Standardized contractions were performed by the subjects in order to normalise muscle activity. For the ED, FDI, APL and APB, maximal voluntary electrical activity (MVE) was obtained while the subject was asked to perform a 5 s maximum contraction against manual resistance. The subject performed these contractions while seated, with the forearm supported on a table surface individually adjusted to elbow height. For the trapezius muscles a submaximal reference voluntary electrical activity (RVE) was used for normalisation. The RVE was determined as the mean activity recorded while the subject was seated and abducting both arms to 90° (in the frontal plane) while holding a 1 kg dumbbell fully pronated in each hand for 15 s