Weaker Seniors Exhibit Motor Cortex Hypoexcitability and Impairments in Voluntary Activation

Clark, Brian C.; Taylor, Janet L.; Hong, S. Lee; Law, Timothy; Russ, David W.

doi:10.1093/gerona/glv030

Cited by 44 publications

(32 citation statements)

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“…Specifically, healthy old versus young adults produced 25% lower CON and 9.5% lower peak ECC quadriceps torque (both p < 0.05). Such reductions in maximal torque generation are in line with the evolution of age-related dynapenic weakness, most likely caused by a loss of muscle proteins [9,10], neuronal hypoexcitability [11,12], and an increase in tendon compliance impeding force transmission to the body levers [13,14]. Our data also agree with previously published data with respect to the ratio between ECC and CON peak torques.…”

Section: Discussionsupporting

confidence: 91%

Functional Relevance of Relative Maintenance of Maximal Eccentric Quadriceps Torque in Healthy Old Adults

Waanders

Beijersbergen

Murgia³

et al. 2016

Gerontology

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Background: Old referenced to young adults show a relative maintenance of maximal eccentric (RELM) compared to concentric muscle torque: ∼76 and ∼59%, respectively. However, it is unknown if RELM affords functional benefits in old adults. Objective: We examined if there is specificity between the two types of peak quadriceps torque (i.e., concentric and eccentric) and timed gait performance measured during level, ramp, and stair walking and if gait performance was higher in old adults with high versus low RELM. Methods: We measured peak concentric and eccentric quadriceps torque at 60 and 120°/s and timed gait at habitual and safe-fast speeds in healthy young (age 22.7 years, n = 24) and old (age 70.0 years, n = 21) adults. Results: Comparable to previous studies, RELM was 21%, but instead of the anticipated specificity, we found that concentric compared with eccentric torque was more strongly associated with gait performance than eccentric torque, independently of walking direction and age (R² = 0.16: eccentric vs. descending gaits; R² = 0.17: eccentric vs. ascending gaits; R² = 0.45: concentric vs. descending gaits; R² = 0.56: concentric vs. ascending gaits, n = 45, all p < 0.01). Furthermore, old adults (n = 10) with ∼30% greater than normal levels of RELM (n = 11) ambulated at similar velocities measured on level and inclined surfaces. Conclusion: Normal and 30% above normal levels of RELM do not seem to increase or predict healthy old adults' gait performance on level and inclined surfaces. Future work should examine if RELM is associated with a heightened performance in other measures of neuromuscular function, such as gait biomechanics, muscle activation, as well as rate and control of voluntary force development in old adults with high or low mobility.

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Section: Discussionsupporting

confidence: 91%

Functional Relevance of Relative Maintenance of Maximal Eccentric Quadriceps Torque in Healthy Old Adults

Waanders

Beijersbergen

Murgia³

et al. 2016

Gerontology

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“…Using magnetic brain stimulation techniques, ageing has been shown to be associated with decreased motor cortical excitability of the wrist flexor muscles, 110 and weaker seniors, in particular, have been reported to exhibit more cortical hypoexcitability than their stronger counterparts. 111 Moreover, ageing has been shown to require significantly higher activation of several motor areas of the brain to perform the same motor grip task as younger adults, 112 as well as reduced deactivation of the ipsilateral primary motor cortex (i.e. the side of the brain not directly responsible for performing a given motor task).…”

Section: Age-related Changes In Supraspinal Propertiesmentioning

confidence: 99%

“…Over the past several decades, numerous studies have investigated the question of 'does voluntary activation become impaired with advancing age?'. 111, These studies largely report discrepant findings, but a critical examination indicates several notable observations. First, many older people, particularly those who are healthy and physically active, do not exhibit impairments in voluntary activation.…”

Section: Age-related Changes In Spinal Propertiesmentioning

confidence: 99%

“…154,160,163,164 Second, weaker older people, as well as the oldest old, do exhibit impairments in voluntary activation. 111,146,159 Thus, it appears that many older people are indeed able to preserve their nervous systems ability to optimally activate their motor units and musculature while many, particularly the older old, the weakest, and/or those with poor physical function exhibit impairments in voluntary activation.…”

Section: Age-related Changes In Spinal Propertiesmentioning

confidence: 99%

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Skeletal muscle performance and ageing

Tieland

Trouwborst

Clark

2017

J cachexia sarcopenia muscle

Self Cite

585

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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“…Exercise-induced alterations in the corticospinal excitability, and therefore the efficacy of this motor pathway to relay neural signals, have the potential to influence skeletal muscle activation and central fatigue (27,42). Interestingly, although not unanimously agreed upon (12), aging has been associated with a diminished corticospinal excitability, potentially influenced by age-related alterations at the motor cortical (33) and motoneuronal level (38). However, the lack of a change in MEPs and CMEPs during exercise suggests that fatiguing aerobic exercise tasks used in the study do not affect the excitability of the corticospinal pathway in either age group and, therefore, confirms earlier observations based on nonfatiguing exercise (12).…”

Section: Impact Of Aging On Corticospinal Excitability During Exercisementioning

confidence: 99%

Impact of age on the development of fatigue during large and small muscle mass exercise

Weavil

Hureau

Thurston

et al. 2018

American Journal of Physiology-Regulatory, Integrative and Comp

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To examine the impact of aging on neuromuscular fatigue following cycling (CYC; large active muscle mass) and single-leg knee-extension (KE; small active muscle mass) exercise, 8 young (25 ± 4 years) and older (72 ± 6 years) participants performed CYC and KE to task failure at a given relative intensity (80% of peak power output). The young also matched CYC and KE workload and duration of the old (iso-work comparison). Peripheral and central fatigue were quantified via pre-/postexercise decreases in quadriceps twitch torque (∆Q, electrical femoral nerve stimulation) and voluntary activation (∆VA). Although young performed 77% and 33% more work during CYC and KE, respectively, time to task failure in both modalities was similar to the old (~9.5 min; P > 0.2). The resulting ΔQ was also similar between groups (CYC ~40%, KE ~55%; P > 0.3); however, ∆VA was, in both modalities, approximately double in the young (CYC ~6%, KE ~9%; P < 0.05). While causing substantial peripheral and central fatigue in both exercise modalities in the old, ∆Q in the iso-work comparison was not significant (CYC; P = 0.2), or ~50% lower (KE; P < 0.05) in the young, with no central fatigue in either modality ( P > 0.4). Based on iso-work comparisons, healthy aging impairs fatigue resistance during aerobic exercise. Furthermore, comparisons of fatigue following exercise at a given relative intensity mask the age-related difference observed following exercise performed at the same workload. Finally, although active muscle mass has little influence on the age-related difference in the rate of fatigue at a given relative intensity, it substantially impacts the comparison during exercise at a given absolute intensity.

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Weaker Seniors Exhibit Motor Cortex Hypoexcitability and Impairments in Voluntary Activation

Abstract: These findings indicate that weaker seniors exhibit significant impairments in voluntary activation, and that this impairment may be mechanistically associated with increased GABAergic inhibition of the motor cortex.

Cited by 44 publications

References 50 publications

Functional Relevance of Relative Maintenance of Maximal Eccentric Quadriceps Torque in Healthy Old Adults

Functional Relevance of Relative Maintenance of Maximal Eccentric Quadriceps Torque in Healthy Old Adults

Skeletal muscle performance and ageing

Impact of age on the development of fatigue during large and small muscle mass exercise

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