Brain and nerves

Can recovery of peripheral muscle function predict cognitive task performance in chronic fatigue syndrome with and without fibromyalgia?


Ickmans K, Meeus M, De Kooning M, Lambrecht L, Pattyn N, Nijs J


Pain in Motion Research Group, Department of Human Physiology and Physiotherapy, Faculty of Physical Education and Physiotherapy, Vrije Universiteit Brussel, Brussels, Belgium


Both good physical and cognitive functioning have a positive influence on the execution of activities of daily living. Patients with chronic fatigue syndrome (CFS) as well as patients with fibromyalgia have marked cognitive deficits. Furthermore, a good physical and functional health status may have a positive impact on a variety of cognitive skills – a link that has been observed in young and old individuals who are healthy, although evidence is limited in patients with CFS.


The purpose of this study was to examine whether recovery of upper limb muscle function could be a significant predictor of cognitive performance in patients with CFS and in patients with CFS and comorbid fibromyalgia. Furthermore, this study determined whether cognitive performance is different between these patient groups.


A case–control design was used.


Seventy-eight participants were included in the study: 18 patients with CFS only (CFS group), 30 patients with CFS and comorbid fibromyalgia (CFS+FM group), and 30 individuals who were healthy and inactive (control group) were studied. Participants first completed 3 performance-based cognitive tests designed to assess selective and sustained attention, cognitive inhibition, and working memory capacity. Seven days later, they performed a fatiguing upper limb exercise test, with subsequent recovery measures.


Recovery of upper limb muscle function was found to be a significant predictor of cognitive performance in patients with CFS. Participants in the CFS+FM group but not those in the CFS group showed significantly decreased cognitive performance compared with the control group.


The cross-sectional nature of this study does not allow for inferences of causation.


The results suggest that better physical health status could predict better mental health in patients with CFS. Furthermore, they underline disease heterogeneity, suggesting that reducing this factor in future research is important to better understand and uncover mechanisms regarding the nature of diverse impairments in these patients.


Physical Therapy. 2014 Apr; 94(4): 511-22

Comment by ME Research UK

This is a companion publication to a previous report in the European Journal of Clinical Investigation, in which Dr Kelly Ickmans (ME Research UK research fellow at Vrije Universiteit Brussel) reported that upper limb muscle recovery was significantly slower in ME/CFS patients with fibromyalgia than healthy people (muscle strength was still recovering 30–45 minutes after the exercise). See our short comment, Recovery of upper limb muscle function.

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