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Hirono T, Takeda R, Nishikawa T, Okudaira M, Kunugi S, Yoshiko A, Ueda S, Yoshimura A, Watanabe K. Motor unit firing patterns in older adults with low skeletal muscle mass. Arch Gerontol Geriatr 2024; 116:105151. [PMID: 37544147 DOI: 10.1016/j.archger.2023.105151] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2023] [Revised: 07/17/2023] [Accepted: 07/31/2023] [Indexed: 08/08/2023]
Abstract
Muscular dysfunctions involving a decline in muscle strength are often induced by loss of muscle mass in older adults. Understanding neural activation in older adults in addition to muscular characteristics may be important to prevent such age-related dysfunctions. This study aimed to investigate the difference in motor unit firing patterns between community-dwelling older individuals with normal and low skeletal muscle mass. Sixty-six older adults (62-90 years) performed muscle strength and function tests. On conducting high-density surface electromyography of the vastus lateralis, individual motor unit firing properties were assessed. Individual motor units were divided into three different recruitment threshold groups and their firing rates were compared. The skeletal muscle quantity and quality were assessed using bioimpedance methods and ultrasound images. They were divided into two groups according to sarcopenia criteria: a normal group (n = 39) and presarcopenia group with low skeletal muscle mass but normal physical functions (n = 21). Skeletal muscle mass and muscle thickness were greater and echo intensity was lower in the normal group than presarcopenia group. Motor units in normal older adults fired at different rates with a hierarchy depending on their recruitment threshold, observed as a normal phenomenon. However, motor units in the presarcopenia group fired without showing the hierarchical pattern. The results suggest that older adults with low skeletal muscle mass exhibited an abnormal neural input pattern, in addition to declines in muscle quantity and quality.
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Affiliation(s)
- Tetsuya Hirono
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan; Human Health Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
| | - Ryosuke Takeda
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan
| | - Taichi Nishikawa
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan
| | - Masamichi Okudaira
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan; Faculty of Education, Iwate University, Iwate, Japan
| | - Shun Kunugi
- Center for General Education, Aichi Institute of Technology, Aichi, Japan
| | - Akito Yoshiko
- Faculty of Liberal Arts and Sciences, Chukyo University, Aichi, Japan
| | - Saeko Ueda
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan; Department of Human Nutrition, School of Life Studies, Sugiyama Jogakuen University, Aichi, Japan
| | - Akane Yoshimura
- Faculty of Education and Integrated Arts and Sciences, Waseda University, Tokyo, Japan
| | - Kohei Watanabe
- Laboratory of Neuromuscular Biomechanics, School of Health and Sport Sciences, Chukyo University, Aichi, Japan
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2
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Bruce CD, Magnuson JR, McNeil CJ. Voluntary activation does not differ when using two different methods to determine transcranial magnetic stimulator output. J Neurophysiol 2023; 130:925-930. [PMID: 37671448 DOI: 10.1152/jn.00132.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 08/30/2023] [Accepted: 08/30/2023] [Indexed: 09/07/2023] Open
Abstract
According to current guidelines, when measuring voluntary activation (VA) using transcranial magnetic stimulation (TMS), stimulator output (SO) should not exceed the intensity that, during a maximal voluntary contraction (MVC), elicits a motor evoked potential (MEP) from the antagonist muscle >15%-20% of its maximal M-wave amplitude. However, VA is based on agonist evoked-torque responses [i.e., superimposed twitch (SIT) and estimated resting twitch (ERT)], which means limiting SO based on electromyographic (EMG) responses will often lead to a submaximal SIT and ERT, possibly underestimating VA. Therefore, the purpose of this study was to compare elbow flexor VA calculated using the original method (i.e., intensity based on MEP size; SOMEP) and a method based solely on eliciting the largest SIT at 50% MVC torque (SOSIT), regardless of triceps brachii MEP size. Fifteen healthy, young participants performed 10 sets of brief contractions at 100%, 75%, and 50% MVC torque, with TMS delivered at SOMEP (73.0 ± 13.5%) or SOSIT (92.0 ± 10.8%) for five sets each. Although the mean ERT torque was greater using SOSIT (15.2 ± 4.8 Nm) compared with SOMEP (13.0 ± 3.7 Nm; P = 0.031), the SIT amplitude at 100% MVC torque was not different (SOMEP: 0.69 ± 0.49 Nm vs. SOSIT: 0.74 ± 0.52 Nm; P = 0.604). Despite the ERT disparity, VA scores were not different between SOMEP (94.6 ± 3.5%) and SOSIT (95.0 ± 3.3%; P = 0.572). Even though SOSIT did not lead to a higher VA score than the SOMEP method, it has the benefit of yielding the same result without the need to record antagonist EMG or perform MVCs when determining SO, which can induce fatigue before measuring VA.NEW & NOTEWORTHY When using transcranial magnetic stimulation (TMS) to determine voluntary activation (VA) of the elbow flexors, we hypothesized that a stimulator output designed to limit antagonist muscle activity would evoke submaximal agonist superimposed twitch amplitudes, thus underestimating VA. Contrary to our hypothesis, VA was not greater with an output based on maximal superimposed twitch amplitude. Nevertheless, our findings advance methodological practices by simplifying the equipment and minimizing the time required to determine VA using TMS.
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Affiliation(s)
- Christina D Bruce
- Integrated Neuromuscular Physiology Laboratory, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Justine R Magnuson
- Integrated Neuromuscular Physiology Laboratory, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Chris J McNeil
- Integrated Neuromuscular Physiology Laboratory, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
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Mack M, Stojan R, Bock O, Voelcker-Rehage C. The association of executive functions and physical fitness with cognitive-motor multitasking in a street crossing scenario. Sci Rep 2023; 13:697. [PMID: 36639402 PMCID: PMC9839686 DOI: 10.1038/s41598-022-26438-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 12/14/2022] [Indexed: 01/15/2023] Open
Abstract
Age-related decline in cognitive-motor multitasking performance has been attributed to declines in executive functions and physical fitness (motor coordinative fitness and cardiovascular fitness). It has been suggested that those cognitive and physical resources strongly depend on lifestyle factors such as long-term regular physical activity and cognitive engagement. Although research suggests that there is covariation between components of executive functions and physical fitness, the interdependence between these components for cognitive-motor multitasking performance is not yet clear. The aim of the study was to examine the contribution and interrelationship between executive functions, motor coordinative fitness, and cardiovascular fitness on street crossing while multitasking. We used the more ecologically valid scenario to obtain results that might be directly transferable to daily life situation. Data from 50 healthy older adults (65-75 years, 17 females, recruited in two different cities in Germany) were analyzed. Participants' executive functions (composite score including six tests), motor coordinative fitness (composite score including five tests), and cardiovascular fitness (spiroergometry), as well as their street crossing performance while multitasking were assessed. Street crossing was tested under single-task (crossing a two-line road), and multitask conditions (crossing a two-line road while typing numbers on a keypad as simulation of mobile phone use). Street crossing performance was assessed by use of cognitive outcomes (typing, crossing failures) and motor outcomes (stay time, crossing speed). Linear mixed-effects models showed beneficial main effects of executive functions for typing (p = 0.004) and crossing failures (p = 0.023), and a beneficial main effect of motor coordinative fitness for stay time (p = 0.043). Commonality analysis revealed that the proportion of variance commonly explained by executive functions, motor coordinative fitness, and cardiovascular fitness was small for all street crossing outcomes. For typing and crossing failures (cognitive outcomes), the results further showed a higher relative contribution of executive functions compared to motor coordinative fitness and cardiovascular fitness. For stay time (motor outcome), the results correspondingly revealed a higher relative contribution of motor coordinative fitness compared to executive functions and cardiovascular fitness. The findings suggest that during cognitive-motor multitasking in everyday life, task performance is determined by the components of executive functions and physical fitness related to the specific task demands. Since multitasking in everyday life includes cognitive and motor tasks, it seems to be important to maintain both executive functions and physical fitness for independent living up to old age.
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Affiliation(s)
- Melanie Mack
- Department of Neuromotor Behavior and Exercise, Institute of Sport and Exercise Sciences, University of Münster, Wilhelm-Schickard-Straße 8, 48149, Muenster, Germany
| | - Robert Stojan
- Department of Neuromotor Behavior and Exercise, Institute of Sport and Exercise Sciences, University of Münster, Wilhelm-Schickard-Straße 8, 48149, Muenster, Germany.,Institute of Human Movement Science and Health, Chemnitz University of Technology, Thueringer Weg 11, 09126, Chemnitz, Germany
| | - Otmar Bock
- Institute of Human Movement Science and Health, Chemnitz University of Technology, Thueringer Weg 11, 09126, Chemnitz, Germany.,Institute of Exercise Training and Sport Informatics, German Sport University, Am Sportpark Muengersdorf 6, 50927, Cologne, Germany
| | - Claudia Voelcker-Rehage
- Department of Neuromotor Behavior and Exercise, Institute of Sport and Exercise Sciences, University of Münster, Wilhelm-Schickard-Straße 8, 48149, Muenster, Germany. .,Institute of Human Movement Science and Health, Chemnitz University of Technology, Thueringer Weg 11, 09126, Chemnitz, Germany.
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Sex-Related Differences in Functional Fitness Outcomes in Older Adults. J Aging Phys Act 2023:1-12. [PMID: 36626909 DOI: 10.1123/japa.2022-0071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 08/31/2022] [Accepted: 10/13/2022] [Indexed: 01/11/2023]
Abstract
Sex-related differences in changes in functional fitness over time were longitudinally assessed in older adults participating in a group-based multimodal exercise program. From a database, functional fitness scores were obtained for 89 older adults (71.6 ± 6.5 years old) who had completed two assessments, 5-8 years apart. Lower body strength, upper body strength, aerobic endurance, flexibility, and change of direction performances were compared over time and with normative values. Females (p = .02), but not males, had an improvement in upper body strength over time. Females were also more flexible than males at both assessments (p ≤ .02). Of those who had five consecutive assessments, females were more flexible than males (p ≤ .05) and had a faster change of direction ability (p < .001). When compared with normative values, our results indicate that typical time-related functional fitness loss can be attenuated with group exercise. Our results further support the need to tailor exercise prescription according to the individual.
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Monteiro-Oliveira BB, Coelho-Oliveira AC, Paineiras-Domingos LL, Sonza A, Sá-Caputo DDCD, Bernardo-Filho M. Use of surface electromyography to evaluate effects of whole-body vibration exercises on neuromuscular activation and muscle strength in the elderly: a systematic review. Disabil Rehabil 2022; 44:7368-7377. [PMID: 34699285 DOI: 10.1080/09638288.2021.1994030] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE Reduction of muscle strength and lean mass, increase in the risk of falls, higher mortality, and morbidity are observed in geriatric syndromes. Physical activity is an effective intervention in reducing signs and symptoms of geriatric syndromes. Whole-body vibration exercise (WBVE) is an intervention with low cost and has been effective. MATERIALS AND METHODS The aim of this systematic review aimed to determine the effects of WBVE on neuromuscular activation and muscle strength in the elderly. Searches in PubMed, Embase, Science direct, and Scopus databases were conducted. Six studies, that analyzed the use of surface electromyography evaluating effects of WBVE on neuromuscular activation and muscle strength in the elderly, published in English, were included. RESULTS Six studies were included. One hundred forty-six individuals participated in the studies and 24 were males (16.43%), with an average age of 74.20 ± 7.66 years. Five publications were defined as "fair" methodological in the PEDro scale, the risk of bias was high and the risk of bias for non-randomized studies was moderate/high. In general, increased strength muscle was reported in the studies. CONCLUSION This systematic review suggests that WBVE might promote desirable neuromuscular responses in healthy elderly. However, it is necessary to perform further studies to reinforce the reported findings.IMPLICATIONS FOR REHABILITATIONThe reduction in lean mass and consequent reduction in muscle strength are present in healthy elderly people and the whole-body vibration exercise can reduce or alleviate these symptoms caused by the geriatric syndrome.Whole-body vibration exercise is a training modality that increases neuromuscular activation and muscle strength.Surface electromyography is a useful tool for the evaluation of the neuromuscular activation of the muscle fibers.
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Affiliation(s)
- Bruno Bessa Monteiro-Oliveira
- Programa de Pós-Graduação em Fisiopatologia Clínica e Experimental, Faculdade de Ciências Médicas, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.,Laboratório de Vibrações Mecânicas e Práticas Integrativas, Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.,Faculdade Bezerra de Araújo, Rio de Janeiro, Brazil
| | - Ana Carolina Coelho-Oliveira
- Programa de Pós-Graduação em Fisiopatologia Clínica e Experimental, Faculdade de Ciências Médicas, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.,Laboratório de Vibrações Mecânicas e Práticas Integrativas, Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Anelise Sonza
- Universidade do Estado de Santa Catarina, Florianopolis, Brazil
| | - Danúbia da Cunha de Sá-Caputo
- Laboratório de Vibrações Mecânicas e Práticas Integrativas, Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil.,Faculdade Bezerra de Araújo, Rio de Janeiro, Brazil.,Programa de Pós-graduação em Ciências Médicas, Faculdade de Ciências Médicas, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Mario Bernardo-Filho
- Laboratório de Vibrações Mecânicas e Práticas Integrativas, Departamento de Biofísica e Biometria, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, Brazil
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6
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Paris MT, McNeil CJ, Power GA, Rice CL, Dalton BH. Age-related performance fatigability: a comprehensive review of dynamic tasks. J Appl Physiol (1985) 2022; 133:850-866. [PMID: 35952347 DOI: 10.1152/japplphysiol.00319.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Adult ageing is associated with a myriad of changes within the neuromuscular system, leading to reductions in contractile function of old adults. One of the consequences of these age-related neuromuscular adaptations is altered performance fatigability, which can limit the ability of old adults to perform activities of daily living. Whereas age-related fatigability of isometric tasks has been well characterized, considerably less is known about fatigability of old adults during dynamic tasks involving movement about a joint, which provides a more functionally relevant task compared to static contractions. This review provides a comprehensive summary of age-related fatigability in dynamic contractions, where the importance of task specificity is highlighted with a brief discussion of the potential mechanisms responsible for differences in fatigability between young and old adults. The angular velocity of the task is critical for evaluating age-related fatigability, as tasks which constrain angular velocity (i.e., isokinetic) produce equivocal age-related differences in fatigability, whereas tasks involving unconstrained velocity (i.e., isotonic-like) consistently induce greater fatigability of old compared to young adults. These unconstrained velocity tasks, that are more closely associated with natural movements, offer an excellent model to uncover the underlying age-related mechanisms of increased fatigability. Future work evaluating the mechanisms of increased age-related fatigability of dynamic tasks should be evaluated using task-specific contractions (i.e., dynamic), particularly for assessment of spinal and supra-spinal components. Advancing our understanding of age-related fatigability is likely to yield novel insights and approaches for improving mobility limitations in old adults.
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Affiliation(s)
- Michael T Paris
- School of Kinesiology, University of Western Ontario, London, ON, Canada
| | - Chris J McNeil
- School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada
| | - Charles L Rice
- School of Kinesiology, University of Western Ontario, London, ON, Canada.,Department of Anatomy and Cell Biology, University of Western Ontario, London, ON, Canada
| | - Brian H Dalton
- School of Health and Exercise Science, University of British Columbia, Kelowna, BC, Canada
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Pearson LT, Behm DG, Goodall S, Mason R, Stuart S, Barry G. Effects of maximal-versus submaximal-intent resistance training on functional capacity and strength in community-dwelling older adults: a systematic review and meta-analysis. BMC Sports Sci Med Rehabil 2022; 14:129. [PMID: 35842655 PMCID: PMC9287903 DOI: 10.1186/s13102-022-00526-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Accepted: 07/12/2022] [Indexed: 11/17/2022]
Abstract
The objective of this systematic review is to investigate the effects of different methods of resistance training (RT) on functional capacity in older adults. A systematic literature search was conducted using PubMed, SPORTDiscus, Web of Science, CINAHL, Cochrane CENTRAL, ClinicalTrials.gov databases, from inception to December 2021. Eligibility criteria consisted of randomised control trials (RCT's) involving maximal-intent resistance training (MIRT), where participants (aged 60+) had specific instruction to move 'as fast as possible' during the concentric phase of the exercise. Twelve studies were included within the meta-analysis. Divided into functional capacity and strength-related outcomes; Improvements were evident for timed-up-and-go (p = 0.001, SMD: - 1.74 [95% CI - 2.79, - 0.69]) and knee extension one-repetition maximum (1RM) (p = 0.01, SMD: - 1.21, [95% CI - 2.17, - 0.25]), both in favour of MIRT, as well as in 30 s sit-to-stand in favour of T-STR (p = 0.04, SMD: 3.10 [95% CI 0.07, 6.14]). No statistical significance was found for combined functional capacity outcomes (p = 0.17, SMD: - 0.84, [95% CI - 2.04, 0.37]), with near-significance observed in strength-related outcomes (p = 0.06. SMD: - 0.57, [95% CI - 1.16, 0.02]) favouring MIRT. Heterogeneity for FC-outcomes was observed as Tau2 = 4.83; Chi = 276.19, df = 14, I2 = 95%, and for strength-outcomes Tau2 = 1.290; Chi = 109.65, df = 115, I2 = 86%. Additionally, MIRT elicited substantial clinically meaningful improvements (CMI) in Short Physical Performance Battery (SPPB) scores but fell short of CMI in 400 m walk test by 0.6 s. In conclusion, this systematic review highlights the lack of sufficient and quality evidence for maximal- versus submaximal-intent resistance training on functional capacity and strength in community-dwelling older adults. Study limitations revolved around lack of research, low quality ("low" PEDro score), and largely due to the fact many comparison studies did not match their loads lifted (1500 kg vs. 500 kg), making comparisons not possible.
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Affiliation(s)
- Liam T Pearson
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK.
| | - David G Behm
- School of Human Kinetics and Recreation, Memorial University of Newfoundland, St. John's, Canada
| | - Stuart Goodall
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK
| | - Rachel Mason
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK
| | - Samuel Stuart
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK
- Northumbria Healthcare NHS Foundation Trust, Tyne and Wear, UK
| | - Gill Barry
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, NE1 8ST, UK
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Varesco G, Luneau E, Féasson L, Lapole T, Rozand V. Very old adults show impaired fatigue resistance compared to old adults independently of sex during a knee-extensors isometric test. Exp Gerontol 2022; 161:111732. [DOI: 10.1016/j.exger.2022.111732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 01/31/2022] [Accepted: 02/02/2022] [Indexed: 11/26/2022]
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Petitet P, Spitz G, Emir UE, Johansen-Berg H, O'Shea J. Age-related decline in cortical inhibitory tone strengthens motor memory. Neuroimage 2021; 245:118681. [PMID: 34728243 PMCID: PMC8752967 DOI: 10.1016/j.neuroimage.2021.118681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 10/21/2021] [Accepted: 10/24/2021] [Indexed: 11/02/2022] Open
Abstract
Ageing disrupts the finely tuned excitation/inhibition balance (E:I) across cortex via a natural decline in inhibitory tone (γ-amino butyric acid, GABA), causing functional decrements. However, in young adults, experimentally lowering GABA in sensorimotor cortex enhances a specific domain of sensorimotor function: adaptation memory. Here, we tested the hypothesis that as sensorimotor cortical GABA declines naturally with age, adaptation memory would increase, and the former would explain the latter. Results confirmed this prediction. To probe causality, we used brain stimulation to further lower sensorimotor cortical GABA during adaptation. Across individuals, how stimulation changed memory depended on sensorimotor cortical E:I. In those with low E:I, stimulation increased memory; in those with high E:I stimulation reduced memory. Thus, we identified a form of motor memory that is naturally strengthened by age, depends causally on sensorimotor cortex neurochemistry, and may be a potent target for motor skill preservation strategies in healthy ageing and neurorehabilitation.
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Affiliation(s)
- Pierre Petitet
- Wellcome Centre for Integrative Neuroimaging, FMRIB Centre, Nuffield Department of Clinical Neurosciences (NDCN), John Radcliffe Hospital, Headington, Oxford, United Kingdom; Centre de Recherche en Neurosciences de Lyon, Equipe Trajectoires, Inserm UMR-S 1028, CNRS UMR 5292, Université Lyon 1, Bron, France.
| | - Gershon Spitz
- Wellcome Centre for Integrative Neuroimaging, FMRIB Centre, Nuffield Department of Clinical Neurosciences (NDCN), John Radcliffe Hospital, Headington, Oxford, United Kingdom; Turner Institute for Brain and Mental Health, Monash University, Melbourne, Australia.
| | - Uzay E Emir
- School of Health Sciences, Purdue University, West Lafayette, Indiana, USA; Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana, USA.
| | - Heidi Johansen-Berg
- Wellcome Centre for Integrative Neuroimaging, FMRIB Centre, Nuffield Department of Clinical Neurosciences (NDCN), John Radcliffe Hospital, Headington, Oxford, United Kingdom.
| | - Jacinta O'Shea
- Wellcome Centre for Integrative Neuroimaging, FMRIB Centre, Nuffield Department of Clinical Neurosciences (NDCN), John Radcliffe Hospital, Headington, Oxford, United Kingdom; Wellcome Centre for Integrative Neuroimaging, Oxford Centre for Human Brain Activity (OHBA), University of Oxford Department of Psychiatry, Warneford Hospital, Warneford Lane, Oxford, United Kingdom.
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10
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Hassan AS, Fajardo ME, Cummings M, McPherson LM, Negro F, Dewald JPA, Heckman CJ, Pearcey GEP. Estimates of persistent inward currents are reduced in upper limb motor units of older adults. J Physiol 2021; 599:4865-4882. [PMID: 34505294 DOI: 10.1113/jp282063] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 09/07/2021] [Indexed: 11/08/2022] Open
Abstract
Ageing is a natural process causing alterations in the neuromuscular system, which contributes to reduced quality of life. Motor unit (MU) contributes to weakness, but the mechanisms underlying reduced firing rates are unclear. Persistent inward currents (PICs) are crucial for initiation, gain control and maintenance of motoneuron firing, and are directly proportional to the level of monoaminergic input. Since concentrations of monoamines (i.e. serotonin and noradrenaline) are reduced with age, we sought to determine if estimates of PICs are reduced in older (>60 years old) compared to younger adults (<35 years old). We decomposed MU spike trains from high-density surface electromyography over the biceps and triceps brachii during isometric ramp contractions to 20% of maximum. Estimates of PICs (ΔFrequency; or simply ΔF) were computed using the paired MU analysis technique. Regardless of the muscle, peak firing rates of older adults were reduced by ∼1.6 pulses per second (pps) (P = 0.0292), and ΔF was reduced by ∼1.9 pps (P < 0.0001), compared to younger adults. We further found that age predicted ΔF in older adults (P = 0.0261), resulting in a reduction of ∼1 pps per decade, but there was no relationship in younger adults (P = 0.9637). These findings suggest that PICs are reduced in the upper limbs of older adults during submaximal isometric contractions. Reduced PIC magnitude represents one plausible mechanism for reduced firing rates and function in older individuals, but further work is required to understand the implications in other muscles and during a variety of motor tasks. KEY POINTS: Persistent inward currents play an important role in the neural control of human movement and are influenced by neuromodulation via monoamines originating in the brainstem. During ageing, motor unit firing rates are reduced, and there is deterioration of brainstem nuclei, which may reduce persistent inward currents in alpha motoneurons. Here we show that estimates of persistent inward currents (ΔF) of both elbow flexor and extensor motor units are reduced in older adults. Estimates of persistent inward currents have a negative relationship with age in the older adults, but not in the young. This novel mechanism may play a role in the alteration of motor firing rates that occurs with ageing, which may have consequences for motor control.
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Affiliation(s)
- Altamash S Hassan
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Melissa E Fajardo
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - Mark Cummings
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy, College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, USA
| | - Laura Miller McPherson
- Program in Physical Therapy, Washington University School of Medicine, St Louis, MO, USA.,Department of Neurology, Washington University School of Medicine, St Louis, MO, USA
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, Universita' degli Studi di Brescia, Brescia, Italy
| | - Julius P A Dewald
- Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, IL, USA.,Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | - C J Heckman
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Shirley Ryan AbilityLab, Chicago, IL, USA
| | - Gregory E P Pearcey
- Department of Physical Therapy and Human Movement Sciences, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Neuroscience, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Department of Physical Medicine and Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.,Shirley Ryan AbilityLab, Chicago, IL, USA
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Allen MD, Dalton BH, Gilmore KJ, McNeil CJ, Doherty TJ, Rice CL, Power GA. Neuroprotective effects of exercise on the aging human neuromuscular system. Exp Gerontol 2021; 152:111465. [PMID: 34224847 DOI: 10.1016/j.exger.2021.111465] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2020] [Revised: 05/31/2021] [Accepted: 06/30/2021] [Indexed: 12/23/2022]
Abstract
Human biological aging from maturity to senescence is associated with a gradual loss of muscle mass and neuromuscular function. It is not until very old age (>80 years) however, that these changes often manifest into functional impairments. A driving factor underlying the age-related loss of muscle mass and function is the reduction in the number and quality of motor units (MUs). A MU consists of a single motoneuron, located either in the spinal cord or the brain stem, and all of the muscle fibres it innervates via its peripheral axon. Throughout the adult lifespan, MUs are slowly, but progressively lost. The compensatory process of collateral reinnervation attempts to recapture orphaned muscle fibres following the death of a motoneuron. Whereas this process helps mitigate loss of muscle mass during the latter decades of adult aging, the neuromuscular system has fewer and larger MUs, which have lower quality connections between the axon terminal and innervated muscle fibres. Whether this process of MU death and degradation can be attenuated with habitual physical activity has been a challenging question of great interest. This review focuses on age-related alterations of the human neuromuscular system, with an emphasis on the MU, and presents findings on the potential protective effects of lifelong physical activity. Although there is some discrepancy across studies of masters athletes, if one considers all experimental limitations as well as the available literature in animals, there is compelling evidence of a protective effect of chronic physical training on human MUs. Our tenet is that high-levels of physical activity can mitigate the natural trajectory of loss of quantity and quality of MUs in old age.
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Affiliation(s)
- Matti D Allen
- Department of Physical Medicine and Rehabilitation, School of Medicine, Faculty of Health Sciences, Queen's University, Kingston, ON K7L 4X3, Canada; School of Kinesiology and Health Studies, Faculty of Arts and Sciences, Queen's University, Kingston, ON K7L 4X3, Canada
| | - Brian H Dalton
- School of Health and Exercise Science, University of British Columbia, Kelowna, BC V1V 1V7, Canada
| | - Kevin J Gilmore
- Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Chris J McNeil
- School of Health and Exercise Science, University of British Columbia, Kelowna, BC V1V 1V7, Canada
| | - Timothy J Doherty
- Department of Clinical Neurological Sciences, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada; Department of Physical Medicine and Rehabilitation, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada
| | - Charles L Rice
- School of Kinesiology, The University of Western Ontario, London, ON, Canada; Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON, Canada.
| | - Geoffrey A Power
- Department of Human Health and Nutritional Sciences, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
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Characteristics of the Electrophysiological Properties of Neuromuscular Motor Units and Its Adaptive Strategy Response in Lower Extremity Muscles for Seniors with Pre-Sarcopenia: A Preliminary Study. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph18063063. [PMID: 33809692 PMCID: PMC8002219 DOI: 10.3390/ijerph18063063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/10/2021] [Accepted: 03/13/2021] [Indexed: 11/16/2022]
Abstract
Older adults with sarcopenia, which is an aging-related phenomenon of muscle mass loss, usually suffer from decreases in both strength and functional performance. However, the causality between function loss and physiological changes is unclear. This study aimed to explore the motor unit characteristics of the neurological factors between normal subjects and those with sarcopenia. Five risk-sarcopenia (age: 66.20 ± 4.44), five healthy (age: 69.00 ± 2.35), and twelve young (age: 21.33 ± 1.15) participants were selected. Each participant performed knee extension exercises at a 50% level of maximal voluntary isometric contraction. Next, electromyogram (EMG) signals were collected, and information on each parameter—e.g., motor unit number, recruitment threshold, the slope of the mean firing rate to recruitment threshold, y-intercept, firing rate per unit force, and mean motor unit firing rate (MFR)—was extracted to analyze muscle fiber discrimination (MFD). Meanwhile, force variance was used to observe the stability between two muscle groups. The results suggested that there was no difference between the three groups for motor unit number, recruitment threshold, y-intercept, mean firing rate, and motor unit discrimination (p > 0.05). However, the slope of MFR and firing rate per unit force in the risk-sarcopenia group were significantly higher than in the young group (p < 0.05). Regarding muscle performance, the force variance in the non-sarcopenia group was significantly higher than the young group (p < 0.05), while the risk-sarcopenia group showed a higher trend than the young group. This study demonstrated some neuromuscular characters between sarcopenia and healthy elderly and young people when performing the same level of leg exercise tasks. This difference may provide some hints for discovering aging-related strength and function loss. Future studies should consider combining the in vivo measurement of muscle fiber type to clarify whether this EMG difference is related to the loss of muscle strength or mass before recruiting symptomatic elderly participants for further investigation.
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Girts RM, MacLennan RJ, Harmon KK, Stock MS. Is skeletal muscle echo intensity more indicative of voluntary or involuntary strength in young women? TRANSLATIONAL SPORTS MEDICINE 2021. [DOI: 10.1002/tsm2.234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Ryan M. Girts
- Neuromuscular Plasticity Laboratory School of Kinesiology and Physical Therapy University of Central Florida Orlando FL USA
- Institute of Exercise Physiology and Rehabilitation Science University of Central Florida Orlando FL USA
| | - Rob J. MacLennan
- Applied Neuromuscular Physiology Laboratory Oklahoma State University Stillwater OK USA
| | - Kylie K. Harmon
- Neuromuscular Plasticity Laboratory School of Kinesiology and Physical Therapy University of Central Florida Orlando FL USA
- Institute of Exercise Physiology and Rehabilitation Science University of Central Florida Orlando FL USA
| | - Matt S. Stock
- Neuromuscular Plasticity Laboratory School of Kinesiology and Physical Therapy University of Central Florida Orlando FL USA
- Institute of Exercise Physiology and Rehabilitation Science University of Central Florida Orlando FL USA
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14
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Moore CW, Fanous J, Rice CL. Fiber type composition of contiguous palmaris longus and abductor pollicis brevis muscles: Morphological evidence of a functional synergy. J Anat 2021; 238:53-62. [PMID: 32790091 PMCID: PMC7754940 DOI: 10.1111/joa.13289] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 06/25/2020] [Accepted: 07/09/2020] [Indexed: 01/03/2023] Open
Abstract
The palmaris longus (PL) tendon is used in surgical opponensplasty to restore functional hand movements in thenar paralysis. Although successful PL autologous tendon transfer has been attributed to an established synergistic relationship between the PL and abductor pollicis brevis (APB) muscles in vivo, this functional relationship may be dependent on the quality of their spatial relationship and properties of their constituent muscle fibers. The purpose was to compare the proportion of type I and type II muscle fibers in the APB based on its contiguous morphological relationship with the PL tendon for indirect insight into their functional synergy, contractile capacity, and digastric arrangement. Twenty-four contiguous PL and APB specimens were harvested from the upper limbs (12 right and 12 left) of twelve formalin-embalmed cadavers (mean age: 74 ± 10 years). The fiber type composition of these muscles was determined by labeling serial cross sections with myosin heavy chain (MyHC) type I and type II monoclonal antibodies. The PL consisted of a relatively heterogeneous fiber type composition irrespective of the presence of a discrete (type I: 41 ± 11%; type II: 55 ± 12%; hybrid: 4 ± 3%) or rudimentary (type I: 49 ± 10%; type II: 45 ± 9%; hybrid: 6 ± 4%) tendinous connection with the APB. The APB fascicles arranged contiguously with the PL through a discrete tendon had significantly greater proportions of type II fibers (41 ± 19%) compared to those with rudimentary PL connections (type II: 15 ± 8%). Therefore, the APB fascicles arranged in a digastric relationship with the PL may have the capacity to produce more powerful contractions than those with rudimentary PL tendons based on the known contractile properties of type II muscle fibers. Knowledge of the spatial relationship between the PL and thenar musculature prior to PL autologous tendon transfer may be a useful indicator of the quality of established synergy in vivo.
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Affiliation(s)
- Colin W. Moore
- Department of Pathology & Anatomical SciencesJacobs School of MedicineUniversity at BuffaloBuffaloNYUSA
| | - Jacob Fanous
- School of Kinesiology, Faculty of Health SciencesThe University of Western OntarioLondonONCanada
| | - Charles L. Rice
- School of Kinesiology, Faculty of Health SciencesThe University of Western OntarioLondonONCanada,Department of Anatomy & Cell BiologySchulich School of Medicine & DentistryThe University of Western OntarioLondonONCanada
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Nojima I, Suwa Y, Sugiura H, Noguchi T, Tanabe S, Mima T, Watanabe T. Smaller muscle mass is associated with increase in EMG-EMG coherence of the leg muscle during unipedal stance in elderly adults. Hum Mov Sci 2020; 71:102614. [PMID: 32452431 DOI: 10.1016/j.humov.2020.102614] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 03/16/2020] [Accepted: 03/16/2020] [Indexed: 11/29/2022]
Abstract
Age-induced decline in the ability to perform daily activities is associated with a deterioration of physical parameters. Changes occur in neuromuscular system with age; however, the relationship between these changes and physical parameters has not been fully elucidated. Therefore, in this study, we aimed to determine the relationship between neuromuscular system evaluated using a coherence analysis of the leg muscles and physical parameters in community-dwelling healthy elderly adults. The participants were required to stand still in bipedal and unipedal stances on a force plate. Then, electromyography (EMG) was recorded from the tibialis anterior (TA) and medial and lateral gastrocnemius (MG/LG) muscles, and intermuscular coherence was calculated between the following pairs: TA and MG (TA-MG), TA and LG (TA-LG), and MG and LG (MG-LG). Furthermore, gait speed, unipedal stance time, and muscle mass were measured. EMG-EMG coherence for the MG-LG pair was significantly greater in the unipedal stance task than in the bipedal one (p = .001). Multiple linear regression analysis revealed that the muscle mass of the leg was negatively correlated with the change in the β-band coherence for the MG-LG pair from bipedal to unipedal stance (R2 = 0.067, standard β = -0.345, p = .044). As the β-band coherence could reflect the corticospinal activity, the increased β-band coherence may be a compensation for the smaller muscle mass, or alternatively may be a sign of changes in the nervous system resulting in the loss of muscle mass.
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Affiliation(s)
- Ippei Nojima
- Department of Physical Therapy, School of Health Sciences, Shinshu University, Matsumoto, Nagano, Japan.
| | - Yuki Suwa
- Department of Physical Therapy, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Hideshi Sugiura
- Department of Physical Therapy, Nagoya University Graduate School of Medicine, Aichi, Japan
| | - Taiji Noguchi
- National Center for Geriatrics and Gerontology, Aichi, Japan
| | - Shigeo Tanabe
- Faculty of Rehabilitation, School of Health Sciences, Fujita Health University, Toyoake, Aichi, Japan
| | - Tatsuya Mima
- Graduate School of Core Ethics and Frontier Sciences, Ritsumeikan University, Kyoto, Japan
| | - Tatsunori Watanabe
- Department of Sensorimotor Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
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Škarabot J, Ansdell P, Temesi J, Howatson G, Goodall S, Durbaba R. Neurophysiological responses and adaptation following repeated bouts of maximal lengthening contractions in young and older adults. J Appl Physiol (1985) 2019; 127:1224-1237. [DOI: 10.1152/japplphysiol.00494.2019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A bout of maximal lengthening contractions is known to produce muscle damage, but confers protection against subsequent damaging bouts, with both tending to be lower in older adults. Neural factors contribute to this adaptation, but the role of the corticospinal pathway remains unclear. Twelve young (27 ± 5 yr) and 11 older adults (66 ± 4 yr) performed two bouts of 60 maximal lengthening dorsiflexions 2 weeks apart. Neuromuscular responses were measured preexercise, immediately postexercise, and at 24 and 72 h following both bouts. The initial bout resulted in prolonged reductions in maximal voluntary torque (MVC; immediately postexercise onward, P < 0.001) and increased creatine kinase (from 24 h onward, P = 0.001), with both responses being attenuated following the second bout ( P < 0.015), demonstrating adaptation. Smaller reductions in MVC following both bouts occurred in older adults ( P = 0.005). Intracortical facilitation showed no changes ( P ≥ 0.245). Motor-evoked potentials increased 24 and 72 h postexercise in young ( P ≤ 0.038). Torque variability ( P ≤ 0.041) and H-reflex size ( P = 0.024) increased, while short-interval intracortical inhibition (SICI; P = 0.019) and the silent period duration (SP) decreased ( P = 0.001) in both groups immediately postexercise. The SP decrease was smaller following the second bout ( P = 0.021), and there was an association between the change in SICI and reduction in MVC 24 h postexercise in young adults ( R = −0.47, P = 0.036). Changes in neurophysiological responses were mostly limited to immediately postexercise, suggesting a modest role in adaptation. In young adults, neural inhibitory changes are linked to the extent of MVC reduction, possibly mediated by the muscle damage–related afferent feedback. Older adults incurred less muscle damage, which has implications for exercise prescription. NEW & NOTEWORTHY This is the first study to have collectively assessed the role of corticospinal, spinal, and intracortical activity in muscle damage attenuation following repeated bouts of exercise in young and older adults. Lower levels of muscle damage in older adults are not related to their neurophysiological responses. Neural inhibition transiently changed, which might be related to the extent of muscle damage; however, the role of processes along the corticospinal pathway in the adaptive response is limited.
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Affiliation(s)
- Jakob Škarabot
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - Paul Ansdell
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - John Temesi
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - Glyn Howatson
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
- Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, South Africa
| | - Stuart Goodall
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
| | - Rade Durbaba
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, England, United Kingdom
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17
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Enoka RM. A primer on motor unit physiology. J Electromyogr Kinesiol 2019; 47:123-124. [DOI: 10.1016/j.jelekin.2019.05.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 05/01/2019] [Indexed: 10/26/2022] Open
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18
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Škarabot J, Ansdell P, Brownstein CG, Hicks KM, Howatson G, Goodall S, Durbaba R. Reduced corticospinal responses in older compared with younger adults during submaximal isometric, shortening, and lengthening contractions. J Appl Physiol (1985) 2019; 126:1015-1031. [PMID: 30730812 DOI: 10.1152/japplphysiol.00987.2018] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The aim of this study was to assess differences in motor performance, as well as corticospinal and spinal responses to transcranial magnetic and percutaneous nerve stimulation, respectively, during submaximal isometric, shortening, and lengthening contractions between younger and older adults. Fifteen younger [26 yr (SD 4); 7 women, 8 men] and 14 older [64 yr (SD 3); 5 women, 9 men] adults performed isometric and shortening and lengthening dorsiflexion on an isokinetic dynamometer (5°/s) at 25% and 50% of contraction type-specific maximums. Motor evoked potentials (MEPs) and H reflexes were recorded at anatomical zero. Maximal dorsiflexor torque was greater during lengthening compared with shortening and isometric contractions ( P < 0.001) but was not age dependent ( P = 0.158). However, torque variability was greater in older compared with young adults ( P < 0.001). Background electromyographic (EMG) activity was greater in older compared with younger adults ( P < 0.005) and was contraction type dependent ( P < 0.001). As evoked responses are influenced by both the maximal level of excitation and background EMG activity, the responses were additionally normalized {[MEP/maximum M wave (Mmax)]/root-mean-square EMG activity (RMS) and [H reflex (H)/Mmax]/RMS}. (MEP/Mmax)/RMS and (H/Mmax)/RMS were similar across contraction types but were greater in young compared with older adults ( P < 0.001). Peripheral motor conduction times were prolonged in older adults ( P = 0.003), whereas peripheral sensory conduction times and central motor conduction times were not age dependent ( P ≥ 0.356). These data suggest that age-related changes throughout the central nervous system serve to accommodate contraction type-specific motor control. Moreover, a reduction in corticospinal responses and increased torque variability seem to occur without a significant reduction in maximal torque-producing capacity during older age. NEW & NOTEWORTHY This is the first study to have explored corticospinal and spinal responses with aging during submaximal contractions of different types (isometric, shortening, and lengthening) in lower limb musculature. It is demonstrated that despite preserved maximal torque production capacity corticospinal responses are reduced in older compared with younger adults across contraction types along with increased torque variability during dynamic contractions. This suggests that the age-related corticospinal changes serve to accommodate contraction type-specific motor control.
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Affiliation(s)
- Jakob Škarabot
- Faculty of Health and Life Sciences, Northumbria University , Newcastle Upon Tyne , United Kingdom
| | - Paul Ansdell
- Faculty of Health and Life Sciences, Northumbria University , Newcastle Upon Tyne , United Kingdom
| | - Callum G Brownstein
- Faculty of Health and Life Sciences, Northumbria University , Newcastle Upon Tyne , United Kingdom.,Université Lyon, UJM-Saint-Etienne, Inter-university Laboratory of Human Movement Biology, Saint-Etienne, France
| | - Kirsty M Hicks
- Faculty of Health and Life Sciences, Northumbria University , Newcastle Upon Tyne , United Kingdom
| | - Glyn Howatson
- Faculty of Health and Life Sciences, Northumbria University , Newcastle Upon Tyne , United Kingdom.,Water Research Group, School of Environmental Sciences and Development, Northwest University , Potchefstroom , South Africa
| | - Stuart Goodall
- Faculty of Health and Life Sciences, Northumbria University , Newcastle Upon Tyne , United Kingdom
| | - Rade Durbaba
- Faculty of Health and Life Sciences, Northumbria University , Newcastle Upon Tyne , United Kingdom
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19
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Gardiner PF, Ljubicic V. Special issue on nervous system and exercise. Appl Physiol Nutr Metab 2018; 43:v. [PMID: 30380929 DOI: 10.1139/apnm-2018-0393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Phillip F Gardiner
- a Spinal Cord Research Center, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Vladimir Ljubicic
- b Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada
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