Muscular co-operation during joint stabilisation, as reflected by EMG

Abstract

The experiment that was carried out consisted of subjects pushing an external object (a heavy pendulum) using stable and unstable handles of increasing mobility. Using this protocol it was possible to distinguish between the motor and stabilising functions of the muscles of the upper extremity. The motor functions were realised by the extensors of the upper extremity, whereas stabilising functions were effected by the muscles spanning the wrist joint. The experiment involved synchronised measurements of the electromyographic (EMG) activity of the muscles in question together with several mechanical quantities revealed against the external object: force, velocity and power. As a result, the instantaneous and global EMG contributions of the extensor and stabilising muscles were determined. It was found that it is the equilibrium state of the object being set in motion and not its mobility (expressed in terms of the number of degrees of freedom) that influences the forces produced by individual muscles. We also suggest that the realisation of stabilising functions by skeletal muscles is a necessary condition of performing any voluntary and co-ordinated movement.

Effects of muscular activation patterns on the ankle joint stabilization: An investigation under different Degrees of Freedom

“…Furthermore, the GM showed patterns, which depended on the dynamic aspects of the movement, reflected in similar delayed onsets of activity in the dynamic conditions (1 and 3 DoF) as compared to the static 0 DoF condition. This sequence is in accordance to studies on the wrist (Kornecki et al, 2001) confirming the idea that not the mobility of the object being set in motion influences the forces produced by individual muscles. Especially multiarticular muscles like the GM bear multiple functions since they operate at several joints and thus develop different torques at the spanned joints simultaneously (Kornecki et al, 2001;van Ingen Schenau et al, 1987).…”

“…This resulted in an advanced onset of stabilizing muscles relative to force producing muscles (Kornecki et al, 2001). These adjustments to changing biomechanical task demands arise, since muscles can cause destabilizing or counterproductive movements at some joints when they are contracted to create desired movements at other joints (Kornecki et al, 2001). In order to control the forces produced by muscles during movement only a certain fraction of the possibly available mobility of the motor system is needed at a given time (Kornecki 1992).…”

“…In addition, it was shown that in the upper extremities the temporal coordination of muscles is phase shifted relative to each other when task demands are changing. This resulted in an advanced onset of stabilizing muscles relative to force producing muscles (Kornecki et al, 2001). These adjustments to changing biomechanical task demands arise, since muscles can cause destabilizing or counterproductive movements at some joints when they are contracted to create desired movements at other joints (Kornecki et al, 2001).…”

“…Addressing the problem of the control of force exertion on an external object during multijoint tasks, Kornecki (2001) suggested that the equilibrium state of the external object and not its mobility influences the forces produced by individual muscles. Together, the question is raised of whether the solution to the problem of controlling different DoF leads to specific changes in the temporal coordination patterns and gain of selected muscles when influenced by an external system of variable Degrees of Freedom.…”

Fonksiyonel Denge Antrenmanının Adölesan Futbolcuların Statik ve Dinamik Denge Performansları Üzerine Etkileri

“…It has been concluded that performing exercises on unstable surfaces enhances joint stabilization by increasing the synergy between muscles (Anderson, 2004). Furthermore, Kornecki et al (2001) emphasized the importance of increased stabilization functions for performing voluntary and coordinated movements. In this regard, the positive impact of functional balance training on training group seemed to transfer the force produced by muscles to the ball rather than stabilizing posture.…”