Brain, Vol. 114A, No. 1, 85-98, 1991
© 1991 Oxford University Press
MUSCLE PERFORMANCE, VOLUNTARY ACTIVATION, TWITCH PROPERTIES AND PERCEIVED EFFORT IN NORMAL SUBJECTS AND PATIENTS WITH THE CHRONIC FATIGUE SYNDROME
Department of Clinical Neurophysiology, Institute of Neurological Sciences and the Departments of Immunology and Infectious Diseases, The Prince Henry Hospital and the School of Medicine, University of New South Wales Sydney, Australia
Correspondence to:
Correspondence to: Dr S. C. Gandevia, Department of Clinical Neurophysiology, The Prince Henry Hospital, PO Box 233, Matraville, Sydney 2036, Australia
The decrease in maximal force-generating capacity, the degree of central activation of the muscle, and the subjective perception of effort were measured during prolonged submaximal isometric exercise in 12 male patients suffering from the ‘chronic fatigue syndrome’ and 13 naive, healthy male subjects. Maximal voluntary isometric torque generated by the elbow flexors was measured before, and at 5 min intervals during an endurance sequence of 45 min of repetitive isometric contractions (6 s duration, 4 s rest interval) producing 30% of the initial maximal voluntary torque. Electrical stimuli were also delivered to the elbow flexors to measure the contractile force in the intervals between voluntary contractions. The degree of central motor activation during maximal voluntary contractions was assessed using a sensitive method of twitch interpolation. In addition, the perceived effort required to achieve the target submaximal contractions was recorded using a standardized self-report scale. A high degree of central activation was achieved in maximal contractions during the endurance sequence both in the patients (mean of maximal force 93.6% SD 7.8%), and in the control subjects (mean 90.9%; SD 9.5%). The relative torque produced by either voluntary or electrically stimulated contractions was not significantly different between patients and control subjects throughout the test. There was no significant difference in the perceived exertion between the patients and control subjects. These findings support the concept that neither poor motivation, nor muscle contractile failure is important in the pathogenesis of ‘fatigue’ in patients with the chronic fatigue syndrome.
Received July 20, 1989. Revised December 19, 1989. Accepted January 9, 1990.