Muscle Activation Patterns Research Articles

Analysis of stress response distribution in patients with lateral ankle ligament injuries: a study of neural control strategies utilizing predictive computing models.

Ankle sprains are prevalent in sports, often causing complex injuries to the lateral ligaments. Among these, anterior talofibular ligament (ATFL) injuries constitute 85%, and calcaneofibular ligament (CFL) injuries comprise 35%. Despite conservative treatment, some ankle sprain patients develop chronic lateral ankle instability (CLAI). Thus, this study aimed to investigate stress response and neural control alterations during landing in lateral ankle ligament injury patients. This study recruited twenty individuals from a Healthy group and twenty CLAI patients performed a landing task using relevant instruments to collect biomechanical data. The study constructed a finite element (FE) foot model to examine stress responses in the presence of laxity of the lateral ankle ligaments. The lateral ankle ligament was modeled as a hyperelastic composite structure with a refined representation of collagen bundles and ligament laxity was simulated by adjusting material parameters. Finally, the validity of the finite element model is verified by a high-speed dual fluoroscopic imaging system (DFIS). CLAI patients exhibited earlier Vastus medialis (p < 0.001) and tibialis anterior (p < 0.001) muscle activation during landing. The FE analysis revealed that with laxity in the ATFL, the peak von Mises stress in the fifth metatarsal was 20.74MPa, while with laxity in the CFL, it was 17.52MPa. However, when both ligaments were relaxed simultaneously, the peak von Mises stress surged to 21.93MPa. When the ATFL exhibits laxity, the CFL is subjected to a higher stress of 3.84MPa. Conversely, when the CFL displays laxity, the ATFL experiences a peak von Mises stress of 2.34MPa. This study found that changes in the laxity of the ATFL and the CFL are linked to shifts in metatarsal stress levels, potentially affecting ankle joint stability. These alterations may contribute to the progression towards CLAI in individuals with posterolateral ankle ligament injuries. Additionally, significant muscle activation pattern changes were observed in CLAI patients, suggesting altered neural control strategies post-ankle ligament injury.

Distinct Motion Control Strategy during Unanticipated Landing: Transitioning from Copers to Chronic Ankle Instability

Background: Patients with chronic ankle instability (CAI) demonstrated altered movement patterns during unanticipated landing compared to coper patients. Understanding the effects of kinematics, dynamics and energetics on individual movement patterns during landing could enhance motor control strategies for patients with ankle sprains while avoiding the transition of coper patients to CAI patients. Therefore, the purpose of this study was to investigate the differences in movement patterns of coper patients compared to CAI patients during the unanticipated landings; Methods: Fifteen individuals with CAI (age: 22.8±1.4 years; height: 180.1±4.2 cm; weight: 81.5±5.8 kg) and fifteen copers (age: 23.1±1.2 years; height: 179.8±4.4 cm, weight: 80.4±6.2 kg) participated in an unanticipated landing task, during which three-dimensional motion capture, ground reaction force (GRF), and muscle activation data were collected. A musculoskeletal model was used to estimate muscle force and joint power among these two groups. Joint power was calculated as the product of angular velocity in the sagittal plane and joint moment data, reflecting the energy transfer at the ankle, knee, and hip joints. Furthermore, energy dissipation and generation within these joints were determined by integrating specific regions of the joint power curve; Results: Individuals with CAI demonstrated a greater muscle force in the vastus lateralis compared copers during the unanticipated landing task, while copers exhibited higher peak muscle forces in the medial gastrocnemius (p=0.007), lateral gastrocnemius (p=0.002), soleus (p=0.004). The muscle activation patterns of CAI patients also differ from those of coper patients. Compared to copers, CAI patients exhibit earlier activation of the rectus femoris (p&lt;0.001) and lateral gastrocnemius muscles (p=0.042). Conversely, copers demonstrate earlier activation of the soleus (p=0.004) and medial gastrocnemius (p=0.003) muscles. In addition, joint power in CAI individuals during unanticipated landing shifted from the ankle to the knee and hip (p&lt;0.001); Conclusions: These findings suggest that individuals with CAI exhibit a change in motion control strategy during unanticipated landing tasks. The variations in peak forces and the ability of proximal muscles to generate force might enable them to offset the deficits noted in distal muscles. Energy redistribution issues observed in CAI patients may help to prevent the transition of coper patients towards developing CAI patients.

Combining Cyproheptadine Hydrochloride With Targeted Muscle Activation Training to Treat Upper Extremity Stroke: A Randomized, Placebo-Controlled Trial

ObjectiveTo examine a treatment for upper extremity impairment in stroke survivors that combines administration of cyproheptadine hydrochloride with repetitive practice focused on control of muscle activation patterns. DesignDouble-blind, randomized controlled trial. SettingsLaboratory within a free-standing rehabilitation hospital. ParticipantsA total of 94 stroke survivors with severe, chronic hand impairment were randomly assigned to 1 of 4 treatment groups. InterventionsParticipants received either a placebo or cyproheptadine hydrochloride in identical pill form. The daily dosage of cyproheptadine/placebo was gradually increased from 8 to 24 mg/d over 3 weeks and then maintained over the next 6 weeks while participants completed 18 therapy sessions. Therapy consisted of either (1) active practice of muscle activation patterns to play “serious” computer games or control a custom hand exoskeleton or (2) passive, cyclical finger stretching imposed by the exoskeleton. Main Outcome MeasuresHand control was evaluated with the primary outcome measure of time to complete the Graded Wolf Motor Function Test (GWMFT) and secondary outcome measures including finger strength and spasticity. ResultsAcross the 88 participants who completed the study, a repeated-measures analysis of variance revealed a significant effect of GroupxEvaluation interaction on GWMFT (F=1.996, P=.026). The 3 groups receiving cyproheptadine and/or actively practicing muscle activation pattern control exhibited significant reduction in mean time to complete the GWMFT tasks; roughly one-third of these participants experienced at least a 10% reduction in completion time. Gains were maintained at the 1-month follow-up evaluation. The group receiving placebo and passive stretching did not show improvement. No significant differences among groups were observed in terms of changes in strength or spasticity. ConclusionsDespite chronic, severe impairment, stroke survivors were able to complete the therapy focused on muscle activations and achieved statistically significant improvement in hand motor control. Cyproheptadine hydrochloride is a potential complementary treatment modality for stroke survivors with hand impairment.

Potential of a New, Flexible Electrode sEMG System in Detecting Electromyographic Activation in Low Back Muscles during Clinical Tests: A Pilot Study on Wearables for Pain Management.

While low back pain (LBP) is the leading cause of disability worldwide, its clinical objective assessment is currently limited. Part of this syndrome arises from the abnormal sensorimotor control of back muscles, involving increased muscle fatigability (i.e., assessed with the Biering-Sorensen test) and abnormal muscle activation patterns (i.e., the flexion-extension test). Surface electromyography (sEMG) provides objective measures of muscle fatigue development (median frequency drop, MDF) and activation patterns (RMS amplitude change). This study therefore assessed the sensitivity and validity of a novel and flexible sEMG system (NSS) based on PEVA electrodes and potentially embeddable in textiles, as a tool for objective clinical LBP assessment. Twelve participants wearing NSS and a commercial laboratory sEMG system (CSS) performed two clinical tests used in LBP assessment (Biering-Sorensen and flexion-extension). Erector spinae muscle activity was recorded at T12-L1 and L4-L5. NSS showed sensitivity to sEMG changes associated with fatigue development and muscle activations during flexion-extension movements (p < 0.05) that were similar to CSS (p > 0.05). Raw signals showed moderate cross-correlations (MDF: 0.60-0.68; RMS: 0.53-0.62). Adding conductive gel to the PEVA electrodes did not influence sEMG signal interpretation (p > 0.05). This novel sEMG system is promising for assessing electrophysiological indicators of LBP during clinical tests.

Data-Driven Identification of Stroke through Machine Learning Applied to Complexity Metrics in Multimodal Electromyography and Kinematics.

A stroke represents a significant medical condition characterized by the sudden interruption of blood flow to the brain, leading to cellular damage or death. The impact of stroke on individuals can vary from mild impairments to severe disability. Treatment for stroke often focuses on gait rehabilitation. Notably, assessing muscle activation and kinematics patterns using electromyography (EMG) and stereophotogrammetry, respectively, during walking can provide information regarding pathological gait conditions. The concurrent measurement of EMG and kinematics can help in understanding disfunction in the contribution of specific muscles to different phases of gait. To this aim, complexity metrics (e.g., sample entropy; approximate entropy; spectral entropy) applied to EMG and kinematics have been demonstrated to be effective in identifying abnormal conditions. Moreover, the conditional entropy between EMG and kinematics can identify the relationship between gait data and muscle activation patterns. This study aims to utilize several machine learning classifiers to distinguish individuals with stroke from healthy controls based on kinematics and EMG complexity measures. The cubic support vector machine applied to EMG metrics delivered the best classification results reaching 99.85% of accuracy. This method could assist clinicians in monitoring the recovery of motor impairments for stroke patients.

Relation Between Abnormal Spontaneous Brain Activity and Altered Neuromuscular Activation of Lumbar Paraspinal Muscles in Chronic Low Back Pain

ObjectiveTo investigate the neural mechanism underlying functional reorganization and motor coordination strategies in patients with chronic low back pain (cLBP). DesignA case-control study based on data collected during routine clinical practice. SettingThis study was conducted at a university hospital. ParticipantsFifteen patients with cLBP and 15 healthy controls. InterventionsNot applicable. Main Outcome MeasuresWhole brain blood oxygen level-dependent signals were measured using functional magnetic resonance imaging and amplitude of low-frequency fluctuation (ALFF) method to identify pain-induced changes in regional spontaneous brain activity. A novel approach based on the surface electromyogram (EMG) system and fine-wire electrodes was used to record EMG signals in the deep multifidus, superficial multifidus, and erector spinae. ResultsIn cLBP, compared with healthy groups, ALFF was higher in the medial prefrontal, primary somatosensory, primary motor, and inferior temporal cortices, whereas it was lower in the cerebellum and anterior cingulate and posterior cingulate cortices. Furthermore, the decrease in the average EMG activity of the 3 lumbar muscles in the cLBP group was positively correlated with the ALFF values of the primary somatosensory cortex, motor cortex, precuneus, and middle temporal cortex but significantly negatively correlated with the ALFF values of the medial prefrontal and inferior temporal cortices. Interestingly, the correlation between the functional activity in the cerebellum and the EMG activity varied in the lumbar muscles. ConclusionsThese findings suggest a functional association between changes in spontaneous brain activity and altered voluntary neuromuscular activation patterns of the lumbar paraspinal muscles, providing new insights into the mechanisms underlying pain chronicity as well as important implications for developing novel therapeutic targets of cLBP.

Hand muscle synergy in chopstick use: effect of object size and weight

This study explains the role of muscle coordination in chopstick manipulation and investigates the effects of object width and weight on intrinsic and extrinsic hand muscle activity when picking up objects with chopsticks. Surface electromyography was used to measure the activity of the intrinsic and extrinsic hand muscles when picking up objects of varying widths and weights using chopsticks. The results revealed coordinated muscle activity patterns in the intrinsic and extrinsic hand muscles and coordination between them during chopstick manipulation. Object widths varying between 1 and 3 cm did not significantly affect muscle activity; however, object weight influenced muscle activity during both chopstick closing and object grasping, with greater muscle activity in the 40 g condition than in the 10 g condition. Intrinsic hand muscles were found to be involved in object grasping, regardless of object weight. These findings suggest that object weight should be considered when practicing picking up objects with chopsticks in scenarios resembling daily dining, to prevent excessive muscle activity during rehabilitation.

Effects of overweight and obesity on lower limb walking characteristics from joint kinematics to muscle activations

BackgroundObesity is a crucial factor that increases the risk of initiating and advancing knee osteoarthritis. However, it remains unclear how obesity directly impacts the biomechanical experience of the lower limb joints, potentially triggering or exacerbating joint degeneration. This study investigated the interactive effects of BMI augmentation on lower limb kinematics, kinetics, and muscle activations during walking. MethodologyA group of 60 participants underwent a three-dimensional gait analysis. These individuals were categorized into three groups based on their body mass index (BMI): those with a BMI below 25 were classified as having a healthy weight, those with a BMI between 25 and 30 were categorized as overweight, and those with a BMI exceeding 30 were considered obese. This study analyzed the gait of 60 participants categorized by BMI. During walking trials, they recorded ground reaction forces electromyography of leg muscles like the gastrocnemii, hamstrings, and quadriceps. Lower limb joint angles and net moments were also calculated. Statistical mapping identified variations in kinematic, kinetic, and muscle activation patterns across the stance phase between BMI groups. ResultsThe results displayed distinct biomechanical patterns in obese individuals. Notably, there was a significant increase in flexion observed in the hip and knee joints (P < 0.001) during the initial stance phase and an increase in hip and knee adduction angles and moments throughout the entire stance phase (P < 0.001). Additionally, muscle activations underwent significant changes (P < 0.01), with a positive correlation noted with the BMI factor. This correlation was most pronounced during the early stance phase for the quadriceps and hamstring muscles and the late stance phase for the gastrocnemius. ConclusionThese findings represent a comprehensive picture that contributes to understanding how excess weight and obesity influence joint biomechanics, highlighting the associated risk of joint osteoarthritis.

Frequency of breaks, amount of muscular rest, and sustained muscle activity related to neck pain in a pooled dataset.

Neck pain remains a persistent challenge in modern society and is frequently encountered across a wide range of occupations, particularly those involving repetitive and monotonous tasks. It might be expected that patterns of trapezius muscle activity at work, characterized by few breaks and prolonged periods of sustained muscle activity, are linked to neck pain. However, previous cross-sectional studies have generally failed to establish a definitive association. While some longitudinal studies have suggested that extended periods of heightened muscle activity could be a risk factor for neck pain, these findings often relied on limited participant numbers or specific professional groups. This study aimed to investigate the relationship between trapezius muscle activity and neck pain by pooling data from seven Scandinavian research institutes encompassing a diverse range of occupational backgrounds. Electromyographic (EMG) data for the upper trapezius muscle, collected during working hours, were coupled with questionnaire responses pertaining to neck pain, individual characteristics, and potential confounding variables for a total of 731 subjects. Additionally, longitudinal data from 258 subjects were available. The various EMG datasets were consolidated into a standardized format, and efforts were made to harmonize inquiries about neck pain. Regression analyses, adjusting for sex and height, were conducted to explore the associations between muscle activity variables and neck pain. An exposure index was devised to quantify the cumulative neck load experienced during working hours and to differentiate between various occupational categories. The cross-sectional data displayed a distinct pattern characterized by positive associations for brief periods of sustained muscle activity (SUMA) and negative associations for prolonged SUMA-periods and neck pain. The longitudinal data exhibited a contrasting trend, although it was not as pronounced as the cross-sectional findings. When employing the exposure index, notable differences in cumulative muscle load emerged among occupational groups, and positive associations with longitudinal neck pain were identified. The results suggest that individuals with neck pain experience higher cumulative workloads and extended periods of muscle activity over the long term. In the short term, they appear to compensate by taking frequent short breaks, resulting in a lower cumulative workload. Regardless of their occupation, it is crucial to distribute work breaks throughout the workday to ensure that the cumulative load remains manageable.

Functional outcome Measure of Programme for Scalular Stabilisation Exercise in Rehabilitation of Frozen Shoulder : An Experimental Study

Background: The signs and symptoms of adhesive capsulitis, another name for frozen shoulder, include shoulder joint stiffness and pain. Conventional rehabilitation methods concentrate on enhancing shoulder range of motion and minimizing discomfort. It has been suggested that by enhancing scapular kinematics and muscle activation patterns, scapular stabilization workouts can improve functional outcomes. Objective: This study aims to evaluate the functional outcomes of a scapular stabilization exercise program in individuals receiving rehabilitation for frozen shoulder. Methods: Forty people who had been diagnosed with frozen shoulder participated in a randomized controlled trial. One of two groups the scapular stability exercise Group A or the standard rehabilitation Group B was assigned at random to each participant. The eight-week intervention consisted of five thirty minute sessions, held five times a week. For eight weeks, Group A supplemented their traditional range of motion exercises with scapular stabilization exercises. Sessions lasted thirty minutes, consisted of ten repetitions each, and were conducted five days a week. Group B carried on with just traditional workouts. Functional outcomes were assessed using the Numerical Pain Rating Scale NPRS Goniometry for range of motion tests, and the Disability Associated with the Arm, Shoulder, and Hand DASH questionnaire at the beginning of the experiment. Follow up assessments were carried out after the eight week intervention phase. Results and Conclusion: When compared to the control group, the scapular stabilization group showed better results in terms of reduced discomfort and increased mobility. This implies that adding scapular stabilization exercises to the adhesive capsulitis treatment regimen could result in improved therapeutic outcomes. Larger sample sizes and longer follow up times are required for future study in order to confirm these results and improve adhesive capsulitis patient’s treatment plans.

Use of computational modeling to examine fingertip force production in children with hemiplegic cerebral palsy

Most children with hemiplegic cerebral palsy (HCP), one of the most prevalent subtypes of cerebral palsy, struggle with grasping and manipulating objects. This impairment may arise from a diminished capacity to properly direct forces created with the finger pad due to aberrant force application. Children with HCP were asked to create maximal force with the index finger pad in the palmar (normal) direction with both the paretic and non-paretic hands. The resulting forces and finger postures were then applied to a computational musculoskeletal model of the hand to estimate the corresponding muscle activation patterns. Subjects tended to create greater shear force relative to normal force with the paretic hand (p < 0.05). The resultant force was directed 33.6°±10.8° away from the instructed palmar direction in the paretic hand, but only 8.0°±7.3° in the non-paretic hand. Additionally, participants created greater palmar force with the non-paretic hand than with the paretic hand (p < 0.05). These differences in force production are likely due to differences in muscle activation pattern, as our computational models showed differences in which muscles are active and their relative activations when recreating the measured force vectors for the two hands (p < 0.01). The models predicted reduced activation in the extrinsic and greater reductions in activation in the intrinsic finger muscles, potentially due to reduced voluntary activation or muscle atrophy. As the large shear forces could lead to objects slipping from grasp, muscle activation patterns may provide an important target for therapeutic treatment in children with HCP.

Differential Impact of Biomechanical Constraints on Control Signal Dimensionality for Gravity Support Versus Propulsion.

Neural control of movement has to overcome the problem of redundancy in the multidimensional musculoskeletal system. The problem can be solved by reducing the dimensionality of the control space of motor commands, i.e., through muscle synergies or motor primitives. Evidence for this solution exists, multiple studies have obtained muscle synergies using decomposition methods. These synergies vary across different workspaces and are present in both dominant and non-dominant limbs. Here we explore the dimensionality of control space by examining muscle activity patterns across reaching movements in different directions starting from different postures performed bilaterally by healthy individuals. We further explore the effect of biomechanical constraints on the dimensionality of control space. We are building on top of prior work showing that muscle activity profiles can be explained by applied moments about the limb joints that reflect the biomechanical constraints. These muscle torques derived from motion capture represent the combined actions of muscle contractions that are under the control of the nervous system. Here we test the generalizability of the relationship between muscle torques and muscle activity profiles across different starting positions and between limbs. We also test a hypothesis that the dimensionality of control space is shaped by biomechanical constraints. We used principal component analysis to evaluate the contribution of individual muscles to producing muscle torques across different workspaces and in both dominant and non-dominant limbs. Results generalize and support the hypothesis. We show that the muscle torques that support the limb against gravity are produced by more consistent combinations of muscle co-contraction than those that produce propulsion. This effect was the strongest in the non-dominant arm moving in the lateral workspace on one side of the body.

A tensor decomposition reveals ageing-induced differences in muscle and grip-load force couplings during object lifting

Do motor patterns of object lifting movements change as a result of ageing? Here we propose a methodology for the characterization of these motor patterns across individuals of different age groups. Specifically, we employ a bimanual grasp-lift-replace protocol with younger and older adults and combine measurements of muscle activity with grip and load forces to provide a window into the motor strategies supporting effective object lifts. We introduce a tensor decomposition to identify patterns of muscle activity and grip-load force ratios while also characterizing their temporal profiles and relative activation across object weights and participants of different age groups. We then probe age-induced changes in these components. A classification analysis reveals three motor components that are differentially recruited between the two age groups. Linear regression analyses further show that advanced age and poorer manual dexterity can be predicted by the coupled activation of forearm and hand muscles which is associated with high levels of grip force. Our findings suggest that ageing may induce stronger muscle couplings in distal aspects of the upper limbs, and a less economic grasping strategy to overcome age-related decline in manual dexterity.

Gender differences in neck muscle activity during near-maximum forward head flexion while using smartphones with varied postures

Women frequently express heightened neck discomfort even though they exhibit smaller neck flexion (NF) during smartphone use. Differences in natural posture while using smartphones may result in varying muscle activation patterns between genders. However, no study focused on this issue. This study investigated the influence of gender on neck muscle activity and NF when using smartphones, ranging from slight (20°) to nearly maximal forward head flexion, across different postures. We analyzed smartphone usage patterns in 16 men and 16 women and examined these behaviors across different scenarios: standing, supported sitting, and unsupported sitting, at 20°, 30°, 40°, and the maximum head angles. During data collection, muscle activity was measured, expressed as a percentage of the maximum voluntary contraction (%MVC), in the cervical erector spinae (CES) and upper trapezius (UTZ), along with NF. Results show significant influences of gender, head angle, and posture on all measures, with notable interactions among these variables. Women displayed higher muscle activities in CES and UTZ, yet exhibited lesser NF, while using smartphones in both standing (12.3%MVC, 10.7% MVC, and 69.0°, respectively) and unsupported sitting (10.8%MVC, 12.3%MVC, and 71.8°, respectively) compared to men (standing: 9.5%MVC, 8.8%MVC, and 76.1°; unsupported sitting: 9.7%MVC, 10.8%MVC, and 76.1°). This study provides a potential rationale for gender-related disparities in injury outcomes, emphasizing that women experience higher neck and shoulder discomfort level, despite their smaller NF during smartphone use, as found in previous research. Additionally, the cervical flexion-relaxation phenomenon may occur when the head angle exceeded 40°. The near-maximum head angle during smartphone use might induce the cervical flexion-relaxation phenomenon, potentially aggravating neck issues. We recommend limiting smartphone usage postures that exceed the near-maximum head angle, as they are commonly adopted by individuals in the daily smartphone activities.

Synaptic inputs to motor neurons underlying muscle coactivation for functionally different tasks have different spectral characteristics.

The central nervous system (CNS) may produce the same endpoint trajectory or torque profile with different muscle activation patterns. What differentiates these patterns is the presence of cocontraction, which does not contribute to effective torque generation but allows to modulate joints' mechanical stiffness. Although it has been suggested that the generation of force and the modulation of stiffness rely on separate pathways, a characterization of the differences between the synaptic inputs to motor neurons (MNs) underlying these tasks is still missing. In this study, participants coactivated the same pair of upper-limb muscles, i.e., the biceps brachii and the triceps brachii, to perform two functionally different tasks: limb stiffness modulation or endpoint force generation. Spike trains of MNs were identified through decomposition of high-density electromyograms (EMGs) collected from the two muscles. Cross-correlogram showed a higher synchronization between MNs recruited to modulate stiffness, whereas cross-muscle coherence analysis revealed peaks in the β-band, which is commonly ascribed to a cortical origin. These peaks did not appear during the coactivation for force generation, thus suggesting separate cortical inputs for stiffness modulation. Moreover, a within-muscle coherence analysis identified two subsets of MNs that were selectively recruited to generate force or regulate stiffness. This study is the first to highlight different characteristics, and probable different neural origins, of the synaptic inputs driving a pair of muscles under different functional conditions. We suggest that stiffness modulation is driven by cortical inputs that project to a separate set of MNs, supporting the existence of a separate pathway underlying the control of stiffness.NEW & NOTEWORTHY The characterization of the pathways underlying force generation or stiffness modulation are still unknown. In this study, we demonstrated that the common input to motor neurons of antagonist muscles shows a high-frequency component when muscles are coactivated to modulate stiffness but not to generate force. Our results provide novel insights on the neural strategies for the recruitment of multiple muscles by identifying specific spectral characteristics of the synaptic inputs underlying functionally different tasks.

Scapula-Focused Exercises With or Without Biofeedback and Corticospinal Excitability in Recreational Overhead Athletes With Shoulder Impingement.

Individuals with shoulder impingement syndrome (SIS) exhibit changes in corticospinal excitability, scapular kinematics, and scapular muscle-activation patterns. To restore the scapular kinematics and muscle-activation patterns in individuals with SIS, treatment protocols usually include scapula-focused exercises, such as scapular-orientation and strength training. To investigate whether scapular-orientation and strength training can reverse the altered corticospinal excitability of recreational overhead athletes with SIS. Randomized controlled clinical trial. University laboratory. Forty-one recreational overhead athletes with SIS: 20 in the scapular-orientation group (age = 26.45 ± 4.13 years, height = 171.85 ± 7.88 cm, mass = 66.70 ± 10.68 kg) and 21 in the strengthening group (age = 26.43 ± 5.55 years, height = 171.62 ± 5.87 cm, mass = 68.67 ± 10.18 kg). Both groups performed a 30-minute training protocol consisting of 3 exercises to strengthen the lower trapezius (LT) and serratus anterior muscles without overactivating the upper trapezius muscles. Participants in the scapular-orientation group were instructed to consciously activate their scapular muscles with electromyographic biofeedback and cues, whereas the strengthening group did not receive biofeedback or cues for scapular motion. Corticospinal excitability was assessed using transcranial magnetic stimulation. Scapular kinematics and muscle activation during arm elevation were also measured. After training, both groups demonstrated an increase in motor-evoked potentials in the LT (P = .004) and increases in scapular upward rotation (P = .03), LT activation (P < .001), and serratus anterior activation (P < .001) during arm elevation. Moreover, the scapular-orientation group showed higher LT activation levels during arm elevation after training than the strengthening group (P = .03). With or without biofeedback and cues, scapula-focused exercises improved scapular control and increased corticospinal excitability. Adding biofeedback and cues for scapular control during exercise helped facilitate greater LT activation, so feedback and cues are recommended during scapula-focused training.

SEMG as complementary tool for VFSS: A synchronized study in patients with neurogenic oropharyngeal dysphagia

The neurogenic oropharyngeal dysphagia is a prevalent functional swallowing disorder resulting from neurological causes. The conventional diagnosis involves ionizing radiation in Videofluoroscopy Swallowing Studies (VFSS). Surface electromyography (sEMG) offers a non-invasive alternative by recording muscle activity. This research compares bolus passage timing through anatomical structures using VFSS and sEMG-related activation times. Fifty confirmed oropharyngeal dysphagia patients underwent synchronized VFSS and sEMG, evaluating muscle groups during cracker and fluid ingestion. sEMG revealed activation patterns in masseters, suprahyoid, and infrahyoid muscles, occurring before bolus passage through the mandibular line and concluding near the upper esophageal sphincter complex. sEMG identified differences in dysphagia severity (EAT-10 score), age, and diagnosis, contrasting VFSS results. Results indicate potential complementarity between sEMG and VFSS for dysphagia screening, diagnosis, and monitoring.

Neuromechanical Differences between Pronated and Supinated Forearm Positions during Upper-Body Wingate Tests.

Arm-cycling is a versatile exercise modality with applications in both athletic enhancement and rehabilitation, yet the influence of forearm orientation remains understudied. Thus, this study aimed to investigate the impact of forearm position on upper-body arm-cycling Wingate tests. Fourteen adult males (27.3 ± 5.8 years) underwent bilateral assessments of handgrip strength in standing and seated positions, followed by pronated and supinated forward arm-cycling Wingate tests. Electromyography (EMG) was recorded from five upper-extremity muscles, including anterior deltoid, triceps brachii lateral head, biceps brachii, latissimus dorsi, and brachioradialis. Simultaneously, bilateral normal and propulsion forces were measured at the pedal-crank interface. Rate of perceived exertion (RPE), power output, and fatigue index were recorded post-test. The results showed that a pronated forearm position provided significantly (p < 0.05) higher normal and propulsion forces and triceps brachii muscle activation patterns during arm-cycling. No significant difference in RPE was observed between forearm positions (p = 0.17). A positive correlation was found between seated handgrip strength and peak power output during the Wingate test while pronated (dominant: p = 0.01, r = 0.55; non-dominant: p = 0.03, r = 0.49) and supinated (dominant: p = 0.03, r = 0.51; don-dominant: p = 0.04, r = 0.47). Fatigue changed the force and EMG profile during the Wingate test. In conclusion, this study enhances our understanding of forearm position's impact on upper-body Wingate tests. These findings have implications for optimizing training and performance strategies in individuals using arm-cycling for athletic enhancement and rehabilitation.

Estimation of patient-reported outcome measures based on features of knee joint muscle co-activation in advanced knee osteoarthritis

Electromyography (EMG) is considered a potential predictive tool for the severity of knee osteoarthritis (OA) symptoms and functional outcomes. Patient-reported outcome measures (PROMs), such as the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and visual analog scale (VAS), are used to determine the severity of knee OA. We aim to investigate muscle activation and co-contraction patterns through EMG from the lower extremity muscles of patients with advanced knee OA patients and evaluate the effectiveness of an interpretable machine-learning model to estimate the severity of knee OA according to the WOMAC (pain, stiffness, and physical function) and VAS using EMG gait features. To explore neuromuscular gait patterns with knee OA severity, EMG from rectus femoris, medial hamstring, tibialis anterior, and gastrocnemius muscles were recorded from 84 patients diagnosed with advanced knee OA during ground walking. Muscle activation patterns and co-activation indices were calculated over the gait cycle for pairs of medial and lateral muscles. We utilized machine-learning regression models to estimate the severity of knee OA symptoms according to the PROMs using muscle activity and co-contraction features. Additionally, we utilized the Shapley Additive Explanations (SHAP) to interpret the contribution of the EMG features to the regression model for estimation of knee OA severity according to WOMAC and VAS. Muscle activity and co-contraction patterns varied according to the functional limitations associated with knee OA severity according to VAS and WOMAC. The coefficient of determination of the cross-validated regression model is 0.85 for estimating WOMAC, 0.82 for pain, 0.85 for stiffness, and 0.85 for physical function, as well as VAS scores, utilizing the gait features. SHAP explanation revealed that greater co-contraction of lower extremity muscles during the weight acceptance and swing phases indicated more severe knee OA. The identified muscle co-activation patterns may be utilized as objective candidate outcomes to better understand the severity of knee OA.

A guiding light for stimulating paralyzed muscles.

Improving the performance of closed-loop optogenetic nerve stimulation can reproduce desired muscle activation patterns.