Effects of Motor Activation Strategies on the Relationship Between EMG and Force
It should be possible to predict muscle force from the electromyogram (EMG), but a general EMG-force relationship has not been identified (reviewed by Basmajian & De Luca, 1985). Apart from technical differences, it is conceivable that different motor activation strategies may result in genuinely different EMG-force characteristics (Lawrence & De Luca, 1983; Woods & Bigland-Ritchie, 1983). Motor unit (MU) action potential size may not be linearly related to twitch amplitude (see Milner-Brown & Stein, 1975). Therefore EMG amplitude will depend on whether a given level of force is generated by uniform activation of all MUs (predominant rate modulation) or by more selective activation of smaller MUs (predominant recruitment). To re-assess the role of different MU activation strategies, a preparation has now been used in which activation of MUs could be controlled precisely and in which finer details of MU activation patterns could also be manipulated.
KeywordsMotor Unit Rate Modulation Activation Strategy Motor Unit Firing Motor Unit Synchronisation
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