[Nature of the "length-force" relationship in mammalian heart muscle]

Alteration of myocardial contractile state (a transitional process) is shown to be associated with changes of muscle length or with 3-min pause. The drugs which block the propagation of AP along the T-tubular system, induce a less obvious response of the lengthening alone. An increase of the muscle length seems to lead to improvement of propagation along the T-tubular system and to involve "additional" functional units.