Prediction of voluntary activation, strength and endurance of elbow flexors in postpolio patients

Allen, G M; Middleton, James; Katrak, Pesi; Lord, Stephen R.; Gandevia, Simon C.

doi:10.1002/mus.20094

Cited by 11 publications

(11 citation statements)

References 38 publications

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“…Thus, prolonged contractions at an absolute force level necessitate an increase in the relative force production over time. This increase in relative force is presumably produced by increasing central drive, a suggestion that is consistent with the increases in EMG,173 facilitation of motor evoked potentials,156 and higher effort scores with fatigue 4, 5. In addition, data from other studies show that judgments of force are based on the magnitude of the centrally generated commands that produce the contractions rather than the sensory signals arising from the muscle 54, 81…”

Section: Poliomyelitismentioning

confidence: 61%

“…Although individuals with PPS regularly report that fatigue limits their daily activities, the few studies that have objectively evaluated the magnitude of motor fatigue (relative decline in maximal force‐generating capacity) show contradictory results. Some studies show that muscles influenced by PPS are more fatigable than muscles of controls, irrespective of strength 4, 5, 164. Other studies show no differences in fatigability 1, 61, 150, 152, 156, 173…”

Section: Poliomyelitismentioning

confidence: 99%

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Fatigue of muscles weakened by death of motoneurons

Thomas

Zijdewind

2005

Muscle and Nerve

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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.

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Section: Poliomyelitismentioning

confidence: 61%

Section: Poliomyelitismentioning

confidence: 99%

Fatigue of muscles weakened by death of motoneurons

Thomas

Zijdewind

2005

Muscle and Nerve

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“…30 The activation deficits measured in persons with incomplete-SCI (42-66%) are larger in magnitude compared to those measured in patients early after surgery or long-term immobilization. 15,31 Accordingly, persons with incomplete-SCI may benefit from rehabilitation strategies that target voluntary activation deficits to maximize skeletal muscle function, that is, functional electrical stimulation or bio-feedback. 32 While these interventions may not directly impact the primary injury, they may be able to ameliorate the loss of muscle function secondary to disuse or lack of neuromuscular activity.…”

Section: Discussionmentioning

confidence: 99%

“…15 Briefly, a single biphasic and supra-maximal pulse was delivered at rest and during maximal voluntary isometric contraction. The voluntary activation deficit was calculated based on the ratio between the torques produced by the superimposition of a supra-maximal twitch on a peak isometric contraction (a) and the torque produced by the same stimulus in the potentiated, resting muscle (b).…”

Section: Voluntary Activation Deficitsmentioning

confidence: 99%

Lower extremity skeletal muscle function in persons with incomplete spinal cord injury

et al. 2005

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Study design: A cross-sectional study design. Objectives: To characterize and specifically quantify impairments in muscle function after chronic incomplete spinal cord injury (SCI). Setting: University of Florida, Gainesville, FL, USA. Methods: Voluntary and electrically elicited contractile measurements were performed and voluntary activation deficits were quantitatively determined in the knee extensor and ankle plantar flexor muscle groups in 10 individuals with chronic incomplete SCI (C5-T8, ASIA C or D) and age-, gender-, height-and body weight matched healthy controls. Results: Persons with incomplete-SCI were able to produce only 36 and 24% of the knee extensor torque and 38 and 26% of the plantar flexor torque generated by noninjured controls in the self-reported less-involved and more-involved limbs, respectively (Po0.05). In addition, both indices of explosive or instantaneous muscle strength, torque 200 (absolute torque reached at 200 ms) and the average rate of torque development (ARTD) were dramatically reduced in the ankle plantar flexor and knee extensor muscle groups in persons with incomplete-SCI. However, the deficit in instantaneous muscle strength was most pronounced in the ankle plantar flexor muscles, with an 11.7-fold difference between the torque 200 measured in the self-reported more involved limb and a 5-fold difference in the less-involved limb compared to control muscles. Voluntary activation deficits ranged between 42 and 66% in both muscle groups. Interestingly, electrically elicited contractile properties did not differ between the groups. Conclusion: The resultant impact of incomplete-SCI is that affected muscles not only become weak, but slow to develop voluntary torque. We speculate that the large deficit in torque 200 and ARTD in the ankle plantar flexors muscles of persons with incomplete-SCI may limit locomotor function. The results presented in this study provide a quantitative and sensitive assessment of muscle function upon which future research examining rehabilitation programs aimed at restoring muscle function and promoting functional recovery after incomplete-SCI may be based.

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“…Since previous studies suggest that the contribution of central fatigue in PPS is only limited, the focus is on peripheral fatigue [6], [9]. Peripheral fatigue is largely determined by the muscle's aerobic muscle capacity and fiber type composition, and investigation of contractile properties can help to understand the origin of fatigue [10], [11].…”

Section: Introductionmentioning

confidence: 99%

Reliability of Contractile Properties of the Knee Extensor Muscles in Individuals with Post-Polio Syndrome

et al. 2014

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ObjectiveTo assess the reliability of contractile properties of the knee extensor muscles in 23 individuals with post-polio syndrome (PPS) and 18 age-matched healthy individuals.MethodsContractile properties of the knee extensors were assessed from repeated electrically evoked contractions on 2 separate days, with the use of a fixed dynamometer. Reliability was determined for fatigue resistance, rate of torque development (MRTD), and early and late relaxation time (RT50 and RT25), using the intraclass correlation coefficient (ICC) and standard error of measurement (SEM, expressed as % of the mean).ResultsIn both groups, reliability for fatigue resistance was good, with high ICCs (>0.90) and small SEM values (PPS: 7.1%, healthy individuals: 7.0%). Reliability for contractile speed indices varied, with the best values found for RT50 (ICCs>0.82, SEM values <2.8%). We found no systematic differences between test and retest occasions, except for RT50 in healthy subjects (p = 0.016).ConclusionsIn PPS and healthy individuals, the reliability of fatigue resistance, as obtained from electrically evoked contractions is high. The reliability of contractile speed is only moderate, except for RT50 in PPS, demonstrating high reliability.SignificanceThis was the first study to examine the reliability of electrically evoked contractile properties in individuals with PPS. Our results demonstrate its potential to study mechanisms underlying muscle fatigue in PPS and to evaluate changes in contractile properties over time in response to interventions or from natural course.

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Prediction of voluntary activation, strength and endurance of elbow flexors in postpolio patients

Cited by 11 publications

References 38 publications

Fatigue of muscles weakened by death of motoneurons

Fatigue of muscles weakened by death of motoneurons

Lower extremity skeletal muscle function in persons with incomplete spinal cord injury

Reliability of Contractile Properties of the Knee Extensor Muscles in Individuals with Post-Polio Syndrome

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