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Hayman O, Ansdell P, Angius L, Thomas K, Horsbrough L, Howatson G, Kidgell DJ, Škarabot J, Goodall S. Changes in motor unit behaviour across repeated bouts of eccentric exercise. Exp Physiol 2024. [PMID: 39226215 DOI: 10.1113/ep092070] [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: 05/29/2024] [Accepted: 08/13/2024] [Indexed: 09/05/2024]
Abstract
Unaccustomed eccentric exercise (EE) is protective against muscle damage following a subsequent bout of similar exercise. One hypothesis suggests the existence of an alteration in motor unit (MU) behaviour during the second bout, which might contribute to the adaptive response. Accordingly, the present study investigated MU changes during repeated bouts of EE. During two bouts of exercise where maximal lengthening dorsiflexion (10 repetitions × 10 sets) was performed 3 weeks apart, maximal voluntary isometric torque (MVIC) and MU behaviour (quantified using high-density electromyography; HDsEMG) were measured at baseline, during (after set 5), and post-EE. The HDsEMG signals were decomposed into individual MU discharge timings, and a subset were tracked across each time point. MVIC was reduced similarly in both bouts post-EE (Δ27 vs. 23%, P = 0.144), with a comparable amount of total work performed (∼1,300 J; P = 0.905). In total, 1,754 MUs were identified and the decline in MVIC was accompanied by a stepwise increase in discharge rate (∼13%; P < 0.001). A decrease in relative recruitment was found immediately after EE in Bout 1 versus baseline (∼16%; P < 0.01), along with reductions in derecruitment thresholds immediately after EE in Bout 2. The coefficient of variation of inter-spike intervals was lower in Bout 2 (∼15%; P < 0.001). Our data provide new information regarding a change in MU behaviour during the performance of a repeated bout of EE. Importantly, such changes in MU behaviour might contribute, at least in part, to the repeated bout phenomenon.
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Affiliation(s)
- Oliver Hayman
- Department of Sport, Exercise, & Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
- School of Cardiovascular and Metabolic Health, BHF Glasgow Cardiovascular Research Center, College of Medical, Veterinary, and Life Sciences, University of Glasgow, Glasgow, UK
| | - Paul Ansdell
- Department of Sport, Exercise, & Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Luca Angius
- Department of Sport, Exercise, & Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Kevin Thomas
- Department of Sport, Exercise, & Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Lauren Horsbrough
- Department of Sport, Exercise, & Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
| | - Glyn Howatson
- Department of Sport, Exercise, & Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
- Water Research Group, North West University, Potchefstroom, South Africa
| | - 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, Melbourne, Australia
| | - Jakob Škarabot
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Stuart Goodall
- Department of Sport, Exercise, & Rehabilitation, Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, UK
- Physical Activity, Sport and Recreation Research Focus Area, Faculty of Health Sciences, North-West University, Potchefstroom, South Africa
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Wilson MT, Hunter AM, Fairweather M, Kerr S, Hamilton DL, Macgregor LJ. Enhanced skeletal muscle contractile function and corticospinal excitability precede strength and architectural adaptations during lower-limb resistance training. Eur J Appl Physiol 2023; 123:1911-1928. [PMID: 37185932 PMCID: PMC10460716 DOI: 10.1007/s00421-023-05201-8] [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: 10/28/2022] [Accepted: 04/06/2023] [Indexed: 05/17/2023]
Abstract
PURPOSE Evolving investigative techniques are providing greater understanding about the early neuromuscular responses to resistance training among novice exercisers. The aim of this study was to investigate the time-course of changes in muscle contractile mechanics, architecture, neuromuscular, and strength adaptation during the first 6-weeks of lower-limb resistance training. METHODS Forty participants: 22 intervention (10 males/12 females; 173.48 ± 5.20 cm; 74.01 ± 13.13 kg) completed 6-week resistance training, and 18 control (10 males/8 females; 175.52 ± 7.64 cm; 70.92 ± 12.73 kg) performed no resistance training and maintained their habitual activity. Radial muscle displacement (Dm) assessed via tensiomyography, knee extension maximal voluntary contraction (MVC), voluntary activation (VA), corticospinal excitability and inhibition via transcranial magnetic stimulation, motor unit (MU) firing rate, and muscle thickness and pennation angle via ultrasonography were assessed before and after 2, 4, and 6-weeks of dynamic lower-limb resistance training or control. RESULTS After 2-weeks training, Dm reduced by 19-25% in the intervention group; this was before any changes in neural or morphological measures. After 4-weeks training, MVC increased by 15% along with corticospinal excitability by 16%; however, there was no change in VA, corticospinal inhibition, or MU firing rate. After 6-weeks training there was further MVC increase by 6% along with muscle thickness by 13-16% and pennation angle by 13-14%. CONCLUSION Enhanced contractile properties and corticospinal excitability occurred before any muscle architecture, neural, and strength adaptation. Later increases in muscular strength can be accounted for by architectural adaptation.
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Affiliation(s)
- Matthew T Wilson
- Physiology, Exercise, and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, UK
| | - Angus M Hunter
- Physiology, Exercise, and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, UK.
- Department of Sports Sciences, School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, UK.
| | | | - Stewart Kerr
- Life Fit Wellness, Healthcare & Exercise Centre, Falkirk, Scotland, UK
| | - D Lee Hamilton
- Faculty of Health, School of Exercise and Nutrition Sciences, Institute for Physical Activity and Nutrition (IPAN), Deakin University, Geelong, Australia
| | - Lewis J Macgregor
- Physiology, Exercise, and Nutrition Research Group, Faculty of Health Sciences and Sport, University of Stirling, Stirling, UK
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Orantes-Gonzalez E, Heredia-Jimenez J, Lindley SB, Richards JD, Chapman GJ. An exploration of the motor unit behaviour during the concentric and eccentric phases of a squat task performed at different speeds. Sports Biomech 2023:1-12. [PMID: 37339268 DOI: 10.1080/14763141.2023.2221682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 05/31/2023] [Indexed: 06/22/2023]
Abstract
Despite squatting being important in strength training and rehabilitation, few studies have investigated motor unit (MU) behaviour. This study explored the MU behaviour of vastus medialis (VM) and vastus lateralis (VL) during the concentric and eccentric phases of a squat exercise performed at two speeds. Twenty-two participants had surface dEMG sensors attached over VM and VL, and IMUs recorded thigh and shank angular velocities. Participants performed squats at 15 and 25 repetitions per minute in a randomised order, and EMG signals were decomposed into their MU action potential trains. A four factor (muscle × speed × contraction phase × sexes) mixed methods ANOVA revealed significant main effects for MU firing rates between speeds, between muscles and between sexes, but not contraction phases. Post hoc analysis showed significantly greater MU firing rates and amplitudes in VM. A significant interaction was seen between speed and the contraction phases. Further analysis revealed significantly greater firing rates during the concentric compared to the eccentric phases, and between speeds during the eccentric phase only. VM and VL respond differently during squatting depending on speed and contraction phase. These new insights in VM and VL MU behvaviour may be useful when designing training and rehabilitation protocols.
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Affiliation(s)
- Eva Orantes-Gonzalez
- Department of Sports and Computer Science, Faculty of Sports, University of Pablo de Olavide, Seville, Spain
| | - Jose Heredia-Jimenez
- Department of Physical Education and Sport, Faculty of Education, Economy and Technology, University of Granada, Ceuta, Spain
| | | | - Jim D Richards
- Allied Health Research Unit, University of Central Lancashire, Preston, UK
| | - Graham J Chapman
- Allied Health Research Unit, University of Central Lancashire, Preston, UK
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Schilaty ND, McPherson AL, Nagai T, Bates NA. Arthrogenic muscle inhibition manifests in thigh musculature motor unit characteristics after anterior cruciate ligament injury. Eur J Sport Sci 2023; 23:840-850. [PMID: 35306977 PMCID: PMC9626399 DOI: 10.1080/17461391.2022.2056520] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Joint trauma induces a presynaptic reflex inhibition termed arthrogenic muscle inhibition (AMI) that prevents complete activation of muscles. Reduced motor unit (MU) output is a hypothesised mechanism for persistent strength deficits. The objective of this study was to determine MU characteristics of thigh musculature and determine how they change with anterior cruciate ligament (ACL) injury compared to healthy controls. A randomised protocol of knee flexion/extension isometric contractions (10-50% maximal voluntary isometric contraction) was performed for each leg with surface EMG 5-pin array electrodes placed on the vastus medialis, vastus lateralis, semitendinosus and biceps femoris. Longitudinal assessments for average rate coding, recruitment thresholds and MU action potentials were acquired at 6-month intervals. With exception of the vastus medialis, all thigh musculature of ACL-injured demonstrated smaller MU action potential peak-to-peak amplitude. For average rate coding, ACL-injured demonstrated lower coding rates than Controls for the quadriceps (p < .05) and higher rates than Controls for the hamstrings (p < .05). These MU characteristics were different from Controls after ACL reconstruction up to 12 months post-surgery, yet maximal strength increased during this time frame. As thigh MU characteristics are known across phases of ACL rehabilitation, future studies can assess these patterns of motor control and their potential to determine risk of re-injury. Further, future rehabilitation can target specific intervention programmes to restore motor control.HighlightsMotor unit strategies of arthrogenic muscle inhibition are characterised for the first time via decomposed EMG.Motor unit deficits of thigh musculature persist throughout all phases of ACL rehabilitation, even after return-to-sport.After ACL injury, motor unit sizes at similar recruitment thresholds were smaller than those of healthy controls.
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Affiliation(s)
- Nathan D. Schilaty
- Department of Neurosurgery & Brain Repair, University of South Florida, Tampa, FL, USA
- Center for Neuromusculoskeletal Research, University of South Florida, Tampa, FL, USA
- Department of Orthopedics, Mayo Clinic, Rochester, MN, USA
| | - April L. McPherson
- Department of Orthopedics, Mayo Clinic, Rochester, MN, USA
- United States Olympic & Paralympic Committee, Colorado Springs, CO, USA
| | - Takashi Nagai
- Department of Orthopedics, Mayo Clinic, Rochester, MN, USA
- United States Army Research Institute of Environmental Medicine, Natick, MA, USA
| | - Nathaniel A. Bates
- Department of Orthopedics, Mayo Clinic, Rochester, MN, USA
- Department of Orthopaedics, The Ohio State University, Columbus, OH, USA
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Varesco G, Coratella G, Rozand V, Cuinet B, Lombardi G, Mourot L, Vernillo G. Downhill running affects the late but not the early phase of the rate of force development. Eur J Appl Physiol 2022; 122:2049-2059. [PMID: 35790580 PMCID: PMC9381441 DOI: 10.1007/s00421-022-04990-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 05/11/2022] [Indexed: 11/25/2022]
Abstract
Purpose This study aimed to evaluate the acute changes in the knee extensors maximum voluntary isometric contraction force (MVIC), rate of force development (RFD), and rate of EMG rise (RER) following a bout of downhill running. Methods MVIC and RFD at 0–50, 50–100, 100–200, and 0–200 ms were determined in thirteen men (22 ± 2 yr) before and after 30 min of downhill running (speed: 10 km h−1; slope: − 20%). Vastus lateralis maximum EMG (EMGmax) and RER at 0–30, 0–50, and 0–75 ms were also recorded. Results MVIC, RFD0–200, and EMGmax decreased by ~ 25% [Cohen’s d = − 1.09 (95% confidence interval: − 1.88/− 0.24)], ~ 15% [d = − 0.50 (− 1.26/0.30)], and ~ 22% [d = − 0.37 (− 1.13/0.42)] (all P < 0.05), respectively. RFD100–200 was also reduced [− 25%; d = − 0.70 (− 1.47/0.11); P < 0.001]. No change was observed at 0–50 ms and 50–100 ms (P ≥ 0.05). RER values were similar at each time interval (all P > 0.05). Conclusion Downhill running impairs the muscle capacity to produce maximum force and the overall ability to rapidly develop force. No change was observed for the early phase of the RFD and the absolute RER, suggesting no alterations in the neural mechanisms underlying RFD. RFD100–200 reduction suggests that impairments in the rapid force-generating capacity are located within the skeletal muscle, likely due to a reduction in muscle–tendon stiffness and/or impairments in the muscle contractile apparatus. These findings may help explain evidence of neuromuscular alterations in trail runners and following prolonged duration races wherein cumulative eccentric loading is high.
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Affiliation(s)
- Giorgio Varesco
- Inter-University Laboratory of Human Movement Biology (EA 7424), UJM-Saint-Etienne, Université de Lyon, 42023, Saint-Etienne, France
| | - Giuseppe Coratella
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Building 2, via G. Colombo 71, 20133, Milan, Italy
| | - Vianney Rozand
- Inter-University Laboratory of Human Movement Biology (EA 7424), UJM-Saint-Etienne, Université de Lyon, 42023, Saint-Etienne, France
| | - Benjamin Cuinet
- Prognostic Factors and Regulatory Factors of Cardiac and Vascular Pathologies (EA3920), Exercise Performance Health Innovation (EPHI) Platform, University of Bourgogne Franche-Comté, 25000, Besançon, France
| | - Giovanni Lombardi
- Laboratory of Experimental Biochemistry and Molecular Biology, IRCCS Orthopedic Institute Galeazzi, 20161, Milan, Italy.,Department of Athletics, Strength and Conditioning, Poznań University of Physical Education, 61-871, Poznań, Poland
| | - Laurent Mourot
- Prognostic Factors and Regulatory Factors of Cardiac and Vascular Pathologies (EA3920), Exercise Performance Health Innovation (EPHI) Platform, University of Bourgogne Franche-Comté, 25000, Besançon, France.,Division for Physical Education, Tomsk Polytechnic University, Tomsk Oblast, 634050, Russia
| | - Gianluca Vernillo
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Building 2, via G. Colombo 71, 20133, Milan, Italy.
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Eccentric and concentric contraction of multifidus lumborum and longissimus muscles during flexion–relaxation test using discrete wavelet transform. SPORT SCIENCES FOR HEALTH 2022. [DOI: 10.1007/s11332-022-00984-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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Richards J, Gechev A, Alexander J, Macedo L, May KA, Lindley SB. The Effect of Local Cooling at the Elbow on Nerve Conduction Velocity and Motor Unit Behaviour: An Exploration of a Novel Neurological Assessment. SENSORS 2021; 21:s21206703. [PMID: 34695914 PMCID: PMC8537108 DOI: 10.3390/s21206703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 09/22/2021] [Accepted: 10/04/2021] [Indexed: 12/02/2022]
Abstract
Background: This study aimed to determine the effects of a standard therapeutic cooling protocol using crushed ice on the elbow to explore if changes in the motor unit (MU) firing rates in the first dorsal interosseous (FDI) muscle are comparable to known changes in sensory and motor nerve conduction velocity (NCV) due to a regional temperature drop around a peripheral nerve. Methods: Twelve healthy individuals were assessed before cooling, immediately after cooling, and 15 min of rewarming. Assessments included two standard non-invasive nerve conduction velocity tests and a non-invasive investigation of the MU firing rates using surface electromyography decomposition (dEMG). Results: Repeated ANOVAs showed significant differences in the MU firing rates and NCV between time points (p = 0.01 and p < 0.001). All measures showed significant differences between pre and post cooling and between pre-cooling and 15 min of passive re-warming, however, no changes were seen between post cooling and rewarming except in the sensory NCV, which increased but did not return to the pre-cooled state. Conclusions: This current study showed a significant, temporary, and reversible reduction in ulnar NCV across the elbow in healthy subjects, which was associated with a significant decrease in mean MU firing rates in the FDI muscle.
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Affiliation(s)
- Jim Richards
- Allied Health Research Unit, University of Central Lancashire, Preston PR1 2HE, UK;
- Correspondence:
| | - Antonin Gechev
- Department of Clinical Neurophysiology, Royal Free London Hospital, London NW3 2QG, UK;
| | - Jill Alexander
- Allied Health Research Unit, University of Central Lancashire, Preston PR1 2HE, UK;
| | - Liane Macedo
- Faculty of Health Sciences of Trairí, Federal University of Rio Grande do Norte, Santa Cruz 59200-000, Brazil;
| | - Karen A. May
- School of Medicine, University of Central Lancashire, Preston PR1 2HE, UK;
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D'Emanuele S, Maffiuletti NA, Tarperi C, Rainoldi A, Schena F, Boccia G. Rate of Force Development as an Indicator of Neuromuscular Fatigue: A Scoping Review. Front Hum Neurosci 2021; 15:701916. [PMID: 34305557 PMCID: PMC8301373 DOI: 10.3389/fnhum.2021.701916] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/16/2021] [Indexed: 11/26/2022] Open
Abstract
Because rate of force development (RFD) is an emerging outcome measure for the assessment of neuromuscular function in unfatigued conditions, and it represents a valid alternative/complement to the classical evaluation of pure maximal strength, this scoping review aimed to map the available evidence regarding RFD as an indicator of neuromuscular fatigue. Thus, following a general overview of the main studies published on this topic, we arbitrarily compared the amount of neuromuscular fatigue between the “gold standard” measure (maximal voluntary force, MVF) and peak, early (≤100 ms) and late (>100 ms) RFD. Seventy full-text articles were included in the review. The most-common fatiguing exercises were resistance exercises (37% of the studies), endurance exercises/locomotor activities (23%), isokinetic contractions (17%), and simulated/real sport situations (13%). The most widely tested tasks were knee extension (60%) and plantar flexion (10%). The reason (i.e., rationale) for evaluating RFD was lacking in 36% of the studies. On average, the amount of fatigue for MVF (−19%) was comparable to late RFD (−19%) but lower compared to both peak RFD (−25%) and early RFD (−23%). Even if the rationale for evaluating RFD in the fatigued state was often lacking and the specificity between test task and fatiguing exercise characteristics was not always respected in the included studies, RFD seems to be a valid indicator of neuromuscular fatigue. Based on our arbitrary analyses, peak RFD and early phase RFD appear even to be more sensitive to quantify neuromuscular fatigue than MVF and late phase RFD.
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Affiliation(s)
- Samuel D'Emanuele
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy
| | | | - Cantor Tarperi
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.,Department of Clinical and Biological Sciences, University of Turin, Turin, Italy
| | - Alberto Rainoldi
- Department of Medical Sciences, University of Turin, Turin, Italy.,NeuroMuscularFunction
- Research Group, School of Exercise and Sport Sciences (SUISM), University of Turin, Turin, Italy
| | - Federico Schena
- Department of Neurosciences, Biomedicine and Movement Sciences, University of Verona, Verona, Italy.,CeRiSM, Sport Mountain and Health Research Centre, University of Verona, Verona, Italy
| | - Gennaro Boccia
- Department of Clinical and Biological Sciences, University of Turin, Turin, Italy.,NeuroMuscularFunction
- Research Group, School of Exercise and Sport Sciences (SUISM), University of Turin, Turin, Italy
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Newell ML, Macgregor LJ, Galloway SDR, Hunter AM. Prolonged cycling exercise alters neural control strategy, irrespective of carbohydrate dose ingested. TRANSLATIONAL SPORTS MEDICINE 2021. [DOI: 10.1002/tsm2.187] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Michael L. Newell
- School of Sport Science and Physical Activity University of Bedfordshire Bedford England UK
| | - Lewis J. Macgregor
- Faculty of Health Sciences and Sport University of Stirling Stirling Scotland UK
| | | | - Angus M. Hunter
- Faculty of Health Sciences and Sport University of Stirling Stirling Scotland UK
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Methenitis S, Mpampoulis T, Spiliopoulou P, Papadimas G, Papadopoulos C, Chalari E, Evangelidou E, Stasinaki AN, Nomikos T, Terzis G. Muscle fiber composition, jumping performance, and rate of force development adaptations induced by different power training volumes in females. Appl Physiol Nutr Metab 2020; 45:996-1006. [PMID: 32203677 DOI: 10.1139/apnm-2019-0786] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study aimed to investigate the effect of 3 different eccentric-only power training volumes on muscle fiber type composition and power performance. Twenty-nine females were assigned into 3 groups and performed 10 weeks of either 3 (low volume), 6 (moderate volume), or 9 (high volume) sets/session of 4 fast-velocity eccentric-only half-squats against 70% of concentric 1-repetition maximum (1RM), followed by 3 maximum countermovement jumps (CMJs) after each set. Half-squat 1RM, CMJ height/power, maximum isometric force, rate of force development (RFD) and muscle fiber cross-sectional area (CSA) were increased in all groups (p = 0.001). Low-volume training induced higher increases in CMJ height/power and early RFD, compared with the moderate- and high-volume training programs (p < 0.001). Significant reductions in type IIx muscle fiber percentages and %CSAs were found after moderate- and high-volume training, with concomitant increases in type IIa fibers (p = 0.001). Significant correlations were found between the changes in type IIa and type IIx percentages, fiber CSA, %CSA, and the changes in performance (r: -0.787 to 0.792; p < 0.05). These results suggest that relatively large eccentric power training volumes may result in detrimental neuromuscular adaptations, minimal changes in early RFD, and a reduction of type IIx muscle fiber percentage. Novelty Low but not high volume of power training maintains type IIx muscle fibers. Early rate of force development increases after a low- or moderate-power training volume, but not after a high-power training volume. Training-induced changes in type IIx muscle fiber percentage is related with changes in early rate of force development.
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Affiliation(s)
- Spyridon Methenitis
- Sports Performance Laboratory, School of Physical Education & Sports Science, National and Kapodistrian University of Athens, 172 37, Daphne, Athens, Greece
| | - Thomas Mpampoulis
- Sports Performance Laboratory, School of Physical Education & Sports Science, National and Kapodistrian University of Athens, 172 37, Daphne, Athens, Greece
| | - Polyxeni Spiliopoulou
- Sports Performance Laboratory, School of Physical Education & Sports Science, National and Kapodistrian University of Athens, 172 37, Daphne, Athens, Greece
| | - George Papadimas
- A'Neurology Clinic, Aiginition Hospital, Medical School, National and Kapodistrian University of Athens, Leof. Vasilissis Sofias 72, Athina 115 28, Greece
| | - Constantinos Papadopoulos
- A'Neurology Clinic, Aiginition Hospital, Medical School, National and Kapodistrian University of Athens, Leof. Vasilissis Sofias 72, Athina 115 28, Greece
| | - Eleanna Chalari
- Department of Nutrition and Dietetics, School of Health Science & Education, Harokopio University of Athens, 70 El. Venizelou, 17671 Athens, Greece
| | - Eftychia Evangelidou
- Department of Infection Control, G.N.N. Ionias "Konstantopouleio-Patision" Hospital, Agias Olgas 3-5, 14233, Nea Ionia, Greece
| | - Angeliki-Nikoletta Stasinaki
- Sports Performance Laboratory, School of Physical Education & Sports Science, National and Kapodistrian University of Athens, 172 37, Daphne, Athens, Greece
| | - Tzortzis Nomikos
- Department of Nutrition and Dietetics, School of Health Science & Education, Harokopio University of Athens, 70 El. Venizelou, 17671 Athens, Greece
| | - Gerasimos Terzis
- Sports Performance Laboratory, School of Physical Education & Sports Science, National and Kapodistrian University of Athens, 172 37, Daphne, Athens, Greece
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Macgregor LJ, Hunter AM. High-threshold motor unit firing reflects force recovery following a bout of damaging eccentric exercise. PLoS One 2018; 13:e0195051. [PMID: 29630622 PMCID: PMC5890972 DOI: 10.1371/journal.pone.0195051] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 03/11/2018] [Indexed: 11/18/2022] Open
Abstract
Exercise-induced muscle damage (EIMD) is associated with impaired muscle function and reduced neuromuscular recruitment. However, motor unit firing behaviour throughout the recovery period is unclear. EIMD impairment of maximal voluntary force (MVC) will, in part, be caused by reduced high-threshold motor unit firing, which will subsequently increase to recover MVC. Fourteen healthy active males completed a bout of eccentric exercise on the knee extensors, with measurements of MVC, rate of torque development and surface electromyography performed pre-exercise and 2, 3, 7 and 14 days post-exercise, on both damaged and control limb. EIMD was associated with decreased MVC (235.2 ± 49.3 Nm vs. 161.3 ± 52.5 Nm; p <0.001) and rate of torque development (495.7 ± 136.9 Nm.s-1 vs. 163.4 ± 163.7 Nm.s-1; p <0.001) 48h post-exercise. Mean motor unit firing rate was reduced (16.4 ± 2.2 Hz vs. 12.6 ± 1.7 Hz; p <0.01) in high-threshold motor units only, 48h post-exercise, and common drive was elevated (0.36 ± 0.027 vs. 0.56 ± 0.032; p< 0.001) 48h post-exercise. The firing rate of high-threshold motor units was reduced in parallel with impaired muscle function, whilst early recruited motor units remained unaltered. Common drive of motor units increased in offset to the firing rate impairment. These alterations correlated with the recovery of force decrement, but not of pain elevation. This study provides fresh insight into the central mechanisms associated with EIMD recovery, relative to muscle function. These findings may in turn lead to development of novel management and preventative procedures.
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Affiliation(s)
- Lewis J. Macgregor
- Faculty of Health Sciences and Sport, University of Stirling, Stirling, Scotland
| | - Angus M. Hunter
- Faculty of Health Sciences and Sport, University of Stirling, Stirling, Scotland
- * E-mail:
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12
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de Souza LML, Cabral HV, de Oliveira LF, Vieira TM. Motor units in vastus lateralis and in different vastus medialis regions show different firing properties during low-level, isometric knee extension contraction. Hum Mov Sci 2018; 58:307-314. [DOI: 10.1016/j.humov.2017.12.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 11/17/2017] [Accepted: 12/15/2017] [Indexed: 11/27/2022]
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Balshaw TG, Pahar M, Chesham R, Macgregor LJ, Hunter AM. Reduced firing rates of high threshold motor units in response to eccentric overload. Physiol Rep 2017; 5:e13111. [PMID: 28108648 PMCID: PMC5269413 DOI: 10.14814/phy2.13111] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 12/08/2016] [Accepted: 12/09/2016] [Indexed: 11/24/2022] Open
Abstract
Acute responses of motor units were investigated during submaximal voluntary isometric tasks following eccentric overload (EO) and constant load (CL) knee extension resistance exercise. Ten healthy resistance-trained participants performed four experimental test sessions separated by 5 days over a 20 day period. Two sessions involved constant load and the other two used eccentric overload. EO and CL used both sessions for different target knee eccentric extension phases; one at 2 sec and the other at 4 sec. Maximal voluntary contractions (MVC) and isometric trapezoid efforts for 10 sec at 70% MVC were completed before and after each intervention and decomposed electromyography was used to measure motor unit firing rate. The firing rate of later recruited, high-threshold motor units declined following the 2-sec EO but was maintained following 2sec CL (P < 0.05), whereas MUFR for all motor units were maintained for both loading types following 4-sec extension phases. MVC and rate of force development where maintained following both EO and CL and 2 and 4 sec phases. This study demonstrates a slower firing rate of high-threshold motor units following fast eccentric overload while MVC was maintained. This suggests that there was a neuromuscular stimulus without cost to the force-generating capacity of the knee extensors.
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Affiliation(s)
- Tom G Balshaw
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
| | - Madhu Pahar
- Computing Science and Mathematics, University of Stirling, Stirling, Scotland, United Kingdom
| | - Ross Chesham
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
| | - Lewis J Macgregor
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
| | - Angus M Hunter
- Physiology, Exercise and Nutrition Research Group, University of Stirling, Stirling, Scotland, United Kingdom
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