Upper and middle trapezius during writing at a keyboard without forearm support.

Right and left map of the distribution of the average rectified value (ARV) of the differential longitudinal signal on the surface of the upper and middle trapezius. Medial region with respect to the innervation zone. ARV is computed on epochs of 0.125s (1/8s).

Grid of 5x13 electrodes with Ø=3mm and inter-electrode distance = 8mm (32 x 96 mm).

Acquisition rate: 8 frames/s Reproduction rate: 24 frames/s with interpolated images.

Color scale: red = 30µV, dark blue = 0µV.

Note the activation of the upper part of the trapezius.