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Meyer BL, Beermann F, Langmann J, Stieglitz T, Pasluosta C, Mrachacz-Kersting N. Interlimb reflexes of the lower limb elicited by femoral nerve stimulation in able-bodied persons. J Neurophysiol 2025; 133:1538-1550. [PMID: 39996601 DOI: 10.1152/jn.00249.2024] [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: 06/13/2024] [Revised: 10/01/2024] [Accepted: 02/20/2025] [Indexed: 02/26/2025] Open
Abstract
Sensory feedback arising from muscles in the lower limb makes an important contribution to the activation of muscles on the opposite side. To date little is known about this interlimb communication for muscles of the upper leg. Here, we quantify interlimb reflexes of the quadriceps muscles elicited by femoral nerve stimulation. The reflex response of 10 able-bodied participants was analyzed at eight stimulation intensities [0.7× motor threshold (MT)-100% maximal M-wave (M-max)], during standing and sitting. Electromyographic (EMG) signals of the contralateral vastus lateralis (cVL), rectus femoris (cRF), biceps femoris (cBF), and soleus (cSOL) muscle were analyzed. Significant inhibitory long-latency responses were observed at stimulation intensities higher than 0.7 × MT, for the cVL and cRF. Onset latencies ranged from 67 ± 12 ms to 70 ± 13 ms during standing and from 61 ± 14 ms to 67 ± 15 ms during sitting. The strongest depression (-32.39% compared with baseline EMG activity) was observed for the cRF during standing at 50% M-max. The cBF showed excitatory long-latency responses during standing (strongest at 100% M-max with +52.36%) and inhibitory once during sitting, and small excitatory short-latency responses during standing. The cSOL showed inhibitory long-latency responses (-18.15% at 25% M-max) during standing. In conclusion, the results show that femoral nerve stimulation elicits consistent contralateral reflex responses in the quadriceps muscles. The occurrence at all intensities suggests that group Ia, Ib, and II afferents are involved in the pathways.NEW & NOTEWORTHY This study introduced a method to consistently elicit contralateral reflex responses in the quadriceps muscles through femoral nerve stimulation. Responses of the contralateral vastus lateralis (cVL), contralateral rectus femoris (cRF), and contralateral soleus (cSOL) occurred only in the long-latency range, whereas the contralateral biceps femoris (cBF) showed small short-latency and long-latency activity.
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Affiliation(s)
- Britta L Meyer
- Department of Sport and Sport Science, University of Freiburg, Freiburg, Germany
| | - Finja Beermann
- Department of Sport and Sport Science, University of Freiburg, Freiburg, Germany
| | - Jakob Langmann
- Department of Sport and Sport Science, University of Freiburg, Freiburg, Germany
| | - Thomas Stieglitz
- Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools Center, University of Freiburg, Freiburg, Germany
- Bernstein Center Freiburg, University of Freiburg, Freiburg, Germany
| | - Cristian Pasluosta
- Laboratory for Biomedical Microtechnology, Department of Microsystems Engineering, University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools Center, University of Freiburg, Freiburg, Germany
| | - Natalie Mrachacz-Kersting
- Department of Sport and Sport Science, University of Freiburg, Freiburg, Germany
- BrainLinks-BrainTools Center, University of Freiburg, Freiburg, Germany
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Inglis JG, Cabral HV, Cosentino C, Bonardi A, Negro F. Motor unit discharge behavior in human muscles throughout force gradation: a systematic review and meta-analysis with meta-regression. J Appl Physiol (1985) 2025; 138:1050-1065. [PMID: 40095845 DOI: 10.1152/japplphysiol.00863.2024] [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: 11/05/2024] [Revised: 12/03/2024] [Accepted: 03/05/2025] [Indexed: 03/19/2025] Open
Abstract
The analysis of motor unit (MU) discharge behavior provides an effective way of assembling information about the generation and control of movement. In this systematic review and meta-analysis, we identified and summarized the literature investigating MU discharge rate and discharge rate variability (CoV-ISI) during voluntary isometric contractions at various force levels. Databases were searched up to January 7, 2025, and a total of 262 studies were included. The meta-means of MU discharge rate and CoV-ISI were estimated and compared across human muscles. The influence of contraction intensity on MU discharge behavior was assessed through linear meta-regressions. At low-to-moderate forces [<60% maximal voluntary contraction (MVC)], the first dorsal interosseous, biceps brachii (BB), and forearm extensors (FEs) had the highest discharge rate, whereas the soleus had the lowest. At high force levels (>60% MVC), the tibialis anterior (TA) had the highest mean discharge rate compared with all other muscles, with the soleus maintaining the lowest. Regarding CoV-ISI results at low forces (<30% MVC), the TA had the lowest CoV-ISI values, except in comparison with the vastii. In addition, the vastii had lower CoV-ISI values than the FE, gastrocnemius medialis, and soleus. Contraction intensity was positively associated with the mean discharge rates in all muscles investigated, although some muscles showed steeper slopes than others. Similar results were observed for CoV-ISI meta-regressions, with muscle-specific differences in slope. These findings suggest potential variations in neural control strategies across muscles during force gradation, such as differences in the relative contribution of rate coding to facilitate increasing force demands.
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Affiliation(s)
- J Greig Inglis
- Department of Clinical and Experimental SciencesUniversità degli Studi di BresciaBresciaItaly
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Kuniki M, Iwamoto Y, Konishi R, Kuwahara D, Yamagiwa D, Kito N. Neural Drive and Motor Unit Characteristics of the Serratus Anterior in Individuals With Scapular Dyskinesis. JOURNAL OF MUSCULOSKELETAL & NEURONAL INTERACTIONS 2024; 24:148-158. [PMID: 38825997 PMCID: PMC11145323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Accepted: 03/07/2024] [Indexed: 06/04/2024]
Abstract
OBJECTIVE Scapular dyskinesis is one of the causes of shoulder disorders and involves muscle weakness in the serratus anterior. This study investigated whether motor unit (MU) recruitment and firing property, which are important for muscle exertion, have altered in serratus anterior of the individuals with scapular dyskinesis. METHODS Asymptomatic adults with (SD) and without (control) scapular dyskinesis were analyzed. Surface electromyography (sEMG) waveforms were collected at submaximal voluntary contraction of the serratus anterior. The sEMG waveform was decomposed into MU action potential amplitude (MUAPAMP), mean firing rate (MFR), and recruitment threshold. MUs were divided into low, moderate, and high thresholds, and MU recruitment and firing properties of the groups were compared. RESULTS High-threshold MUAPAMP was significantly smaller in the SD group than in the control group. The control group also exhibited recruitment properties that reflected the size principle, however, the SD group did not. Furthermore, the SD group had a lower MFR than the control group. CONCLUSIONS Individuals with scapular dyskinesis exhibit altered MU recruitment properties and lower firing rates of the serratus anterior; this may be detrimental to muscle performance. Thus, it may be necessary to improve the neural drive of the serratus anterior when correcting scapular dyskinesis.
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Affiliation(s)
- Masahiro Kuniki
- Graduate School of Medical Welfare Sciences, Medical Engineering, Hiroshima International University, Higashi-hiroshima, Hiroshima, Japan
| | - Yoshitaka Iwamoto
- Department of Neuromechanics, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Rei Konishi
- Department of Rehabilitation, Faculty of Rehabilitation, Hiroshima International University, Higashi-hiroshima, Hiroshima, Japan
| | - Daisuke Kuwahara
- Graduate School of Medical Welfare Sciences, Medical Engineering, Hiroshima International University, Higashi-hiroshima, Hiroshima, Japan
| | - Daiki Yamagiwa
- Graduate School of Medical Welfare Sciences, Medical Engineering, Hiroshima International University, Higashi-hiroshima, Hiroshima, Japan
| | - Nobuhiro Kito
- Department of Rehabilitation, Faculty of Rehabilitation, Hiroshima International University, Higashi-hiroshima, Hiroshima, Japan
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Torres-Banduc M, Chirosa-Ríos I, Chirosa-Ríos L, Jerez-Mayorga D. Impact of Starting Knee Flexion Angle on Muscle Activity and Performance during Plyometrics without Jumping. SENSORS (BASEL, SWITZERLAND) 2023; 24:44. [PMID: 38202906 PMCID: PMC10780924 DOI: 10.3390/s24010044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 11/22/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024]
Abstract
Most of the existing research has focused on jump plyometrics, where landing reaction forces must be dissipated among lower limb articulations. In contrast, the investigation of resisted plyometrics without jumping, devoid of such landing forces, remains relatively limited. This study aimed to (i) investigate the impact of resisted plyometrics without jumping at two knee flexion angles (60 and 90 degrees) on vastus muscle activity relative to limb dominance and (ii) assess strength, power, and work during the concentric-eccentric phases of these exercises. Thirty-one healthy participants underwent quantification of lower limb muscle amplitude, strength, power, and work during resisted plyometrics without jumping from both 60° and 90° knee flexion positions. After anthropometric evaluations, participants used a dynamometer with a load equal to 80% of body weight while wireless surface electromyography electrodes recorded data. Statistical analyses utilized paired t-tests or nonparametric equivalents and set significance at p ≤ 0.05. Results showed significantly higher muscle activity in the vastus medialis (VM) (dominant: 47.4%, p = 0.0008, rs = 0.90; nondominant: 54.8%, p = 0.047, rs = 0.88) and vastus lateralis (VL) (dominant: 46.9%, p = 0.0004, rs = 0.86; nondominant: 48.1%, p = 0.021, rs = 0.67) muscles when exercises started at 90° knee flexion, regardless of limb dominance. Substantial intermuscle differences occurred at both 60° (50.4%, p = 0.003, rs = 0.56) and 90° (54.8%, p = 0.005, rs = 0.62) knee flexion, favoring VM in the nondominant leg. Concentric and eccentric strength, power, and work metrics significantly increased when initiating exercises from a 90° position. In conclusion, commencing resisted plyometrics without jumping at a 90° knee flexion position increases VM and VL muscle activity, regardless of limb dominance. Furthermore, it enhances strength, power, and work, emphasizing the importance of knee flexion position customization for optimizing muscle engagement and functional performance.
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Affiliation(s)
- Maximiliano Torres-Banduc
- Escuela de Kinesiología, Facultad de Ciencias de la Salud, Universidad de Las Américas, Viña Del Mar 2520000, Chile;
- Department of Physical Education and Sports, Faculty of Sports Sciences, University of Granada, 18071 Granada, Spain;
| | - Ignacio Chirosa-Ríos
- Department of Physical Education and Sports, Faculty of Sports Sciences, University of Granada, 18071 Granada, Spain;
| | - Luis Chirosa-Ríos
- Department of Physical Education and Sports, Faculty of Sports Sciences, University of Granada, 18071 Granada, Spain;
| | - Daniel Jerez-Mayorga
- Exercise and Rehabilitation Sciences Institute, School of Physical Therapy, Faculty of Rehabilitation Sciences, Universidad Andres Bello, Santiago 7570172, Chile;
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Haggie L, Schmid L, Röhrle O, Besier T, McMorland A, Saini H. Linking cortex and contraction-Integrating models along the corticomuscular pathway. Front Physiol 2023; 14:1095260. [PMID: 37234419 PMCID: PMC10206006 DOI: 10.3389/fphys.2023.1095260] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 04/21/2023] [Indexed: 05/28/2023] Open
Abstract
Computational models of the neuromusculoskeletal system provide a deterministic approach to investigate input-output relationships in the human motor system. Neuromusculoskeletal models are typically used to estimate muscle activations and forces that are consistent with observed motion under healthy and pathological conditions. However, many movement pathologies originate in the brain, including stroke, cerebral palsy, and Parkinson's disease, while most neuromusculoskeletal models deal exclusively with the peripheral nervous system and do not incorporate models of the motor cortex, cerebellum, or spinal cord. An integrated understanding of motor control is necessary to reveal underlying neural-input and motor-output relationships. To facilitate the development of integrated corticomuscular motor pathway models, we provide an overview of the neuromusculoskeletal modelling landscape with a focus on integrating computational models of the motor cortex, spinal cord circuitry, α-motoneurons and skeletal muscle in regard to their role in generating voluntary muscle contraction. Further, we highlight the challenges and opportunities associated with an integrated corticomuscular pathway model, such as challenges in defining neuron connectivities, modelling standardisation, and opportunities in applying models to study emergent behaviour. Integrated corticomuscular pathway models have applications in brain-machine-interaction, education, and our understanding of neurological disease.
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Affiliation(s)
- Lysea Haggie
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Laura Schmid
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany
| | - Oliver Röhrle
- Institute for Modelling and Simulation of Biomechanical Systems, University of Stuttgart, Stuttgart, Germany
- Stuttgart Center for Simulation Sciences (SC SimTech), University of Stuttgart, Stuttgart, Germany
| | - Thor Besier
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Angus McMorland
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Department of Exercise Sciences, University of Auckland, Auckland, New Zealand
| | - Harnoor Saini
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
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