|Active force-length relationship of human lower-leg muscles estimated from morphological data : a comparison of geometric muscle models.
Spoor, C.W. ; Leeuwen, J.L. van; Meulen, W.J. van der; Huson, A. - \ 1991
European journal of morphology 29 (1991)3. - ISSN 0924-3860 - p. 137 - 160.
Muscle fibre lengths, pennation angles, and sarcomere lengths were measured (the latter by a diffraction technique) for each of the muscles of three embalmed lower-leg specimens. From these data and filament lengths from Walker & Schrodt (1973), the optimum fibre lengths were determined. Relationships between length and active force (at full activation) of the lower-leg muscles were calculated by use of (i) a unipennate muscle model, (ii) a bipennate model, and (iii) bipennate models in which the cosine of the pennation angle is approximated as length independent. It is concluded that the first two models are equally useful and that the use of the last models is discouraged in case of strongly pennated muscles. Non-uniformity of fibre parameters within one muscle appears to have little effect on the force-length relationship.
Spoor, C.W. ; Leeuwen, J.L. van; Huson, A. - \ 1991
Journal of Biomechanics 24 (1991)9. - ISSN 0021-9290 - 1 p.
Estimation of instantaneous moment arms of lower-leg muscles
Spoor, C.W. ; Leeuwen, J.L. van; Meskers, C.G.M. ; Titulaer, A.F. ; Huson, A. - \ 1990
Journal of Biomechanics 23 (1990)12. - ISSN 0021-9290 - p. 1247 - 1259.
Muscle moment arms at the human knee and ankle were estimated from muscle length changes measured as a function of joint flexion angle in cadaver specimens. Nearly all lower-leg muscles were studied: extensor digitorum longus, extensor hallucis longus, flexor digitorum longus, flexor hallucis longus, gastrocnemius lateralis, gastrocnemius medialis, peroneus brevis, peroneus longus, peroneus tertius, plantaris, soleus, tibialis anterior, and tibialis posterior. Noise in measured muscle length was filtered by means of quintic splines. Moment arms of the mm. gastrocnemii appear to be much more dependent on joint flexion angles than was generally assumed by other investigators. Some consequences for earlier analyses are mentioned.
A model study of muscle forces and joint-force direction in normal and dysplastic neonatal hips
Spoor, C.W. ; Leeuwen, J.L. van; Windt, F.H.J. de; Huson, A. - \ 1989
Journal of Biomechanics 22 (1989)8-9. - ISSN 0021-9290 - p. 873 - 884.
Orthopaedic treatment of congenital hip dysplasia does not always give the desired result. With the present model, prediction of the effects of various treatments on the force direction in the hip joint could help to improve and select treatment (the force direction is presumed to control the collum growth direction). The model contains three-dimensional mathematical descriptions of all muscles passing the hip joint, for various degrees of femoral dysplasia, and for various hip postures. Muscles run straight or curve round some skeletal parts. Muscle forces (all isometric) are calculated from muscle mass, density, pennation angle, mean fibre length, muscle elongation, and assumed activation levels. The latter serve as parameters for optimization. Resting lengths are taken from an assumed fetal posture, and from the observed neonatal posture. Differences between force directions before and after birth, as calculated with the model, agree with collum direction changes described by von Lanz and Mayet (1953).
An experimental setup for the measurement of forces on a human cadaveric foot during inversion
Ottevanger, E.J.C. ; Spoor, C.W. ; Leeuwen, J.L. van; Sauren, A.A.H.J. ; Janssen, J.D. ; Huson, A. - \ 1989
Journal of Biomechanics 22 (1989)8-9. - ISSN 0021-9290
An experimental setup was developed for statically measuring seven vertical and three horizontal reaction forces on the foot. In the setup, the leg can be simultaneously loaded (1) by a vertical force, (2) by an externally applied axial moment, and (3) by simulated muscle forces. The foot is free to invert under influence of the external loads. Statical analysis and test experiments were used for evaluation. The setup can be used in combination with Roentgen photogrammetry to measure bone positions simultaneously with forces.