Cancer-Related Fatigue (CRF) and Chronic Fatigue Syndrome (CFS) are common, yet their pathophysiology is poorly understood. Aetiology may be central or peripheral and originate anywhere from the brain to muscle fibre. Studies have shown a dissociation between brain and muscle signals during voluntary muscle fatigue1,2,3. This suggests weakened corticomuscular coherence.
To objectively evaluate the effect of muscle fatigue on corticomuscular coherence by determining EEG-EMG coherence during a fatiguing motor task.
We hypothesize that corticomuscular coherence in βeta-band frequency would decrease significantly with fatigue in CRF and CFS compared to healthy controls (HC).
12 newly diagnosed, pre-treatment, non-small cell lung cancer CRF, 12 CFS and 12 HC were enrolled. Participants completed a (subjective) Brief Fatigue Inventory (BFI) and performed a sustained isometric forearm contraction (Flexor Carpi Ulnaris (FCU) & Flexor Carpi Radialis (FCR) muscles) at 30% maximal level (MVC) until failure. Endurance Time (ET) was noted. Task evaluated in two stages; mild & severe fatigue. EEG-EMG β-band frequency (associated with voluntary motor activity) coherence and power spectrum in each stage was computed.
CRF and CFS had weaker MVC and earlier perceived exhaustion than HC (Table 1). EMG power (but not EEG) increased while coherence at lower βeta-band (15-25 Hz) significantly decreased in severe fatigue compared to mild fatigue (Figure 2).
CRF was associated with weakened corticomuscular coherence in a sustained submaximal motor activity at lower βeta-band frequencies. This suggests central neural mechanisms contribute to both CRF (and CFS) with associated performance impairment. Interventions to improve coherence may reduce fatigue.
1 Yang, Q., Fang, Y., Sun, C. K. et al., "Weakening of functional corticomuscular coupling during muscle fatigue," Brain Res, vol. 1250, pp. 101-12, Jan 23 2009.
2 Conway BA, Halliday DM, Farmer SF, Shahani U, Maas P, Weir AI, et al. Synchronization between motor cortex and spinal motoneuronal pool during the performance of a maintained motor task in man. J Physiol. 1995;489(Pt 3):917–24