Confounding factors in water EMG recordings: an approach to a definitive standard.

This work presents a study on the influence of the aqueous environment on the surface EMG (sEMG) signal recorded in bipolar montage from the abductor pollicis brevis muscle, when only the forearm is immersed in water. Ten men, 30.1+/-4.0 (mean +/- SD) years old, performed ten 2-s 40% MVC isometric contractions of the abductor pollicis brevis muscle in two controlled environments (air and water, at a temperature of 32 degrees C). They were always equipped with electrodes protected with a waterproof adhesive tape. No significant variations (paired Wilcoxon test) due to the environments were observed in the median frequency of the power spectrum (MDF) and in the root mean square (RMS) value of the sEMG signal. These results allow us to assess the methodological criteria to properly record sEMG signals in water and provide the basis to explain different findings obtained by other authors.