Motor units in incomplete spinal cord injury: electrical activity, contractile properties and the effects of biofeedback.

Stein, Richard B.; Brucker, B.; Ayyar, D. R.

doi:10.1136/jnnp.53.10.880

Cited by 39 publications

(39 citation statements)

References 16 publications

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“…4A), as found in control muscles. 19 These data were also consistent with recruitment of weak to strong units reported for thenar muscles after SCI 25 and other muscles after reinnervation 8 or various central and peripheral nervous system disorders. 5,18,34 In these latter cases, use-dependent changes were suggested to explain much of the recovery of recruitment by increasing force.…”

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confidence: 84%

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Motor unit forces and recruitment patterns after cervical spinal cord injury

1997

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supporting

confidence: 84%

“…36 After incomplete spinal cord injury, human thenar motor unit twitch forces were similar to control data. 25 In most of these studies force was examined in muscles that were innervated from spinal segments well below the level of injury. But in humans, damage to the cervical cord often occurs at C5 or C6, close to the triceps brachii motor pool.…”

mentioning

confidence: 99%

Motor unit forces and recruitment patterns after cervical spinal cord injury

1997

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“…Operant conditioning training induces neuroplasticity in supraspinal and spinal reflex pathways. Such training increases voluntary EMG responses (Brucker and Bulaeva 1996;Seymour and Bassler 1977;Stein et al 1990) and firing rates of spared motor units (Stein et al 1990) after motor-incomplete SCI and decreases stretch reflex excitability in individuals with and without spasticity (Evatt et al 1989;Segal 1997;Wolf and Segal 1996). Successful SOL H-reflex suppression in animals (Wolpaw and Herchenroder 1990;Chen 2001, 2006) and humans (Thompson et al 2006(Thompson et al , 2013 provides clear evidence of activity-dependent plasticity in spinal circuitry induced by operant conditioning training.…”

mentioning

confidence: 96%

Operant conditioning to increase ankle control or decrease reflex excitability improves reflex modulation and walking function in chronic spinal cord injury

Manella

Roach

Field-Fote

2013

Journal of Neurophysiology

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Ankle clonus is common after spinal cord injury (SCI) and is attributed to loss of supraspinally mediated inhibition of soleus stretch reflexes and maladaptive reorganization of spinal reflex pathways. The maladaptive reorganization underlying ankle clonus is associated with other abnormalities, such as coactivation and reciprocal facilitation of tibialis anterior (TA) and soleus (SOL), which contribute to impaired walking ability in individuals with motor-incomplete SCI. Operant conditioning can increase muscle activation and decrease stretch reflexes in individuals with SCI. We compared two operant conditioning-based interventions in individuals with ankle clonus and impaired walking ability due to SCI. Training included either voluntary TA activation (TA↑) to enhance supraspinal drive or SOL H-reflex suppression (SOL↓) to modulate reflex pathways at the spinal cord level. We measured clonus duration, plantar flexor reflex threshold angle, timed toe tapping, dorsiflexion (DF) active range of motion, lower extremity motor scores (LEMS), walking foot clearance, speed and distance, SOL H-reflex amplitude modulation as an index of reciprocal inhibition, presynaptic inhibition, low-frequency depression, and SOL-to-TA clonus coactivation ratio. TA↑ decreased plantar flexor reflex threshold angle (-4.33°) and DF active range-of-motion angle (-4.32°) and increased LEMS of DF (+0.8 points), total LEMS of the training leg (+2.2 points), and nontraining leg (+0.8 points), and increased walking foot clearance (+ 4.8 mm) and distance (+12.09 m). SOL↓ decreased SOL-to-TA coactivation ratio (-0.21), increased nontraining leg LEMS (+1.8 points), walking speed (+0.02 m/s), and distance (+6.25 m). In sum, we found increased voluntary control associated with TA↑ outcomes and decreased reflex excitability associated with SOL↓ outcomes.

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“…The intramuscular EMG signal represents the final output of the motoneuron pool and so provides a direct view of neural function at the spinal level. [14][15][16] In particular, EMG signals from muscles affected by SCI can show reduced numbers of active motor units (MUs) and increased motor unit action potential (MUAP) amplitudes, which are signs of motoneuron loss and subsequent collateral reinnervation, and irregular recruitment and firing patterns, which can indicate impairment of the descending or peripheral drive to the motoneuron pool. We studied 4 individuals with C5, C6, or C7 level SCI to explore the use dynamometry and quantitative EMG for characterizing motor resources in their triceps brachii muscles.…”

mentioning

confidence: 99%

Triceps Brachii in Incomplete Tetraplegia: EMG and Dynamometer Evaluation of Residual Motor Resources and Capacity for Strengthening

Johanson

Lateva

Jaramillo

et al. 2013

Topics in Spinal Cord Injury Rehabilitation

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cortical4-6 and spinal excitability 7 and to improve upper limb function. [4][5][6][7] However, it is not clear that all individuals with incomplete tetraplegia are necessarily good candidates for these types of programs. If the motoneuron pool of a particular muscle remains largely intact, then an activity-based therapy program that targets the re-establishment of neural connections to activate those motoneurons may increase strength and contribute to improved function. On the other hand, if there has been a major loss of lower motoneurons (gray matter), then the remaining ones may not be able to support an intense schedule of exercise. For these individuals, activitybased therapy might result in overuse weakness and fatigue, as it does in post-polio syndrome. 8,9The conventional clinical measures for assessing motor impairment after cSCI may not be adequate Background: Candidates for activity-based therapy after spinal cord injury (SCI) are often selected on the basis of manual muscle test scores and the classification of the injury as complete or incomplete. However, these scores may not adequately predict which individuals have sufficient residual motor resources for the therapy to be beneficial. Objective: We performed a preliminary study to see whether dynamometry and quantitative electromyography (EMG) can provide a more detailed assessment of residual motor resources. Methods: We measured elbow extension strength using a hand-held dynamometer and recorded fine-wire EMG from the triceps brachii muscles of 4 individuals with C5, C6, or C7 level SCI and 2 able-bodied controls. We used EMG decomposition to measure motor unit action potential (MUAP) amplitudes and motor unit (MU) recruitment and firing-rate profiles during constant and ramp contractions. Results: All 4 subjects with cervical SCI (cSCI) had increased MUAP amplitudes indicative of denervation. Two of the subjects with cSCI had very weak elbow extension strength (<4 kg), dramatically reduced recruitment, and excessive firing rates (>40 pps), suggesting profound loss of motoneurons. The other 2 subjects with cSCI had stronger elbow extension (>6 kg), more normal recruitment, and more normal firing rates, suggesting a substantial remaining motoneuron population. Conclusions: Dynamometry and quantitative EMG may provide information about the extent of gray matter loss in cSCI to help guide rehabilitation strategies.

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Motor units in incomplete spinal cord injury: electrical activity, contractile properties and the effects of biofeedback.

Abstract: The electrical and contractile properties of hand muscles in a selected population of quadriplegic subjects were studied intensively before and after EMG biofeedback.

Cited by 39 publications

References 16 publications

Motor unit forces and recruitment patterns after cervical spinal cord injury

Motor unit forces and recruitment patterns after cervical spinal cord injury

Operant conditioning to increase ankle control or decrease reflex excitability improves reflex modulation and walking function in chronic spinal cord injury

Triceps Brachii in Incomplete Tetraplegia: EMG and Dynamometer Evaluation of Residual Motor Resources and Capacity for Strengthening

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