Does local immersion in thermo-neutral bath influence surface EMG measurements? Results of an experimental trial.

ABSTRACT

This study investigated the effect of water immersion on surface electromyography (EMG) signals recorded from the brachioradial muscle of 11 healthy subjects, both in a dry environment and a thermo-neutral forearm bath (36 degrees C). EMG measurements were registered in a sitting position, using waterproof electrodes under 3 conditions relaxed muscle, maximum voluntary isometric contraction (MVC, 1s, grip test) and 70% of the MVC (5 s). In relaxed muscle, mean EMG values were significantly higher under immersion compared to the dry conditions (dry 5.4+/-3.6 microV; water 19.5+/-14.9 microV; p=0.014). In maximum voluntary isometric contraction, there was a significant difference, though not in the same direction (dry 145.9+/-58.9 microV; water 73.2+/-35.0 microV; p=0.003). Under 70% MVC, there was no difference between wet and dry conditions (dry 102.4+/-75.0 microV; water 100.4+/-65.3 microV; p=0.951). Results suggest that dry and underwater conditions influence EMG readings; however, the results are inconsistent. These findings indicate additional influences on resting muscle activity, as well as MVC. Further measurements with other muscle groups and different types of immersion are needed to clarify conflicting observations.