Fatigue of muscles weakened by death of motoneurons

Christine K. Thomas, Inge Zijdewind

Research output: Contribution to journalReview articlepeer-review

55 Scopus citations


Weakness is a characteristic of muscles influenced by the postpolio syndrome (PPS), amyotrophic lateral sclerosis (ALS), and spinal cord injury (SCI). The strength deficits relate to changes in muscle use and to the chronic denervation that can follow the spinal motoneuron death common to these disorders. PPS, ALS, and SCI also involve variable amounts of supraspinal neuron death, the effects of which on muscle weakness remains unclear. Nevertheless, weakness of muscle itself defines the functional consequences of these disorders. A weaker muscle requires an individual to work that muscle at higher than usual intensities relative to its maximal capacity, inducing progressive fatigue and an increased sense of effort. Little evidence is available to suggest that the fatigue commonly experienced by individuals with these disorders relates to an increase in the intrinsic fatigability of the muscle fibers. The only exception is when SCI induces chronic muscle paralysis. To reduce long-term functional deficits in these disorders, studies must identify the signaling pathways that influence neuron survival and determine the factors that encourage and limit sprouting of motor axons. This may ensure that a greater proportion of the fibers in each muscle remain innervated and available for use.

Original languageEnglish (US)
Pages (from-to)21-41
Number of pages21
JournalMuscle and Nerve
Issue number1
StatePublished - Jan 2006


  • Amyotrophic lateral sclerosis
  • Motor axon sprouting
  • Muscle atrophy
  • Postpolio syndrome
  • Spinal cord injury

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)


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