The effect of cognitive behaviour therapy on central activation failure in Chronic Fatigue Syndrome

Chronic fatigue syndrome (CFS) is defined by severe fatigue of at least 6
months duration that substantially interferes with occupational, educational,
social and personal activities, is not alleviated by rest, and is accompanied
by at least four of eight specific symptoms (Fukuda et al.). Despite ample
research into the etiopathology of CFS, physiological processes playing a role
in this disease remain uncertain.
Experienced fatigue has been defined as a difficulty in initiating or
sustaining voluntary activities (Chaudhuri et al. 2004). An element of
experienced fatigue is physiological fatigue, i.e. a reduction in muscle force
during a prolonged muscle contraction (Gandevia 2001).
This loss of force is caused by fatigue in the muscle itself and by a decline
in activation of the muscle by the central nervous system. Both can be measured
by stimulating a muscle with short electrical pulses during a prolonged
contraction. Decline in the force exerted during electrical stimulation is
caused by fatigue of the muscle itself, whereas decline in the force exerted
without electrical stimulation is caused by a decline in activation of the
muscle by the central nervous system. The difference between both represents
the failure of the nervous system to activate the muscle and is therefore
called Central Activation Failure (CAF).
An earlier study of our department (Schillings et al. 2004) found that in CFS
patients, central activation failure was already present at the start of
sustained voluntary muscle contraction. This could be caused by changed
perception, impaired concentration, reduced effort and physiologically defined
changes. As a result, demands on the muscle are lower and peripheral fatigue is
decreased.
Cognitive Behaviour Therapy (CBT) is an effective treatment for CFS: it leads
to a significant reduction of fatigue and disabilities (Whiting et al. 2001).
About 70% of treated patients benefit from this therapy and do no longer meet
criteria for CFS (Knoop et al. 2007). It is conceivable that successful CBT
leads to a normalization of CAF, while CAF is unaffected by unsuccessful CBT.
Therefore we would like to measure central activation during sustained Maximal
Voluntary Contraction (MVC) before and after CBT for CFS.

The aim of this study is to determine whether treatment outcome in CBT for CFS
is related to Central Activation Failure.

In this observational study, participants will perform a maximal voluntary
contraction of the m. Biceps brachii for two minutes. During the MVC, the m.
biceps brachii will be stimulated electrically every 15 seconds to measure
central activation failure. MFVC will be measured with surface-EMG.These
measurements will be done both before and after cognitive therapy.

Patients do not have to make extra visits to the study site because
measurements will be combined with therapy-related visits. The two measurements
will take about 1.5 hour each. Patients do not have to fill in extra
questionnaires, besides those for usual clinical care.
The risk of these measurements are minimal. The electrical stimulation and the
MVC itself may be somewhat painful but we think the burden for participants is
acceptable. Results of this study may give more insight into the nature of
Chronic Fatigue Syndrome and the process through which Cognitive Behaviour
Therapy exerts its therapeutic effect.