The estimation of MU position and MU properties from the surface EMG

Spatial topographical amplitude maps over the skin of unipolarly as w ell as of bipolarly recorded EMG interference patterns show a signifi cant shif main muscle activity from distal to proximal and from later al to medial sites of the biceps brachii with increasing contraction level. All bipolar maps and also the unipolar maps at high contractio n levels follow the single MU distributions analysed for superficial MUs. Unipolar maps for low contraction levels are not explained from single MU maps. It is concluded that MUs in the biceps brachii are no t homogeneously distributed. With increasing contraction level, more superficial MUs with more proximal and more medial innervation zones are recruited.