ACTIVE FORCE-LENGTH RELATIONSHIP OF HUMAN LOWER-LEG MUSCLES ESTIMATEDFROM MORPHOLOGICAL DATA - A COMPARISON OF GEOMETRIC MUSCLE MODELS

Muscle fibre lengths, pennation angles, and sarcomere lengths were mea sured (the latter by a diffraction technique) for each of the muscles of three embalmed lower-leg specimens. From these data and filament le ngths from Walker & Schrodt (1973), the optimum fibre lengths were det ermined. Relationships between length and active force (at full activa tion) of the lower-leg muscles were calculated by use of (i) a unipenn ate muscle model, (ii) a bipennate model, and (iii) bipennate models i n which the cosine of the pennation angle is approximated as length in dependent. It is concluded that the first two models are equally usefu l and that the use of the last models is discouraged in case of strong ly pennated muscles. Non-uniformity of fibre parameters within one mus cle appears to have little effect on the force-length relationship.