Follow-up on the PWCft

In my last post, I said I would defer to an EMG expert with regards to the PWCft test. So, I did.

I fired off an email to one of my former office-mates while I was in grad school, who was doing her PhD in Kinesiology, and is a content-expert in EMG studies. She didn’t have a lot of time to give a really detailed answer, but here’s what she said:

“- the EMG-force relationship is very tricky and non-linearly related. People are very sceptical to relate the two because of limitations like effort of the subject, the unquantified nonlinearity of the relation, attenuation of the surface EMG signal by adipose tissue and EMG signal crosstalk. Some researchers are currently trying to quantify the relationship, but most seem sceptical.

– NM fatigue – I know that James Wakeling did both running and cycling EMG experiments that looked at how well surface EMG can predict “fatigue”. He was very cautious in the description, so that he stated they were quantifying a decrease in the signal amplitude, or a shift in the frequency of the EMG signal with muscular fatigue. Relating subsequent trials with a t-test would make me a bit nervous, as you would need to control many variables like, electrode placement (especially if over several days), sweat has been shown to attenuate
signals and can cause electrode movement, etc., etc.”

Isn’t collaboration wonderful?