Control of an external force in leg extensions in humans.
- 1 November 1992
- journal article
- Published by Wiley in The Journal of Physiology
- Vol. 457 (1), 611-626
- https://doi.org/10.1113/jphysiol.1992.sp019397
Abstract
1. We investigated the hypothesis that mono- and bi-articular muscles perform different functions: the former are chiefly dependent on their mechanical advantage, while the latter are considered to be mainly concerned with controlling the direction of an external force. 2. Seven subjects were asked to exert a constant external force in various directions from three different positions. Feedback was given on the amplitude (300 and 600 N) and direction of the force vector. 3. During each trial the position of the subject was registered. Ground reaction force and muscle activity (EMG) from the main mono- and bi-articular upper leg muscles were recorded. Link segment modelling was used to obtain net moments about the knee and hip joints. For each muscle the mechanical advantage was calculated in each force direction. 4. The task of controlling the ground reaction force was performed with little interindividual variation as reflected by the variability of the different force and EMG variables. 5. A linear relationship between the difference in activity of rectus femoris and hamstrings and the difference in net moment around the knee and hip was found. This relationship showed very high correlation coefficients of 0.96 (300 N) and 0.97 (600 N) and was independent of position. Mean correlations between this activity difference and the angle of the force vector were also high: -0.95 (300 N) and -0.94 (600 N). 6. The mono- as well as the bi-articular muscles increased in activity when a larger mechanical advantage could be obtained from them, except for the biceps femoris (short head). 7. The results support the hypothesis that bi-articular muscles have a unique role in controlling the distribution of net moments about the joints, and as a consequence, in controlling the direction of the external force exerted on the environment.Keywords
This publication has 26 references indexed in Scilit:
- Intermuscular coordination in a sprint push-offJournal of Biomechanics, 1992
- Coordination of leg muscles during speed skatingJournal of Biomechanics, 1991
- A method for determining lower extremity muscle-tendon lengths during flexion/extension movementsJournal of Biomechanics, 1990
- Muscular coactivationThe American Journal of Sports Medicine, 1988
- Coordination in vertical jumpingJournal of Biomechanics, 1988
- Neuronal Population Coding of Movement DirectionScience, 1986
- A General Method for Determining the Functional Role of a MuscleJournal of Biomechanical Engineering, 1985
- Changes in leg movements and muscle activity with speed of locomotion and mode of progression in humansActa Physiologica Scandinavica, 1985
- In vivo moment arm lengths for hip extensor muscles at different angles of hip flexionJournal of Biomechanics, 1985
- Role of Mono- and Biarticular Muscles in Explosive MovementsInternational Journal of Sports Medicine, 1984