Fatigue properties of human thenar motor units paralysed by chronic spinal cord injury

The Journal of Physiology
C S KleinChristine K Thomas

Abstract

Human muscles paralysed chronically by spinal cord injury (SCI) fatigue excessively. Whether these reductions in force reflect a decrease in the fatigue resistance of the motor units is unknown. Our aim was to determine the fatigability of thenar motor units paralysed chronically (10 +/- 2 years) by cervical SCI. Surface electromyographic activity (EMG) and force were recorded from 17 paralysed motor units (n = 7 subjects) in response to intraneural motor axon stimulation (13 pulses at 40 Hz, 1 s(-1) for 2 min). Unit force decreased progressively, reaching 8-60% of initial after 2 min, whereas both the amplitude and area of the first EMG potentials in the trains increased significantly (both P < 0.05). Thus, transmission of neural signals to the sarcolemma was effective and the reduction in force must reflect impaired processes in the muscle fibres. The median fatigue index for paralysed units (0.31), the ratio of the force at 2 min compared to the initial force, was significantly lower than that for units from control subjects (0.85, P < 0.05), but the distribution of fatigue indices for each population had a similar shape (ranges: 0.08-0.60 and 0.41-0.95, respectively). Hence, chronic paralysis did not limit the range of fati...Continue Reading

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Citations

Nov 12, 2009·Brain : a Journal of Neurology·Christine K ThomasCliff S Klein
Feb 24, 2009·Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology·Todor I ArabadzhievGeorge V Dimitrov
Aug 2, 2013·Acta Physiologica·C K ThomasI Zijdewind
Sep 10, 2014·Medicine and Science in Sports and Exercise·Anita D Christie, Nick R Miller
Jul 8, 2016·Journal of Neurophysiology·Paola ContessaJoshua C Kline
Jun 9, 2018·International Journal of Molecular Sciences·Dana M OtzelJoshua F Yarrow
Jan 31, 2014·Muscle & Nerve·Maria PapaiordanidouDavid Guiraud
Aug 26, 2009·Muscle & Nerve·Bo Biering-SørensenFin Biering-Sørensen
Apr 14, 2006·Journal of Neurophysiology·C K Häger-RossC K Thomas

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