title: Tension changes during and after stretch in frog muscle fibres.
abstract: 1. Small fibre bundles from the semitendinosus muscles of the frog were stretched during tetanic stimulation, and the resulting tension changes were studied over a wide range of stretch velocities from 0.1 to 150 cm/sec (0.1-100 length/sec). The experiments were performed within the range of fibre lengths where the resting tension was negligible.2. With stretch velocities of more than 30 cm/sec (20 length/sec), the tension rose abruptly at first, and then started to fall while the stretch still continued, indicating the ;slip' of the contractile component. When the fibres were stretched at 80-150 cm/sec (70-100 length/sec), the tension fell quickly below the initial isometric level at the end of the stretch, and then began to rise again to the initial isometric value.3. Following stretches of 30-60 cm/sec (20-50 length/sec), the tension showed a delayed transient rise. The delayed rise of tension became more marked as the amount of stretch was increased.4. In some preparations, oscillatory tension changes were observed following stretches of 50-100 cm/sec (40-70 length/sec).5. The tension developed above the isometric level during moderate-velocity stretches of less than 15 cm/sec (10 length/sec) increased by lowering temperature, and showed a tendency to decay when the stretch velocity was suddenly reduced during a stretch.6. These results are discussed in relation to the sliding filament hypothesis, which provides an explanation for the findings of the present work.
mesh_terms: D000818:Animals; D001001:Anura; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009119:Muscle Contraction; D009132:Muscles / Q000502:physiology*; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors