Quadriceps muscle strength, contractile properties, and motor unit firing rates in young and old men

Roos, Martin R.; Rice, Charles L.; Connelly, Denise M.; Vandervoort, Anthony A.

doi:10.1002/(sici)1097-4598(199908)22:8<1094::aid-mus14>3.0.co;2-g

Cited by 226 publications

(161 citation statements)

References 41 publications

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“…On the other hand, our results are inconsistent with those of Roos et al (1999), who investigated the vastus medialis muscle (Roos et al 1999). They showed no difference in motor unit firing rates between the young and elderly at 20~100 % of MVC during isometric knee extension.…”

Section: Discussioncontrasting

confidence: 99%

“…It is well known that quadriceps femoris muscles play important roles in standing, walking, and other daily living movements and this muscle group is highly susceptible to age-related muscle atrophy (Abe et al 2014(Abe et al , 2011b. Roos et al (1999) compared motor unit firing rates in the young and elderly in the vastus medialis muscle and found no significant differences between the groups (Roos et al 1999). Their results were not in agreement with the other studies on small hand muscles (Erim et al 1999;Kamen et al 1995;Knight and Kamen 2007;Nelson et al 1983Nelson et al , 1984Patten et al 2001;Soderberg et al 1991).…”

Section: Introductionmentioning

confidence: 78%

“…This discrepancy between the studies is believed to be due to the process of calculating the motor unit firing rate. Roos et al (1999) calculated the mean motor unit firing rate from the motor units with various recruitment thresholds, while we divided motor units into four or three groups with different recruitment thresholds for calculation of the motor unit firing rate. It is well known that there exists an inverse relationship between the firing rate and recruitment threshold of motor units at any specified force level during gradual increases in force during isometric contraction in healthy young subjects Hostage 2010, 1982;Erim et al 1996).…”

Section: Discussionmentioning

confidence: 99%

“…Thus, firing rates of motor units should vary as a function of their recruitment threshold. We suspect that in the case of Roos et al (1999), the firing behaviors of individual motor units with different recruitment thresholds were masked by the mixture of firing rates of all motor units recruited at each force level. The separation of motor units by the recruitment threshold may be necessary to detect differences in the motor unit firing rate between the elderly and young groups.…”

Section: Discussionmentioning

confidence: 99%

“…From these studies, there has been a gradual accumulation of knowledge about the effects of aging on motor unit firing characteristics, such as a decrease in the firing rate. On the other hand, insufficient research has been conducted in the field of motor unit behavior in the elderly for locomotor muscles such as the quadriceps femoris muscles (Knight and Kamen 2008;Piasecki et al 2015;Roos et al 1999;Welsh et al 2007). It is well known that quadriceps femoris muscles play important roles in standing, walking, and other daily living movements and this muscle group is highly susceptible to age-related muscle atrophy (Abe et al 2014(Abe et al , 2011b.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussioncontrasting

confidence: 99%

Section: Introductionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Measurement of central activation failure of the quadriceps femoris in healthy adults

et al. 2000

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Motor unit physiology: Some unresolved issues

2001

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The purpose of this review was to examine three issues that limit our understanding of motor unit physiology: (1) the range and distribution of the innervation ratios in a muscle; (2) the association between discharge rate and force; and (3) the variation in motor unit activity across contractions that differ in speed and type. We suggest that if more data were available on these issues, the understanding of neuromuscular function would be enhanced substantially, especially with regard to plasticity in the motor neuron pool, adequacy of the neural drive to muscle, and flexibility of activation patterns across various types of contractions. Current data are limited and these limitations influence our ability to interpret adaptations in muscle function in health and disease. © 2001 John Wiley & Sons, Inc. Muscle Nerve 24: 4–17, 2001

show abstract

Quadriceps muscle strength, contractile properties, and motor unit firing rates in young and old men

Cited by 226 publications

References 41 publications

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

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

Measurement of central activation failure of the quadriceps femoris in healthy adults

Motor unit physiology: Some unresolved issues

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