Increased motor unit potential shape variability across consecutive motor unit discharges in the tibialis anterior and vastus medialis muscles of healthy older subjects

Hourigan, Maddison L.; McKinnon, Neal B.; Johnson, Marjorie; Rice, Charles L.; Stashuk, Daniel W.; Doherty, Timothy J.

doi:10.1016/j.clinph.2015.02.002

Cited by 67 publications

(88 citation statements)

References 72 publications

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“…properties are in accordance with previously reported data on the TA [11,19,26,36,37,[39][40][41][42][43][44][45]; CMAP negative peak amplitude did not differ between young and old adults, but due to significantly larger S-MUP values in older adults MUNEs were significantly reduced. In contrast, relatively fewer studies have investigated MU properties of the VM muscle.…”

Section: Accepted Manuscriptsupporting

confidence: 93%

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

McKinnon

Montero‐Odasso

Doherty

2015

Experimental Gerontology

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Section: Accepted Manuscriptsupporting

confidence: 93%

“…Reductions in MUNEs have been reported in a number of upper [13,[32][33][34][35], and lower limb [10,11,[36][37][38][39] muscles studies. Our obtained values for MU…”

Section: Accepted Manuscriptmentioning

confidence: 83%

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

McKinnon

Montero‐Odasso

Doherty

2015

Experimental Gerontology

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“…7 The relationship between the maximal voluntary contraction force and firing rate at 60 % of the maximal voluntary contraction (MVC) during ramp contraction to 70 % of MVC for motor units recruited at <20 % of MVC (left panel) and 20-40 % of MVC (right panel) in the elderly group Fig. 8 The relationship between the maximal voluntary contraction force and firing rate slope during ramp contraction to 70 % of the maximal voluntary contraction (MVC) for motor units recruited at <20 % of MVC (left panel) and 20-40 % of MVC (right panel) in the elderly group potential area in the EMG signal (Hourigan et al 2015;Ling et al 2009;Piasecki et al 2015), meaning that one motor unit innervates a greater number of muscle fibers (increase in innervation ratio). e, thus, also considered that the lower firing rate in the elderly is compensated for by greater contributions of individual motor units compared with the young to generate the required force.…”

Section: Discussionmentioning

confidence: 99%

Age-related changes in motor unit firing pattern of vastus lateralis muscle during low-moderate contraction

Watanabe

Holobar

Kouzaki

et al. 2016

AGE

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Age-related changes in motor unit activation properties remain unclear for locomotor muscles such as quadriceps muscles, although these muscles are preferentially atrophied with aging and play important roles in daily living movements. The present study investigated and compared detailed motor unit firing characteristics for the vastus lateralis muscle during isometric contraction at low to moderate force levels in the elderly and young. Fourteen healthy elderly men and 15 healthy young men performed isometric ramp-up contraction to 70 % of the maximal voluntary contractions (MVC) during knee extension. Multichannel surface electromyograms were recorded from the vastus lateralis muscle using a two-dimensional grid of 64 electrodes and decomposed with the convolution kernel compensation technique to extract individual motor units. Motor unit firing rates in the young were significantly higher (~+29.7 %) than in the elderly (p < 0.05). There were significant differences in firing rates among motor units with different recruitment thresholds at each force level in the young (p < 0.05) but not in the elderly (p > 0.05). Firing rates at 60 % of the MVC force level for the motor units recruited at <20 % of MVC were significantly correlated with MVC force in the elderly (r = 0.885, p < 0.0001) but not in the young (r = 0.127, p > 0.05). These results suggest that the motor unit firing rate in the vastus lateralis muscle is affected by aging and muscle strength in the elderly and/or age-related strength loss is related to motor unit firing/ recruitment properties.

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“…Loss of skeletal muscle mass and force inherent with ageing has a profound effect on the quality of life of older people. Human investigations have shown that by the age of 70, there is a 25–30% reduction in the cross‐sectional area (CSA) of skeletal muscle and a decline in muscle strength by 30–40%,2 associated with neurological impairments including loss of motor units,3, 4 neuromuscular junction (NMJ) instability,5 a decline in motor nerve function6 and increased fibre‐type grouping due to continual cycles of denervation and reinnervation7 (Figure 1). The reduction in muscle strength with age is associated with an increased mortality risk,8 an increased susceptibility to risk of falls and, subsequently, an increased need for residential care.…”

Section: Introductionmentioning

confidence: 99%

Redox homeostasis and age‐related deficits in neuromuscular integrity and function

Sakellariou

Lightfoot

Earl

et al. 2017

J cachexia sarcopenia muscle

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Skeletal muscle is a major site of metabolic activity and is the most abundant tissue in the human body. Age‐related muscle atrophy (sarcopenia) and weakness, characterized by progressive loss of lean muscle mass and function, is a major contributor to morbidity and has a profound effect on the quality of life of older people. With a continuously growing older population (estimated 2 billion of people aged >60 by 2050), demand for medical and social care due to functional deficits, associated with neuromuscular ageing, will inevitably increase. Despite the importance of this ‘epidemic’ problem, the primary biochemical and molecular mechanisms underlying age‐related deficits in neuromuscular integrity and function have not been fully determined. Skeletal muscle generates reactive oxygen and nitrogen species (RONS) from a variety of subcellular sources, and age‐associated oxidative damage has been suggested to be a major factor contributing to the initiation and progression of muscle atrophy inherent with ageing. RONS can modulate a variety of intracellular signal transduction processes, and disruption of these events over time due to altered redox control has been proposed as an underlying mechanism of ageing. The role of oxidants in ageing has been extensively examined in different model organisms that have undergone genetic manipulations with inconsistent findings. Transgenic and knockout rodent studies have provided insight into the function of RONS regulatory systems in neuromuscular ageing. This review summarizes almost 30 years of research in the field of redox homeostasis and muscle ageing, providing a detailed discussion of the experimental approaches that have been undertaken in murine models to examine the role of redox regulation in age‐related muscle atrophy and weakness.

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Increased motor unit potential shape variability across consecutive motor unit discharges in the tibialis anterior and vastus medialis muscles of healthy older subjects

Cited by 67 publications

References 72 publications

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

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

Age-related changes in motor unit firing pattern of vastus lateralis muscle during low-moderate contraction

Redox homeostasis and age‐related deficits in neuromuscular integrity and function

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