Individuals with chronic ankle instability show altered regional activation of the peroneus longus muscle during ankle eversion.

Individuals with chronic ankle instability (CAI) present muscular weakness and potential changes in the activation of the peroneus longus muscle, which likely explains the high recurrence of ankle sprains in this population. However, there is conflicting evidence regarding the role of the peroneus longus activity in CAI, possibly due to the limited spatial resolution of the surface electromyography (sEMG) methods (i.e., bipolar sEMG). Recent studies employing high-density sEMG (HD-sEMG) have shown that the peroneus longus presents differences in regional activation, however, it is unknown whether this regional activation is maintained under pathological conditions such as CAI. This study aimed to compare the myoelectric activity, using HD-sEMG, of each peroneus longus compartment (anterior and posterior) between individuals with and without CAI. Eighteen healthy individuals (No-CAI group) and 18 individuals with CAI were recruited. In both groups, the center of mass (COM) and the sEMG amplitude at each compartment were recorded during ankle eversion at different force levels. For the posterior compartment, the sEMG amplitude of CAI group was significantly lower than the No-CAI group (mean difference = 5.6% RMS; 95% CI = 3.4-7.6; p = 0.0001). In addition, it was observed a significant main effect for group (F1,32 = 9.608; p = 0.0040) with an anterior displacement of COM for the CAI group. These findings suggest that CAI alters the regional distribution of muscle activity of the peroneus longus during ankle eversion. In practice, altered regional activation may impact strengthening programs, prevention, and rehabilitation of CAI.

Effect of M-wave Amplitude on Inter-evaluator Concordance and Number of Detected Innervation Zones in the Medial Gastrocnemius Using Multichannel Electromyography / Efecto de la Amplitud de la Onda M sobre la Concordancia entre Evaluadores y el Número de Zonas de Inervación Detectadas en el Gastrocnemio Medial Mediante Electromiografía Multicanal

SUMMARY: The Innervation Zones (IZ) correspond to clusters of neuromuscular junctions. The traditional method of locating IZs through voluntary muscle contractions may not be feasible in individuals with motor disorders. Imposed contractions by electrostimulation are an alternative. However, there is limited evidence regarding the factors that affect inter-evaluator concordance and the number of localized IZs when using imposed contraction. The main objective of this research was to determine the effect of the amplitude of compound motor action potentials (CMAPs) containing the M-wave on inter-evaluator agreement. As a secondary objective, was investigate the effect on the number of detected IZs. Twenty-four healthy volunteers (age: 21.2 ± 1.5years, weight: 67.4 ± 13.2kg, height: 1.68 ± 0.80m) participated in the study. Electrostimulation was applied to the tibial nerve to induce contraction of the medial gastrocnemius. The IZ were identified based on the M-wave recorded through multichannel electromyography. A receiver operating characteristic (ROC) analysis was conducted to assess sensitivity and specificity in detecting the IZs. Inter-rater agreement was evaluated using a two-way mixed effects test to determine the intraclass correlation coefficients (ICC). A p-value less than 0.05 was considered statistically significant. The ROC analysis revealed that for both evaluators, a specificity of 95% was achieved with an amplitude ≥30 %. The area under the ROC curve was 0.980 [0.964, 0.996], indicating a strong influence of CMAP amplitude on detection of IZs. The highest level of agreement (ICC = 0.788 [0.713, 0.844]) among the evaluators was observed with CMAP amplitudes equal to or greater than 80 % of the maximum M-wave. The findings of this study demonstrate that both the number and the inter-evaluator concordance for detecting IZs using imposed contractions are strongly influenced by the amplitude of the M-wave. Higher M-wave amplitudes were associated with improved concordance and increased IZ detection, making it crucial to standardize amplitude settings for reliable outcomes.

Las Zonas de Inervación (IZ) corresponden a grupos de uniones neuromusculares. El método tradicional para localizar IZs mediante contracciones musculares voluntarias puede no ser factible en personas con trastornos motores. Las contracciones impuestas mediante electro estimulación son una alternativa. Sin embargo, existe poca evidencia sobre los factores que afectan la concordancia entre evaluadores y el número de IZs localizadas al usar este tipo de contracciones. El objetivo de esta investigación fue determinar el efecto de la amplitud de los potenciales de acción motores compuestos (PAMCs) que contienen la onda M sobre la concordancia entre evaluadores. Como objetivo secundario, se investigó el efecto sobre el número de IZs detectadas. Veinticuatro voluntarios sanos (edad: 21.2 ± 1.5 años, peso: 67.4 ± 13.2 kg, altura: 1.68 ± 0.80 m) participaron en el estudio. Se aplicó electroestimulación al nervio tibial para inducir la contracción del gastrocnemio medial. Las IZs se identificaron según la onda M registrada mediante electromiografía multicanal. Se realizó un análisis de curva de las característica del receptor (ROC) para evaluar la sensibilidad y especificidad en la detección de las IZs. La concordancia entre evaluadores se evaluó utilizando una prueba de efectos mixtos de dos vías para determinar los coeficientes de correlación intraclase (ICC). Se consideró un valor de p menor que 0.05 como estadísticamente significativo. El análisis ROC reveló que para ambos evaluadores se logró una especificidad del 95% con una amplitud ≥30 %. El área bajo la curva ROC fue de 0.980 [0.964, 0.996], lo que indica una fuerte influencia de la amplitud del CMAP en la detección de las IZs. El nivel más alto de concordancia (ICC = 0.788 [0.713, 0.844]) entre los evaluadores se observó con amplitudes de CMAP iguales o mayores al 80 % de la onda M máxima. Los hallazgos de este estudio demuestran que tanto el número como la concordancia entre evaluadores para detectar IZs mediante contracciones impuestas están fuertemente influenciados por la amplitud de la onda M. Las amplitudes más altas de la onda M se asociaron con una concordancia mejorada y un aumento en la detección de IZs, lo que hace crucial estandarizar los ajustes de amplitud para obtener resultados confiables.

Acute Deltoid Injury in Ankle Fractures: A Biomechanical Analysis of Different Repair Constructs.

BACKGROUND: The importance of the deltoid ligament in the congruency and coupling of the tibiotalar joint is well known. The current trend is to repair it in cases of acute injuries in the context of ankle fractures; however, there is limited information on how it should be reconstructed. The objective of this study was to compare different deltoid ligament repair types in an ankle fracture cadaveric model. METHODS: Sixteen cadaveric foot-ankle-distal tibia specimens were used. All samples were prepared as a supination external rotation ankle fracture model. Axial load and cyclic axial rotations were applied on every specimen using a specifically designed frame. This test was performed without deltoid injury, with deltoid injury, and after repair. The reconstruction was performed in 4 different ways (anterior, posterior, middle, and combined). Medial clear space (MCS) was measured for each condition on simulated weightbearing (WB) and gravity stress (GS) radiographs. Reflective markers were used in tibia and talus, registering the kinematics through a motion analysis system to record the tibiotalar uncoupling. RESULTS: After deltoid damage, in all cases the MCS increased significantly on GS radiographs, but there was no increase in the MCS on WB radiographs. After repair, in all cases, the MCS was normalized. Kinematically, after deltoid damage, the tibiotalar uncoupling increased significantly. All isolated repairs achieved a similar tibiotalar uncoupling value as its baseline condition. The combined repair resulted in a significant decrease in tibiotalar uncoupling. CONCLUSION: Our results show that deltoid repair recovers the tibiotalar coupling mechanism in an ankle fracture model. Isolated deltoid repairs recovered baseline MCS and tibiotalar uncoupling values. Combined repairs may lead to overconstraint, which could lead to postoperative stiffness. Clinical studies are needed to prove these results and show clinically improved outcomes. CLINICAL RELEVANCE: This study helps in finding the optimum deltoid repair to use in an acute trauma setting.

Task-related differences in peroneus longus muscle fiber conduction velocity.

It has been identified that the peroneus longus presents a regional activity. Specifically, a greater activation of the anterior and posterior compartments has been observed during eversion, whereas a lower activation of the posterior compartment has been reported during plantarflexion. In addition to myoelectrical amplitude, motor unit recruitment can be inferred indirectly from muscle fiber conduction velocity (MFCV). However, there are few reports of MFCV of the regions that make up a muscle, and even less, MFCV of the peroneus longus compartments. This study aimed to analyze the MFCV of peroneus longus compartments during eversion and plantarflexion. Twenty-one healthy individuals were assessed. High-density surface electromyography was recorded from the peroneus longus during eversion and plantarflexion at 10%, 30%, 50%, and 70% of maximal voluntary isometric contraction. The posterior compartment presented a lower MFCV than the anterior compartment during plantarflexion, and both compartments did not show differences in MFCV during eversion; however, the posterior compartment showed an increase in MFCV during eversion compared to plantarflexion. Differences observed in the MFCV of the peroneus longus compartments could support a regional activation strategy and, to some extent, explain different motor unit recruitment strategies of the peroneus longus during ankle movements.

Temporal differences in the myoelectric activity of lower limb muscles during rearfoot and forefoot running: A statistical parametric mapping approach.

Forefoot (FF) and rearfoot (RF) running techniques can induce different lower-limb muscle activation patterns. However, few studies have evaluated temporal changes in the electromyographic activity (EMG) of lower limb muscles during running. The aim of this study was to compare temporal changes in EMG amplitude between RF and FF running techniques. Eleven recreational runners ran on a treadmill at a self-selected speed, once using a RF strike pattern and once using a FF strike pattern (randomized order). The EMG of five lower limb muscles [rectus femoris (RFe), biceps femoris (BF), tibialis anterior (TA), medial and lateral gastrocnemius (MG and LG)] was evaluated, using bipolar electrodes. EMG data from the RF and FF running techniques was then processed and compared with statistical parametric mapping (SPM), dividing the analysis of the running cycle into stance and swing phases. The MG and LG muscles showed higher activation during FF running at the beginning of the stance phase and at the end of the swing phase. During the end of the swing phase, the TA muscle's EMG amplitude was higher, when the RF running technique was used. A higher level of co-activation between the gastrocnemius and TA muscles was observed in both stance and swing phases using RF. The myoelectric behaviour of the RFe and BF muscles was similar during both running techniques. The current findings highlight that the two running techniques predominately reflect adjustments of the shank and not the thigh muscles, in both phases of the running cycle.HighlightsStatistical parametric mapping (SPM) can reveal temporal differences in muscle activity between running techniques.The medial and lateral gastrocnemius muscles were more active at specific time-instants of the initial stance and late swing phases during forefoot (FF) running compared to rearfoot (RF) running.Higher activation was observed for the tibialis anterior muscle at the end of the swing phase during RF runningContrary to the muscle activity differences observed in the leg muscles, the muscle activity of the thigh muscles was similar during RF and FF running.

Electromyographic and kinematic parameters of the shoulder in wheelchair rugby players: case reports.

Wheelchair rugby was created as part of the rehabilitation for patients with spinal cord injury. The biomechanical analysis of wheelchair propulsion (WP) in these athletes seems to be a key element to understand the reasons behind musculoskeletal injuries. This case reports study aimed to describe the electromyographic activity and kinematic parameters of the shoulder during the propulsion phases on the wheelchair in two Paralympic rugby players (A1 and A2) with spinal cord injury. Myoelectric activity (three portions of the deltoid, biceps and triceps brachii) and kinematics of the shoulder were assessed during the push (PP) and recovery (RP) phases. These variables were calculated considering ten propulsion cycles by each athlete. The results showed a different muscle activation between players, A1 described a high average amplitude of the anterior deltoid (PP = 58.44 ± 16.35%MVC; RP = 43.16 ± 13.48%MVC) in both propulsion phases, while A2 generated high average activity of triceps brachii (29.28 ± 10.63%MVC) and middle deltoid (46.53 ± 14.48%MVC), during PP and RP, respectively. At the same time, the player with a C7-T1 spinal cord injury (A2) showed a higher range of motion in the three plans, considering both propulsion phases.

Location In Vivo of the Innervation Zone in the Human Medial Gastrocnemius Using Imposed Contractions: A Comparison of the Usefulness of the M-Wave and H-Reflex.

The anatomical territory where the neuromuscular junctions are grouped corresponds to the innervation zone (IZ). This can be located in-vivo using high-density electromyography and voluntary muscle contractions. However, in patients with motor impairment, the use of contractions imposed by electrical stimulation (ES) could be an alternative. The present study has two aims: Firstly, to describe the location of the IZ in-vivo of the medial gastrocnemius (MG) using imposed contractions by ES. Secondly, to compare the usefulness of M-waves and H-reflexes to localize the IZs. Twenty-four volunteers participated (age: 21.2 ± 1.5 years). ES was elicited in the tibial nerve to obtain M-waves and H-reflexes in the MG. The evaluators used these responses to localize the IZs relative to anatomical landmarks. M-wave and H-reflex IZ frequency identification were compared. The IZs of the MG were mostly located in the cephalocaudal direction, at 39.7% of the leg length and 34% of the knee's condylar width. The IZs were most frequently identified in the M-wave (83.33%, 22/24) compared to the H-reflex (8.33%, 2/24) (p > 0.001). Imposed contractions revealed that the IZ of the MG is located at 39.7% of the leg length. To locate the IZs of the MG muscle, the M-wave is more useful than the H-reflex.

Coactivación Muscular. Una Propuesta para Calcular su Índice utilizando Python / Muscle coactivation. A proposal to calculate its index utilising Python

Introducción. Fenómenos neurofisiológicos, como la coactivación muscular, se han utilizado para identificar tareas motoras que requieren una mayor estabilidad articular en personas sanas o con trastornos del movimiento. Sin embargo, existen varias formas de calcular el índice de coactivación (IC) muscular. Objetivo. El objetivo de este artículo fue crear una propuesta de procesamiento para calcular el IC muscular mediante el diseño de dos funciones utilizando el lenguaje Python. La primera función calcula el IC utilizando la fórmula planteada por Falconer y Winter, definida como "coactivation index". Se requiere introducir dos señales de músculos antagonistas con una misma longitud de datos y frecuencia de muestreo. Estas señales son previamente normalizadas a la contracción voluntaria máxima utilizando valores promedios rectificados. La segunda función definida como "plot_coactivacion" despliega una figura con los cambios de amplitud de ambos músculos y su área común. Estas funciones fueron creadas con un lenguaje de libre acceso (Python), destacando su clara sintaxis y la amplia gama de librerías en el procesamiento de señales biomédicas.

Introduction. Neurophysiological phenomena, such as muscle coactivation, have been used to identify motor tasks requiring greater joint stability in healthy people or with movement disorders. Nonetheless, there are many ways to calculate the coactivation index (CI). This article aimed to create a processing pipeline to calculate the muscular CI by designing two functions with the Python language. The first function calculates the CI utilising the formula proposed by Falconer and Winter, defined as "coactivation_index". It is required to introduce two signals of antagonist muscles with the same data long and sample frequency. These signals were previously normalised to the maximum voluntary contraction using the averaged rectified values. The second function was defined as "plot_coactivacion", which unfolds a figure that describes the amplitude changes for both muscles and their common area. These functions were designed with a freely accessible language (Python), highlighting its clear syntax and the number of libraries associated with biomedical signal processing.

Biomechanical Cadaveric Evaluation of the Role of Medial Column Instability in Hallux Valgus Deformity.

BACKGROUND: Medial column instability is a frequent finding in patients with flatfeet and hallux valgus, within others. The etiology of hallux valgus is multifactorial, and medial ray axial rotation has been mentioned as having an individual role. Our objective was to design a novel cadaveric foot model where we could re-create through progressive medial column ligament damage some components of a hallux valgus deformity. METHODS: Ten fresh-frozen lower leg specimens were used, and fluorescent markers were attached in a multisegment foot model. Constant axial load and cyclic tibial rotation (to simulate foot pronation) were applied, including pull on the flexor hallucis longus tendon (FHL). We first damaged the intercuneiform (C1-C2) ligaments, second the naviculocuneiform (NC) ligaments, and third the first tarsometatarsal ligaments, leaving the plantar ligaments unharmed. Bony axial and coronal alignment was measured after each ligament damage. Statistical analysis was performed. RESULTS: A significant increase in pronation of multiple segments was observed after sectioning the NC ligaments. Damaging the tarsometatarsal ligament generated small supination and varus changes mainly in the medial ray. No significant change was observed in axial or frontal plane alignment after damaging the C1-C2 ligaments. The FHL pull exerted a small valgus change in segments of the first ray. DISCUSSION: In this biomechanical cadaveric model, the naviculocuneiform joint was the most important one responsible for pronation of the medial column. Bone pronation occurs along the whole medial column, not isolated to a certain joint. Flexor hallucis longus pull appears to play some role in frontal plane alignment, but not in bone rotation. This model will be of great help to further study medial column instability as one of the factors influencing medial column pronation and its relevance in pathologies like hallux valgus. CLINICAL RELEVANCE: This cadaveric model suggests a possible influence of medial column instability in first metatarsal pronation. With a thorough understanding of a condition's origin, better treatment strategies can be developed.

La rotación axial de la clavícula que plantea la maniobra de Mulligan ¿produce una reducción de la presión en el espacio subacromial? Un estudio ex vivo exploratorio / Does the axial rotation of the clavicle posed by the Mulligan maneuver produce a pressure reduction in the subacromial space? An exploratory ex vivo study

RESUMEN: El pinzamiento de hombro es la principal causa del hombro doloroso. Dentro de las estrategias terapéuticas propuestas se encuentra la terapia manual. En este contexto, la maniobra de Mulligan, implica una rotación axial en sentido anterior de la clavícula, emulando la acción del músculo subclavio, lo cual hipotéticamente aumentaría el espacio subacromial. Sin embargo, no existen antecedentes que proporcionen sustento experimental a dicha hipótesis. El objetivo del presente estudio fue explorar si la rotación axial de la clavícula, producida por la maniobra de Mulligan, tiene efecto sobre la presión registrada en el espacio subacromial, con el propósito disponer de antecedentes metodológicos que puedan contribuir al diseño de futuros estudios que aborde la problemática expuesta y consideren un mayor tamaño de muestra. Mediante un estudio exploratorio ex-vivo, se evaluaron dos preparados anatómicos que comprendían la escapula, la clavícula y los dos tercios proximales del humero, ambos con indemnidad de la articulación glenohumeral y acromioclavicular. En estos se registraron la presión en el espacio subacromial y la rotación axial de la clavícula, todo durante la realización de una maniobra de rotación axial clavicular en sentido anterior. Se analizaron las diferencias de presión entre una condición basal y durante la maniobra, como también la máxima rotación axial de clavícula. Dichas variables fueron registradas mediante un sensor de presión y un sistema de análisis de movimiento. La presión en el espacio subacromial durante la maniobra, disminuyó en todas las repeticiones en un rango comprendido entre el 21-51 % de la presión basal. La máxima rotación axial registrada estuvo entre los 3.9-10°. Los resultados de este estudio exploratorio, dan pie para hipotetizar que la maniobra de rotación axial anterior de la clavícula produce una disminución de la presión subacromial, en el área comprendida inmediatamente bajo el acromion.

SUMMARY: Shoulder impingement is the main cause of shoulder pain. Manual therapy is one of the proposed therapeutic strategies. In this context, the Mulligan maneuver implies anterior axial rotation of the clavicle, emulating the action of the subclavius muscle, which hypothetically would increase the subacromial space. However, there are no antecedents that provide experimental support for this hypothesis. The objective of the present study was to explore whether the axial rotation of the clavicle, produced by the Mulligan maneuver, has an effect on the pressure registered in the subacromial space, with the purpose of having methodological antecedents that can contribute to the design of future studies that address the problem exposed and consider a larger sample size. Through an ex-vivo exploratory study, two anatomical preparations comprising the scapula, clavicle, and proximal two-thirds of the humerus, both with glenohumeral and acromioclavicular joint sparing, were evaluated. In these, the pressure in the subacromial space and the axial rotation of the clavicle were recorded, all during the performance of an anterior clavicular axial rotation maneuver. Pressure differences between a basal condition and during the maneuver were analyzed, as well as the maximum axial rotation of the clavicle. These variables were recorded using a pressure sensor and a movement analysis system. The pressure in the subacromial space during the maneuver decreased in all repetitions in a range between 21-51% of the basal pressure. The maximum axial rotation recorded was between 3.9-10°. The results of this exploratory study give rise to the hypothesis that the anterior axial rotation maneuver of the clavicle produces a decrease in subacromial pressure, in the area immediately below the acromion.

Changes in muscle coactivation during running: a comparison between two techniques, forefoot vs rearfoot / Cambios en la coactivación muscular durante la carrera: una comparación entre dos técnicas (antepié vs retropié)

Introduction: Surface electromyography has been a technique used to describe muscle activity during running. However, there is little literature that analyses the behaviour of muscle coactivation in runners, describing the effect between two techniques associated with the initial contact, such as the use of rearfoot (RF) and forefoot (FF). Material and method: The purpose of this study was to compare muscle coactivation levels developed in the lower limb during two running techniques, FF vs RF. Fourteen amateur runners were evaluated (eight men, six women; age= 23.21 ± 3.58 years, mass= 63.89 ± 8.13 kg, height= 1.68 ± 0.08m). Surface electromyography was used to measure muscle activity during both running techniques evaluated on a treadmill, considering the muscle pairs: Rectus femoris- Biceps femoris (RFe-BF), Lateral Gastrocnemius–Tibialis Anterior (LG-TA), and Medial Gastrocnemius - Tibialis Anterior (MG-TA). These were calculated in three windows considering ten running cycles (0-5%, 80-100%, and 0-100%). To compare FF vs RF t-student test for paired data was used. Results: It was observed significant differences in the MG-TA pair (FF= 18.42 ± 11.84% vs RF = 39.05 ± 13.28%, p = 0.0018 during 0-5%, and RFe-BF pair (FF = 42.38 ± 18.11% vs RF = 28.37 ± 17.2%, p = 0.0331) during 80-100% of the race. Conclusion: Our findings show that the behaviour of muscle coactivation is different between FF vs RF techniques if we analyze little windows in the running cycle. This could be associated with an increase in the joint stability between these short intervals, represented in the initial and final regions of the running cycle.(AU)

Introducción: La electromiografía de superficie ha sido una técnica usada para describir la actividad muscular durante la carrera. Sin embargo, hay poca literatura que analice el comportamiento de la coactivación muscular en corredores, descri­biendo el efecto entre dos técnicas asociadas al contacto inial, tal como el uso de retropié y antepié. Material y método: El propósito de este estudio fue comparar los niveles de coactivación desarrollados en la extremidad inferior, utilizando dos técnicas de carrera, antepié (FF) vs retropié (RF). Catorce corredores amateurs fueron evaluados (8 hombres, 6 mujeres; edad = 23,21 ± 3,58 años, masa = 63,89± 8,13 kg, estatura = 1,68 ± 0,08 m). Se utilizó electromiografía de superficie para medir la actividad muscular al momento de ejecutar ambas técnicas de carrera sobre una trotadora, conside­rando los siguientes pares musculares: Recto Femoral- Bíceps Femoral (RFe-BF), Gastrocnemio Lateral – Tibial Anterior (LG-TA) y Gastrocnemio Medial - Tibial Anterior (MG-TA). Estos se calcularon en tres ventanas considerando diez ciclos de ejecución (0-5%, 80-100% y 0-100%). Para comparar FF vs RF se utilizó la prueba t-student para datos pareados. Resultados: Se observan diferencias significativas en el par MG-TA (FF = 18,42 ± 11,84% vs RF = 39,05 ± 13,28%, p = 0,0018) durante el 0-5%, y el par RFe-BF (FF = 42,38 ± 18,11% vs RF = 28,37 ± 17,2%, p = 0,0331) durante el 80-100% de la carrera. Conclusión: Nuestros hallazgos muestran que el comportamiento de la coactivación muscular es diferente entre las técnicas de FF y RF si analizamos pequeñas ventanas en el ciclo de carrera. Esto podría estar asociado con un aumento de la estabilidad articular entre estos cortos intervalos, representados en la región inicial y final del ciclo de carrera.(AU)

Ejercicio excéntrico y velocidad de conducción de la fibra muscular: una revisión bibliográfica / Eccentric exercise and muscle fiber conduction velocity: a literature review

Introducción: Según la literatura, el ejercicio excéntrico ha sido considerado como un precursor de cambios neuromus-culares generado por el daño post-ejercicio, causando principalmente una alteración en la permeabilidad de la membranacelular muscular. Una de las variables fisiológicas que ha permitido cuantificar esta alteración, es la velocidad de conducciónde la fibra muscular (VCFM). Algunas investigaciones han mostrado una disminución de esta variable posterior a protocolosde ejercicio excéntrico; sin embargo, existen pocos estudios que confirmen este hallazgo. Este estudio tuvo como objetivodescribir la evidencia científica reciente que reporte cambios en la VCFM después de protocolos de ejercicio excéntrico.Material y método: De 265 artículos, se seleccionaron 6 artículos de las plataformas EBSCO y MEDLINE con un filtro temporalde 10 años (entre 2010 y abril de 2020), usando criterios de inclusión/exclusión predeterminados. En primer lugar, se describióel efecto del ejercicio excéntrico sobre la VCFM y los protocolos de ejercicios. Secundariamente, se reportaron las técnicasutilizadas para registrar la señal electromiográfica, y algunos criterios para determinar la VCFM.Resultados: Es posible observar modificaciones de la VCFM luego del ejercicio excéntrico en casi todos los artículos selecciona-dos. Al mismo tiempo, se observa una disminución de esta variable en cuatro estudios, asociado a los músculos bíceps braquialy dos porciones del cuádriceps. Sin embargo, un artículo describe un incremento de la VCFM en el vasto lateral del cuádriceps.Conclusión: Los artículos sugieren que las contracciones excéntricas podrían modificar el comportamiento de la VCFM dealgunos músculos. Sin embargo, aún falta evidencia para describir la real causa de estos cambios.(AU)

Introduction: According to the literature, eccentric exercise has been considered a precursor of neuromuscular changes ge-nerated by post-exercise damage, mainly causing an alteration in the muscle cell membrane. Muscle fiber conduction velocity(MFCV) has been one of the physiological variables that have allowed to quantify this alteration. Some investigations haveshown a decrease in the MFCV after eccentric exercise protocols; however, few studies have confirmed these findings. Thisreview aimed to describe the recent scientific evidence that reports changes in the MFCV after eccentric exercise protocols.Material and method: From 265 articles, 6 articles were selected from EBSCO and MEDLINE platforms with a temporal filter of10 years (between 2010 and April 2020), using inclusion/exclusion criteria predetermined. Firstly, the information from eccentricexercise effect on MFCV, and exercise protocols were described. Secondly, the techniques used to record electromyographicsignals and some criteria to determine the MFCV were reported.Results: Modifications of MFCV can be observed after eccentric exercise in almost all selected articles. At the same time, adecrease of this variable was observed in four studies, associated with the biceps brachii and two portions of the quadricepsmuscles. However, one article describes an increase of the MFCV in the vastus lateralis quadriceps.Conclusion: The articles suggest that eccentric contractions could modify the MFCV behavior of some muscles. However,evidence is still lacking to describe the real cause of these changes.(AU)

Contribution of the peroneus longus neuromuscular compartments to eversion and plantarflexion of the ankle.

Compartmentalization of animal and human skeletal muscle by multiple motor nerve branches known as the neuromuscular compartment (NMC) has been observed primarily in muscles that participate in a plane of motion. In this context, the peroneus longus muscle contributes to eversion and plantarflexion of the ankle and the presence of NMCs has been reported. However, no research has reported the selective activation of the compartments of the peroneus longus during the performance of different ankle movements. The purpose of this research was to determine the contribution of peroneus longus NMCs, through multi-channel surface electromyography (sEMG), to eversion and plantarflexion movements. Multi-channel sEMG was recorded from the peroneus longus muscle by using an electrode grid during eversion and plantarflexion of the ankle at 10%, 30%, 50%, and 70% of maximal voluntary isometric contraction (MVIC). The root mean square and displacement of the center of mass position in the X (COMx) and Y (COMy) components were calculated. The primary finding was that eversion showed significantly higher sEMG amplitude than plantarflexion in the posterior compartment in low, moderate, and high percentages of MVIC. However, no significant difference in sEMG amplitude was observed in the anterior compartment between eversion and plantarflexion. In addition, a posterior displacement of the COMx in eversion compared to plantarflexion in all MVIC percentages, with greater topographic distancing of the COMx at higher levels of activation. In conclusion, the peroneus longus muscle presented NMCs; the anterior compartment contributed to both eversion and plantarflexion movements, whereas the posterior compartment mainly contributed to the eversion movement of the ankle in low, moderate, and high percentages of MVIC.

Comparison of the electromyographic activity of different zones of the abductor digiti minimi manus muscle in search of a functional compartmentalisation / Comparación de la actividad electromiográfica de diferentes zonas del músculo abductor digiti minimi manus en busca de una compartimentación funcional

SUMMARY: There is evidence demonstrating the presence of functional compartmentalisation (FC) in some skeletal muscles. This means that the motor units (MU), grouped in certain areas of the muscle, show different levels of activation in comparison to those located in other zones. This has only been described in large muscles whose morphology proves the existence of a FC. However, there is no background information about small muscles, such as the Abductor digiti minimi manus (ADM). The objective of this study was to compare the activation of the MU in different zones of the ADM to support the hypothesis of the existence of a FC in the ADM. By using a cross- sectional, analytical, observational study, the activity of the MUs in the ADM was assessed in 12 volunteers (age 21 ± 1.6 years old; weight 75.3 ± 8 kg; height 176.2 ± 7.3 cm; average ± standard deviation). The activity of MUs was evaluated using high-density surface electromyography (HD-sEMG) with an array of 64 electrodes arranged two-dimensionally. This allowed us to record the activity of the MUs in three zones of the ADM (Z1: dorsal zone; Z2: dorsal-palmar zone and Z3: palmar zone). Electromyographic recordings were obtained during voluntary isometric contractions of the ADM at 20, 40, 60 and 80 % of the maximum voluntary contraction (MVC). The comparison of the activation levels of MUs between the three zones was carried out using a mixed model analysis of covariance. The results showed a significant difference between the dorsal and palmar zones at 40 % of the MVC (p= 0.03), and between the dorsal and dorsal- palmar zone at 80 % of the MVC (p= 0.03). The results obtained in the evaluated sample support the hypothesis of the existence of FC in the ADM. However, further research is needed to determine with greater certainty the presence of this compartmentalisation in the ADM.

RESUMEN: Existe evidencia que demuestra la presencia de una compartimentalización funcional (CF) en algunos músculos esqueléticos. Aquello se traduce en que las unidades motoras (UM) agrupadas en ciertas zonas del músculo, presentan diferentes niveles de activación a las ubicadas en otras regiones. Esto solo ha sido descrito en músculos grandes, cuya morfología justifica la existencia de una CF. Sin embargo, no existen antecedentes de aquello en músculos pequeños, tales como el abductor digiti minimi manus (ADM). El objetivo de este estudio fue comparar la activación de las UM en distintas zonas del ADM, con la finalidad sostener la hipótesis de la existencia de una CF en el ADM. Mediante un estudio observacional analítico transversal se evaluó la actividad de las UM del ADM en 12 voluntarios (edad 21±1,6 años; peso 75,3±8 kg; altura 176,2 ± 7,3 cm; promedio ± desviación estándar). La actividad de las UM, se evaluó mediante electromiografía de superficie alta densidad usando una matriz de 64 electrodos dispuestos bidimensionalmente. Esta permitió registrar la actividad de las UM en tres zonas del ADM (Z1: zona dorsal; Z2: zona dorso-palmar y Z3: zona palmar). Los registros electromiográficos fueron obtenidos durante contracciones isométricas voluntarias del ADM al 20, 40, 60 y 80 % de la contracción voluntaria máxima (CVM). La comparación de los niveles de activación de las UM entre las tres zonas fue realizada mediante un análisis de modelos mixtos de covarianza. Los resultados indicaron que existió diferencia significativa entre la zona dorsal y palmar al 40 % de la CVM (p=0,03), y entre la zona dorsal y dorso-palmar al 80 % de la CVM (p=0,03). Los resultados obtenidos en la muestra evaluada sostienen la hipótesis de la existencia de una CF en el ADM. Sin embargo, son necesarias más investigaciones para establecer con mayor certeza la presencia de esta compartimentalización en el ADM.

Neuromuscular compartmentalization of the vastus medialis muscle: comparison of the activity of the vastus medialis obliquus and the vastus medialis longus by high density electromyography / Compartimentación neuromuscular del músculo vasto medial: comparación de la actividad del vasto medial oblicuo y del vasto medial largo mediante electromiografía de alta densidad

SUMMARY: Anatomical studies describe the vastus medialis (VM) as being subdivided into two morphologically distinct components, the vastus medialis obliquus (VMO) and the vastus medialis longus (VML). However, there are discrepancies regarding the functional differentiation of these components. The aim of this study was to compare the levels of activation of the VMO and the VML by high density surface electromyography. Twelve healthy young women (age: 21.4 ± 2.0 years; weight: 58.1 ± 7.5 kg; height: 1.6 ± 0.1 m), performed an open kinetic chain knee exercise during which the EMG activity of the VMO and the VML was recorded with two- dimensional matrices of 32 surface electrodes. The exercises were performed with three levels of resistance (5, 10 and 15 % of the body weight (BW)), considering three phases: concentric, isometric and excentric. In the isometric phase the VMO had greater activation than the VML with the three levels of resistance (p<0.05). In the excentric phase, the VMO also showed greater activation than the VML with the 10 and 15 % BW resistance levels, while in the concentric phase, the VMO showed greater activity than the VML with only the 15 % BW resistance. The results indicated significant differences in the activation level of the two components of the VM. This bears importance in the development of exercises intended to achieve a greater or more selective activation of the VMO. In the sample subjected to evaluation, the EMG recordings describe a greater activation of the VMO in comparison to the VML, which is more important in the isometric and excentric phases of the flexion/extension of the knee in an open kinetic chain. These findings suggest a functional compartmentalization of the VM.

RESUMEN: Los estudios anatómicos describen que el músculo vasto medial (VM) se subdivide en dos componentes morfológicamente distintos, el vasto medial obliquus (VMO) y el vasto medial largo (VML). Sin embargo, existen discrepancias con respecto a la diferenciación funcional de estos componentes. El objetivo de este estudio fue comparar los niveles de activación del VMO y el VML mediante electromiografía de superficie de alta densidad. Doce mujeres jóvenes sanas (edad: 21,4 ± 2,0 años; peso: 58,1 ± 7,5 kg; altura: 1,6 ± 0,1 m), realizaron un ejercicio de rodilla de cadena cinética abierta durante el cual se registró la actividad EMG de la VMO y la VML con dos matrices dimensionales de 32 electrodos de superficie. Los ejercicios se realizaron con tres niveles de resistencia (5, 10 y 15% del peso corporal (PC)), considerando tres fases: concéntrica, isométrica y excéntrica. En la fase isométrica el VMO tuvo mayor activación que el VML con los tres niveles de resistencia (p <0,05). En la fase excéntrica, el VMO también mostró mayor activación que el VML con los niveles de resistencia de 10 y 15% BW, mientras que en la fase concéntrica, el VMO mostró mayor actividad que el VML con solo el 15 % de resistencia al BW. Los resultados indicaron diferencias significativas en el nivel de activación de los dos componentes de la VM. Esto tiene importancia en el desarrollo de ejercicios destinados a lograr una activación mayor o más selectiva del VMO. En la muestra sometida a evaluación, los registros EMG describen una mayor activación del VMO en comparación con el VML, que es más importante en las fases isométrica y excéntrica de la flexión / extensión de la rodilla en cadena cinética abierta. Estos hallazgos sugieren una compartimentación funcional de la VM.

An Isolated Transosseous Flexible Suture Frame in the Treatment of Patellar Tendon Rupture Provides Adequate Mechanical Resistance.

INTRODUCTION: Acute patellar tendon ruptures are frequently observed in patients with metabolic comorbidities, and the benchmark treatment is surgical repair. It is desirable not to harm an already fragile biologic environment with sutures and hardware. We aimed to compare the mechanical requirements of an isolated, flexible, high-strength nonabsorbable transosseous suture frame with that of the Krackow suture technique. METHODS: A total of 12 cadaveric pieces were randomized into two groups: the isolated flexible frame group (n = 6) and the standard Krackow fixation group (n = 6). A traumatic rupture of the patellar tendon was performed, and a transosseous displacement sensor was installed on a validated biomechanical system. Gap formation was measured during 50 cycles of flexion and extension with traction on the quadriceps (250 N). Subsequently, specimens underwent progressive loading in a fixed flexion position until failure occurred. The data were analyzed using nonparametric statistical tools with a significance level of 5%. RESULTS: The isolated frame group had a smaller gap formation (1.7 mm) than the Krackow group (3.4 mm; P = 0.01). No significant difference existed in the median failure end points of the two groups (676 and 530 N, respectively; P = 0.11). DISCUSSION: Patellar tendon repair using an isolated, transosseous, flexible, suture frame outperformed using the traditional Krakow repair technique in gap formation. Further studies are needed to determine if this will result in better functional outcomes or fewer clinical failures. LEVEL OF EVIDENCE: Level IV, experimental case series.

Regional changes in muscle activity do not underlie the repeated bout effect in the human gastrocnemius muscle.

The repeated bout effect (RBE) confers protection following exercise-induced muscle damage. Typical signs of this protective effect are significantly less muscle soreness and faster recovery of strength after the second bout. The aim of this study was to compare regional changes in medial gastrocnemius (MG) muscle activity and mechanical hyperalgesia after repeated bouts of eccentric exercise. Twelve healthy male participants performed two bouts of eccentric heel drop exercise (separated by 7 days) while wearing a vest equivalent to 20% of their body weight. High-density MG electromyographic amplitude maps and topographical pressure pain sensitivity maps were created before, two hours (2H), and two days (2D) after both exercise bouts. Statistical parametric mapping was used to identify RBE effects on muscle activity and mechanical hyperalgesia, using pixel-level statistics when comparing maps. The results revealed a RBE, as a lower strength loss (17% less; P < .01) and less soreness (50% less; P < .01) were found after the second bout. However, different muscle regions were activated 2H and 2D after the initial bout but not following the repeated bout. Further, no overall changes in EMG distribution or mechanical hyperalgesia were found between bouts. These results indicate that muscle activation is unevenly distributed during the initial bout, possibly to maintain muscle function during localized mechanical fatigue. However, this does not reflect a strategy to confer protection during the repeated bout by activating undamaged/non-fatigued muscle areas.

Coordination of the rotational movement of the pelvis and the hip in men without low back pain, with control impairment of the lumbopelvic region in the sagittal plane.

Purpose To assess the presence of control impairment (CI) of the lumbopelvic region in the axial plane in men without low back pain (LBP) with CI in the sagittal plane. Methods : Twenty-four males, between 18 and 23 of age, BMI = normal, who did not report episodes of LBP in the 12 months prior to the study, were studied. Assessment of the sagittal control of the lumbopelvic region was performed during stand to sit. Nine participants demonstrated CI in sagittal plane and 15 did not. An active hip lateral rotation (HLR) test was performed, in which lumbopelvic rotation during HLR was assessed using a three-dimensional motion analysis system. Results : Patients with CI in sagittal plane had a greater percentage of their total lumbopelvic pelvic rotation at 60% of HLR range compared to those without CI (p < 0.05; d = 0.93). No significant differences in the total lumbopelvic and HLR range of motion were found between the groups. Conclusion : Men without LBP who experience CI of the lumbopelvic region in the sagittal plane also show CI in the axial plane. The control deficiencies were not related to the total range of lumbopelvic or HLR range of motion.

Proximal and Distal Failure Site Analysis in Percutaneous Achilles Tendon Rupture Repair.

BACKGROUND: Different techniques have been described for percutaneous Achilles tendon rupture repair, but no biomechanical evaluation has been performed separately for proximal and distal suturing techniques. The purpose of this study was to biomechanically analyze proximal versus distal percutaneous Achilles suture configurations during cyclic loading and load to failure. METHODS: A simulated, midsubstance rupture was created 6 cm proximal to the calcaneal insertion in fresh-frozen cadaveric Achilles tendons. Fifteen proximal specimens were divided into 3 groups: (A1) triple locking technique, (A2) Bunnell-type technique, and (A3) double Bunnell-type technique. Twelve distal specimens were divided into 2 groups: (B1) triple nonlocking technique and (B2) oblique technique. Repairs were subjected to cyclic testing and load to failure. Load to failure, cause of failure, and tendon elongation were evaluated. RESULTS: None of the proximal specimens and 7/12 of the distal ones failed in cyclic testing. The proximal fixation groups demonstrated significantly more strength than the distal groups (P = .001), achieving up to 710 N of failure load in Group A3. Groups B1and B2 failed on average at 380 N with no difference between them (P > .05). The majority of all repairs failed in the suture-tendon interface. Distal groups had more elongation during cyclic testing (13.7 mm) than proximal groups (9.4 mm) (P = .02). CONCLUSION: The distal fixation site in this Achilles tendon repair was significantly weaker than the proximal fixation site. A proximal modified suture configuration increased resistance to cyclic loading and load to failure significantly. CLINICAL RELEVANCE: A modification can be suggested to improve strength of the Achilles repair.

Use of accelerometers for automatic regional chest movement recognition during tidal breathing in healthy subjects.

Recognition of breathing patterns helps clinicians to understand acute and chronic adaptations during exercise and pathological conditions. Wearable technologies combined with a proper data analysis provide a low cost option to monitor chest and abdominal wall movements. Here we set out to determine the feasibility of using accelerometry and machine learning to detect chest-abdominal wall movement patterns during tidal breathing. Furthermore, we determined the accelerometer positions included in the clusters, considering principal component domains. Eleven healthy participants (age: 21 ±â€¯0.2 y, BMI: 23.4 ±â€¯0.7 kg/m2, FEV1: 4.1 ±â€¯0.3 L, VO2: 4.6 ±â€¯0.2 mL/min kg) were included in this cross-sectional study. Spirometry and ergospirometry assessments were performed with participants seated with 13 accelerometers placed over the thorax. Data collection lasted 10  min. Following signal pre-processing, principal components and clustering analyses were performed. The Euclidean distances in respect to centroids were compared between the clusters (p < 0.05), identifying two clusters (p < 0.001). The first cluster included sensors located at the right and left second rib midline, body of sternum, left fourth rib midline, right and left second thoracic vertebra midline, and fifth thoracic vertebra. The second cluster included sensors at the fourth right rib midline, right and left seventh ribs, abdomen at linea alba, and right and left tenth thoracic vertebra midline. Costal-superior and costal-abdominal patterns were also recognized. We conclude that accelerometers placed on the chest and abdominal wall permit the identification of two clusters of movements regarding respiration biomechanics.