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

Gilmore, Kevin J.; Morat, Tobias; Doherty, Timothy J.; Rice, Charles L.

doi:10.1002/mus.25394

Cited by 36 publications

(36 citation statements)

References 48 publications

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“…The elbow extensor torque of the older men was approximately 50% lower than that of the young participants; however, similar levels of voluntary activation were achieved. Although we cannot assess the independent contribution of the anconeus to elbow extensor torque and we did not measure muscle volume, it is reasonable to expect that overall extensor weakness is the result of general muscle atrophy and other related factors . In addition to MU loss, there are other nonneurological factors that could contribute to sarcopenia.…”

Section: Resultsmentioning

confidence: 97%

Effect of very old age on anconeus motor unit loss and compensatory remodelling

et al. 2017

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Section: Resultsmentioning

confidence: 97%

Effect of very old age on anconeus motor unit loss and compensatory remodelling

et al. 2017

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“…A recent study compared TA motor unit numbers in groups described as pre‐sarcopenic, sarcopenic and severe sarcopenic (Gilmore et al . ). In agreement with our findings for TA, they found that motor unit numbers were similar across groups.…”

Section: Discussionmentioning

confidence: 97%

Failure to expand the motor unit size to compensate for declining motor unit numbers distinguishes sarcopenic from non‐sarcopenic older men

Piasecki

Ireland

Piasecki

et al. 2018

The Journal of Physiology

119

100

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Key points The age‐related loss of muscle mass is related to the loss of innervating motor neurons and denervation of muscle fibres.Not all denervated muscle fibres are degraded; some may be reinnervated by an adjacent surviving neuron, which expands the innervating motor unit proportional to the numbers of fibres rescued.Enlarged motor units have larger motor unit potentials when measured using electrophysiological techniques.We recorded much larger motor unit potentials in relatively healthy older men compared to young men, but the older men with the smallest muscles (sarcopenia) had smaller motor unit potentials than healthy older men.These findings suggest that healthy older men reinnervate large numbers of muscle fibres to compensate for declining motor neuron numbers, but a failure to do so contributes to muscle loss in sarcopenic men. AbstractSarcopenia results from the progressive loss of skeletal muscle mass and reduced function in older age. It is likely to be associated with the well‐documented reduction of motor unit numbers innervating limb muscles and the increase in size of surviving motor units via reinnervation of denervated fibres. However, no evidence exists to confirm the extent of motor unit remodelling in sarcopenic individuals. The aim of the present study was to compare motor unit size and number between young (n = 48), non‐sarcopenic old (n = 13), pre‐sarcopenic (n = 53) and sarcopenic (n = 29) men. Motor unit potentials (MUPs) were isolated from intramuscular and surface EMG recordings. The motor unit numbers were reduced in all groups of old compared with young men (all P < 0.001). MUPs were higher in non‐sarcopenic and pre‐sarcopenic men compared with young men (P = 0.039 and 0.001 respectively), but not in the vastus lateralis of sarcopenic old (P = 0.485). The results suggest that extensive motor unit remodelling occurs relatively early during ageing, exceeds the loss of muscle mass and precedes sarcopenia. Reinnervation of denervated muscle fibres probably expands the motor unit size in the non‐sarcopenic and pre‐sarcopenic old, but not in the sarcopenic old. These findings suggest that a failure to expand the motor unit size distinguishes sarcopenic from pre‐sarcopenic muscles.

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“…Whereas some studies suggest that lifelong high‐intensity physical activity, such as running, may minimize the loss of motor units associated with ageing in the biceps brachii and tibialis anterior, others showed that tibialis anterior motor units were not spared in older adults athletes . Moreover, it is unclear whether sarcopenia is associated with reductions in motor unit number …”

Section: Physiological Systems That Contribute To the Decline In Eldementioning

confidence: 99%

Skeletal muscle performance and ageing

Tieland

Trouwborst

Clark

2017

J cachexia sarcopenia muscle

593

429

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The world population is ageing rapidly. As society ages, the incidence of physical limitations is dramatically increasing, which reduces the quality of life and increases healthcare expenditures. In western society, ~30% of the population over 55 years is confronted with moderate or severe physical limitations. These physical limitations increase the risk of falls, institutionalization, co‐morbidity, and premature death. An important cause of physical limitations is the age‐related loss of skeletal muscle mass, also referred to as sarcopenia. Emerging evidence, however, clearly shows that the decline in skeletal muscle mass is not the sole contributor to the decline in physical performance. For instance, the loss of muscle strength is also a strong contributor to reduced physical performance in the elderly. In addition, there is ample data to suggest that motor coordination, excitation–contraction coupling, skeletal integrity, and other factors related to the nervous, muscular, and skeletal systems are critically important for physical performance in the elderly. To better understand the loss of skeletal muscle performance with ageing, we aim to provide a broad overview on the underlying mechanisms associated with elderly skeletal muscle performance. We start with a system level discussion and continue with a discussion on the influence of lifestyle, biological, and psychosocial factors on elderly skeletal muscle performance. Developing a broad understanding of the many factors affecting elderly skeletal muscle performance has major implications for scientists, clinicians, and health professionals who are developing therapeutic interventions aiming to enhance muscle function and/or prevent mobility and physical limitations and, as such, support healthy ageing.

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

Abstract: Unlike MU number estimates, strength and MU stability differed across groups and related to degree of sarcopenia. Muscle Nerve 55: 676-684, 2017.

Cited by 36 publications

References 48 publications

Effect of very old age on anconeus motor unit loss and compensatory remodelling

Effect of very old age on anconeus motor unit loss and compensatory remodelling

Failure to expand the motor unit size to compensate for declining motor unit numbers distinguishes sarcopenic from non‐sarcopenic older men

Skeletal muscle performance and ageing

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