Forearm Muscle Activity During Motorsport: A Case Study

INTRODUCTION: Surgeons with smaller hands report increased difficulty using laparoscopic instruments and have been shown to experience increased strain and muscle fatigue. Percent maximum voluntary contraction (%MVC) provides a normalized assessment of muscle exertion that can be compared between individuals. A higher %MVC during tasks can lead to more rapid muscle fatigue and risk of injury. This study evaluates the %MVC of forearm muscles while manipulating laparoscopic energy devices and compares the differences in muscle activity between surgeons with different hand sizes. OBJECTIVE: The objective of this study was to quantify the level of muscle activation required by different hand sizes while using common laparoscopic energy devices, with the goal of providing data for improved, inclusive design of widely used instruments. We hypothesized that smaller-handed surgeons would require higher levels of %MVC when using common laparoscopic instruments when compared to larger-handed surgeons. METHODS: This is a nonexperimental correlational study. Demographic information, glove size, and grip strength were collected. Four laparoscopic advanced energy devices were assessed: Harmonic, Enseal, and two variations of Ligasure. Surface electromyography (sEMG) electrodes were applied to the flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor carpi radialis (ECR), and extensor pollicis longus (EPL) of the dominant hand. MVC was performed on each muscle. Participants performed opening, closing, and activation cycles for each instrument. EMG output was filtered and normalized to provide %MVC. A cutoff of 15%MVC has historically been used as the level below which prolonged muscle activation could be performed without concern for fatigue and was thus selected as a cutoff point for comparison between groups. RESULTS: Twenty-four individuals participated. Fourteen were female. Glove sizes ranged from 5.5 to 8.5, with 6.5 being most common (n=8). Glove size analysis was split between small (≤6.5) and large (>6.5). Mean %MVC in small-handed participants for FDS, ECU, ECR, and EPL were 21.5, 16.0, 15.75, and 10.73, respectively. In large-handed participants, the same values were 11.42, 14.09, 8.56, and 6.52. When adjusting for training level and instrument used, FDS and ECR displayed significantly higher levels of activation in the small-handed group (P=0.0012 and 0.013, respectively) when evaluated across all instruments. The FDS had the largest difference between hand sizes at 10.8% (95% CI (4.8, 16.8)). Across the 16 combinations of muscle and instrument, 10 showed a mean %MVC greater than 15% for small hands, with only 1 combination over 15% for large hands. In the instruments studied, there does not appear to be an optimal instrument for smaller-handed surgeons in the context of low overall %MVC requirements. CONCLUSIONS: Smaller-handed surgeons demonstrate increased forearm exertion when using laparoscopic instruments. This may increase their risk of injury in comparison to surgeons with larger hands. Future research should seek to further characterize the risk posed to small-handed surgeons. Industry partners should consider variations in surgeon hand size when developing instruments to prevent disproportionate risk of injury to surgeons with smaller hands.Figure 1Table 1Table 2

Evaluation of the Effect of Hand Size on Forearm Muscle Activity While Using Laparoscopic Instruments.

This research aimed to explore the feasibility of using forearm electromyography (EMG) data for identifying different hand gestures.The study involved 10 participants (7 males and 3 females) who performed eight different hand gestures while their flexor digitorum superficialis (FDS) and extensor digitorum communis (EDC) muscles were recorded.The recorded data was split into 80% for training and 20% for testing.The study compared the effectiveness of Deep Neural Network and Random Forest algorithms based on five different levels of moving window sizes (200, 400, 600, 800, and 1000 milliseconds).A wavelet approach was used to reconstruct the data and remove noise that does not represent the EMG signals accurately.Eighteen features were then extracted from the time and frequency domains of the analysis to characterize the complex signals.The study found that larger moving window sizes had higher accuracy rates than small moving window sizes due to the larger temporal resolution it provides.The Deep Neural Network showed a higher performance with a 1000millisecond stream, achieving an accuracy rate of 97.13%, while the Random Forest algorithm achieved the highest accuracy rate of 96.65% with the same stream duration.In conclusion, the study found that a Deep Neural Network based on a 1000millisecond stream was the most accurate, with an accuracy rate of 97.13%, while a Random Forest based on a 200millisecond stream was the most efficient, with an accuracy rate of 84.77%.Future research could expand the sample size, include more hand gestures, and use different feature extraction methods and modeling algorithms to further improve the accuracy and efficiency of the system.

An Anomaly of Flexor Muscles of the Fifth (Little) Finger of the Hand: An Anatomical Case Report

Individuals with lateral epicondyle tendinopathy (LET) commonly experience gripping deficits, which are marked by pain and altered motor control of the forearm extensors and flexors. Although delayed activation of the anconeus muscle during rapid wrist extension has been observed in LET, its role during gripping is not well understood. This study aimed to investigate anconeus activation and its relation to forearm muscle activity during gripping in individuals with LET. Eleven participants with LET and 11 healthy, age-, sex-, and limb-matched controls performed steady-state isometric gripping at 15% and 30% of their maximum voluntary contraction (MVC). Surface electromyography was recorded from anconeus and 6 forearm muscles. Standard clinical assessments for LET were conducted to evaluate the severity of the condition. Participants with LET exhibited increased relative activation of the anconeus compared with the forearm flexors, but not with the extensors, during both 15% and 30% MVC gripping. In addition, the LET group demonstrated an increased coactivation ratio between anconeus and extensor carpi radialis brevis, as well as the flexor digitorum superficialis, during 15% MVC. At 30% MVC, this increased coactivation was observed between anconeus and all 3 flexors (flexor digitorum superficialis, flexor carpi radialis, and flexor carpi ulnaris). Lower anconeus activation was associated with greater LET-related disability, whereas higher anconeus activation was associated with increased anconeus tenderness. This study presents novel evidence of an adaptive motor pattern in LET, characterized by increased relative activation and coactivation of the anconeus muscle depending on grip force. Signs of maladaptive motor patterns emerge when grip force becomes painful. These findings enhance our understanding of anconeus dysfunction in LET and the gripping deficits that accompany it, offering new insights into potential management strategies for this condition.

Assessment of skeletal muscle function is an active research area in rehabilitation and sports medicine. An effective assessment methodology can be used to evaluate muscle recovery or response to treatments or interventions, and for early diagnosis of skeletal muscle diseases when combined with corresponding biomarkers. The main objective of this study is to develop an engineering technique for detecting muscle activation by combined ultrasound imaging and high-density electromyography (HDEMG). An ultrasound speckle tracking algorithm was employed to measure the impulsive kinetic energy released by muscle contraction while the processed HDEMG depicted the spatial-temporal electrical response of the activated muscle. The location and time course of the muscle activation can then be quantified by detecting the precise onset of the mechanical and electrical signals from ultrasound imaging and HDEMG, respectively. To demonstrate the conceptual feasibility, experiments were performed, with synchronized dual-probe ultrasound imaging and HDEMG recorded, on the forearm of one human participant without an injury or disability. To test detections of different activation patterns, single electrical pulses were sent to the flexor carpi radialis (FCR), flexor digitorum superficialis (FDS) and the median nerve, respectively, to intentionally create cases where FCR and FDS can contract individually or simultaneously.

Cerebral Palsy (CP) is a group of permanent, but not unchanging, disorders of movement and/or posture and motor function, which are due to a non-progressive interference, lesion, or abnormality of the developing/immature brain. One clinical presentation is muscle spasticity, which leads to a significant impact on the individual's functionality and quality of life. Spasticity treatment is multidisciplinary and includes pharmacological and physical intervention; intrathecal baclofen shows a positive effect in severe spasticity and suboptimal response to oral drugs, while local injection of Botulinum toxin type A (BTXA) improves muscle tone, motion and pain. The aim of this study was to evaluate the efficacy of the combined intrathecal baclofen infusion (ITB) - botulinum toxin treatment in the management of spasticity in CP. 8 patients with spastic tetraparesis were enrolled. All patients were treated with intrathecal Baclofen; in lower limbs, no spastic symptoms appeared, while marked spasticity was noted in upper limbs. We injected the right and left Biceps Brachial (BB) and Flexor Digitorum Superficialis (FDS) muscles with botulinum toxin type A. All patients underwent Myometric measurement, Ashworth Scale, Numerical Rating Scale, and Visual Analogic Scale evaluation before infiltration (T0), 30 days after injection (T1), 60 days after injection (T2), and 90 days after treatment (T3). All data demonstrated an improvement in spasticity, pain, quality of life, and self-care during the study, with p < 0.05. No side effects appeared. This study demonstrated the efficacy and safety of intrathecal baclofen infusion and botulinum toxin combined treatment in the management of spasticity, pain, quality of life, and selfcare in CP patients.

We assess the corticomuscular coherence (CMC) of the contralateral primary motor cortex and the hand muscles during a finger force-tracking task and explore whether the pattern of finger coordination has an impact on the CMC level. Six healthy subjects (three men and three women) were recruited to conduct the force-tracking tasks comprising two finger patterns, i.e., natural combination of index and middle fingers and unnatural combination of index and middle fingers (i.e., simultaneously producing equal force strength in index and middle finger). During the conducting of the tasks with right index and middle finger, MEG and sEMG signals were recorded from left primary motor cortex (M1) and right flexor digitorum superficialis (FDS), respectively; the contralateral CMC was calculated to assess the neuromuscular interaction. Finger force-tracking tasks of Common-IM only induce beta-band CMC, whereas Uncommon-IM tasks produce CMC in both beta and low-gamma band. Compared to the force-tracking tasks of Common-IM, the Uncommon-IM task is associated with the most intensive contralateral CMC. Our study demonstrated that the pattern of finger coordination had significant impact on the CMC between the contralateral M1 and hand muscles, and more corticomuscular interaction was necessary for unnaturally coordinated finger activities to regulate the fixed neural drive of hand muscles.

This study examined total forearm muscle activities in five different hand postures of pinching with two fingers (2P), three fingers (3P), four fingers (4P), five fingers (5P), and power grip (5G). Male students participated in the experiment. EMG signals were recorded by using nine dual surface electrodes to record the activities of forearm muscles of flexor carpi radialis (FCR), flexor carpi ulnaris (FCU), extensor carpi radialis (ECR), extensor carpi ulnaris (ECU), flexor digitorum superficialis (FDS), flexor digitorum profundus (FDP), extensor digitorum (ED), flexor pollicis longus (FPL), and extensor pollicis longus (EPL). The nine muscles were combined to estimate total muscle activities by the summation method of the EMG index. Analysis of variance showed that the total muscle activities were significant for the hand postures. The muscle activities for 2P and 3P hand postures were about 20 % higher than those for the 5P and 5G postures. Overall, the summation value of % MVC decreased as the number of fingers used increased.

Increasing level of neuromusculoskeletal model personalisation to investigate joint contact forces in cerebral palsy: A twin case study

Objectives:To investigate forearm muscle activity in individuals with lateral epicondylalgia (LE) when gripping at different wrist postures, and investigate the association between muscle activity and clinical characteristics of LE.Methods:Eleven LE and 11 healthy participants performed isometric handgrips at 15% and 30% of maximum grip force (MVC). Gripping was performed in wrist extension, wrist flexion, and wrist neutral. Surface electromyography was collected from six forearm muscles. Standard clinical and tendon structural measures for LE were obtained.Results:LE group had reduced magnitude of extensor carpi radialis brevis (ECRB) with increased contribution of extensor carpi ulnaris (ECU) during 15% MVC. However, during 30% MVC the LE group had reduced flexor carpi radialis and flexor digitorum superficialis activity, which was coupled with increased contribution from extensor digitorum communis (EDC) and ECU. Although ECRB and ECU activity differed in wrist flexion compared to other wrist postures for controls, different wrist posture had no effect on forearm muscle activation in LE. Pain and disability, and tendon thickness had significant associations with EDC and ECRB activity respectively in LE.Conclusion:Individuals with LE use different neuromuscular strategies when gripping with different wrist postures which appears to be dependent on the level of grip force.

Pexa, BS, Johnston, CD, Elder, EE, Ford, KR, Patterson, MQ, and Myers, JB. Pool-based surfboard elicits activation of posterior shoulder muscles during a surfing stroke. J Strength Cond Res 38(7): 1300-1304, 2024-Surfboard paddling may activate posterior shoulder muscles, which are critical to baseball pitchers' injury risk and performance. The purpose of this study was to measure posterior shoulder muscle activation during different phases of the surf stroke (propulsion vs. recovery) on a pool-based surfboard. Twenty healthy active adult subjects completed a familiarization and testing session with the pool-based surfboard. During the testing session, electromyography (EMG) sensors were placed on 6 posterior shoulder muscles: latissimus dorsi, infraspinatus, posterior deltoid, upper trapezius, middle trapezius, and lower trapezius. Subjects completed 4 laps in a pool at 3 separate resistances (low, moderate, and heavy) in a randomized order. The peak EMG signal during each phase (propulsion and recovery) was recorded. A 2-way within subject ANOVA (resistance-by-phase) with post hoc Bonferroni's corrections was used to identify differences in EMG activation. There was a significant main effect of phase for the latissimus dorsi (F = 91.3, p < 0.001), upper trapezius (F = 36.5, p < 0.001), middle trapezius (F = 33.8, p < 0.001), and lower trapezius (F = 21.6, p < 0.001). The latissimus dorsi demonstrated higher activation during the propulsion phase (p < 0.001), and all trapezius muscles demonstrated higher activation during the recovery phase (p < 0.001). There was a significant main effect of resistance for the posterior deltoid (F = 3.4, p = 0.043), with higher muscle activation in the low resistance trials compared with the heavy resistance trials (p = 0.036). Recreationally active individuals demonstrate activation of the posterior shoulder when using a pool-based surfboard. This pool-based surfboard may be beneficial to activate the posterior musculature and may be more accessible than standard surfing to baseball athletes.

The relationship between training-related improvement in standing balance of hemiparetic patients and changes in the EMG recordings of the medial gastrocnemius (MG) and tibialis anterior (TA) muscles was investigated. Ten hemiparetic patients in the treatment group and six in the control group comprised the subjects. Data from seventeen healthy adults served as normal reference points. The training and testing apparatus was a platform that moved back and forth in a sinusoidal profile. The highest amplitude of movement tolerated by the subject without hand support, called the maximal movement amplitude (MMA), was determined for each patient upon admission and after two, four, and six weeks. At these times, while the patient was moved at his MMA, EMG recordings were taken from the TA and MG muscles. Healthy subjects underwent the same evaluation once. Patients belonging to the treatment group were trained on the platform during fifteen sessions in the two-week intervals between test sessions. Results indicated an increase in the MMA of the treatment group that significantly exceeded values achieved by the control patients. However, this difference was not accompanied by improvement (approximation to normal values) in the EMG variables of the treated patients; nor was there a significant difference between their EMG data and those of the control patients. Key Words: Hemiplegia—Stance— Balance.

The aim of this study was to develop an ambulatory bruxism recording system capable of sleep-stage analysis. A portable EMG system was used to record masseter muscle activity. An EMG sensor was attached onto the masseter muscle belly at either side. EMG data were stored on a notebook type personal computer. A sound level meter was used to assess the sound level of bruxism. Sound level (dB) readings were taken every second and recorded on the same computer. A prototype of sleep sensor, a wristwatch-style biological signal sensor-recorder device, recorded and stored pulse wave, acceleration and temperature on a memory card. All stored data were transferred to a personal computer and analyzed. The whole system was transportable within a protective case and weighed approximately 5kg. Raw EMG signals were processed to derive integrated EMG data. TOSHIBA Sleep Analysis Program classified sleep-stages as awake, shallow sleep, deep sleep and REM based on the activity of the autonomic nervous system that was estimated from the fluctuations of pulse intervals. An EMG, sound level and sleep-stage analysis program was developed to analyze all data simultaneously. Using this program, the masseter muscle activity, sound level and sleep-stage could be quantified and correlated. We developed an ambulatory bruxism recording system that analyzes sleep-stage. We expect that this system will enable us to measure sleep bruxism activity in each sleep-stage on an electromyographical and auditory basis at the subject's home.

The present research work recalls a control-theoretic approach to the synchronization of a first-order master/slave oscillators pair on $\mathbb{R}^3$ and extends such technique to the case of curved Riemannian manifolds. As theoretical results, this paper proves the asymptotic convergence of the feedback controller and studies the entity of the 'control effort'. As a case study, the complete equations for the controller of a slave oscillator on the unit hypersphere $\mathbb{S}^{n-1}$ are laid out and are illustrated by numerical examples for $n = 3$ and $n = 10$, even in the hypothesis of noisy master-system state measurement.