Helical muscle contraction mechanism has been analyzed on a geometrical model, consisting of a multiple system of parallel helicae, around a single axis. By setting out mathematical conditions for this model, certain conclusions can be drawn: a) Contraction depends entirely on the degree of interdigitation between thick and thin myofilaments. This also applies to shearing (or variation in stagger) between homologous myofilaments, b) Angle variations between helica and its axis are functions of interdigitation between thick and thin myofilaments, c) Contraction of one or more sarcomeres is not possible without variation in the above angle; neither can the oblique striation become transversal, d) Helical and transversally striated muscles have the same contraction capacity, given identical thick and thin myofilament overlap capacities.