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Lecce E, Conti A, Nuccio S, Felici F, Bazzucchi I. Characterising sex-related differences in lower- and higher-threshold motor unit behaviour through high-density surface electromyography. Exp Physiol 2024; 109:1317-1329. [PMID: 38888901 PMCID: PMC11291872 DOI: 10.1113/ep091823] [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: 02/14/2024] [Accepted: 05/28/2024] [Indexed: 06/20/2024]
Abstract
Emerging questions in neuromuscular physiology revolve around whether males and females share similar neural control in diverse tasks across a broad range of intensities. In order to explore these features, high-density electromyography was used to record the myoelectrical activity of biceps brachii during trapezoidal isometric contractions at 35% and 70% of maximal voluntary force (MVF) on 11 male and 13 female participants. Identified motor units were then classified as lower-threshold (recruited at ≤30%MVF) and higher-threshold (recruited at >30%MVF). The discharge rate, interspike interval variability, recruitment and derecruitment thresholds, and estimates of neural drive to motor neurons were assessed. Female lower-threshold motor units showed higher neural drive (P < 0.001), accompanied by higher discharge rate at recruitment (P = 0.006), plateau (P = 0.001) and derecruitment (P = 0.001). On the other hand, male higher-threshold motor units showed greater neural drive (P = 0.04), accompanied by higher discharge rate at recruitment (P = 0.005), plateau (P = 0.04) and derecruitment (P = 0.01). Motor unit discharge rate normalised by the recruitment threshold was significantly higher in female lower-threshold motor units (P < 0.001), while no differences were observed in higher-threshold motor units. Recruitment and derecruitment thresholds are higher in males across all intensities (P < 0.01). However, males and females have similar activation and deactivation strategies, as evidenced by similar recruitment-to-derecruitment ratios (P > 0.05). This study encompasses a broad intensity range to analyse motor unit sex-related differences, highlighting higher neural drive and discharge rates in female lower-threshold motor units, elevated recruitment and derecruitment thresholds in males, and convergences in activation and deactivation strategies. HIGHLIGHTS: What is the central question of the study? Do male and female motor units behave similarly in low- and high-intensity contractions? What is the main finding and its importance? Female motor units show higher discharge rates in low-intensity tasks and lower discharge rates in high-intensity tasks, with no differences in recruitment behaviour. A broader inter-spike interval variability was also observed in females. These findings underline that there are sex-specific differences concern the firing strategies based on task intensity.
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Affiliation(s)
- Edoardo Lecce
- Department of Movement, Human and Health Sciences, Laboratory of Exercise PhysiologyUniversity of Rome ‘Foro Italico’RomeItaly
| | - Alessandra Conti
- Department of Movement, Human and Health Sciences, Laboratory of Exercise PhysiologyUniversity of Rome ‘Foro Italico’RomeItaly
| | - Stefano Nuccio
- Department of Movement, Human and Health Sciences, Laboratory of Exercise PhysiologyUniversity of Rome ‘Foro Italico’RomeItaly
| | - Francesco Felici
- Department of Movement, Human and Health Sciences, Laboratory of Exercise PhysiologyUniversity of Rome ‘Foro Italico’RomeItaly
| | - Ilenia Bazzucchi
- Department of Movement, Human and Health Sciences, Laboratory of Exercise PhysiologyUniversity of Rome ‘Foro Italico’RomeItaly
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2
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Siddique U, Frazer AK, Avela J, Walker S, Ahtiainen JP, Tanel M, Uribe S, Akalu Y, Rostami M, Tallent J, Kidgell DJ. Differential modulation of corticomotor excitability in older compared to young adults following a single bout of strength -exercise. Arch Gerontol Geriatr 2024; 122:105384. [PMID: 38394740 DOI: 10.1016/j.archger.2024.105384] [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: 11/09/2023] [Revised: 02/09/2024] [Accepted: 02/19/2024] [Indexed: 02/25/2024]
Abstract
Evidence shows corticomotor plasticity diminishes with age. Nevertheless, whether strength-training, a proven intervention that induces corticomotor plasticity in younger adults, also takes effect in older adults, remains untested. This study examined the effect of a single-session of strength-exercise on corticomotor plasticity in older and younger adults. Thirteen older adults (72.3 ± 6.5 years) and eleven younger adults (29.9 ± 6.9 years), novice to strength-exercise, participated. Strength-exercise involved four sets of 6-8 repetitions of a dumbbell biceps curl at 70-75% of their one-repetition maximum (1-RM). Muscle strength, cortical, corticomotor and spinal excitability, before and up to 60-minutes after the strength-exercise session were assessed. We observed significant changes over time (p < 0.05) and an interaction between time and age group (p < 0.05) indicating a decrease in corticomotor excitability (18% p < 0.05) for older adults at 30- and 60-minutes post strength-exercise and an increase (26% and 40%, all p < 0.05) in younger adults at the same time points. Voluntary activation (VA) declined in older adults immediately post and 60-minutes post strength-exercise (36% and 25%, all p < 0.05). Exercise had no effect on the cortical silent period (cSP) in older adults however, in young adults cSP durations were shorter at both 30- and 60- minute time points (17% 30-minute post and 9% 60-minute post, p < 0.05). There were no differences in short-interval cortical inhibition (SICI) or intracortical facilitation (ICF) between groups. Although the corticomotor responses to strength-exercise were different within groups, overall, the neural responses seem to be independent of age.
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Affiliation(s)
- Ummatul Siddique
- Monash University Exercise Neuroplasticity Research Unit, School of Primary and Allied Care, Monash University, Frankston, Australia
| | - Ashlyn K Frazer
- Monash University Exercise Neuroplasticity Research Unit, School of Primary and Allied Care, Monash University, Frankston, Australia
| | - Janne Avela
- NeuroMuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Simon Walker
- NeuroMuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Juha P Ahtiainen
- NeuroMuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Meghan Tanel
- NeuroMuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Sergio Uribe
- Department of Medical Imaging and Radiation Sciences, School of Primary and Allied Care, Monash University, Clayton, Australia
| | - Yonas Akalu
- Monash University Exercise Neuroplasticity Research Unit, School of Primary and Allied Care, Monash University, Frankston, Australia; Department of Human Physiology, School of Medicine, University of Gondar, Gondar, Ethiopia
| | - Mohamad Rostami
- Monash University Exercise Neuroplasticity Research Unit, School of Primary and Allied Care, Monash University, Frankston, Australia
| | - Jamie Tallent
- Monash University Exercise Neuroplasticity Research Unit, School of Primary and Allied Care, Monash University, Frankston, Australia; School of Sport, Rehabilitation and Exercise Sciences, University of Essex, Colchester, UK
| | - Dawson J Kidgell
- Monash University Exercise Neuroplasticity Research Unit, School of Primary and Allied Care, Monash University, Frankston, Australia.
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3
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Akalu Y, Tallent J, Frazer AK, Siddique U, Rostami M, Vallance P, Howatson G, Walker S, Kidgell DJ. Strength-trained adults demonstrate greater corticoreticular activation versus untrained controls. Eur J Neurosci 2024; 59:2336-2352. [PMID: 38419404 DOI: 10.1111/ejn.16297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Revised: 02/08/2024] [Accepted: 02/12/2024] [Indexed: 03/02/2024]
Abstract
The rapid increase in strength following strength-training involves neural adaptations, however, their specific localisation remains elusive. Prior focus on corticospinal responses prompts this study to explore the understudied cortical/subcortical adaptations, particularly cortico-reticulospinal tract responses, comparing healthy strength-trained adults to untrained peers. Fifteen chronically strength-trained individuals (≥2 years of training, mean age: 24 ± 7 years) were compared with 11 age-matched untrained participants (mean age: 26 ± 8 years). Assessments included maximal voluntary force (MVF), corticospinal excitability using transcranial magnetic stimulation (TMS), spinal excitability (cervicomedullary stimulation), voluntary activation (VA) and reticulospinal tract (RST) excitability, utilizing StartReact responses and ipsilateral motor-evoked potentials (iMEPs) for the flexor carpi radialis muscle. Trained participants had higher normalized MVF (6.4 ± 1.1 N/kg) than the untrained participants (4.8 ± 1.3 N/kg) (p = .003). Intracortical facilitation was higher in the strength-trained group (156 ± 49%) (p = .02), along with greater VA (98 ± 3.2%) (p = .002). The strength-trained group displayed reduced short-interval-intracortical inhibition (88 ± 8.0%) compared with the untrained group (69 ± 17.5%) (p < .001). Strength-trained individuals exhibited a greater normalized rate of force development (38.8 ± 10.1 N·s-1/kg) (p < .009), greater reticulospinal gain (2.5 ± 1.4) (p = .02) and higher ipsilateral-to-contralateral MEP ratios compared with the untrained group (p = .03). Strength-trained individuals displayed greater excitability within the intrinsic connections of the primary motor cortex and the RST. These results suggest greater synaptic input from the descending cortico-reticulospinal tract to α-motoneurons in strength-trained individuals, thereby contributing to the observed increase in VA and MVF.
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Affiliation(s)
- Yonas Akalu
- Monash Exercise Neuroplasticity Research Unit, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Frankston, Victoria, Australia
- Department of Human Physiology, School of Medicine, University of Gondar, Gondar, Ethiopia
| | - Jamie Tallent
- Monash Exercise Neuroplasticity Research Unit, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Frankston, Victoria, Australia
- School of Sport, Rehabilitation and Exercise Sciences, University of Essex, Colchester, UK
| | - Ashlyn K Frazer
- Monash Exercise Neuroplasticity Research Unit, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Frankston, Victoria, Australia
| | - Ummatul Siddique
- Monash Exercise Neuroplasticity Research Unit, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Frankston, Victoria, Australia
| | - Mohamad Rostami
- Monash Exercise Neuroplasticity Research Unit, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Frankston, Victoria, Australia
| | - Patrick Vallance
- Monash Exercise Neuroplasticity Research Unit, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Frankston, Victoria, Australia
| | - Glyn Howatson
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
- Water Research Group, North-West University, Potchefstroom, South Africa
| | - Simon Walker
- NeuroMuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Dawson J Kidgell
- Monash Exercise Neuroplasticity Research Unit, Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Frankston, Victoria, Australia
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4
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Akalu Y, Frazer AK, Howatson G, Pearce AJ, Siddique U, Rostami M, Tallent J, Kidgell DJ. Identifying the role of the reticulospinal tract for strength and motor recovery: A scoping review of nonhuman and human studies. Physiol Rep 2023; 11:e15765. [PMID: 37474275 PMCID: PMC10359156 DOI: 10.14814/phy2.15765] [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: 06/06/2023] [Accepted: 06/26/2023] [Indexed: 07/22/2023] Open
Abstract
In addition to the established postural control role of the reticulospinal tract (RST), there has been an increasing interest on its involvement in strength, motor recovery, and other gross motor functions. However, there are no reviews that have systematically assessed the overall motor function of the RST. Therefore, we aimed to determine the role of the RST underpinning motor function and recovery. We performed a literature search using Ovid Medline, Embase, CINAHL Plus, and Scopus to retrieve papers using key words for RST, strength, and motor recovery. Human and animal studies which assessed the role of RST were included. Studies were screened and 32 eligible studies were included for the final analysis. Of these, 21 of them were human studies while the remaining were on monkeys and rats. Seven experimental animal studies and four human studies provided evidence for the involvement of the RST in motor recovery, while two experimental animal studies and eight human studies provided evidence for strength gain. The RST influenced gross motor function in two experimental animal studies and five human studies. Overall, the RST has an important role for motor recovery, gross motor function and at least in part, underpins strength gain. The role of RST for strength gain in healthy people and its involvement in spasticity in a clinical population has been limitedly described. Further studies are required to ascertain the role of the RST's role in enhancing strength and its contribution to the development of spasticity.
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Affiliation(s)
- Yonas Akalu
- Monash Exercise Neuroplasticity Research UnitDepartment of PhysiotherapySchool of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health ScienceMonash UniversityMelbourneVictoriaAustralia
- Department of Human PhysiologySchool of MedicineUniversity of GondarGondarEthiopia
| | - Ashlyn K. Frazer
- Monash Exercise Neuroplasticity Research UnitDepartment of PhysiotherapySchool of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health ScienceMonash UniversityMelbourneVictoriaAustralia
| | - Glyn Howatson
- Department of Sport, Exercise and RehabilitationNorthumbria UniversityNewcastleUK
- Water Research GroupNorth West UniversityPotchefstroomSouth Africa
| | - Alan J. Pearce
- College of Science, Health and EngineeringLa Trobe UniversityMelbourneVictoriaAustralia
| | - Ummatul Siddique
- Monash Exercise Neuroplasticity Research UnitDepartment of PhysiotherapySchool of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health ScienceMonash UniversityMelbourneVictoriaAustralia
| | - Mohamad Rostami
- Monash Exercise Neuroplasticity Research UnitDepartment of PhysiotherapySchool of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health ScienceMonash UniversityMelbourneVictoriaAustralia
| | - Jamie Tallent
- Monash Exercise Neuroplasticity Research UnitDepartment of PhysiotherapySchool of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health ScienceMonash UniversityMelbourneVictoriaAustralia
- School of Sport, Rehabilitation and Exercise SciencesUniversity of EssexColchesterUK
| | - Dawson J. Kidgell
- Monash Exercise Neuroplasticity Research UnitDepartment of PhysiotherapySchool of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health ScienceMonash UniversityMelbourneVictoriaAustralia
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5
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Desachy M, Alexandre F, Varray A, Molinier V, Four E, Charbonnel L, Héraud N. High Prevalence of Non-Responders Based on Quadriceps Force after Pulmonary Rehabilitation in COPD. J Clin Med 2023; 12:4353. [PMID: 37445388 DOI: 10.3390/jcm12134353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/15/2023] Open
Abstract
Pulmonary rehabilitation (PR) in patients with COPD improves quality of life, dyspnea, and exercise tolerance. However, 30 to 50% of patients are "non-responders" (NRs) according to considered variables. Surprisingly, peripheral muscle force is never taken into account to attest the efficacy of PR, despite its major importance. Thus, we aimed to estimate the prevalence of force in NRs, their characteristics, and predictors of non-response. In total, 62 COPD patients were included in this retrospective study (May 2019 to December 2020). They underwent inpatient PR, and their quadriceps isometric maximal force (QMVC) was assessed. The PR program followed international guidelines. Patients with a QMVC increase <7.5 N·m were classified as an NR. COPD patients showed a mean improvement in QMVC after PR (10.08 ± 12.97 N·m; p < 0.001). However, 50% of patients were NRs. NRs had lower pre-PR values for body mass, height, body mass index, PaO2, and QMVC. Non-response can be predicted by low QMVC, high PaCO2, and gender (when male). This model has a sensitivity of 74% and specificity of 81%. The study highlights the considerable number of NRs and potential risk factors for non-response. To systematize the effects, it may be interesting to implement blood gas correction and/or optimize the programs to enhance peripheral and central effects.
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Affiliation(s)
- Marion Desachy
- EuroMov Digital Health in Motion, University Montpellier, IMT Mines Ales, Montpellier, France
- Direction de la Recherche et de l'Innovation en Santé (Research and Health Innovation Department), Clariane, France
| | - François Alexandre
- Direction de la Recherche et de l'Innovation en Santé (Research and Health Innovation Department), Clariane, France
| | - Alain Varray
- EuroMov Digital Health in Motion, University Montpellier, IMT Mines Ales, Montpellier, France
| | - Virginie Molinier
- Direction de la Recherche et de l'Innovation en Santé (Research and Health Innovation Department), Clariane, France
| | - Elodie Four
- Clinique du Souffle Les Clarines, Inicea, France
| | | | - Nelly Héraud
- Direction de la Recherche et de l'Innovation en Santé (Research and Health Innovation Department), Clariane, France
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6
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Morrison S, Newell KM. Strength training as a dynamical model of motor learning. J Sports Sci 2023:1-16. [PMID: 37270792 DOI: 10.1080/02640414.2023.2220177] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 05/22/2023] [Indexed: 06/06/2023]
Abstract
This paper outlines a framework for strength training as a dynamical model of perceptual-motor learning. We show, with emphasis on fixed-point attractor dynamics, that strength training can be mapped to the general dynamical principles of motor learning that arise from the constraints on action, including the distribution of practice/training. The time scales of the respective dynamics of performance change (increment and decrement) in discrete strength training and motor learning tasks reveal superposition of exponential functions in fixed-point dynamics, but distinctive attractor and parameter dynamics in oscillatory limit cycle and more continuous tasks, together with unique timescales to process influences (including practice, learning, strength, fitness, fatigue, warm-up decrement). Increments and decrements of strength can be viewed within a dynamical model of change in motor performance that reflects the integration of practice and training processes at multiple levels of learning and skill development.
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Affiliation(s)
- Steven Morrison
- School of Rehabilitation Sciences, Old Dominion University, Norfolk, VA, USA
| | - Karl M Newell
- Department of Kinesiology, University of Georgia, Athens, GA, USA
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Nuzzo JL. Narrative Review of Sex Differences in Muscle Strength, Endurance, Activation, Size, Fiber Type, and Strength Training Participation Rates, Preferences, Motivations, Injuries, and Neuromuscular Adaptations. J Strength Cond Res 2023; 37:494-536. [PMID: 36696264 DOI: 10.1519/jsc.0000000000004329] [Citation(s) in RCA: 45] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
ABSTRACT Nuzzo, JL. Narrative review of sex differences in muscle strength, endurance, activation, size, fiber type, and strength training participation rates, preferences, motivations, injuries, and neuromuscular adaptations. J Strength Cond Res 37(2): 494-536, 2023-Biological sex and its relation with exercise participation and sports performance continue to be discussed. Here, the purpose was to inform such discussions by summarizing the literature on sex differences in numerous strength training-related variables and outcomes-muscle strength and endurance, muscle mass and size, muscle fiber type, muscle twitch forces, and voluntary activation; strength training participation rates, motivations, preferences, and practices; and injuries and changes in muscle size and strength with strength training. Male subjects become notably stronger than female subjects around age 15 years. In adults, sex differences in strength are more pronounced in upper-body than lower-body muscles and in concentric than eccentric contractions. Greater male than female strength is not because of higher voluntary activation but to greater muscle mass and type II fiber areas. Men participate in strength training more frequently than women. Men are motivated more by challenge, competition, social recognition, and a desire to increase muscle size and strength. Men also have greater preference for competitive, high-intensity, and upper-body exercise. Women are motivated more by improved attractiveness, muscle "toning," and body mass management. Women have greater preference for supervised and lower-body exercise. Intrasexual competition, mate selection, and the drive for muscularity are likely fundamental causes of exercise behaviors in men and women. Men and women increase muscle size and strength after weeks of strength training, but women experience greater relative strength improvements depending on age and muscle group. Men exhibit higher strength training injury rates. No sex difference exists in strength loss and muscle soreness after muscle-damaging exercise.
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Affiliation(s)
- James L Nuzzo
- School of Medical and Health Sciences, Edith Cowan University, Joondalup, Western Australia, Australia
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8
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Qiu F, Liu X, Xu Y, Shi L, Sheng X, Chen C. Neural inputs from spinal motor neurons to lateralis vastus muscle: Comparison between sprinters and nonathletes. Front Physiol 2022; 13:994857. [PMID: 36277210 PMCID: PMC9585313 DOI: 10.3389/fphys.2022.994857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 09/21/2022] [Indexed: 11/13/2022] Open
Abstract
The adaptation of neural contractile properties has been observed in previous work. However, the neural changes on the motor unit (MU) level remain largely unknown. Voluntary movements are controlled through the precise activation of MU populations. In this work, we estimate the neural inputs from the spinal motor neurons to the muscles during isometric contractions and characterize the neural adaptation during training by comparing the MU properties decomposed from sprinters and nonathletes. Twenty subjects were recruited and divided into two groups. The high-density surface electromyography (EMG) signals were recorded from the lateralis vastus muscle during the isometric contraction of knee extension and were then decomposed into MU spike trains. Each MU’s action potentials and discharge properties were extracted for comparison across subject groups and tasks. A total of 1097 MUs were identified from all subjects. Results showed that the discharge rates and amplitudes of MUAPs from athletes were significantly higher than those from nonathletes. These results demonstrate the neural adaptations in physical training at the MU population level and indicate the great potential of EMG decomposition in physiological investigations.
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Affiliation(s)
- Fang Qiu
- Department of Exercise Physiology, Beijing Sport University, Beijing, China
| | - Xiaodong Liu
- School of Kinesiology, Shanghai University of Sport, Shanghai, China
| | - Yilin Xu
- Sports Biomechanics Laboratory, Jiangsu Research Institute of Sports Science, Nanjing, China
| | - Lijun Shi
- Department of Exercise Physiology, Beijing Sport University, Beijing, China
| | - Xinjun Sheng
- State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai, China
| | - Chen Chen
- State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai, China
- *Correspondence: Chen Chen,
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9
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Alix-Fages C, Del Vecchio A, Baz-Valle E, Santos-Concejero J, Balsalobre-Fernández C. The role of the neural stimulus in regulating skeletal muscle hypertrophy. Eur J Appl Physiol 2022; 122:1111-1128. [PMID: 35138447 DOI: 10.1007/s00421-022-04906-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 01/28/2022] [Indexed: 02/06/2023]
Abstract
Resistance training is frequently performed with the goal of stimulating muscle hypertrophy. Due to the key roles motor unit recruitment and mechanical tension play to induce muscle growth, when programming, the manipulation of the training variables is oriented to provoke the correct stimulus. Although it is known that the nervous system is responsible for the control of motor units and active muscle force, muscle hypertrophy researchers and trainers tend to only focus on the adaptations of the musculotendinous unit and not in the nervous system behaviour. To better guide resistance exercise prescription for muscle hypertrophy and aiming to delve into the mechanisms that maximize this goal, this review provides evidence-based considerations for possible effects of neural behaviour on muscle growth when programming resistance training, and future neurophysiological measurement that should be tested when training to increase muscle mass. Combined information from the neural and muscular structures will allow to understand the exact adaptations of the muscle in response to a given input (neural drive to the muscle). Changes at different levels of the nervous system will affect the control of motor units and mechanical forces during resistance training, thus impacting the potential hypertrophic adaptations. Additionally, this article addresses how neural adaptations and fatigue accumulation that occur when resistance training may influence the hypertrophic response and propose neurophysiological assessments that may improve our understanding of resistance training variables that impact on muscular adaptations.
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Affiliation(s)
- Carlos Alix-Fages
- Applied Biomechanics and Sport Technology Research Group, Autonomous University of Madrid, C/ Fco Tomas y Valiente 3, Cantoblanco, 28049, Madrid, Spain.
| | - Alessandro Del Vecchio
- Neuromuscular Physiology and Neural Interfacing Group, Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University, Erlangen-Nürnberg, Germany
| | - Eneko Baz-Valle
- Department of Physical Education and Sport, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - Jordan Santos-Concejero
- Department of Physical Education and Sport, University of the Basque Country UPV/EHU, Vitoria-Gasteiz, Spain
| | - Carlos Balsalobre-Fernández
- Applied Biomechanics and Sport Technology Research Group, Autonomous University of Madrid, C/ Fco Tomas y Valiente 3, Cantoblanco, 28049, Madrid, Spain
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10
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Silva MH, Andre Barbosa De Lira C, Steele J, Fisher JP, Mota JF, Gomes AC, Gentil P. Cycle ergometer training and resistance training similarly increase muscle strength in trained men. J Sports Sci 2021; 40:583-590. [PMID: 34789054 DOI: 10.1080/02640414.2021.2005282] [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] [Indexed: 10/19/2022]
Abstract
The aim of this study was to compare two different maximal intensity exercise modality training protocols of similar durations on muscle strength, cardiorespiratory fitness, and lower limb composition in recreationally trained men. Twenty-five trained men (28.9 ± 5.6 years) were randomly divided into Cycle ergometer (4 sets of 30 seconds sprints) and Leg press (4 sets of 10-12 repetitions to momentary failure). Both groups trained three times a week for 5 weeks. Before and after the training period, the participants performed a 10-repetition maximum (10RM) test for knee extension, an incremental exercise test on a treadmill for time to exhaustion (TTE) and peak oxygen consumption (V˙O2peak) and underwent dual energy X-ray absorptiometry to assess lower limb composition. Knee extension 10RM and TTE increased in both groups with no statistically significant between group (p = 0.614 and p = 0.210). Only cycle ergometer group increased V˙O2peak (p = 0,012). For all lower limb composition outcomes, changes were minimal. The results suggest that 5 weeks of effort and duration matched exercise protocols using cycle ergometer training or leg press may produce similar strength adaptations.
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Affiliation(s)
- Marcelo Henrique Silva
- College of Physical Education and Dance, Federal University of Goias, Goiânia, Brazil.,Uniaraguaia University Center Goiânia, Goiás, Brazil
| | | | - James Steele
- School of Sport, Health, and Social Sciences, Solent University, UK.,Ukactive Research Institute, London, UK
| | - James P Fisher
- School of Sport, Health, and Social Sciences, Solent University, UK
| | | | | | - Paulo Gentil
- College of Physical Education and Dance, Federal University of Goias, Goiânia, Brazil
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11
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Del Vecchio A, Casolo A, Dideriksen JL, Aagaard P, Felici F, Falla D, Farina D. Lack of increased rate of force development after strength training is explained by specific neural, not muscular, motor unit adaptations. J Appl Physiol (1985) 2021; 132:84-94. [PMID: 34792405 DOI: 10.1152/japplphysiol.00218.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
While maximal force increases following short-term isometric strength training, the rate of force development (RFD) may remain relatively unaffected. The underlying neural and muscular mechanisms during rapid contractions after strength training are largely unknown. Since strength training increases the neural drive to muscles, it may be hypothesized that there are distinct neural or muscular adaptations determining the change in RFD independently of an increase in maximal force. Therefore, we examined motor unit population data acquired from surface electromyography during the rapid generation of force before and after four weeks of strength training. We observed that strength training did not change the RFD because it did not influence the number of motor units recruited per second or their initial discharge rate during rapid contractions. While strength training did not change motoneuron behaviour in the force increase phase of rapid contractions, it increased the discharge rate of motoneurons (by ~4 spikes/s) when reaching the plateau phase (~150 ms) of the rapid contractions, determining an increase in maximal force production. Computer simulations with a motor unit model that included neural and muscular properties, closely matched the experimental observations and demonstrated that the lack of change in RFD following training is primarily mediated by an unchanged maximal recruitment speed of motoneurons. These results demonstrate that maximal force and contraction speed are determined by different adaptations in motoneuron behaviour following strength training and indicate that increases in the recruitment speed of motoneurons are required to evoke training-induced increases in RFD.
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Affiliation(s)
- Alessandro Del Vecchio
- Department of Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University, Erlangen, Bavaria, Germany
| | - Andrea Casolo
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | | | - Per Aagaard
- Department of Sports Science and Clinical Biomechanics, Muscle Physiology and Biomechanics Research Unit, University of Southern Denmark, Odense, Denmark
| | - Francesco Felici
- Department of Movement, Human and Health Sciences, University of Rome "Foro Italico", Rome, Italy
| | - Deborah Falla
- Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, United Kingdom
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12
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Casolo A, Del Vecchio A, Balshaw TG, Maeo S, Lanza MB, Felici F, Folland JP, Farina D. Behavior of motor units during submaximal isometric contractions in chronically strength-trained individuals. J Appl Physiol (1985) 2021; 131:1584-1598. [PMID: 34617822 DOI: 10.1152/japplphysiol.00192.2021] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Neural and morphological adaptations combine to underpin the enhanced muscle strength following prolonged exposure to strength training, although their relative importance remains unclear. We investigated the contribution of motor unit (MU) behavior and muscle size to submaximal force production in chronically strength-trained athletes (ST) versus untrained controls (UT). Sixteen ST (age: 22.9 ± 3.5 yr; training experience: 5.9 ± 3.5 yr) and 14 UT (age: 20.4 ± 2.3 yr) performed maximal voluntary isometric force (MViF) and ramp contractions (at 15%, 35%, 50%, and 70% MViF) with elbow flexors, whilst high-density surface electromyography (HDsEMG) was recorded from the biceps brachii (BB). Recruitment thresholds (RTs) and discharge rates (DRs) of MUs identified from the submaximal contractions were assessed. The neural drive-to-muscle gain was estimated from the relation between changes in force (ΔFORCE, i.e. muscle output) relative to changes in MU DR (ΔDR, i.e. neural input). BB maximum anatomical cross-sectional area (ACSAMAX) was also assessed by MRI. MViF (+64.8% vs. UT, P < 0.001) and BB ACSAMAX (+71.9%, P < 0.001) were higher in ST. Absolute MU RT was higher in ST (+62.6%, P < 0.001), but occurred at similar normalized forces. MU DR did not differ between groups at the same normalized forces. The absolute slope of the ΔFORCE - ΔDR relationship was higher in ST (+66.9%, P = 0.002), whereas it did not differ for normalized values. We observed similar MU behavior between ST athletes and UT controls. The greater absolute force-generating capacity of ST for the same neural input demonstrates that morphological, rather than neural, factors are the predominant mechanism for their enhanced force generation during submaximal efforts.NEW & NOTEWORTHY In this study, we observed that recruitment strategies and discharge characteristics of large populations of motor units identified from biceps brachii of strength-trained athletes were similar to those observed in untrained individuals during submaximal force tasks. We also found that for the same neural input, strength-trained athletes are able to produce greater absolute muscle forces (i.e., neural drive-to-muscle gain). This demonstrates that morphological factors are the predominant mechanism for the enhanced force generation during submaximal efforts.
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Affiliation(s)
- Andrea Casolo
- Department of Bioengineering, Imperial College London, London, United Kingdom.,Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Alessandro Del Vecchio
- Department Artificial Intelligence in Biomedical Engineering, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Germany
| | - Thomas G Balshaw
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, United Kingdom
| | - Sumiaki Maeo
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,College of Sport and Health Sciences, Ritsumeikan University, Kusatsu, Japan
| | - Marcel Bahia Lanza
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,Department of Physical Therapy and Rehabilitation Science, University of Maryland, Baltimore, Maryland
| | - Francesco Felici
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Jonathan P Folland
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, United Kingdom
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, United Kingdom
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13
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Škarabot J, Balshaw TG, Maeo S, Massey GJ, Lanza MB, Maden-Wilkinson TM, Folland JP. Neural adaptations to long-term resistance training: evidence for the confounding effect of muscle size on the interpretation of surface electromyography. J Appl Physiol (1985) 2021; 131:702-715. [PMID: 34166110 DOI: 10.1152/japplphysiol.00094.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study compared elbow flexor (EF; experiment 1) and knee extensor (KE; experiment 2) maximal compound action potential (Mmax) amplitude between long-term resistance trained (LTRT; n = 15 and n = 14, 6 ± 3 and 4 ± 1 yr of training) and untrained (UT; n = 14 and n = 49) men, and examined the effect of normalizing electromyography (EMG) during maximal voluntary torque (MVT) production to Mmax amplitude on differences between LTRT and UT. EMG was recorded from multiple sites and muscles of EF and KE, Mmax was evoked with percutaneous nerve stimulation, and muscle size was assessed with ultrasonography (thickness, EF) and magnetic resonance imaging (cross-sectional area, KE). Muscle-electrode distance (MED) was measured to account for the effect of adipose tissue on EMG and Mmax. LTRT displayed greater MVT (+66%-71%, P < 0.001), muscle size (+54%-56%, P < 0.001), and Mmax amplitudes (+29%-60%, P ≤ 0.010) even when corrected for MED (P ≤ 0.045). Mmax was associated with the size of both muscle groups (r ≥ 0.466, P ≤ 0.011). Compared with UT, LTRT had higher absolute voluntary EMG amplitude for the KE (P < 0.001), but not the EF (P = 0.195), and these differences/similarities were maintained after correction for MED; however, Mmax normalization resulted in no differences between LTRT and UT for any muscle and/or muscle group (P ≥ 0.652). The positive association between Mmax and muscle size, and no differences when accounting for peripheral electrophysiological properties (EMG/Mmax), indicates the greater absolute voluntary EMG amplitude of LTRT might be confounded by muscle morphology, rather than providing a discrete measure of central neural activity. This study therefore suggests limited agonist neural adaptation after LTRT.NEW & NOTEWORTHY In a large sample of long-term resistance-trained individuals, we showed greater maximal M-wave amplitude of the elbow flexors and knee extensors compared with untrained individuals, which appears to be at least partially mediated by differences in muscle size. The lack of group differences in voluntary EMG amplitude when normalized to maximal M-wave suggests that differences in muscle morphology might impair interpretation of voluntary EMG as an index of central neural activity.
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Affiliation(s)
- Jakob Škarabot
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom
| | - Thomas G Balshaw
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, United Kingdom
| | - Sumiaki Maeo
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,Faculty of Sport and Health Science, Ritsumeikan University, Shiga, Japan
| | - Garry J Massey
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,School of Sport and Health Sciences, University of Exeter, Exeter, United Kingdom
| | - Marcel B Lanza
- Department of Physical Therapy and Rehabilitation, University of Maryland, Baltimore, Maryland
| | - Thomas M Maden-Wilkinson
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,Academy of Sport and Physical Activity, Faculty of Health and Wellbeing, Sheffield Hallam University, Sheffield, United Kingdom
| | - Jonathan P Folland
- School of Sport, Exercise and Health Sciences, Loughborough University, Leicestershire, United Kingdom.,Versus Arthritis Centre for Sport, Exercise and Osteoarthritis Research, Loughborough University, Leicestershire, United Kingdom
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14
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Chronic resistance training: is it time to rethink the time course of neural contributions to strength gain? Eur J Appl Physiol 2021; 121:2413-2422. [PMID: 34052876 DOI: 10.1007/s00421-021-04730-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 05/22/2021] [Indexed: 10/20/2022]
Abstract
Resistance training enhances muscular force due to a combination of neural plasticity and muscle hypertrophy. It has been well documented that the increase in strength over the first few weeks of resistance training (i.e. acute) has a strong underlying neural component and further enhancement in strength with long-term (i.e. chronic) resistance training is due to muscle hypertrophy. For obvious reasons, collecting long-term data on how chronic-resistance training affects the nervous system not feasible. As a result, the effect of chronic-resistance training on neural plasticity is less understood and has not received systematic exploration. Thus, the aim of this review is to provide rationale for investigating neural plasticity beyond acute-resistance training. We use cross-sectional work to highlight neural plasticity that occurs with chronic-resistance training at sites from the brain to spinal cord. Specifically, intra-cortical circuitry and the spinal motoneuron seem to be key sites for this plasticity. We then urge the need to further investigate the differential effects of acute versus chronic-resistance training on neural plasticity, and the role of this plasticity in increased strength. Such investigations may help in providing a clearer definition of the continuum of acute and chronic-resistance training, how the nervous system is altered during this continuum and the causative role of neural plasticity in changes in strength over the continuum of resistance training.
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15
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Maitland S, Baker SN. Ipsilateral Motor Evoked Potentials as a Measure of the Reticulospinal Tract in Age-Related Strength Changes. Front Aging Neurosci 2021; 13:612352. [PMID: 33746734 PMCID: PMC7966512 DOI: 10.3389/fnagi.2021.612352] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 02/11/2021] [Indexed: 12/31/2022] Open
Abstract
Background: The reticulospinal tract (RST) is essential for balance, posture, and strength, all functions which falter with age. We hypothesized that age-related strength reductions might relate to differential changes in corticospinal and reticulospinal connectivity. Methods: We divided 83 participants (age 20-84) into age groups <50 (n = 29) and ≥50 (n = 54) years; five of which had probable sarcopenia. Transcranial Magnetic Stimulation (TMS) was applied to the left cortex, inducing motor evoked potentials (MEPs) in the biceps muscles bilaterally. Contralateral (right, cMEPs) and ipsilateral (left, iMEPs) MEPs are carried by mainly corticospinal and reticulospinal pathways respectively; the iMEP/cMEP amplitude ratio (ICAR) therefore measured the relative importance of the two descending tracts. Grip strength was measured with a dynamometer and normalized for age and sex. Results: We found valid iMEPs in 74 individuals (n = 44 aged ≥50, n = 29 < 50). Younger adults had a significant negative correlation between normalized grip strength and ICAR (r = -0.37, p = 0.045); surprisingly, in older adults, the correlation was also significant, but positive (r = 0.43, p = 0.0037). Discussion: Older individuals who maintain or strengthen their RST are stronger than their peers. We speculate that reduced RST connectivity could predict those at risk of age-related muscle weakness; interventions that reinforce the RST could be a candidate for treatment or prevention of sarcopenia.
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Affiliation(s)
- Stuart Maitland
- Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Stuart N Baker
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
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16
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Tallent J, Woodhead A, Frazer AK, Hill J, Kidgell DJ, Howatson G. Corticospinal and spinal adaptations to motor skill and resistance training: Potential mechanisms and implications for motor rehabilitation and athletic development. Eur J Appl Physiol 2021; 121:707-719. [PMID: 33389142 DOI: 10.1007/s00421-020-04584-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Accepted: 12/12/2020] [Indexed: 12/12/2022]
Abstract
Optimal strategies for enhancing strength and improving motor skills are vital in athletic performance and clinical rehabilitation. Initial increases in strength and the acquisition of new motor skills have long been attributed to neurological adaptations. However, early increases in strength may be predominantly due to improvements in inter-muscular coordination rather than the force-generating capacity of the muscle. Despite the plethora of research investigating neurological adaptations from motor skill or resistance training in isolation, little effort has been made in consolidating this research to compare motor skill and resistance training adaptations. The findings of this review demonstrated that motor skill and resistance training adaptations show similar short-term mechanisms of adaptations, particularly at a cortical level. Increases in corticospinal excitability and a release in short-interval cortical inhibition occur as a result of the commencement of both resistance and motor skill training. Spinal changes show evidence of task-specific adaptations from the acquired motor skill, with an increase or decrease in spinal reflex excitability, dependant on the motor task. An increase in synaptic efficacy of the reticulospinal projections is likely to be a prominent mechanism for driving strength adaptations at the subcortical level, though more research is needed. Transcranial electric stimulation has been shown to increase corticospinal excitability and augment motor skill adaptations, but limited evidence exists for further enhancing strength adaptations from resistance training. Despite the logistical challenges, future work should compare the longitudinal adaptations between motor skill and resistance training to further optimise exercise programming.
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Affiliation(s)
- Jamie Tallent
- Faculty of Sport, Health and Applied Sciences, St Mary's University, Waldgrave Road, Twickenham, TW1 4SX, UK.
| | - Alex Woodhead
- Faculty of Sport, Health and Applied Sciences, St Mary's University, Waldgrave Road, Twickenham, TW1 4SX, UK
| | - Ashlyn K Frazer
- Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia
| | - Jessica Hill
- Faculty of Sport, Health and Applied Sciences, St Mary's University, Waldgrave Road, Twickenham, TW1 4SX, UK
| | - Dawson J Kidgell
- Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, Melbourne, Australia
| | - Glyn Howatson
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle-upon-Tyne, UK.,Water Research Group, Faculty of Natural and Agricultural Sciences, North West University, Potchefstroom, South Africa
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17
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Škarabot J, Brownstein CG, Casolo A, Del Vecchio A, Ansdell P. The knowns and unknowns of neural adaptations to resistance training. Eur J Appl Physiol 2020; 121:675-685. [PMID: 33355714 PMCID: PMC7892509 DOI: 10.1007/s00421-020-04567-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 11/18/2020] [Indexed: 12/22/2022]
Abstract
The initial increases in force production with resistance training are thought to be primarily underpinned by neural adaptations. This notion is firmly supported by evidence displaying motor unit adaptations following resistance training; however, the precise locus of neural adaptation remains elusive. The purpose of this review is to clarify and critically discuss the literature concerning the site(s) of putative neural adaptations to short-term resistance training. The proliferation of studies employing non-invasive stimulation techniques to investigate evoked responses have yielded variable results, but generally support the notion that resistance training alters intracortical inhibition. Nevertheless, methodological inconsistencies and the limitations of techniques, e.g. limited relation to behavioural outcomes and the inability to measure volitional muscle activity, preclude firm conclusions. Much of the literature has focused on the corticospinal tract; however, preliminary research in non-human primates suggests reticulospinal tract is a potential substrate for neural adaptations to resistance training, though human data is lacking due to methodological constraints. Recent advances in technology have provided substantial evidence of adaptations within a large motor unit population following resistance training. However, their activity represents the transformation of afferent and efferent inputs, making it challenging to establish the source of adaptation. Whilst much has been learned about the nature of neural adaptations to resistance training, the puzzle remains to be solved. Additional analyses of motoneuron firing during different training regimes or coupling with other methodologies (e.g., electroencephalography) may facilitate the estimation of the site(s) of neural adaptations to resistance training in the future.
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Affiliation(s)
- Jakob Škarabot
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Callum G Brownstein
- Laboratoire Interuniversitaire de Biologie de la Motricité, Université Jean Monnet Saint-Etienne, Université Lyon, Saint-Étienne, France
| | - Andrea Casolo
- Department of Bioengineering, Imperial College London, London, UK.,Department of Biomedical Sciences, University of Padova, Padua, Italy
| | - Alessandro Del Vecchio
- Department of Artificial Intelligence and Biomedical Engineering, Faculty of Engineering, Friedrich-Alexander University, Erlangen-Nurnberg, 91052, Erlangen, Germany
| | - Paul Ansdell
- Department of Sport, Exercise and Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST, UK.
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18
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Gittings PM, Wand BM, Hince DA, Grisbrook TL, Wood FM, Edgar DW. The efficacy of resistance training in addition to usual care for adults with acute burn injury: A randomised controlled trial. Burns 2020; 47:84-100. [PMID: 33280953 DOI: 10.1016/j.burns.2020.03.015] [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: 01/06/2020] [Revised: 03/13/2020] [Accepted: 03/27/2020] [Indexed: 12/16/2022]
Abstract
Resistance training immediately after a burn injury has not been investigated previously. This randomised, controlled trial assessed the impact of resistance training on quality of life plus a number of physical, functional and safety outcomes in adults with a burn injury. Patients were randomly assigned to receive, in addition to standard physiotherapy, four weeks of high intensity resistance training (RTG) or sham resistance training (CG) three days per week, commenced within 72h of the burn injury. Outcome data was collected at six weeks, three and six months after burn injury. Quality of life at 6 months was the primary endpoint. Data analysis was an available cases analysis with no data imputed. Regression analyses were used for all longitudinal outcome data and between-group comparisons were used for descriptive analyses. Forty-eight patients were randomised resistance training (RTG) (n=23) or control group (CG) (n=25). The RTG demonstrated improved outcomes for the functional domain of the Burn Specific Health Scale-Brief (p=0.017) and the Quick Disability of Arm Shoulder and Hand (p<0.001). Between group differences were seen for C-reactive protein and retinol binding protein (p=0.001). Total quality of life scores, lower limb disability, muscle strength and volume were not seen to be different between groups (p>0.05). Resistance training in addition to usual rehabilitation therapy showed evidence of improving functional outcomes, particularly in upper limb burn injuries. Additionally, resistance training commenced acutely after a burn injury was not seen to be harmful to patients.
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Affiliation(s)
- Paul M Gittings
- State Adult Burns Service, South Metropolitan Area Health Service, Fiona Stanley Hospital, Murdoch, Western Australia, Australia; School of Physiotherapy, University of Notre Dame Australia, Fremantle, Western Australia, Australia; Fiona Wood Foundation, Murdoch, Western Australia, Australia.
| | - Benedict M Wand
- School of Physiotherapy, University of Notre Dame Australia, Fremantle, Western Australia, Australia
| | - Dana A Hince
- Institute for Health Research, University of Notre Dame Australia, Fremantle, Western Australia, Australia
| | - Tiffany L Grisbrook
- School of Physiotherapy and Exercise Science, Curtin University, Bentley, Western Australia, Australia
| | - Fiona M Wood
- State Adult Burns Service, South Metropolitan Area Health Service, Fiona Stanley Hospital, Murdoch, Western Australia, Australia; Fiona Wood Foundation, Murdoch, Western Australia, Australia; Burn Injury Research Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia
| | - Dale W Edgar
- State Adult Burns Service, South Metropolitan Area Health Service, Fiona Stanley Hospital, Murdoch, Western Australia, Australia; Fiona Wood Foundation, Murdoch, Western Australia, Australia; Institute for Health Research, University of Notre Dame Australia, Fremantle, Western Australia, Australia; Burn Injury Research Unit, School of Medicine and Pharmacology, University of Western Australia, Crawley, Western Australia, Australia; Burn Injury Research Node, Institute of Health Research, University of Notre Dame Australia, Fremantle, Western Australia, Australia
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19
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Aagaard P, Bojsen-Møller J, Lundbye-Jensen J. Assessment of Neuroplasticity With Strength Training. Exerc Sport Sci Rev 2020; 48:151-162. [DOI: 10.1249/jes.0000000000000229] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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20
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Neige C, Grosprêtre S, Martin A, Lebon F. Influence of Voluntary Contraction Level, Test Stimulus Intensity and Normalization Procedures on the Evaluation of Short-Interval Intracortical Inhibition. Brain Sci 2020; 10:brainsci10070433. [PMID: 32650395 PMCID: PMC7407177 DOI: 10.3390/brainsci10070433] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/02/2020] [Accepted: 07/06/2020] [Indexed: 12/13/2022] Open
Abstract
Short-interval intracortical inhibition (SICI) represents an inhibitory phenomenon acting at the cortical level. However, SICI estimation is based on the amplitude of a motor-evoked potential (MEP), which depends on the discharge of spinal motoneurones and the generation of compound muscle action potential (M-wave). In this study, we underpin the importance of taking into account the proportion of spinal motoneurones that are activated or not when investigating the SICI of the right flexor carpi radialis (normalization with maximal M-wave (Mmax) and MEPtest, respectively), in 15 healthy subjects. We probed SICI changes according to various MEPtest amplitudes that were modulated actively (four levels of muscle contraction: rest, 10%, 20% and 30% of maximal voluntary contraction (MVC)) and passively (two intensities of test transcranial magnetic stimulation (TMS): 120 and 130% of motor thresholds). When normalized to MEPtest, SICI remained unchanged by stimulation intensity and only decreased at 30% of MVC when compared with rest. However, when normalized to Mmax, we provided the first evidence of a strong individual relationship between SICI and MEPtest, which was ultimately independent from experimental conditions (muscle states and TMS intensities). Under similar experimental conditions, it is thus possible to predict SICI individually from a specific level of corticospinal excitability in healthy subjects.
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Affiliation(s)
- Cécilia Neige
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, F-21078 Dijon, France; (A.M.); (F.L.)
- Correspondence: ; Tel.: +33-3-8039-6761
| | - Sidney Grosprêtre
- EA4660-C3S Laboratory—Culture, Sport, Health and Society, Université Bourgogne Franche-Comté, 25000 Besançon, France;
| | - Alain Martin
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, F-21078 Dijon, France; (A.M.); (F.L.)
| | - Florent Lebon
- INSERM UMR1093-CAPS, Université Bourgogne Franche-Comté, UFR des Sciences du Sport, F-21078 Dijon, France; (A.M.); (F.L.)
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21
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Ansdell P, Brownstein CG, Škarabot J, Angius L, Kidgell D, Frazer A, Hicks KM, Durbaba R, Howatson G, Goodall S, Thomas K. Task‐specific strength increases after lower‐limb compound resistance training occurred in the absence of corticospinal changes in vastus lateralis. Exp Physiol 2020; 105:1132-1150. [DOI: 10.1113/ep088629] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 04/30/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Paul Ansdell
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
| | - Callum G. Brownstein
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
- Laboratoire Interuniversitaire de Biologie de la MotricitéUniversité Jean Monnet Saint Etienne, Université Lyon Lyon France
| | - Jakob Škarabot
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
- School of SportExercise and Health SciencesLoughborough University Loughborough UK
| | - Luca Angius
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
| | - Dawson Kidgell
- Department of PhysiotherapySchool of Primary and Allied Health CareFaculty of MedicineNursing and Health SciencesMonash University Melbourne Australia
| | - Ashlyn Frazer
- Department of PhysiotherapySchool of Primary and Allied Health CareFaculty of MedicineNursing and Health SciencesMonash University Melbourne Australia
| | - Kirsty M. Hicks
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
| | - Rade Durbaba
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
| | - Glyn Howatson
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
- Water Research GroupSchool of Biological SciencesNorth West University Potchefstroom South Africa
| | - Stuart Goodall
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
| | - Kevin Thomas
- Faculty of Health and Life SciencesNorthumbria University Newcastle upon Tyne UK
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22
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Tracking the corticospinal responses to strength training. Eur J Appl Physiol 2020; 120:783-798. [DOI: 10.1007/s00421-020-04316-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 02/03/2020] [Indexed: 01/07/2023]
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23
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Siddique U, Rahman S, Frazer AK, Pearce AJ, Howatson G, Kidgell DJ. Determining the Sites of Neural Adaptations to Resistance Training: A Systematic Review and Meta-analysis. Sports Med 2020; 50:1107-1128. [DOI: 10.1007/s40279-020-01258-z] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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24
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Colomer-Poveda D, Hortobágyi T, Keller M, Romero-Arenas S, Márquez G. Training intensity-dependent increases in corticospinal but not intracortical excitability after acute strength training. Scand J Med Sci Sports 2019; 30:652-661. [PMID: 31785009 DOI: 10.1111/sms.13608] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/04/2019] [Accepted: 11/25/2019] [Indexed: 11/27/2022]
Abstract
The purpose of this study was to determine whether the increases in corticospinal excitability (CSE) observed after one session of unilateral isometric strength training (ST) are related to changes in intracortical excitability measured by magnetic brain stimulation (TMS) in the trained and the contralateral untrained biceps brachii (BB) and whether such changes scale with training intensity. On three separate days, 15 healthy young men performed one ST session of 12 sets of eight isometric contractions of the right elbow flexors at 0% (control session), 25%, or 75% of the maximal voluntary contraction (MVC) in a random order. Before and after each session separated at least by 1 week, motor evoked potential (MEP) amplitude, short-interval intracortical inhibition (SICI), contralateral silent period (SP), and intracortical facilitation (ICF) generated by TMS were measured in the trained and the untrained BBs. Compared with baseline, MEPs recorded from the trained BB increased by ~47% after training at 75% of MVC (P < .05) but not after training at 0% (~4%) or 25% MVC (~5%, both P > .05). MEPs in the untrained BB and SICI, SP, and ICF in either BB did not change. Therefore, acute high-intensity but not low-intensity unilateral isometric ST increases CSE in the trained BB without modifications in intracortical inhibition or facilitation. Thus, increases in corticospinal neurons or α-α-motoneuron excitability could underlie the increases in CSE. Regardless of contraction intensity, acute isometric ST did not modify the excitability of the ipsilateral primary motor cortex measured by TMS.
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Affiliation(s)
- David Colomer-Poveda
- Department of Physical Education and Sport, Faculty of Sport, Catholic University of Murcia (UCAM), Murcia, Spain
| | - Tibor Hortobágyi
- Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Martin Keller
- Department of Sport, Exercise and Health, University of Basel, Basel, Switzerland
| | - Salvador Romero-Arenas
- Department of Physical Education and Sport, Faculty of Sport, Catholic University of Murcia (UCAM), Murcia, Spain
| | - Gonzalo Márquez
- Department of Physical Education and Sport, Faculty of Sport, Catholic University of Murcia (UCAM), Murcia, Spain
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CASOLO ANDREA, FARINA DARIO, FALLA DEBORAH, BAZZUCCHI ILENIA, FELICI FRANCESCO, DEL VECCHIO ALESSANDRO. Strength Training Increases Conduction Velocity of High-Threshold Motor Units. Med Sci Sports Exerc 2019; 52:955-967. [DOI: 10.1249/mss.0000000000002196] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Siddique U, Rahman S, Frazer AK, Howatson G, Kidgell DJ. RETRACTED ARTICLE: Determining the Sites of Neural Adaptations to Resistance Training: A Systematic Review and Meta-Analysis. Sports Med 2019; 49:1809. [PMID: 31359349 DOI: 10.1007/s40279-019-01152-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Ummatul Siddique
- Department of Neurology, Institute of Neurosciences, Kolkata, India
| | - Simin Rahman
- Department of Neurology, Institute of Neurosciences, Kolkata, India
| | - Ashlyn K Frazer
- Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, PO Box 527, Frankston, VIC, 3199, Australia
| | - Glyn Howatson
- Faculty of Health and Life Sciences, Northumbria University, Newcastle-upon-Tyne, UK
- Water Research Group, School of Environmental Sciences and Development, Northwest University, Potchefstroom, South Africa
| | - Dawson J Kidgell
- Department of Physiotherapy, School of Primary and Allied Health Care, Faculty of Medicine, Nursing and Health Science, Monash University, PO Box 527, Frankston, VIC, 3199, Australia.
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Colomer-Poveda D, Romero-Arenas S, Lundbye-Jensen J, Hortobágyi T, Márquez G. Contraction intensity-dependent variations in the responses to brain and corticospinal tract stimulation after a single session of resistance training in men. J Appl Physiol (1985) 2019; 127:1128-1139. [PMID: 31436513 DOI: 10.1152/japplphysiol.01106.2018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The aim of this study was to determine the effects of acute resistance training (RT) intensity on motor-evoked potentials (MEPs) generated by transcranial magnetic brain stimulation and on cervicomedullary motor-evoked potentials (CMEPs) produced by electrical stimulation of the corticospinal tract. In four experimental sessions, 14 healthy young men performed 12 sets of eight isometric contractions of the elbow flexors at 0 (Control session), 25, 50, and 75% of the maximal voluntary contraction (MVC). Before and after each session, MEPs, CMEPs, and the associated twitch forces were recorded at rest. MEPs increased by 39% (P < 0.05 versus 25% in the control condition, Effect size (ES) = 1.04 and 1.76, respectively) after the 50% session and by 70% (P < 0.05 vs. all other conditions, ES = 0.91-2.49) after the 75% session. In contrast, CMEPs increased similarly after the 25%, 50%, and 75% sessions with an overall increase of 27% (P < 0.05 vs. control condition, ES = 1.34). The amplitude of maximal compound muscle action potentials (Mmax) was unchanged during the experiment. The MEP- and CMEP-associated twitch forces also increased after RT, but training intensity affected only the increases in MEP twitch forces. The data tentatively suggest that the intensity of muscle contraction used in acute bouts of RT affects cortical excitability.NEW & NOTEWORTHY Resistance training (RT) can acutely increase the efficacy of the corticospinal-motoneuronal synapse, motoneuron excitability and motor cortical excitability. We show that motor-evoked potential generated by transcranial magnetic stimulation but not cervicomedullary electrical stimulation increased in proportion to the intensity of training used during a single session of RT. The data suggest that the intensity of muscle contraction used in acute bouts of RT affects cortical excitability.
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Affiliation(s)
- David Colomer-Poveda
- Department of Physical Education and Sport, Faculty of Sport, Catholic University of Murcia, Murcia, Spain
| | - Salvador Romero-Arenas
- Department of Physical Education and Sport, Faculty of Sport, Catholic University of Murcia, Murcia, Spain
| | - Jesper Lundbye-Jensen
- Department of Nutrition, Exercise and Sports, University of Copenhagen, Copenhagen, Denmark
| | - Tibor Hortobágyi
- Center for Human Movement Sciences, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Gonzalo Márquez
- Department of Physical Education and Sport, Faculty of Sport, Catholic University of Murcia, Murcia, Spain
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28
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Nuzzo JL, Taylor JL, Gandevia SC. CORP: Measurement of upper and lower limb muscle strength and voluntary activation. J Appl Physiol (1985) 2019; 126:513-543. [DOI: 10.1152/japplphysiol.00569.2018] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Muscle strength, the maximal force-generating capacity of a muscle or group of muscles, is regularly assessed in physiological experiments and clinical trials. An understanding of the expected variation in strength and the factors that contribute to this variation is important when designing experiments, describing methodologies, interpreting results, and attempting to replicate methods of others and reproduce their findings. In this review (Cores of Reproducibility in Physiology), we report on the intra- and inter-rater reliability of tests of upper and lower limb muscle strength and voluntary activation in humans. Isometric, isokinetic, and isoinertial strength exhibit good intra-rater reliability in most samples (correlation coefficients ≥0.90). However, some tests of isoinertial strength exhibit systematic bias that is not resolved by familiarization. With the exception of grip strength, few attempts have been made to examine inter-rater reliability of tests of muscle strength. The acute factors most likely to affect muscle strength and serve as a source of its variation from trial-to-trial or day-to-day include attentional focus, breathing technique, remote muscle contractions, rest periods, temperature (core, muscle), time of day, visual feedback, body and limb posture, body stabilization, acute caffeine consumption, dehydration, pain, fatigue from preceding exercise, and static stretching >60 s. Voluntary activation, the nervous system’s ability to drive a muscle to create its maximal force, exhibits good intra-rater reliability when examined with twitch interpolation (correlation coefficients >0.80). However, inter-rater reliability has not been formally examined. The methodological factors most likely to influence voluntary activation are myograph compliance and sensitivity; stimulation location, intensity, and inadvertent stimulation of antagonists; joint angle (muscle length); and the resting twitch.
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Affiliation(s)
- James L. Nuzzo
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, Australia
| | - Janet L. Taylor
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- School of Medical Sciences, University of New South Wales, Sydney, Australia
- School of Medical and Health Sciences, Edith Cowan University, Perth, Western Australia, Australia
| | - Simon C. Gandevia
- Neuroscience Research Australia, Randwick, New South Wales, Australia
- Prince of Wales Hospital Clinical School, University of New South Wales, Sydney, Australia
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29
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Del Vecchio A, Casolo A, Negro F, Scorcelletti M, Bazzucchi I, Enoka R, Felici F, Farina D. The increase in muscle force after 4 weeks of strength training is mediated by adaptations in motor unit recruitment and rate coding. J Physiol 2019; 597:1873-1887. [PMID: 30727028 DOI: 10.1113/jp277250] [Citation(s) in RCA: 176] [Impact Index Per Article: 35.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 12/03/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Previous studies have indicated that several weeks of strength training is sufficient to elicit significant adaptations in the neural drive sent to the muscles. There are few data, however, on the changes elicited by strength training in the recruitment and rate coding of motor units during voluntary contractions. We show for the first time that the discharge characteristics of motor units in the tibialis anterior muscle tracked across the intervention are changed by 4 weeks of strength training with isometric voluntary contractions. The specific adaptations included significant increases in motor unit discharge rate, decreases in the recruitment-threshold force of motor units and a similar input-output gain of the motor neurons. The findings suggest that the adaptations in motor unit function may be attributable to changes in synaptic input to the motor neuron pool or to adaptations in intrinsic motor neuron properties. ABSTRACT The strength of a muscle typically begins to increase after only a few sessions of strength training. This increase is usually attributed to changes in the neural drive to muscle as a result of adaptations at the cortical or spinal level. We investigated the change in the discharge characteristics of large populations of longitudinally tracked motor units in tibialis anterior before and after 4 weeks of strength training the ankle-dorsiflexor muscles with isometric contractions. The adaptations exhibited by 14 individuals were compared with 14 control subjects. High-density electromyogram grids with 128 electrodes recorded the myoelectric activity during isometric ramp contractions to the target forces of 35%, 50% and 70% of maximal voluntary force. The motor unit recruitment and derecruitment thresholds, discharge rate, interspike intervals and estimates of synaptic inputs to motor neurons were assessed. The normalized recruitment-threshold forces of the motor units were decreased after strength training (P < 0.05). Moreover, discharge rate increased by 3.3 ± 2.5 pps (average across subjects and motor units) during the plateau phase of the submaximal isometric contractions (P < 0.001). Discharge rates at recruitment and derecruitment were not modified by training (P < 0.05). The association between force and motor unit discharge rate during the ramp-phase of the contractions was also not altered by training (P < 0.05). These results demonstrate for the first time that the increase in muscle force after 4 weeks of strength training is the result of an increase in motor neuron output from the spinal cord to the muscle.
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Affiliation(s)
- Alessandro Del Vecchio
- Department of Bioengineering, Imperial College London, London, UK.,Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Andrea Casolo
- Department of Bioengineering, Imperial College London, London, UK.,Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy
| | - Matteo Scorcelletti
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Ilenia Bazzucchi
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Roger Enoka
- Department of Integrative Physiology, University of Colorado Boulder, CO, USA
| | - Francesco Felici
- Department of Movement, Human and Health Sciences, University of Rome 'Foro Italico', Rome, Italy
| | - Dario Farina
- Department of Bioengineering, Imperial College London, London, UK
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Frazer AK, Pearce AJ, Howatson G, Thomas K, Goodall S, Kidgell DJ. Determining the potential sites of neural adaptation to cross-education: implications for the cross-education of muscle strength. Eur J Appl Physiol 2018; 118:1751-1772. [PMID: 29995227 DOI: 10.1007/s00421-018-3937-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 07/05/2018] [Indexed: 12/11/2022]
Abstract
Cross-education describes the strength gain in the opposite, untrained limb following a unilateral strength training program. Since its discovery in 1894, several studies now confirm the existence of cross-education in contexts that involve voluntary dynamic contractions, eccentric contraction, electrical stimulation, whole-body vibration and, more recently, following mirror feedback training. Although many aspects of cross-education have been established, the mediating neural mechanisms remain unclear. Overall, the findings of this review show that the neural adaptations to cross-education of muscle strength most likely represent a continuum of change within the central nervous system that involves both structural and functional changes within cortical motor and non-motor regions. Such changes are likely to be the result of more subtle changes along the entire neuroaxis which include, increased corticospinal excitability, reduced cortical inhibition, reduced interhemispheric inhibition, changes in voluntary activation and new regions of cortical activation. However, there is a need to widen the breadth of research by employing several neurophysiological techniques (together) to better understand the potential mechanisms mediating cross-education. This fundamental step is required in order to better prescribe targeted and effective guidelines for the clinical practice of cross-education. There is a need to determine whether similar cortical responses also occur in clinical populations where, perhaps, the benefits of cross-education could be best observed.
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Affiliation(s)
- Ashlyn K Frazer
- Department of Physiotherapy, Faculty of Medicine, Nursing and Health Sciences, School of Primary and Allied Health Care, Monash University, PO Box 527, Frankston, Melbourne, VIC, 3199, Australia.
| | - Alan J Pearce
- Discipline of Exercise Science, School of Allied Health, La Trobe University, Melbourne, Australia
| | - Glyn Howatson
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle-upon-Tyne, UK.,Water Research Group, School of Biological Sciences, North West University, Potchefstroom, South Africa
| | - Kevin Thomas
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle-upon-Tyne, UK
| | - Stuart Goodall
- Department of Sport, Exercise and Rehabilitation, Northumbria University, Newcastle-upon-Tyne, UK
| | - Dawson J Kidgell
- Department of Physiotherapy, Faculty of Medicine, Nursing and Health Sciences, School of Primary and Allied Health Care, Monash University, PO Box 527, Frankston, Melbourne, VIC, 3199, Australia
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Giboin LS, Weiss B, Thomas F, Gruber M. Neuroplasticity following short-term strength training occurs at supraspinal level and is specific for the trained task. Acta Physiol (Oxf) 2018; 222:e12998. [PMID: 29144602 DOI: 10.1111/apha.12998] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 11/10/2017] [Accepted: 11/10/2017] [Indexed: 11/29/2022]
Abstract
AIMS Different modalities of strength training cause performance enhancements, which are specific for the trained task. However, the involved mechanisms are still largely unknown. It has been demonstrated that strength training could induce neuroplasticity, which might underlie the performance improvements during the first training sessions. Thus, we hypothesized to find task-specific neuroplasticity after a short-term strength training of two distinct strength tasks. METHODS Young healthy male subjects were exposed to 4 sessions of either maximal isometric explosive (EXPL group, N = 9) or slow sustained (SUS group, N = 10) knee extensions. Pre- and post-training, we measured H-reflexes and motor evoked potentials (MEPs) in the vastus lateralis (VL) at the onset of both strength tasks. RESULTS Pre- and post-training, H-reflexes remained unchanged in both groups. MEP areas were lower in the trained task in both groups and remained unchanged in the untrained task. CONCLUSION This study demonstrated that short-term strength training induces specific neuroplasticity for the trained task only. The fact that MEPs were lower but H-reflex amplitudes remained unchanged at the onset of the trained tasks suggests that strength training elicited neuroplasticity at supraspinal level that most likely reflect an improved task-specific corticospinal efficiency.
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Affiliation(s)
- L.-S. Giboin
- Sensorimotor Performance Lab; Department of Sport Science; University of Konstanz; Konstanz Germany
| | - B. Weiss
- Sensorimotor Performance Lab; Department of Sport Science; University of Konstanz; Konstanz Germany
| | - F. Thomas
- Sensorimotor Performance Lab; Department of Sport Science; University of Konstanz; Konstanz Germany
| | - M. Gruber
- Sensorimotor Performance Lab; Department of Sport Science; University of Konstanz; Konstanz Germany
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32
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The ipsilateral corticospinal responses to cross-education are dependent upon the motor-training intervention. Exp Brain Res 2018; 236:1331-1346. [PMID: 29511785 DOI: 10.1007/s00221-018-5224-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 03/01/2018] [Indexed: 01/06/2023]
Abstract
This study aimed to identify the ipsilateral corticospinal responses of the contralateral limb following different types of unilateral motor-training. Three groups performing unilateral slow-paced strength training (SPST), non-paced strength training (NPST) or visuomotor skill training (VT) were compared to a control group. It was hypothesised that 4 weeks of unilateral SPST and VT, but not NPST, would increase ipsilateral corticospinal excitability (CSE) and reduce short-interval cortical inhibition (SICI), resulting in greater performance gains of the untrained limb. Tracking error of the untrained limb reduced by 29 and 41% following 2 and 4 weeks of VT. Strength of the untrained limb increased by 8 and 16% following 2 and 4 weeks of SPST and by 6 and 13% following NPST. There was no difference in cross-education of strength or tracking error. For the trained limb, SPST and NPST increased strength (28 and 26%), and VT improved by 47 and 58%. SPST and VT increased ipsilateral CSE by 89 and 71% at 2 weeks. Ipsilateral CSE increased 105 and 81% at 4 weeks following SPST and VT. The NPST group and control group showed no changes at 2 and 4 weeks. SPST and VT reduced ipsilateral SICI by 45 and 47% at 2 weeks; at 4 weeks, SPST and VT reduced SICI by 48 and 38%. The ipsilateral corticospinal responses are determined by the type of motor-training. There were no differences in motor performance between SPST, NPST and VT. The data suggests that the corticospinal responses to cross-education are different and determined by the type of motor-training.
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