The contribution of single motor units of the biceps brachii muscle in man to the momentum in elbow flexion.
The attempt of evaluation of motor unit in vivo force in biceps brachii muscle in man shows a methodological important fact: On principle it is impossible to measure or to calculate the contribution of a single motor unit to the force output of a certain muscle. Most of the physiological data of motor units are indicated as forces measured in isolated muscles. The effect of a muscular action in joints is a momentum always. The way from muscular force to the momentum in the joint is a multidimensional and nonlinear one. Moreover some synergistic muscles act upon one joint in each case. Because we can't know their current contribution to the summarized momentum in the joint which can be measured only, it is impossible to estimate the percentage of the force of one muscle in the synergistic ensemble. It is not possible finally to calculate exactly the percentage of the single motor unit force inside one muscle, because we have motor units of different extend. An exact strategy for estimation of momenta is shown including the steps of uncertainty for calculation.
Ebert
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Carl-Ludwig-Institute of Physiology, Karl-Marx University, Leipzig, GDR.
D004550:Elbow / Q000294:innervation / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D004594:Electrophysiology; D006801:Humans; D066298:In Vitro Techniques; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction; D009132:Muscles / Q000294:innervation / Q000502:physiology*