I need to characterize two kind of EMG electrodes and perform a comparison between them. The shape, the area of the two type are equal. I think that the best way is by passing the same EMG signal under the two pairs of electrode and record both signals. Placing the two pairs of electrode on the biceps, in the transverse direction of the muscular fiber guarantees that the two signals are (almost) equal. For my opinion, this help a lot in the offline analysis and ensure a better comparison between them. This placement runs counter the SENIAM recommendations for SEMG data collection that tell us to place the electrode in parallel way. What do you think on?
Hi Sergio Tarantino,
I am not sure whether you should place the electrodes perpendicularly across the muscle fibers. Because motor unit action potentials propagates parallel to fiber direction.
Best,
Suman
I would place them across the fiber direction instead of parrallel. You want to maximize the amount of Action potentials. When placing parrallel your signal is extra vulnerable for cross talk. And also you would have à larger delay between your electrodes which also would influence your signal structure.
for basic Reading: the abc of emg.
good luck
The SENIAM recommendations have been updated (according to a paper of the team of Prof. Merletti). The inter-distance should be fixed in the range of few millimeters and one cm to avoid spatial aliasing. In addition, small electrodes radius (2 or 3 mm) ensures a good spatial selectivity. The positioning should also be done carefully to avoid the motor plate and the myotendinous junctions. If you need to compare to kinds of electrodes, you have to respect the same protocol. For example, bipolar (or monopolar) recording with the first kind along the fiber and after, at the same place, the recording with the second kind. You repeat many time the operation at the same contraction level and perform statistical analysis.
Regards,
The Seniam recommendations are just recommendations from experienced users, no law. Even when you place two sets of electrodes close together, you will probably not find the same EMG r.m.s. value. When repeated the amplitude ratio's between sets of electrodes will probably not systematically depend on electrode type, unless the electrode areas are very different. EMG amplidudes depend very critically on anatomical details, and are thus hard to reproduce.
"Paired t-tests indicated that absolute EMG amplitude values for the parallel electrode orientation were greater (p < 0.05) than those for the perpendicular orientation at all isometric torque levels except 10% MVIC For normalized EMG amplitude values, however, there were no significant mean differences between electrode orientations."
REFER TO THIS PAPER:
THEY TRIED BOTH PARALLE AND PERPENDICUALR PLACEMENT AND SAW THE REULTS:
http://www.ncbi.nlm.nih.gov/pubmed/20405784
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