A mechanism accounting for independence on starting length of tension increase in ramp stretches of active skeletal muscle at short half-sarcomere lengths.
Based on previous experimental results of independence on starting length of the tension gradient in constant-velocity stretches of active skeletal muscle at muscle lengths including the ascending limb and the plateau of the tension-length relation, a possible physiological mechanism determining the tension increase in lengthening active muscle is discussed. Considering the sliding filament theory, it is suggested that the tension-length relation of a half-sarcomere in lengthening contractions is different from that in isometric contractions. The assumed mechanism predicts, among others, that the thick filament retains its shortened length in lengthening contractions starting from a half-sarcomere length where this filament is compressed. An example model is implemented and checked with simulations.
Till
Olaf
O
Division of Motion Science, Institute of Sport Science, Friedrich Schiller University, Seidelstrass e20, D-07749 Jena, Germany. olaf.till@uni-jena.de
Siebert
Tobias
T
Blickhan
Reinhard
R
D008841:Actin Cytoskeleton / Q000502:physiology; D000465:Algorithms; D003198:Computer Simulation; D064211:Connectin; D004548:Elasticity; D007537:Isometric Contraction; D008954:Models, Biological; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins / Q000502:physiology; D009129:Muscle Tonus / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D011494:Protein Kinases / Q000502:physiology; D012518:Sarcomeres / Q000502:physiology*
D064211:Connectin; D009124:Muscle Proteins; D011494:Protein Kinases