Voluntary Muscle Activation and Exercise Recovery in CFS - Taub (Master's thesis)

[Dolphin]

Couldn't find full text on the net for free (but perhaps some can access it).

Voluntary Muscle Activation and Exercise Recovery in Chronic Fatigue Syndrome
by Taub, Elana, M.Sc., University of Calgary (Canada), 2010, 135 pages; AAT MR69608

Abstract (Summary)

Individuals with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) commonly experience symptom exacerbations after exercise (post-exertional malaise). Interpolated twitch analysis and electromyography were used to quantify central and peripheral fatigue in the right quadriceps femoris muscles of 9 women with ME/CFS and 9 sedentary but otherwise healthy control subjects (CON) before and after 2 incremental cycle ergometer exercise tests to exhaustion 24 hrs apart. Peak O 2 consumption, heart rate and aerobic power were the same in both groups and on both tests. Although baseline MVC was similar (ME/CFS 85.124.1 N m; CON 90.519.4 N m), MVC was significantly decreased in ME/CFS after the 2 nd test (p=0.040). Voluntary activation ratio was lower in ME/CFS than CON (81.9 vs. 93.2 %, p=0.012) but there was no group by time interaction, suggesting that central fatigue did not cause the decreased MVC. Instead, low-frequency fatigue combined with central activation failure may explain the results and may contribute to post-exertional malaise.

Indexing (document details)
School: University of Calgary (Canada)
School Location: Canada
Source: MAI 49/03, Jun 2011
Source type: Dissertation
Subjects: Health sciences, Kinesiology
Publication Number: AAT MR69608
ISBN: 9780494696088
Document URL: http://proquest.umi.com/pqdlink?did=2260545911&Fmt=7&clientI d=79356&RQT=309&VName=PQD
ProQuest document ID: 2260545911

 

[eric_s]

Thanks. I don't really understand this part

but there was no group by time interaction, suggesting that central fatigue did not cause the decreased MVC. Instead, low-frequency fatigue combined with central activation failure may explain the results and may contribute to post-exertional malaise.

When i first read the title, i was scared that it's another paper that said "you're alright, don't worry". Interesting that at baseline the values were similar, so it seems you really need to do the repeat challenge, to see something with that kind of testing. 9 subjects is of course a bit small a sample size though, i guess. It would be interesting to always also check some other measures if you put people through such a test, i think. Things like NK cell function, mitochondrial function, cell free DNA or whatever...

 

[eric_s]

I remeber Tessie Tess said some time ago she wanted to make that kind of testing available in Quebec. Maybe she could find some people to help with that where that paper came from...

 

[eric_s]

Hm, wait... Doesn't this contradict what the Pacific Fatigue Lab people have reported

Peak O 2 consumption, heart rate and aerobic power were the same in both groups and on both tests. Although baseline MVC was similar (ME/CFS 85.124.1 N m; CON 90.519.4 N m),

?
I didn't realize this, when i read the text 10 minutes ago, because i just woke up...

 

[Dolphin]

Hm, wait... Doesn't this contradict what the Pacific Fatigue Lab people have reported?

I reckon it's the Ellie Stein study. I read somewhere before (piece by Cort?) that they hadn't replicated the Pacific Fatigue Lab study.

 

[eric_s]

I googled a bit and found this:

http://aboutmecfs.org.violet.arvixe.com/Conf/IACFS09Exercise.aspx

In this article about the 2009 IACFS/ME conference Cort mentions the studies that couldn't confirm the Pacific Fatigue Lab's findings.

And i also found this: http://sacfs.asn.au/download/cardio.pdf
It's from 2001, but could still have some interesting information for some.

 

[Dolphin]

The MVC bit shows muscle weakness (to an extent) post exertion (as I understand) - but would like to see more info.

 

[Snow Leopard]

http://www.cfids-cab.org/cfs-inform/Neuroendocrin/schillings.etal04.pdf

*shrugs*

http://ptjournal.apta.org/content/86/8/1146.long (about low frequency fatigue)

 

[Valentijn]

They do seem to be rejecting the psychological explanations:

The role of motivational problems in CFS is still controversial, although some authors have argued that motivation does not seem to be changed (Gordon et al., 1999).

In our protocol, we tried to keep motivation as strong as possible in both subject groups by active verbal encouragement.

In a task originally designed to detect malingering, van der Werf et al. (2000) showed that 30% of the CFS patients obtained scores indicative of reduced effort.

Because the present study showed increased CAF in 100% rather than in about 30% of the patients, we propose that reduced effort will at least not totally account for the diminished central activation.

And they seem to be suggesting that this sort of testing could be used as a biomarker for ME/CFS:

Our data showed that all individual CFS patients, diagnosed according to the CDC criteria (Fukuda et al., 1994), could have been identified only based on their CAF value at the start of sustained contraction (.30%).

Therefore, our study does not only serve a theoretical understanding of the disease, but also provides an additional practical method that could support diagnosis.