The method of controlled releasewas applied to obtain the tension-extensioncurve characterizingthe elastic behaviourof the SEC (serieselasticcomponent)of the soleusmuscle.The stretchshorteningcycle training induceda fiber type transition as follows: trainedmusclespresenteda lower numberof type I fibers (11.45%; p
ENERGY DYNAMICS OF SKELETAL MUSCLE DURING LOAD MOVING CONTRACTIONS Richard V. Baratta, Moshe Solomonow, Robert L. Best, Robert D'Ambrosia Bioengineering Laboratory, Dept. of Orthopaedics, Louisiana State University Medical School, New Orleans, Louisiana The mechanical energy (potential and kinetic) and force fluctuations associated with skeletal muscles contracting from rest against gravitational loads were examined in nine. different muscles in the cat's hindlimb. Contraction phases of acceleration and deceleration were observed which were associated with force variations of up to 25% of the nominal load in fast twitch muscles. Slow twitch muscles exhibited smaller force variations (up to 10X of the nominal load). Load: which maximized both the potential and kinetic energies were found in the mid portion of the load range tested for each muscle. The Kinetic energy attained during contraction was a small fraction of what was expected from the isometric length-force relationship. This was especially true at low loads, were the calculated kinetic energy efficiency was at a minimum. At higher loads however, efficiency increased. The results of this study substantiate earlier findings with heat evolution (Hill, 1938) and with metabolic energy (Curtin and Woledge, 1991). Another finding was that parallel fibered muscles tend to have their peak energies at lower forces than muscles with sharp pennation angles, which tend to present a broad energy peak. As a consequence it is expected that parallel fiber muscles are better suited to perform low load, high velocity movements, whereas pennate muscles are better suited for medium to high loads at low contractile velocities.