Journal of Neurophysiology, Vol 76, Issue 4 2402-2411, Copyright © 1996 by APS

ARTICLES

Two functional muscle groupings during postural equilibrium tasks in standing cats

R. Jacobs and J. M. Macpherson
R. S. Dow Neurological Sciences Institute, Portland, Oregon 97209, USA.

1. This study examined the relation between electromyographic (EMG) activation and the contact force and joint torques of the left hindlimb during postural equilibrium tasks in the standing cat. It is the appropriate application of force by the limbs against the support surface that allows the animal to control its center of mass and maintain equilibrium. 2. Cats were trained to stand quietly on a moveable force platform. During quiet stance, the cat was perturbed by a platform translation in each of 12 directions evenly spaced in the horizontal plane. EMG activity of mono- and biarticular thigh muscles, three-dimensional ground reaction force under the paw (contact force), and kinematics of the hindlimb segments were recorded Net joint torques were computed using inverse dynamics. The analysis focused on the functional organization of the rapid, automatic postural response in relation to the sagittal plane contact force and joint torques. 3. The muscles of the thigh were subdivided into two functional groups, based on the relationship of the evoked response to the various components of the sagittal plane contact force or joint torques. The first group, consisting of the monoarticular and some biarticular muscles, was correlated with the vertical force component, Fz. The second group, consisting of a separate group of biarticular muscles, was correlated with the difference between knee and hip torque. This torque difference is a function of both sagittal plane force components, Fz and Fy, and is related to contact force direction. 4. It is suggested that this subdivision of muscle activations reflects a neural strategy of parallel control of the two muscle groups in relation to their influence on Fz and Fy. Such a control mechanism could be a strategy for simplifying the control of the multisegmented limb in contact force tasks such as maintaining postural equilibrium.

This article has been cited by other articles:

				G. Torres-Oviedo, J. M. Macpherson, and L. H. Ting Muscle Synergy Organization Is Robust Across a Variety of Postural Perturbations J Neurophysiol, September 1, 2006; 96(3): 1530 - 1546. [Abstract] [Full Text] [PDF]

				T. G. Deliagina, M. G. Sirota, P. V. Zelenin, G. N. Orlovsky, and I. N. Beloozerova Interlimb postural coordination in the standing cat J. Physiol., May 15, 2006; 573(1): 211 - 224. [Abstract] [Full Text] [PDF]

				M. C. Tresch, V. C. K. Cheung, and A. d'Avella Matrix Factorization Algorithms for the Identification of Muscle Synergies: Evaluation on Simulated and Experimental Data Sets J Neurophysiol, April 1, 2006; 95(4): 2199 - 2212. [Abstract] [Full Text] [PDF]

				L. H. Ting and J. M. Macpherson A Limited Set of Muscle Synergies for Force Control During a Postural Task J Neurophysiol, January 1, 2005; 93(1): 609 - 613. [Abstract] [Full Text] [PDF]

				L. H. Ting and J. M. Macpherson Ratio of Shear to Load Ground-Reaction Force May Underlie the Directional Tuning of the Automatic Postural Response to Rotation and Translation J Neurophysiol, August 1, 2004; 92(2): 808 - 823. [Abstract] [Full Text] [PDF]

				I. N. Beloozerova, P. V. Zelenin, L. B. Popova, G. N. Orlovsky, S. Grillner, and T. G. Deliagina Postural Control in the Rabbit Maintaining Balance on the Tilting Platform J Neurophysiol, December 1, 2003; 90(6): 3783 - 3793. [Abstract] [Full Text] [PDF]

				P. Saltiel, K. Wyler-Duda, A. D'Avella, M. C. Tresch, and E. Bizzi Muscle Synergies Encoded Within the Spinal Cord: Evidence From Focal Intraspinal NMDA Iontophoresis in the Frog J Neurophysiol, February 1, 2001; 85(2): 605 - 619. [Abstract] [Full Text] [PDF]

				C. C. Raasch and F. E. Zajac Locomotor Strategy for Pedaling: Muscle Groups and Biomechanical Functions J Neurophysiol, August 1, 1999; 82(2): 515 - 525. [Abstract] [Full Text] [PDF]

				A. L. Ridgel, S. F. Frazier, R. A. Dicaprio, and S. N. Zill Active Signaling of Leg Loading and Unloading in the Cockroach J Neurophysiol, March 1, 1999; 81(3): 1432 - 1437. [Abstract] [Full Text] [PDF]

				S. M. Henry, J. Fung, and F. B. Horak EMG Responses to Maintain Stance During Multidirectional Surface Translations J Neurophysiol, October 1, 1998; 80(4): 1939 - 1950. [Abstract] [Full Text] [PDF]

				L. Bianchi, D. Angelini, G. P. Orani, and F. Lacquaniti Kinematic Coordination in Human Gait: Relation to Mechanical Energy Cost J Neurophysiol, April 1, 1998; 79(4): 2155 - 2170. [Abstract] [Full Text] [PDF]