OBJECTIVE: We have investigated the possibility of a central
basis for the complaints of fatigue and poor exercise
tolerance in subjects with chronic fatigue syndrome (CFS).
METHODS: Transcranial magnetic stimulation of the motor cortex
was used to measure sequential changes in motor evoked
potential (MEP) amplitude, post-excitatory silent period (SP)
duration and twitch force of the biceps brachii muscle during
a 20% maximum isometric elbow flexor contraction maintained to
the point of exhaustion. Ten patients with post-infectious CFS
and 10 age- and sex-matched control subjects were studied.
Results were analysed using non-parametric repeated measures
analysis of variance (Friedman’s test) and Mann-Whitney
U-tests for intra- and inter-group comparisons respectively.
RESULTS: Mean endurance time for the CFS group was lower
(13.1+/-3.2 min, mean +/- SEM) than controls (18.6+/-2.6 min,
P < 0.05) and CFS subjects reported higher ratings of
perceived exertion. During the exercise period MEP amplitude
and SP duration increased in both groups but to a lesser
extent in CFS subjects. Interpolated twitch force amplitude
also increased during exercise, being more pronounced in CFS
CONCLUSION: The findings are in keeping with an
exercise-related diminution in central motor drive in
association with an increased perception of effort in CFS.
Sacco P, Hope PA, Thickbroom GW, Byrnes ML, Mastaglia FL