EMG placement

[Andy Roberts]

We are currently setting up a study looking at EMG activity of the Tibialis anterior (TA) and Gastrocnemius medialis (GM). The most up to date guidelines for placement come from a 2009 paper (A method for better positioning bipolar electrodes for lower limb EMG recordings during dynamic contractions (Sacco 2009). We have tried to implement these however the guidelines are not fully clear. Has anyone had any experience with using these?

For both muscles, do you follow the SENIAM guidelines for starting posture (supine/sitting for TA, Lying on the belly with the face down, the knee extended and the foot projecting over the end of the table for the GM)?

For the TA, do you have any recommendations for laterality or should the electrodes be placed directly on the line described in the paper (47.5% the distance from tuberosity of tibia to inter-malleolus line, starting from the tuberosity of tibia).

For the GM (38% the distance from the medial side of the popliteal cavity to the medial side of the Achilles tendon insertion, starting from the Achilles tendon) we are having difficulty defining the exact point on the popliteal cavity and also how the Achilles insertion position is defined (a recent article shows that this is not as described in anatomical textbooks). Is anyone able to provide a bit more detail on these descriptions (I also checked the Rainoldi paper that also uses these definitions but could not find any further details)?

Thanks

Andy

[Andy Roberts]

Re: EMG placement

I have had a reply from the authors of the study:

In their study, 'the recommended place for TA was 47.5% of the distance from between the tip of the fibula and the tip of the medial malleolus, starting from the the tip of the fibula, placing the electrodes right in the center of this line virtually traced. This muscle location follow the SENIAM recommendation. The distance from tuberosity of tibia to inter-malleolus line to find TA electrodes positioning was used by Rainold et al. (2004) in their study.'

They 'followed supine posture for TA placement and prone posture with the foot projecting over the end of the table, keeping the ankle in 90 degrees for GM.'

They 'agreed that all anatomical reference points are not exact and vary greatly among subjects. But, we tried to be as rigorous as we could in palpation procedures and we use as reference:
(i) the most medial site of the semitendinosus and semimembranosus muscles tendons where it intersects with popliteal cavity;
(ii) we performed palpation of both gastroc muscles following them down till we touched the calcaneous tendon and then we referred as the calcaneous insertion where the tendon join the calcaneus bone.'

[Mark Goss-Sampson]

Re: EMG placement

Hi Andy
We have had no problems with the SENIAM recommendations for good sEMG recordings - I believe that if you are rigorously consistent each time within and between subjects you can't really go wrong. Obviously slightly different if you are using arrays for conduction velocity.
Regards
Mark