SOME NEUROMUSCULAR ASPECTS OF HUMAN MOVEMENTS AND THE CONSEQUENCES FOR THE MUSCULAR REHABILITATION

  • Dietmar Schmidtbleicher

Abstract

INTRODUCTION After a review. of training regimen normally used in sports and rehabilitation exercises the importance of the configuration of the stimuli with respect to the neuronal and muscular adaptations are discussed. Additionally it is important if rotatoric or translatoric movements are practiced and which type of muscle action is exercised: concentric, isometric, eccentric, stretch-shortening cycles with which contraction and movement velocity (for example isokinetic) or if combinations of the different possibilities are performed. METHODS The described investigations are based on dynamography, kinemetry, electro-myography, muscle biopsie techniques, computertomography, electrogoniometry and accelerometry as well as biochemical methods and others. RESULTS In training practice it is often believed that strength training merely calls for changes in enzymatic quantity or quality within the muscle which ultimately results in muscle cross-sectional increases. This can be true for different fiber types. Beside these effects the adaptation of the nervous system to the training stimulus plays an important role. Longitudinal studies on humans showed clear evidence that following a high intensity strength training there is an improvement in the ability to quickly mobilize greater innervations activities (faster recruitment, increases firing rate of motor units and more synchronized discharge of motoneurons). Another possibility for the improvement of the movement depends on the relation between excitatory and inhibitory mechanisms for one muscle for a specific movement. This can be shown very clearly in stretch-shortening cycles for inhibitory effects as well as for excitatory a. phenomena. Those inhibitory effects occur if the stretching load is to high. Consequently trained subjects are able to tolerate higher stretch loads. Same is true for unskilled and skilled persons. If subjects are fatigued or injured they also show a reduction of the EMG-pattern of the extensor muscles. In all described situations the inhibitory effects serve for a mrse regulation of the stiffness of the tendomuscular system in the initial ground contact. It is concluded that the inhibitory mechanisms are part of the dynamic performance dependent reaction, functionally serving as a protection system. A further way to improve movements results from better intermuscular coordination. lntermuscular coordination describes the ability of all muscles involved in a movement, agonists, antagonists and synergists, to cooperate wholly with respect to the aim of the movement. This type of adaptation is therefore movement specific and not transferable to another movement. CONCLUSIONS Based on the described results and con- siderations a model for neuromuscular rehabilitation is presented which involves a step-wise periodrsation of the training process. Especially movements which consist of stretch-shortening cycles must be a substantial part of the rehabilitation concept.