Theoretical basis for patterning EMG amplitudes to assess muscle dysfunction.

A theoretical basis for assessing muscle dysfunction due to sprain/strain injuries is presented. We propose that muscle tissue trauma results in an alteration in the patterns of neural recruitment, a reduction in the force-generating capability of the injured muscle, and/or pain sensations. Furthermore, a lower than normal recruitment of motoneuron pools in the injured area can result in elevated recruitment levels from compensating motoneuron pools for a given motor task. It is proposed that these changes in motoneuron recruitment can be readily apparent in the ratios of EMG amplitudes among multiple pairs of muscles associated kinoffologically with the affected muscle. Chronic compensating actions, such as those resulting from faulty neural feedback of the force-length-velocity relationships for a stretched tendon or muscle unit, could cause further injuries. It is proposed that consistent and valid measures of ratios of EMG amplitudes between many muscle pairs acquired for well-defined motor tasks can be used to facilitate diagnoses and direct treatment strategies for sprain/strain injuries and pain.