Quantitative EMG and Biomechanics
Lippold (1952) was a pioneer in studying relationships between the surface EMG and muscle force. Since then, an easy recording of surface EMG and close relation between muscle force and integrated EMG under isometric contraction, attract investigators to searching for force-EMG quantitative relationships. The general force-EMG relationships, however, are still not obtained probably due to incomplete knowledge of EMG quantitative characteristics. The greater the number of active fibres the greater both the integrated EMG and muscle force. The opposite statement is, however, not true because not only the number of fibres producing extracellular potentials affects the surface EMG, but so does the profile of intracellular action potential (IAP) along each fibre. Could variations in the IAP profile induce significant changes in the motor unit potentials (MUPs) and thus in the EMG signals?
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