Motor unit loss is accompanied by decreased peak muscle power in the lower limb of older adults

McKinnon, Neal B.; Montero‐Odasso, Manuel; Doherty, Timothy J.

doi:10.1016/j.exger.2015.07.007

Cited by 30 publications

(18 citation statements)

References 62 publications

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“…Thus, the age-related flattening of the fatigue slopes MF-SEMG in older individuals likely indicates an early decrease in both muscle power and muscle strength as a diagnostic and predictive marker rather than muscle endurance function in aging individuals. The rate of MF fatigue would not be affected in a major way even if an awaited decline in mechanic output from muscle strength and power measurements (due to axonal and glycolytic muscle fiber loss) was well compensated (McKinnon et al 2015). It is worth noting that early declines in muscle power function seem more greatly associated with limitations in activities and mobility than muscle strength (Reid and Fielding 2012;Suetta et al 2019).…”

Section: Discussionmentioning

confidence: 99%

Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain

et al. 2019

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The impact of aging on the back muscles is not well understood, yet may hold clues to both normal aging and chronic low back pain (cLBP). This study sought to investigate whether the median frequency (MF) surface electromyographic (SEMG) back muscle fatigue method-a proxy for glycolytic muscle metabolismwould be able to detect age-and sex-specific differences in neuromuscular and muscle metabolic functions in individuals with cLBP in a reliable way, and whether it would be as sensitive as when used on healthy individuals. With participants seated on a dynamometer (20°t runk anteflexion), paraspinal SEMG activity was recorded bilaterally from the multifidus (L5), longissimus (L2), and iliolumbalis (L1) muscles during isometric, sustained back extensions loaded at 80% of maximum from 117 younger (58 females) and 112 older (56 female) cLBP individuals. Tests were repeated after 1-2 days and 6 weeks. Median frequency, the SEMG variable indicating neuromuscular fatigue, was analyzed. Maximum back extensor strength was comparable between younger and older participants. Significantly less MF-SEMG back muscle fatigue was observed in older as compared to younger, and in older female as compared to older male cLBP individuals. Relative reliability was excellent, but absolute reliability appeared large for this SEMG-fatigue measure. Findings suggest that cLBP likely does not mask the age-specific diagnostic potential of the MF-SEMG back extensor fatigue method. Thus, this method possesses a great potential to be further developed into a valuable biomarker capable of detecting back muscle function at risk of sarcopenia at very early stages.

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Section: Discussionmentioning

confidence: 99%

Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain

et al. 2019

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“…In addition, adequate dorsiflexor function is critical for balance and gait and thus relates to risk of falls in aging . Furthermore, it has been suggested from several recent studies that dorsiflexor muscle group function related to ankle joint movements (together with hip joint movements) contributes strongly to lower limb functional capacity …”

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confidence: 99%

“…15 Furthermore, it has been suggested from several recent studies that dorsiflexor muscle group function related to ankle joint movements (together with hip joint movements) contributes strongly to lower limb functional capacity. [17][18][19][20]…”

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confidence: 99%

Motor unit number estimation and neuromuscular fidelity in 3 stages of sarcopenia

et al. 2017

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“…Many factors are considered as causes including genetic predisposition, lack of exercise, and changes in endocrine function (Clark & Fielding, ; Doherty, ). Decline of motor unit number and associated muscle denervation is, however, considered as a primary cause of sarcopenia because failure of reinnervation can cause muscle wasting (McKinnon, Montero‐Odasso, & Doherty, ). To prevent sarcopenia in aging, facilitation of muscle reinnervation is important.…”

Section: Discussionmentioning

confidence: 99%

Schwann cell guidance of nerve growth between synaptic sites explains changes in the pattern of muscle innervation and remodeling of synaptic sites following peripheral nerve injuries

Kang

Tian

Thompson

2019

J of Comparative Neurology

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Terminal Schwann cells (SCs) are nonmyelinating glia that are a prominent component of the neuromuscular junction (NMJ) where motor neurons form synapses onto muscle fibers. These cells play important roles not only in development and maintenance of the neuromuscular synapse but also restoring synaptic function after nerve damage. In response to muscle denervation, terminal SCs undergo dramatic changes in their gene expression patterns as well as in their morphology, such as extending elaborate processes into inter‐junctional space. These SC processes serve as a path to guide axon terminal sprouts from nearby innervated junctions, promoting rapid reinnervation of denervated fibers. We studied the role of terminal SCs in synapse reformation by using two different fluorescent proteins to simultaneously label motor axons and SCs; we examined these junctions repeatedly in living animals using a fluorescence microscope. Here, we show that alterations in the patterns of muscle innervation following recovery from nerve injury can be explained by SC guidance of regenerating axons. In turn, this guidance leads to remodeling of the NMJ itself.

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Motor unit loss is accompanied by decreased peak muscle power in the lower limb of older adults

Cited by 30 publications

References 62 publications

Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain

Age- and sex-specific effects in paravertebral surface electromyographic back extensor muscle fatigue in chronic low back pain

Motor unit number estimation and neuromuscular fidelity in 3 stages of sarcopenia

Schwann cell guidance of nerve growth between synaptic sites explains changes in the pattern of muscle innervation and remodeling of synaptic sites following peripheral nerve injuries

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