Measure Muscle Activity Research Articles

Muscle coactivation during gait in children with and without cerebral palsy

BackgroundChildren with Cerebral Palsy (CP) walk with an uncoordinated gait compared to Typically Developing (TD) children. This behavior may reflect greater muscle co-activation in the lower limb; however, findings are inconsistent, and the determinants of this construct are unclear. Research objectives(i) Compare lower-limb muscle co-activation during gait in children with, and without CP, and (ii) determine the extent to which muscle co-activation is influenced by electromyography normalization procedures and Gross Motor Function Classification System (GMFCS) class. MethodsAn electromyography system measured muscle activity in the rectus femoris, semitendinosus, gastrocnemius, and tibialis anterior muscles during walking in 46 children (19 CP, 27 TD). Muscle co-activation was calculated for the tibialis anterior-gastrocnemius (TA-G), rectus femoris-gastrocnemius (RF-G), and rectus femoris-semitendinosus (RF-S) pairings, both using root mean squared (RMS)-averaged and dynamically normalized data, during stance and swing. Mann-Whitney U and independent t-tests examined differences in muscle co-activation by group (CP vs. TD) and GMFCS class (CP only), while mean difference 95% bootstrapped confidence intervals compared electromyography normalization procedures. ResultsUsing dynamically normalized data, the CP group had greater muscle co-activation for the TA-G and RF-G pairs during stance (p < 0.01). Using RMS-averaged data, the CP group had greater muscle co-activation for TA-G (stance and swing, p < 0.01), RF-G (stance, p < 0.05), and RF-S (swing, p < 0.01) pairings. Muscle co-activation calculated with dynamically normalized, compared to RMS-averaged data, were larger in the RF-S and RF-G (stance) pairs, but smaller during swing (RF-G). Children with CP classified as GMFCS II had greater muscle co-activation during stance in the TA-G pair (p < 0.05). SignificanceGreater muscle co-activation observed in children with CP during stance may reflect a less robust gait strategy. Although data normalization procedures influence muscle co-activation ratios, this behavior was observed independent of normalization technique.

Gym training muscle fatigue monitoring using EMG myoware and arduino with envelope and sliding window methods

&lt;p&gt;&lt;span&gt;Muscles are an important organ in the movement of the body's skeleton to carry out sports activities. Measurement of muscle activity during the exercise process can be done using electromyography (EMG). This research uses Myoware muscle sensor (AT-04-001) which is integrated with Arduino Uno and Xbee to monitor biceps brachii muscle fatigue wirelessly. Fatigue data processing is carried out objectively using the envelope and sliding window method and subjectively verbally from the respondents. From this study, it was found that muscle fatigue can be measured using the method objectively when there is an increase in EMG amplitude with a window size of 5 s. The indication of biceps brachii muscle fatigue for the right arm is stronger to withstand the load during exercise with the average duration of the measurement of the right arm is 41.87 s from 69.67 s; 53.53 s from 98.90 s and 76.87 s from 98.80 s with the ratio of the left arm tending to fatigue more quickly is 23.53 s from 42.13 s; 41.87 s from 51.60 s and 23.53 s from 44.73 s.&lt;/span&gt;&lt;/p&gt;

Dual-Task Interference Effects on Lower-Extremity Muscle Activities during Gait Initiation and Steady-State Gait among Healthy Young Individuals, Measured Using Wireless Electromyography Sensors.

To maintain a healthy lifestyle, adults rely on their ability to walk while simultaneously managing multiple tasks that challenge their coordination. This study investigates the impact of cognitive dual tasks on lower-limb muscle activities in 21 healthy young adults during both gait initiation and steady-state gait. We utilized wireless electromyography sensors to measure muscle activities, along with a 3D motion capture system and force plates to detect the phases of gait initiation and steady-state gait. The participants were asked to walk at their self-selected pace, and we compared single-task and dual-task conditions. We analyzed mean muscle activation and coactivation in the biceps femoris, vastus lateralis, gastrocnemius, and tibialis anterior muscles. The findings revealed that, during gait initiation with the dual-task condition, there was a decrease in mean muscle activation and an increase in mean muscle coactivation between the swing and stance limbs compared with the single-task condition. In steady-state gait, there was also a decrease in mean muscle activation in the dual-task condition compared with the single-task condition. When participants performed dual-task activities during gait initiation, early indicators of reduced balance capability were observed. Additionally, during dual-task steady-state gait, the knee stabilizer muscles exhibited signs of altered activation, contributing to balance instability.

Validation of a lower limb exoskeleton assist device focusing on viscous properties: verification of assist effectiveness by measuring muscle activity

Because exoskeletal assistive devices are worn directly by a person, enhancing cooperation is important. However, existing assistive devices have problems in terms of their cooperation with human behaviors. This is because existing assistive devices are driven by estimating the wearer’s movement intention based on predetermined movement time and device angle information. Although these methods are expected to work as expected, in practice, it is difficult to achieve the expected behavior. Therefore, an assistance method is required to reduce such misalignment with time and misalignment between the device and wearer. Therefore, this study focused on the viscoelastic properties that generate force in response to movement and are expected to enhance coordination. In a previous study, the authors confirmed the effects of viscoelastic properties or an assistive device with variable stiffness. However, viscous characteristics during movement have not been considered. In this study, we aimed to improve the coordination by focusing on the viscous characteristics. The viscous torque outputs in response to the angular velocity are expected to be driven in response to actual human motion. In this study, the viscous torque was calculated as the product of the command viscosity coefficient and the joint angular velocity and was applied to a lower-limb exoskeleton-type assist device equipped with a magneto-viscous fluid brake and a planetary gear mechanism. In addition, a viscous command that changes the torque according to speed (proposed method), a time command that changes the output value according to the passage of time, and an angle command that changes the command value according to the angle information of the device were applied to the assist device, and surface EMG measurements and command signals were compared. The target movement was a seated movement, and the left and right vastus medialis and semimembranosus muscles were measured. More than half of the subjects showed a decrease in myopotential for five subjects for all three command methods, confirming the effectiveness of the viscous command.

Understanding corticomotor mechanisms for activation of non-target muscles during unilateral isometric contractions of leg muscles after stroke

Purpose Muscle activation often occurs in muscles ipsilateral to a voluntarily activated muscle and to a greater extent after stroke. In this study, we measured muscle activation in non-target, ipsilateral leg muscles and used transcranial magnetic stimulation (TMS) to provide insight into whether corticomotor pathways contribute to involuntary activation. Materials and methods Individuals with stroke performed unilateral isometric ankle dorsiflexion, ankle plantarflexion, knee extension, and knee flexion. To quantify involuntary muscle activation in non-target muscles, muscle activation was measured during contractions from the ipsilateral tibialis anterior (TA), medial gastrocnemius (MG), rectus femoris (RF), and biceps femoris (BF) and normalized to resting muscle activity. To provide insight into mechanisms of involuntary non-target muscle activation, TMS was applied to the contralateral hemisphere, and motor evoked potentials (MEPs) were recorded. Results We found significant muscle activation in nearly every non-target muscle during isometric unilateral contractions. MEPs were frequently observed in non-target muscles, but greater non-target MEP amplitude was not associated with greater non-target muscle activation. Conclusions Our results suggest that non-target muscle activation occurs frequently in individuals with chronic stroke. The lack of association between non-target TMS responses and non-target muscle activation suggests that non-target muscle activation may have a subcortical or spinal origin. Non-target muscle activation has important clinical implications because it may impair torque production, out-of-synergy movement, and muscle activation timing.

Is it safe to control the car pedal with the lower limb of the unaffected side in patients with stroke?

Objectives Few studies have examined motor function in determining the suitability of patients with stroke to resume driving a car. Patients with hemiplegia usually control car pedals with the unaffected lower limb. However, motor control on the unaffected side is also impaired in patients with stroke. This study aimed to clarify the neurophysiological characteristics of pedal switching control during emergency braking in patients with hemiplegia. Methods The study participants consisted of 10 drivers with left hemiplegia and 10 age-matched healthy drivers. An experimental pedal was used to measure muscle activity and kinematic data during braking, triggered by the light from a light-emitting diode placed in front of the drivers. Results The patient group took the same reaction time as the healthy group. However, from the visual stimulus to the release of the accelerator pedal, the patient group had higher muscle activity in the tibialis anterior and rectus femoris and had faster angular velocities of hip and knee flexion than the healthy group. In addition, the patient group had higher co-contraction activities between flexors and extensors. From the accelerator pedal release to brake contact, the patient group had slower angular velocities of hip adduction, internal rotation, ankle dorsiflexion, internal return, and internal rotation than the healthy group. Conclusions Patients with hemiplegia exhibited poor control of pedal switching using their unaffected side throughout the pedal-switching task. These results indicate that the safety related to car-pedal control should be carefully evaluated while deciding whether a patient can resume driving a car after a stroke.

Poster (Technology Innovation) ID 1984794

Background Cervical spinal cord injury (SCI) can cause significant impairment and disability with an impact on individuals’ quality of life and independence. Surface electromyography (SEMG) is a sensitive and non-invasive technique to measure muscle activity and has demonstrated great potential in capturing the impact from SCI. The mechanisms of SCI damage on SEMG signal characteristics are multi-faceted and difficult to study in vivo. Objective Use validated computational models to characterize changes in SEMG signal after SCI and identify SEMG features that are sensitive and specific to the impact from different aspects of SCI. Method Starting from existing computational models for motor neuron pool organization and for motor unit action potential generation for healthy neuromuscular systems, we set up scenarios to model alterations in upper motor neurons, lower motor neurons, and the number of muscle fibers within each motor unit after SCI. After simulating SEMG signals from each scenario, we extracted time and frequency domain features and investigated the impact of SCI disruptions on SEMG features using the Pearson correlation between a feature and the extent of a given disruption. Findings Commonly used amplitude-based SEMG features cannot differentiate between injury scenarios. A broader set of features provides greater specificity to the type of damage present. Conclusion We demonstrated a novel approach to mechanistically relate SEMG features to different types of neuromuscular alterations after SCI. This work contributes to a deeper understanding and exploitation of SEMG in clinical applications, which will ultimately improve patient outcomes after SCI.

Textile smart sensors based on a biomechanical and multi-layer perceptron hybrid method

Resistance training is becoming increasingly important and widespread. Decomposition of the muscle loads applied is important for injury prevention and determining the load on the targeted muscles. In this study, a flexible textile PET (polyethylene terephthalate)/SP(Spandex) SWCNT (Single-walled carbon nanotube) stretch sensor was fabricated and attached at four locations: the elbow, brachioradialis/flexor carpi radialis, biceps brachii, and triceps brachii. The stretch sensors attached to the elbow can measure the angle of elbow flexion without an IMU 9-axis sensor using quadratic fitting. A Multi-Layer Perceptron (MLP) was used to decompose the muscle volume expansions of the 3muscle by angle. The model provided a good fit for all three muscles, with R-squared values ranging from Test set 0.98725 to 0.99815. Through one input and three ouput fitting, the muscle volume expansion quantities during the bicep barbell curl were decomposed and compared with data. The results showed that the brachioradialis/flexor carpi radialis muscle maintained 13% of the arm muscle volume up to 60°, then increased to 44% at 100°. The biceps brachii muscle steadily increased to 70% from 0° up to 60°, and then maintained 40% at 100° due to the volume increase of other muscles. The triceps brachii muscle maintained 9% of the arm muscle volume up to 90°, then increased to 20% at 100°. This study shows that muscle volume expansion can be easily measured with a non-body contact wearable device, unlike many existing contact methods for measuring muscle activity like EMG (electro-myography), etc. This study provides a novel approach for easily measuring muscle volume expansion and decomposition in wearable devices, which can indirectly indicate injury prevention and muscle loading in target areas through balance optimization among local muscles.

Biomechanical changes, acceptance, and usability of a passive shoulder exoskeleton in manual material handling. A field study

Occupational exoskeletons contribute to diminish the biomechanical load during manual work. However, familiarization to the use of exoskeletons is rarely considered, which may lead to failure of acceptance and implementation. In this study, ten logistic workers underwent a 5-week progressive familiarization to a passive shoulder exoskeleton, while ten workers acted as controls. Tests pre and post the familiarization applied measurements of muscle activity and kinematics of back, neck, and shoulder, perceived effort, and usability-ratings of the exoskeleton. Exoskeleton use resulted in lower muscle activity of anterior deltoid (13–39%) and upper trapezius (16–60%) and reduced perceived effort. Additionally, it induced an offset in shoulder flexion and abduction during resting position (8–10°). No conclusions on familiarization could be drawn due to low adherence to the protocol. However, the emotions of the workers towards using the exoskeleton decreased making it questionable whether the shoulder exoskeleton is suitable for use in the logistics sector.

A comparative analysis of global optimization algorithms for surface electromyographic signal onset detection

Surface Electromyography (sEMG) is a technique for measuring muscle activity by recording electrical signals from the surface of the body. It is widely used in fields such as medical diagnosis, human–computer interaction, and sports injury rehabilitation. The detection of the onset and offset of muscle activation is a longstanding challenge in sEMG analysis. This study pioneers the implementation, configuration, and evaluation of Particle Swarm Optimization (PSO) against other optimization algorithms for sEMG signal detection, including Genetic algorithms (GA), Simulated Annealing (SA), Ant Colony Optimization (ACO), and Tabu Search (TS). The results show that the PSO algorithm achieves the highest median accuracy and F1-Score and is the fastest among the selected algorithms but has lower stability compared to Genetic algorithms and Ant colony optimization. The design and value of the cost function had a significant impact on the results, with optimal results obtained when the cost value was between 0.1203 and 0.1384. The use of these algorithms improved detection efficiency and reduced the need for manual parameter adjustment. To the best of our knowledge, no published studies have utilized Simulated Annealing, Ant colony optimization, and Tabu search meta-heuristic algorithms to detect sEMG signal onsets.

A Multi-Day Wearable Surface EMG E-Tattoo for Fatigue Monitoring.

Surface electromyography (sEMG) is a commonly used technique for the non-invasive measurement of muscle activity. However, the traditional electrodes used for sEMG often have limitations regarding their long-term wearability. This study explored the feasibility of a wearable platform using a tattoo-like epidermal electrode (e-tattoo) for multi-day sEMG monitoring. Our sEMG e-tattoo provided stable and reliable sEMG signals over three days of application comparable to conventional gel electrodes. In addition, the e-tattoo has great resistance to motion artifacts and, therefore, maintains a high signal-to-noise ratio (SNR) and signal-to-motion ratio (SMR) during dynamic activities such as cycling. This robust wearable platform opens up new avenues for developing future wearable sEMG devices and advancing dynamic muscle fatigue research.Clinical relevance- The proposed wearable sEMG system can provide continuous and non-invasive monitoring of muscle activity, providing insights for improving rehabilitation and EMG-based prosthesis development for patients.

Correlations between Ratings and Technical Measurements in Hand-Intensive Work.

An accurate rating of hand activity and force is essential in risk assessment and for the effective prevention of work-related musculoskeletal disorders. However, it is unclear whether the subjective ratings of workers and observers correlate to corresponding objective technical measures of exposure. Fifty-nine workers were video recorded while performing a hand-intensive work task at their workplace. Self-ratings of hand activity level (HAL) and force (Borg CR10) using the Hand Activity Threshold Limit Value® were assessed. Four ergonomist observers, in two pairs, also rated the hand activity and force level for each worker from video recordings. Wrist angular velocity was measured using inertial movement units. Muscle activity in the forearm muscles flexor carpi radialis (FCR) and extensor carpi radialis (ECR) was measured with electromyography root mean square values (RMS) and normalized to maximal voluntary electrical activation (MVE). Kendall's tau-b correlations were statistically significant between self-rated hand activity and wrist angular velocity at the 10th, 50th, and 90th percentiles (0.26, 0.31, and 0.23) and for the ratings of observers (0.32, 0.41, and 0.34). Significant correlations for force measures were found only for observer-ratings in five of eight measures (FCR 50th percentile 0.29, time > 10%MVE 0.43, time > 30%MVE 0.44, time < 5% -0.47) and ECR (time > 30%MVE 0.26). The higher magnitude of correlation for observer-ratings suggests that they may be preferred to the self-ratings of workers. When possible, objective technical measures of wrist angular velocity and muscle activity should be preferred to subjective ratings when assessing risks of work-related musculoskeletal disorders.

Surface Electromyographic Activity of the Masseter Muscle During Regular and Effortful Saliva Swallows: A Preliminary Study.

Biofeedback is a critical component in motor learning of new, complex behaviors such as modifications to swallowing. Surface electromyography (sEMG) is a commonly employed biofeedback tool in swallowing management to assess muscle activity patterns, determine amplitude and duration of swallowing, and train swallowing strategies such as the effortful swallow (EFS) maneuver. The EFS can potentially change multiple physiological components of the swallowing process such as pressure generation and movement of biomechanical structures. The purposes of this study were to determine whether the masseter muscle could differentiate a normal swallow (NS) from an EFS and whether there was a relationship between perceived muscle effort used to swallow and objective measures of muscle activity. Twenty healthy young adults participated in this study. Masseter sEMG peak amplitude and duration were measured across five regular saliva swallows and five effortful saliva swallows. Additionally, participants rated their perceived swallowing effort using a visual analog scale (VAS). Two swallowing conditions, NSs and EFSs were compared with hierarchical models, and repeated measures correlation was used to determine the relationships between the VAS and sEMG peak amplitude. Participants produced swallows with greater masseter sEMG peak amplitude and duration during the EFS. Moreover, a positive correlation was identified between perceived swallowing effort and masseter sEMG peak amplitude. These findings support the potential use of the masseter muscle to differentiate NSs from EFSs and implement the VAS during therapy for tracking patients' performance, particularly in settings with limited access to sEMG.

Unveiling the Correlations between Clinical Assessment of Spasticity and Muscle Strength and Neurophysiological Testing of Muscle Activity in Incomplete Spinal Cord Injury Patients: The Importance of a Comprehensive Evaluation

Spasticity and muscle weakness are prevalent symptoms of incomplete spinal cord injury (iSCI) and can significantly impact patients’ quality of life. Clinical spasticity and muscle strength assessments are often used to monitor iSCI patients’ progress and plan rehabilitation interventions. However, these assessment methods are subjective, may have limited accuracy, and may not provide a detailed understanding of the underlying neurophysiological changes that occur following spinal trauma. In this study, we aimed to explore correlations between standard clinical assessments of spasticity and muscle strength and objective, non-invasive neurophysiological measures of muscle activity using surface electromyography (sEMG) in iSCI patients up to 2 months after injury. We evaluated 85 iSCI patients (ASIA C = 24, and D = 61) 1.3 ± 0.3 months after C3-L1 spinal injury and 80 healthy volunteers (for comparison), using standard clinical assessment tools such as the Modified Ashworth Scale (MAS) and the Lovett Scale (Lovett), and neurophysiological tests, including surface electromyography at rest (rsEMG) and during the attempt of maximal contraction (mcsEMG) performed in chosen key muscles for the trunk (rectus abdominis), upper (abductor pollicis brevis), and lower extremities (rectus femoris and extensor digitorum brevis). We analysed pain in Visual Analog Scale (VAS) and also performed electroneurography to evaluate the peripheral motor impulse transmission. We confirmed a similar level of pain and moderate advancement of axonal injury type in all patients, which, therefore, had no significant effect on the differences in the assessment of patients’ muscle activity. Considering evaluation of the iSCI patients in the early post-traumatic stage, depending on the level of the injury, the highest MAS and rsEMG values and the lowest Lovett and mcsEMG scores were found in C3–C5 iSCI patients in most of the key muscles. Patients with Th7–L1 injuries represented moderate MAS and rsEMG results, while the muscle strength and motor units’ activity were the worst in the extensor digitorum brevis muscle. Patients with Th3–Th6 incomplete injuries generally presented a moderate level of muscle pathology compared to the above groups. Considering results in all patients, we found strong positive correlations between MAS and rsEMG (rε = 0.752, p = 0.009), and Lovett and mcsEMG (rs = 0.602, p = 0.008) results, and negative correlations between rsEMG and mcsEMG scores (rs = −0.504, p = 0.008) and MAS and Lovett (rs = −0.502, p = 0.03). The changes in muscle motor units’ properties, recorded in rsEMG and mcsEMG, although they follow a similar pattern, are, however, different depending on the level of injury in an early post-traumatic stage of iSCI patients. The established correlations between clinical evaluations and neurophysiological assessments, as well as electromyography at rest and during the attempt of maximal contraction, depict a fundamental phenomenon that should be considered during the initial stages of formulating rehabilitation strategies in applied medicine. The value of neurophysiological sEMG testing seems to be superior to the standard clinical assessment in evaluating spasticity and muscle strength decrease as pathological symptoms found in iSCI patients. Neurophysiological testing, including sEMG, offers a more comprehensive and precise characterisation of muscle activity, thereby enabling the detection of subclinical changes that may otherwise go unnoticed.

A Correction Method for Muscle Stiffness Sensors to Measure Transversus Abdominis Activity

The transversus abdominis muscle is important for various human functions, including the prevention of back pain and the use of muscle activity values as an indicator for the treatment of urinary incontinence. Measuring muscle activity is an effective means of evaluating whether correct training has been performed. The transversus abdominis muscle stiffness sensor developed in a previous study used a method in which a belt with a sensor attached was wrapped around the lower back, which made measurement simple but also caused problems owing to the influence of phenomena other than muscle activity on the measurement data. Therefore, we propose a novel correction method to calculate the muscle activity of this sensor accurately, which can be used for simple measurements. We propose a formula to compensate for effects other than muscle activity based on a model equation that includes contact conditions and belt tension, which affect the muscle stiffness sensor value. We evaluated the validity of the correction equation from simulations and the change in similarity owing to the correction by simultaneously measuring the muscle action potentials and muscle stiffness sensor values during breathing movements with muscle activity. The proposed correction method improved the muscle stiffness data during respiration and contraction. It is possible to improve the measurement accuracy by improving the calibration method and hardware.

A Stepper Motor-Powered Lower Limb Exoskeleton with Multiple Assistance Functions for Daily Use by the Elderly

With the increase in the aging population, the demand for healthcare devices has increased. Among the aging population, many experience joint pain, muscle weakness, or poor balance. Without external help, such persons may have difficulty walking, fall easily, or experience poor quality of life. To provide this category of the population with the opportunity to exercise and walk safely and take care of themselves in daily activities, a stepper motor-powered walking assistive device is proposed and built. The device enables users with different heights to walk in suitable gaits; assists users to stand up, sit down, and step up or down stairs; automatically detects user’s intention using pressure sensors and potentiometers; and can be used outdoors for long periods. In this study, the effectiveness of the device is verified using muscle-activity measurements.

Influence of Robot-Assisted Gait Training on Lower-Limb Muscle Activity in Patients With Stroke: Comparison With Conventional Gait Training.

To measure muscle activity before and after robot-assisted gait training (RAGT) in patients with stroke and examine the differences in muscle activity changes compared with conventional gait training (CGT). Thirty patients with stroke (RAGT group, n=17; CGT group, n=13) participated in the study. All patients underwent RAGT using a footpad locomotion interface or CGT for 20 minutes for a total of 20 sessions. Outcome measures were lower-limb muscle activity and gait speed. Measurements were performed before the start of the intervention and after the end of the 4-week intervention. The RAGT group showed increased muscle activity in the gastrocnemius, whereas the CGT group showed high muscle activity in the rectus femoris. In the terminal stance of the gait cycle, the gastrocnemius, the increase in muscle activity was significantly higher in the RAGT group than in the CGT group. The results suggest that RAGT with end-effector type is more effective than CGT to increase the gastrocnemius muscle activity.

Neuromechanical Properties of the Vastus Medialis and Vastus Lateralis in Adolescents With Patellofemoral Pain

Background: An alteration in the force distribution among quadriceps heads is one possible underlying mechanism of patellofemoral pain. However, this hypothesis cannot be directly tested as there are currently no noninvasive experimental techniques to measure individual muscle force or torque in vivo in humans. In this study, the authors considered a combination of biomechanical and muscle activation measures, which enabled us to estimate the mechanical impact of the vastus medialis (VM) and vastus lateralis (VL) on the patella. Purpose/Hypothesis: The purpose of this study was to determine whether the relative index of torque distribution for the VM and VL differs between adolescents with and without patellofemoral pain. It was hypothesized that, relative to the VL, the VM would contribute less to knee extension torque in adolescents with patellofemoral pain compared with controls. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Twenty adolescents with patellofemoral pain and 20 matched control participants were included (38 female; age, 15.3 ± 1.8 years; weight, 58 ± 13 kg; height, 164 ± 8 cm). Muscle volumes and resting moment arms were quantified from magnetic resonance images, and fascicle lengths were obtained from panoramic B-mode ultrasonography. Muscle activation was estimated using surface electromyography during submaximal isometric tasks (wall-squat and seated tasks). Muscle torque was estimated as the product of muscle physiological cross-sectional area (ie, muscle volume/fascicle length), muscle activation (normalized to maximal activation), and moment arm. Results: Across tasks and force levels, the relative contribution of the VM to the overall medial and lateral vastii torque was 31.0% ± 8.6% for controls and 31.5 ± 7.6% for adolescents with patellofemoral pain (group effect, P &gt; .34). Conclusion: For the tasks and positions investigated in this study, the authors found no evidence of lower VM torque generation (relative to the VL) in adolescents with patellofemoral pain compared with controls.

Surgical stress: the muscle and cognitive demands of robotic and laparoscopic surgery.

Surgeons are among the most at-risk professionals for work-related musculoskeletal decline and experience high mental demands. This study examined the electromyographic (EMG) and electroencephalographic (EEG) activities of surgeons during surgery. Surgeons who performed live laparoscopic (LS) and robotic (RS) surgeries underwent EMG and EEG measurements. Wireless EMG was used to measure muscle activation in four muscle groups bilaterally (biceps brachii, deltoid, upper trapezius, and latissimus dorsi), and an 8-channel wireless EEG device was used to measure cognitive demand. EMG and EEG recordings were completed simultaneously during (i) noncritical bowel dissection, (ii) critical vessel dissection, and (iii) dissection after vessel control. Robust ANOVA was used to compare the %MVCRMS and alpha power between LS and RS. Thirteen male surgeons performed 26 laparoscopic surgeries (LS) and 28 robotic surgeries (RS). Muscle activation was significantly higher in the right deltoid (p = 0.006), upper trapezius (left, p = 0.041; right, p = 0.032), and latissimus dorsi (left, p = 0.003; right, p = 0.014) muscles in the LS group. There was greater muscle activation in the right biceps than in the left biceps in both surgical modalities (both p = 0.0001). There was a significant effect of the time of surgery on the EEG activity (p <0.0001). A significantly greater cognitive demand was observed in the RS than in the LS with alpha, beta, theta, delta, and gamma (p = 0.002 - p <0.0001). These data suggest greater muscle demands in laparoscopic surgery, but greater cognitive demands in robotic surgery.

Micromagnetic stimulation (µMS) dose-response of the rat sciatic nerve

Objective. The objective of this study was to investigate the effects of micromagnetic stimuli strength and frequency from the Magnetic Pen (MagPen) on the rat right sciatic nerve. The nerve’s response was measured by recording muscle activity and movement of the right hind limb. Approach. The MagPen was custom-built to be stably held over the sciatic nerve. Rat leg muscle twitches were captured on video, and movements were extracted using image processing algorithms. EMG recordings were also used to measure muscle activity. Main results. The MagPen prototype, when driven by an alternating current, generates a time-varying magnetic field, which, according to Faraday’s law of electromagnetic induction, induces an electric field for neuromodulation. The orientation-dependent spatial contour maps of the induced electric field from the MagPen prototype have been numerically simulated. Furthermore, in this in vivo work on µMS, a dose-response relationship has been reported by experimentally studying how varying the amplitude (Range: 25 mV p-p through 6 V p-p) and frequency (range: 100 Hz through 5 kHz) of the MagPen stimuli alters hind limb movement. The primary highlight of this dose-response relationship (repeated over n rats, where n = 7) is that for a µMS stimuli of higher frequency, significantly smaller amplitudes can trigger hind limb muscle twitch. This frequency-dependent activation can be justified by Faraday’s Law, which states that the magnitude of the induced electric field is directly proportional to the frequency. Significance. This work reports that µMS can successfully activate the sciatic nerve in a dose-dependent manner. The impact of this dose-response curve addresses the controversy in this research community about whether the stimulation from these μcoils arise from a thermal effect or micromagnetic stimulation. MagPen probes do not have a direct electrochemical interface with tissue and therefore do not experience electrode degradation, biofouling, and irreversible redox reactions like traditional direct contact electrodes. Magnetic fields from the μcoils create more precise activation than electrodes because they apply more focused and localized stimulation. Finally, unique features of µMS, such as the orientation dependence, directionality, and spatial specificity, have been discussed.