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epratt96
06-29-2010, 01:07 AM
Hi,

At our clinical gait lab we have an 8 channel Aurion Zerowire surface EMG system, and have recently started to collect sEMG data during gait to form our normal adult database. So far we have struggled to collect ‘clean’ sEMG data from the Rectus Femoris (RF), and were wondering if anyone with experience of using sEMG for measuring timing of the quadriceps could offer us some advice/tips etc.

A brief summary of our protocol - We used the SENIAM guidelines for electrode placement, but simply prepped the skin using alcohol wipes. We checked our electrode position (extend knee from sitting position with resistance) and got strong signals, however data during gait had a lot of noise associated with it and no distinct pattern. The sampling rate was 2000Hz, data was bandwidth filtered 20-500Hz , and we displayed both raw and linear enveloped data (25ms bins, GCV woltring filter). As an aside, we are currently completing work looking at the affect of different filtering and cut-off parameters but are using the above as a starting point.

The signals seen could of course be because the ‘normals’ tested don’t use their RF much, however this raises a very important point for us. Our main clinical aim is to use sEMG is to know when (and indeed if) the RF and hamstrings are firing in the gait cycle. How can we be confident enough in our data to conclude this?

I have done a literature search on the use of sEMG to measure RF. So far I have read Zipp et al. 1982, Rainoldi et al. 2004, Ounpuu et al. 1997 and Byrne et al. 2005. There are a few contradictions, and the latter two papers have different conclusions whether sEMG measurement of RF activity is possible reliably. There does seem evidence to change our placement check for RF to being voluntary hip flexion in the sitting position (against resistance) if this is possible for the patient. We could also consider shaving patients legs (although we would prefer not to) and measuring the vasti (lateralis or medialis) instead if these produce more reliable signals practically (which is suggested by Rainoldis work).

Any help/thoughts would be much appreciated.

Many Thanks

Emma

Emma Pratt
Clinical Scientist
Sheffield Teaching Hospitals Foundation Trust
Clinical Engineering (Room I100)
Royal Hallamshire Hospital
Glossop Rd
Sheffield S10 2JF
Emma.Pratt@sth.nhs.uk
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