Changes in neurophysiological processing from distal upper limb muscles in response to motor skill acquisition and cervical extensor muscle fatigue


Following tracing a sinusoidal waveform with the thumb, differential changes are seen in short latency (<30 ms) somatosensory evoked potentials (SEPs) in subclinical neck pain vs. healthy controls (Andrew et al, 2018). Neck fatigue alters upper limb proprioception (Zabihhosseinian et al, 2015) and is likely to alter the body schema, with the potential to impact upper limb performance accuracy. This study aimed to determine the differential effects of cervical extensor muscle (CEM) fatigue on motor training acquisition, and retention; and on sensory processing from distal upper-limb muscles, via median nerve SEP amplitudes. Twenty-four healthy individuals were randomly assigned to either CEM fatigue or control group. SEPs were recorded, in response to median nerve stimulation at wrist (1500 sweeps), at baseline and post motor training. Both groups completed a novel motor tracing task with their right thumb. Task retention was measuring 24 hours later. Both groups improved following motor acquisition (P=.001) and retention (p=.001), with less improvement for the fatigue group. Post motor acquisition, the fatigue group showed significantly increased amplitudes of the N24, N30 and P25 SEP peaks, while the control group only showed an increase in the N24. Results indicate that neck fatigue impair upper limb motor acquisition and leads to differential changes in SEP peak amplitudes related to sensorimotor integration. The increased potential for CEM fatigue due to technology use with the neck held in a flexed posture indicates that this research has important clinical and workplace implications.

Acknowledgments: Natural Science and Engineering Research Council of Canada (NSERC), Ontario Graduate Scholarships, and University of Ontario Institute of Technology