This study tested the common assumption that skeletal muscle shortens uniformly in the direction of its fascicles during low-load contraction. Cine phase contrast magnetic resonance imaging was used to characterize shortening of the biceps brachii muscle in 12 subjects during repeated elbow flexion against 5 and 15% maximum voluntary contraction (MVC) loads. Mean shortening was relatively const...

Force depression after active shortening has been observed in different muscle preparations. It has been assumed that force depression is caused by the development of sarcomere length nonuniformities after shortening. However, this hypothesis has never been investigated in a preparation where individual sarcomere lengths could be directly measured. Here, we investigated force depression in sing...

Cellular cardiac preparations in which spontaneous activity was suppressed by EGTA buffering were isolated by microdissection. Uniform and reproducible contractions were induced by iontophoretically released calcium ions. No effects of a diffusional barrier to calcium ions between the micropipette and the contractile system were detected since the sensitivity of the mechanical performance for c...