Muscle Activity Research Articles

Future spinal reflex is embedded in primary motor cortex output.

Mammals can execute intended limb movements despite the fact that spinal reflexes involuntarily modulate muscle activity. To generate appropriate muscle activity, the cortical descending motor output must coordinate with spinal reflexes, yet the underlying neural mechanism remains unclear. We simultaneously recorded activities in motor-related cortical areas, afferent neurons, and forelimb muscles of monkeys performing reaching movements. Motor-related cortical areas, predominantly primary motor cortex (M1), encode subsequent afferent activities attributed to forelimb movement. M1 also encodes a subcomponent of muscle activity evoked by these afferent activities, corresponding to spinal reflexes. Furthermore, selective disruption of the afferent pathway specifically reduced this subcomponent of muscle activity, suggesting that M1 output drives muscle activity not only through direct descending pathways but also through the "transafferent" pathway composed of descending plus subsequent spinal reflex pathways. Thus, M1 provides optimal motor output based on an internal forward model that prospectively computes future spinal reflexes.

Exploratory Analysis of Upper Facial Muscle Interplay During Emotional Expressions: Magnetic Resonance Imaging (MRI) Insights from Young, Caucasian, Toxin-naïve Individuals.

Understanding the interplay of muscle activity in the upper face is crucial as it can significantly impact the effectiveness and safety of aesthetic treatments. Traditional injection algorithms typically focus on the general 2D and 3D anatomy of muscles, often neglecting the areas where muscles exert the greatest force during facial expressions. To analyze the location of greatest morphological change in upper facial muscles procerus muscle (PM), corrugator supercilia muscle (CSM), orbicularis oculi muscle (OOM) and frontalis muscle (FM) during various facial expressions. A total of 34 healthy young individuals (17 females, 17 males), with a mean age of 23.6±2.4 years [range 20-30], were examined using MRI to assess the length, thickness and width of upper facial muscles (PM, CSM, OOM, FM) for five different facial expressions: repose, anger, joy, surprise, and sadness. Facial muscle thickness is a key indicator of activity during expressions like anger, joy, surprise, and sadness. During anger, the PM and CSM decreased in length and width but increased in thickness, while FM passively contracted to stabilize the expression. The OOM showed increased thickness in its medial, inferior, lateral, and superior portions during various expressions, with specific regions activating differently depending on the expression, such as the medial and lateral parts during surprise and the inferior and lateral parts during joy. The medial third of the CSM was the most active region during contraction. Upper facial muscles - regardless of them agonists or antagonists - act together during facial expressions to stabilize facial expressions, emphasizing the need to assess both groups in neuromodulator treatments. The medial third of the corrugator supercillii shows the most significant MRI changes, making it the primary target for injections.

Biomechanical analysis of seated posture and ergonomics in workspace interior design for improved user comfort

Prolonged sitting in office environments poses significant occupational health risks, necessitating effective ergonomic interventions. This study investigated the biomechanical aspects of seated posture and the effectiveness of ergonomic interventions in a technology park setting. A 12-week randomized controlled study was conducted with 39 office workers divided into three groups: Control Group (n = 13), Intervention Group A (ergonomic setup, n = 13), and Intervention Group B (ergonomic setup with feedback, n = 13). Measurements included spinal angles, muscle activity (%MVC), seat pressure distribution, and postural compliance. Spinal alignment improved significantly in intervention groups, with Intervention Group B showing superior improvement (+32.6 ± 3.8°) compared to Intervention Group A (+24.8 ± 3.5°) and control group (−2.5 ± 1.2°, p < 0.001). Muscle activity in the trapezius reduced significantly in Intervention Group B (from 22.4% ± 3.2%MVC to 13.1% ± 2.1%MVC, p < 0.001). Peak pressure at ischial tuberosities decreased by 29.5% in Intervention Group B compared to control. By week 12, postural compliance reached 85.4% ± 6.8% in Intervention Group B versus 47.2% ± 5.0% in the control group, with user adaptation rates achieving 86.1% ± 6.9% compared to 45.6% ± 4.8% in the control (p < 0.001). The combination of ergonomic setup and real-time feedback demonstrated superior outcomes in improving seated posture, reducing muscle fatigue, and optimizing pressure distribution. Intervention Group B showed significantly better results across all parameters, with sustained improvements over the 12 weeks. These findings suggest that integrated ergonomic interventions with feedback mechanisms are more effective than traditional approaches in promoting healthy sitting behavior in office environments.

Does lower limb kinesio taping affect pain, muscle strength, and balance following fatigue in healthy subjects? A systematic review and meta analysis of parallel randomized controlled trials

BackgroundKinesio tape (KT) has gained popularity in sports and rehabilitation due to its ease of use and potential benefits. However, its effectiveness is not well understood especially in addressing fatigue, a condition that can impair muscle function and increase the musculoskeletal risk of injury. Given KT's potential impact on muscle activity and recovery, this review aims to evaluate the effects of lower limb KT on pain, strength, and balance following fatigue.MethodsA comprehensive search was conducted in five databases (Scopus, PubMed, Cochrane, ScienceDirect, and PEDRO) up to January 2024. The search employed keywords related to KT, fatigue, and delayed onset muscle soreness. We included parallel randomized controlled trials that compared KT to control groups, including sham tape, rigid tape, or no-tape. The methodological quality of the included studies was assessed using the Cochrane risk-of-bias tool. Meta-analyses were conducted for pain and strength outcomes, but not balance due to the limited number of articles addressing this outcome.ResultsAfter screening 320 initial records, 16 studies were included in the analysis, all of which were characterized by a high risk of methodological bias. The meta-analysis on 837 subjects demonstrated that KT significantly reduced fatigue-related pain, with a moderate effect size (SMD = -0.44, p < 0.0001, I2 = 32%). Subgroup analysis revealed significant pain reduction after 48 h, with no substantial effects immediately or at 24 h. The meta-analysis on muscle strength, involving 605 subjects, showed a significant improvement in the KT group, with a moderate to strong effect size (SMD = 0.46, p < 0.0001, I2 = 45%). Subgroup analysis indicated strength improvements at all time points: immediate, 48 h, and beyond 48 h. Results regarding balance were mixed; two studies reported a positive effect of KT on balance, while two others showed no significant impact.ConclusionsKT effectively reduces pain following fatigue, particularly noticeable after 48 h, and significantly enhances muscle strength, with potential balance improvements. These findings highlight KT's non-invasive, and cost-effective advantages. However, due to high risk of bias and methodological variability, further rigorous research is essential to substantiate these benefits and refine the therapeutic application of KT.

Postural adjustment and muscle activity during each phase of gait initiation in chronic ankle instability: an observational study

BackgroundGait initiation (GI) can be divided into three sections according to the center of pressure (COP) trace (S1, S2, and S3). Almost all studies do not separate each phase of the GI profile in postural control assessment and muscular investigation, whereas differences in the COP and muscles are found in each phase of the GI profile in people with gait problems.MethodsTwenty individuals with CAI and twenty healthy controls were included in the present study. A force plate synchronized with Qualisys motion analysis, MEGAWIN electromyography, and a pair of auditory cues were used for data capture. The participants carried out five trials of GI with the affected leg (dominant leg). The peak and mean COP excursions; the mean and maximum velocities of COP excursion during S1, S2,, S3, and the total phases in the mediolateral (ML) and anterior‒posterior (AP) directions; the root mean square (RMS); and the onset activity of the Tibialis Anterior (TA) and Soleus (SOL) muscles for both legs were used for statistical analysis. Independent t tests and Mann‒Whitney U tests were used for statistical analysis on the basis of a significance level of ≤ 0.05.ResultsCompared with those of healthy controls, independent t tests revealed a significant decrease in the peak COP excursion in the AP direction during S2 (P = 0.021) and in the mean velocity of COP excursion in the AP direction during S1 (P = 0.044) in the CAI group. Additionally, there was a significant increase in the duration of S1 in the GI profile (P = 0.045) in the CAI group compared with the healthy control group. There was no significant difference in the other COP variables, TA or SOL RMS or onset activity for either leg during S1, S2, or S3 between the two groups (P > 0.065).ConclusionIndividuals with CAI exhibit increased stiffness in the AP direction in the injured ankle. This leads to a reduction in the velocity and peak of COP excursion, as well as an increase in the time required for postural control adjustment. These findings highlight the challenges individuals with CAI may face in meeting postural demands when trying to unload the affected foot.Ethical codeIR.SBMU.RETECH.REC.1402.095, 2023–5-28.

EMG-assessed paratonia: A novel approach to investigating motor response inhibition in healthy subjects.

Paratonia is an involuntary muscle activity that occurs during passive joint mobilization and is common in people with dementia. It includes oppositional paratonia, in which muscle activity resists passive movement, and facilitatory paratonia, in which it assists movement. This phenomenon reflects a defect in motor response inhibition. In a recently published paper, we demonstrated that paratonia can be detected using surface electromyography (EMG) not only in patients with dementia but also in healthy individuals, the majority of whom do not exhibit clinically observable paratonia. This finding suggests that EMG-assessed paratonia may provide a novel approach to studying motor response inhibition in healthy subjects. The present study investigates this possibility for the first time. We recruited 120 healthy subjects under the age of 30, divided equally into three groups: sedentary, amateur, and professional athletes with low, moderate, and high levels of physical activity, respectively. Paratonia was assessed in the triceps and biceps brachii muscles during passive forearm movements performed manually. The results indicate that paratonia is more pronounced during fast and continuous passive movements, with facilitatory paratonia being more prevalent than oppositional paratonia. It is also more pronounced in the biceps than in the triceps. These findings, which mirror those previously observed in patients with dementia, suggest a similarity between paratonia in healthy subjects and those with cognitive impairment, supporting the hypothesis that paratonia in healthy individuals represents a form of impaired motor response inhibition. Furthermore, the comparison between groups showed that paratonia decreased with increasing physical activity, being least evident in athletes, more noticeable in amateurs, and most pronounced in sedentary individuals. This pattern confirms a key feature of motor response inhibition that has been shown in studies using traditional methods. Overall, our findings suggest that EMG-assessed paratonia provides a new method for studying motor response inhibition in healthy individuals.

Pilot Study on the Relationship Between Different Lower Limb Raising Velocities and Trunk Muscle Contraction in Active Straight Leg Raise

Background/Objectives: The active straight leg raise requires intricate coordination between the hip, knee, pelvis, and spine. Despite its complexity, limited research has explored the relationship between lower limb raising velocity and trunk muscle motor control during an active straight leg raise in healthy individuals. This study aimed to explore the potential effects of increased lower limb raising velocity on core muscle contractions during active straight leg raises. Methods: Six healthy adult men (mean age: 24.5 ± 2.5 years) participated in this study. Electromyography signals were recorded using surface electrodes placed on the rectus abdominis, external oblique, and internal oblique/transverse abdominis muscles. The participants performed active straight leg raises at three different velocities: 3 s, 2 s, and as fast as possible (max). The electromyography data were analyzed from 250 ms before to 1000 ms after movement initiation, with muscle activity expressed as a percentage of the maximal voluntary isometric contraction. Statistical analyses were conducted using non-parametric tests, including the Friedman test for overall differences, followed by pairwise Wilcoxon signed-rank tests with Bonferroni correction for multiple comparisons (p &lt; 0.05). Results: During the 250 ms before movement initiation, the internal oblique/transverse abdominis, external oblique, and rectus abdominis muscles showed greater activity in the max condition compared to the 3 s and 2 s conditions (Friedman test, p &lt; 0.05), but no significant differences were found in pairwise comparisons (Wilcoxon test, p &gt; 0.05). Similarly, during the 500 ms after movement initiation, internal oblique/transverse abdominis activity was higher in the max condition, with no significant pairwise differences observed. Conclusions: Faster lower limb raising velocities during active straight leg raise may enhance core stability by activating anticipatory and sustained internal oblique/transverse abdominis, external oblique, and rectus abdominis activity on the raised limb side. Training to promote this activation could improve dynamic stability in rapid or asymmetric movements.

Development of a Wearable Electromyographic Sensor with Aerosol Jet Printing Technology

Electromyographic (EMG) sensors are essential tools for analyzing muscle activity, but traditional designs often face challenges such as motion artifacts, signal variability, and limited wearability. This study introduces a novel EMG sensor fabricated using Aerosol Jet Printing (AJP) technology that addresses these limitations with a focus on precision, flexibility, and stability. The innovative sensor design minimizes air interposition at the skin–electrode interface, thereby reducing variability and improving signal quality. AJP enables the precise deposition of conductive materials onto flexible substrates, achieving a thinner and more conformable sensor that enhances user comfort and wearability. Performance testing compared the novel sensor to commercially available alternatives, highlighting its superior impedance stability across frequencies, even under mechanical stress. Physiological validation on a human participant confirmed the sensor’s ability to accurately capture muscle activity during rest and voluntary contractions, with clear differentiation between low and high activity states. The findings highlight the sensor’s potential for diverse applications, such as clinical diagnostics, rehabilitation, and sports performance monitoring. This work establishes AJP technology as a novel approach for designing wearable EMG sensors, providing a pathway for further advancements in miniaturization, strain-insensitive designs, and real-world deployment. Future research will explore optimization for broader applications and larger populations.

Exoskeleton gait training on real-world terrain improves spatiotemporal performance in cerebral palsy

IntroductionWalking is essential for daily life but poses a significant challenge for many individuals with neurological conditions like cerebral palsy (CP), which is the leading cause of childhood walking disability. Although lower-limb exoskeletons show promise in improving walking ability in laboratory and controlled overground settings, it remains unknown whether these benefits translate to real-world environments, where they could have the greatest impact.MethodsThis feasibility study evaluated whether an untethered ankle exoskeleton with an adaptable controller can improve spatiotemporal outcomes in eight individuals with CP after low-frequency exoskeleton-assisted gait training on real-world terrain.ResultsComparing post- and pre-assessment, assisted walking speed increased by 11% and cadence by 7% (p = 0.003; p = 0.006), while unassisted walking speed increased by 8% and cadence by 5% (p = 0.009; p = 0.012). In the post-assessment, assisted walking speed increased by 9% and stride length by 8% relative to unassisted walking (p &amp;lt; 0.001; p &amp;lt; 0.001). Improvements in walking speed were more strongly associated with longer strides than higher cadence (R2 = 0.92; R2 = 0.68). Muscle activity outcomes, including co-contraction of the soleus and tibialis anterior, did not significantly change after training.DiscussionThese findings highlight the spatiotemporal benefits of an adaptive ankle exoskeleton for individuals with CP in real-world settings after short-term training. This work paves the way for future randomized controlled trials (RCTs) to evaluate the isolated effects of adaptive ankle exoskeletons on gait performance and neuromuscular outcomes in individuals with CP in real-world environments

Targeted Motor Control Considering Sternal Position Improves Spinal Alignment in Pregnant Women at Risk for Preterm Birth with Low Back Pain

Background: Lumbopelvic pain (LBP) is a prevalent condition during pregnancy, affecting a significant proportion of pregnant women. It arises from hormonal, biomechanical, and postural changes, often exacerbating discomfort and impairing quality of life. This study aimed to evaluate the effects of targeted motor control interventions focusing on sternal alignment on spinal alignment, pain, and muscle activity in pregnant women at risk of preterm birth. Methods: This pre–post quasi-experimental study included 32 pregnant women at 28–32 weeks of gestation, who were hospitalized due to the risk of preterm birth. Inclusion criteria required participants to have LBP lasting at least two weeks and the ability to walk and stand for 40 min. The intervention involved targeted motor control exercises designed to optimize sternal and sacral alignment. Spinal alignment, pain intensity, and muscle activity were measured pre- and post-intervention using the DIERS formetric system, numerical rating scale (NRS), and electromyography (EMG), respectively. Data were analyzed using Wilcoxon signed-rank tests. Results: Significant improvements were observed in spinal alignment parameters, including reductions in the sternal angle, sacral angle, cervical and lumbar lordosis depths, thoracic kyphosis angle, and pelvic tilt (p &lt; 0.05). Pain intensity decreased significantly from a mean NRS score of 5.77 ± 1.42 in the relaxed posture to 2.54 ± 0.71 in the corrected posture (p &lt; 0.05). Muscle activity of the rhomboid muscles increased in the corrected posture, correlating with improved thoracic kyphosis, while activity of the serratus anterior muscle showed reductions (p &lt; 0.05). Conclusions: Targeted motor control focusing on sternal alignment effectively improved spinal alignment and reduced pain in pregnant women at risk of preterm birth with LBP. The intervention offers a safe, non-invasive, and practical approach to managing pregnancy-related musculoskeletal challenges. Future research should validate these findings in diverse populations and explore long-term effects and broader clinical applications.

Effect of Respiratory Training on Pulmonary Functions and Cervical ROM in Non-Specific Chronic Neck Pain

Objectives: Non-Specific Chronic Neck (NS-CNP) is a multifactorial condition with excessive activity of accessory muscles of respiration in the neck. Studies have portrayed significant relationships between chronic neck pain and respiratory parameters. The study intends to find the impact of respiratory training on lung function and cervical ROM in NS CNP. Methods : The study recruited 64 subjects with pain who were advised to undergo conventional electrotherapy for a week. Pre-intervention measurements were taken, and subjects were divided into 2 groups. Group A received respiratory training and conventional therapy, while Group B received conventional therapy. Post-test measurements were recorded and statistically analyzed. Findings: The post-values of all the outcome measures were significant with an obtained p-value of 0.00, which is &lt;0.05 in both Group A and Group B. Comparing all the outcome measures between the groups showed a significant difference in Cervical flexion along with FVC, SVC, and MVV with the obtained p values of &lt;0.05 which is below the threshold chosen for the statistical analysis. Novelty: The novelty of this study is to implement respiratory training along with conventional neck exercises in the management of NS-CNP. Conclusion: This study concludes that respiratory training and conventional neck exercises significantly improved neck mobility and pulmonary function. Keywords: Cervical pain, Respiratory training, Neck range of motion, Pulmonary functions, Forced vital capacity

Quantification of gait characteristics and muscle activation in patients with chronic ankle instability during walking on sand: A randomized crossover trial.

Limited evidence exists regarding the movement control patterns of individuals with chronic ankle instability (CAI) during sand walking. This study aimed to analyze gait characteristics and muscle activation in patients with CAI while walking on sand. This study recruited 30 participants, including 15 patients with CAI and 15 healthy controls. Patients with CAI were selected based on having experienced at least a lateral ankle sprain within 12 months before recruitment. They also had to scoring ≤ 27 on the Cumberland ankle instability tool. This study was conducted using a randomized crossover trial. All participants were asked to walk three times each at their natural speed on both sand and paving blocks for a distance of 50m. There was at least a week between each trial. The lower limb gait kinematics, spatiotemporal, and muscle activity parameters while walking on sand and paving blocks were compared between both groups. Significant differences in knee angle were observed between 60.83% and 75.34% of the gait cycle during walking on sand in the patients with CAI. Regarding spatiotemporal parameters, cadence (P = .001) and stride length (P = .049) showed significant differences as the main effect. In the CAI group, the recruitment threshold for the peroneus longus muscle was significantly lower during walking on sand than on paving blocks (P < .001). In contrast, the motor unit action potential (MUAP) was significantly higher (P < .001). For the tibialis anterior muscle, the recruitment threshold and number of motor units were significantly lower during walking on sand than on paving blocks (P = .006 and P = .003, respectively), and the MUAP was significantly higher (P < .001). During walking on sand, patients with CAI exhibited increased knee flexion angle, stride length, and MUAP, along with decreased cadence and recruitment thresholds. These results suggest that sand can influence gait characteristics and muscle activation in patients with CAI. Our findings indicate that gait characteristics and muscle activation changes in patients with CAI could potentially benefit CAI rehabilitation.

Biomechanics of physical exercise: A data-driven approach to enhancing mental health in college students

With growing awareness of the importance of mental health, the biomechanical mechanisms of physical exercise have gained attention as an effective intervention for improving mental well-being, particularly among college students. Physical activity not only enhances physical fitness and disease resistance but also contributes to cognitive and emotional health through specific biomechanical pathways. This study explores the interplay between exercise biomechanics and mental health by investigating the psychological challenges faced by college students. Utilizing advanced data analysis and correlation techniques, we refine the Apriori algorithm through a novel database partitioning strategy, achieving a 23.68% improvement in accuracy and a 10.17% reduction in runtime compared to the baseline. Additionally, this study examines how biomechanical factors, such as joint movement and muscle activity, influence brain function and mental health outcomes. The findings offer innovative perspectives for integrating biomechanical insights into mental health education and exercise-based interventions for college students.

The Reverse Lunge: A Descriptive Electromyographic Study

Limited studies exist examining the reverse lunge. The purpose of this study was to describe the activation of the rectus femoris (RF), biceps femoris (BF), gluteus medius (GMed), and gluteus maximus (GMax) of both limbs during a bodyweight reverse lunge movement. A secondary purpose was to describe the phases of the stationary (non-moving) and lead (moving) limbs during the reverse lunge. Surface electromyography (EMG) was used to record the activity of the target muscles in 20 healthy adults (10 male, 10 female; aged 22–25). Root mean squared values for mean maximum and average percent activation normalized to maximum voluntary isometric contraction (MVIC) activation were calculated. Descriptive terminology was created to describe the phases of the lunge for both limbs. The mean maximum percentage of muscle activation for the RF and BF was greater in the lead limb, while GMed and GMax activations were greater in the stationary limb. Only the lead limb RF and stationary limb GMed reached a strengthening stimulus in mean maximum percentage measurements. Clinically, it may be important to consider when each muscle is maximally active and at what percentage of its MVIC to properly prescribe the reverse lunge in a safe manner.

The Interplay Between Muscular Activity and Pattern Recognition of Electro-Stimulated Haptic Cues During Normal Walking: A Pilot Study

This pilot study explored how muscle activation influences the pattern recognition of tactile cues delivered using electrical stimulation (ES) during each 10% window interval of the normal walking gait cycle (GC). Three healthy adults participated in the experiment. After identifying the appropriate threshold, ES as the haptic cue was applied to the gastrocnemius lateralis (GL) and biceps brachii (BB) of participants walking on a treadmill. Findings revealed variable recognition patterns across participants, with the BB showing more variability during walking due to its minimal activity compared to the actively engaged GL. Dynamic time warping (DTW) was used to assess the similarity between muscle activation and electro-stimulated haptic perception. The DTW distance between electromyography (EMG) signals and muscle recognition patterns was significantly smaller for the GL (4.87 ± 0.21, mean ± SD) than the BB (8.65 ± 1.36, mean ± SD), showing a 78.6% relative difference, indicating that higher muscle activation was generally associated with more consistent haptic perception. However, individual differences and variations in recognition patterns were observed, suggesting personal variability influenced the perception outcomes. The study underscores the complexity of human neuromuscular responses to artificial sensory stimuli and suggests a potential link between muscle activity and haptic perception.

Central mechanisms of muscle tone regulation: implications for pain and performance

Muscle tone represents a foundational property of the motor system with the potential to impact musculoskeletal pain and motor performance. Muscle tone is involuntary, dynamically adaptive, interconnected across the body, sensitive to postural demands, and distinct from voluntary control. Research has historically focused on pathological tone, peripheral regulation, and contributions from passive tissues, without consideration of the neural regulation of active tone and its consequences, particularly for neurologically healthy individuals. Indeed, simplistic models based on the stretch reflex, which neglect the central regulation of tone, are still perpetuated today. Recent advances regarding tone are dispersed across different literatures, including animal physiology, pain science, motor control, neurology, and child development. This paper brings together diverse areas of research to construct a conceptual model of the neuroscience underlying active muscle tone. It highlights how multiple tonic drive networks tune the excitability of complex spinal feedback circuits in concert with various sources of sensory feedback and in relation to postural demands, gravity, and arousal levels. The paper also reveals how tonic muscle activity and excitability are disrupted in people with musculoskeletal pain and how tone disorders can lead to marked pain and motor impairment. The paper presents evidence that integrative somatic methods address the central regulation of tone and discusses potential mechanisms and implications for tone rehabilitation to improve pain and performance.

How Does Induced Deceleration of One Treadmill’s Belt in the Pre-Swing Gait Phase Change Gait Pattern?

This study aimed to investigate how external perturbations caused by the treadmill belt’s deceleration during the pre-swing phase affect gait kinematics and kinetics in young adults. Twenty-one healthy young females walked on a treadmill in a virtual environment (GRAIL, Motek), where unexpected perturbations were applied to the left belt, mimicking a ‘trip-like’ effect at toe-off. The spatiotemporal, kinematic, and kinetic parameters were analyzed during two cycles. The first cycle involved the first perturbation and the response to it. The second included a gait cycle without the perturbation (treadmill gait). The perturbation resulted in an increased stride duration for both limbs when compared to the treadmill gait. The perturbed limb had a longer support phase, while the reactive limb had the longest double stance phase. The responding limb exhibited more than double the ankle plantarflexion compared to the normal treadmill gait and the perturbed limb. At the hip joint, both limbs showed significantly higher values, with a 40.8% increase in flexion and a 227% increase in extension for the perturbed limb, and a 24.5% increase in flexion and a 212% increase in extension for the responding limb, compared to the treadmill gait. Muscle torque was generally lower in most joints for both limbs, except for notably higher hip and knee extensor values for the perturbed limb. The responding limb exhibited lower values for the ankle, knee, and hip joints, indicating unexpected muscle activity patterns. Studying treadmill belt deceleration during pre-swing gait can provide valuable insights into biomechanical adaptations and motor control strategies.

Comparing the Pressure on the Carpal Tunnel When Using an Ergonomic Pointer Driver and an Optical Alternative

Objectives: The objective of this paper is to introduce a method to measure the force or pressure over the carpal tunnel indirectly, using a new device to drive the pointer of a computer system. The measurements were compared with those obtained using an ergonomic mouse. Simultaneously, measurements of muscular stress on the digitorum extensor muscle were performed to correlate the applied force against muscle activity. Methods: An experimental setup was constructed using an infrared static receiver plus two wearable moving light emitters, which can be displaced inside a rectangular projected region. The pointer functions are performed through two finger gestures, while the hand is naturally extended. A microcontroller was used to communicate with the computer, which works as a human interface device and possesses firmware to associate the position of each light source with the pointer functions. Meanwhile, force and electromyography sensing circuits were developed to transmit and measure carpal tunnel strength and muscular stress. The system was tested on five healthy volunteers, who were encouraged to solve the same computational tasks using this new device and a trademark ergonomic mouse. Results: Our results show great differences (greater than one magnitude) between the efforts of the same volunteers performing the same predefined tasks using both pointer controllers. Only when the new device was used did the Pearson’s correlation coefficients show a higher correlation between the effort measured on the carpal tunnel and the muscular activity. Conclusions: The optic pointer driver diminishes the strength on the carpal tunnel, causing slightly increased stress on the digitorum extensor muscle.

Impact of different muscle lengthening amplitudes combined with electrical nerve stimulation on torque production.

This study investigated torque production resulting from the combined application wide-pulse neuromuscular electrical stimulation (NMES), delivered over the posterior tibial nerve, and muscle lengthening at two distinct amplitudes. Wide-pulse NMES (pulse duration: 1ms; stimulation intensity: 5 - 10% of maximal voluntary contraction) was delivered at both low (20 Hz) and high (100 Hz) stimulation frequencies, either alone (NMES condition) or combined with a muscle lengthening at two amplitudes (10 or 20° ankle joint rotation; NMES+LEN10 and NMES+LEN20 conditions, respectively). For each frequency, the torque-time integral (TTI) and the muscle activity following the cessation of stimulation trains (sustained EMG activity) were calculated. At 20 Hz, TTI was higher (P=0.007) during NMES+LEN10 (233.2 ± 101.5 Nm.s) and NMES+LEN20 (229.2 ± 92.1 Nm.s) than during the NMES condition (187.5 ± 74.5 Nm.s), without any change in sustained EMG activity (P=0.54). At 100 Hz, TTI was higher (P=0.038) during NMES+LEN10 (226.6 ± 115.3 Nm.s) than during NMES+LEN20 (180.6 ± 84.0 Nm.s) and NMES (173.9 ± 94.9 Nm.s). This torque enhancement was accompanied by a higher sustained EMG activity (P=0.045) in the NMES+LEN10 condition. These findings show that, for low-frequency NMES, significant torque increases were observed with both a 10- or a 20-degree lengthening amplitude, probably linked to increased afferents' activation. In contrast, with high-frequency NMES, a significant TTI enhancement was observed only with the 10-degree amplitude, accompanied by increased sustained EMG activity, suggesting neural mechanisms' involvement. When a greater lengthening amplitude was superimposed during high-frequency NMES, these mechanisms were probably inhibited, precluding torque enhancement.

Is the YES/NO classification accurate in screening scapular dyskinesis in asymptomatic individuals? – A novel validation study utilizing surface electromyography as a surrogate measure in identifying movement asymmetries

ABSTRACT Background Scapular dyskinesis is a known risk factor for shoulder pain, making it important to screen for prevention. Physical therapists screen scapular dyskinesis by visually comparing asymmetries in scapular movement during overhead reach using the Scapular Dyskinesis Test Yes/No classification (Y/N). Although scapular kinematics has been used to quantify scapular dyskinesis, current measurement techniques are inaccurate. Optimal scapular muscle activity is crucial for normal shoulder function and is measured using surface electromyography (sEMG). Research suggests that impaired scapular muscles can lead to scapular dyskinesis. Despite kinematics being a poor reference standard, there is currently no validated method to identify movement asymmetries using muscle activity as an alternative. We utilized sEMG to establish Y/N’s validity. We hypothesized that Y/N is a valid tool using sEMG as a viable surrogate measure for identifying scapular dyskinesis. Methods We employed a known-groups (symmetrical vs. asymmetrical shoulders) validity design following the Standards for Reporting Diagnostic Accuracy Studies. Seventy-two asymptomatic subjects were evaluated using Y/N as the index test and sEMG as the reference standard. We created a criterion to assign the sEMG as the reference standard to establish the known groups. We calculated the sensitivity (Sn), specificity (Sp), positive and negative predictive values (PPV, NPV), likelihood ratios (LR+, LR-), and diagnostic odds ratio (DOR) using a 2 × 2 table analysis. Results The diagnostic accuracy values were Sn = 0.56 (0.37–0.74), Sp = 0.36 (0.08–0.65), PPV = 0.68 (0.49–0.88), NPV = 0.25 (0.04–0.46), LR+ = 0.87 (0.50–1.53), and LR- = 1.22 (0.50–2.97). Conclusion The Y/N’s diagnostic accuracy was poor against the sEMG, suggesting clinicians should rely less on Y/N to screen scapular dyskinesis in the asymptomatic population. Our study demonstrated that sEMG might be a suitable alternative as a reference standard in validating methods designed to screen movement asymmetries.