Wrist Position Research Articles

Predicting Wrist Posture during Occupational Tasks Using Inertial Sensors and Convolutional Neural Networks.

Current methods for ergonomic assessment often use video-analysis to estimate wrist postures during occupational tasks. Wearable sensing and machine learning have the potential to automate this tedious task, and in doing so greatly extend the amount of data available to clinicians and researchers. A method of predicting wrist posture from inertial measurement units placed on the wrist and hand via a deep convolutional neural network has been developed. This study has quantified the accuracy and reliability of the postures predicted by this system relative to the gold standard of optoelectronic motion capture. Ten participants performed 3 different simulated occupational tasks on 2 occasions while wearing inertial measurement units on the hand and wrist. Data from the occupational task recordings were used to train a convolutional neural network classifier to estimate wrist posture in flexion/extension, and radial/ulnar deviation. The model was trained and tested in a leave-one-out cross validation format. Agreement between the proposed system and optoelectronic motion capture was 65% with κ = 0.41 in flexion/extension and 60% with κ = 0.48 in radial/ulnar deviation. The proposed system can predict wrist posture in flexion/extension and radial/ulnar deviation with accuracy and reliability congruent with published values for human estimators. This system can estimate wrist posture during occupational tasks in a small fraction of the time it takes a human to perform the same task. This offers opportunity to expand the capabilities of practitioners by eliminating the tedium of manual postural assessment.

A Randomized, Double-Blind Placebo Control Study on the Effect of a Blood Flow Restriction by an Inflatable Cuff Worn around the Arm on the Wrist Joint Position Sense in Healthy Recreational Athletes.

The number of blood flow restriction (BFR) training practitioners is rapidly increasing, so understanding the safety issues associated with limb occlusion is strongly needed. The present study determined the effect of BFR by an inflatable cuff worn around the arm on the wrist joint position sense (JPS) in healthy recreational athletes. In the prospective randomized, double-blind placebo control study, sixty healthy right-handed recreational athletes aged x = 22.93 ± 1.26 years were assigned to groups of equal size and gender rates: BFR, placebo, and control. The active wrist JPS was assessed in two separate sessions using an isokinetic dynamometer. The first assessment was performed with no cuffs. In the second session, a cuff with a standardized pressure was worn on the examined limb in the BFR group. In the placebo group, the cuff was uninflated. A between-session comparison in each group of collected angular errors expressed in degrees was carried out. The angular error in the BFR group was larger during the second measurement than the first one (p = 0.011-0.336). On the contrary, in the placebo (p = 0.241-0.948) and control (p = 0.093-0.904) groups, the error value in the second session was comparable or smaller. It was determined that BFR by an inflatable cuff around the arm impairs the wrist position sense. Hence, BFR training should be performed with caution.

Exoskeleton Design Using Kinematics Analysis for Upper Limb Rehabilitation in Post-Stroke Patients

Robotic technology in the last decade has developed to support the rehabilitation of post-stroke patients. The exoskeleton design model approach is carried out to simulate kinematics according to the needs of upper limb rehabilitation. The simulated design is identical to the structure of the human arm, so it requires planning and method according to the needs of human arm anatomy movements. The exoskeleton model must meet comfort and adjustment for medical rehabilitation, so it is essential to consider the kinematic analysis in its design. In this paper, we will analyze the kinematics of the exoskeleton and simulate flexion/extension and supination/pronation movements, with the targeted area being the forearm with the 3 Degrees of Freedom (DoF) mechanism consisting of two DoF. Kinematic simulations are carried out with the RoboAnalyzer software using predefined Denavit-Hartenberg parameters. The simulation results show that the end effector's initial position on the X axis is to coordinate 0 on the base 45o joint shoulder, then the rotational movement on the elbow is 1150 . In the wrist position, the action is supination and pronation because the joint is parallel to the elbow. Hence, the coordinates of the x and y-axis rotation changes follow elbow coordinates.

IoT Based Health Monitoring System for Physiological Investigation

The health monitoring system is emerged in the recent times since it is most desirable for checking physiological conditions. Internet of Things (IoT) based health care is one of the growing research which helps to monitor the physiological conditions in a repeated span of time. This technology is much obliged especially during epidemic conditions. Hence, present study focuses on development of distembot system which is used to measure temperature, pulse rate and respiratory rate of a person for a repeated span of time. It is identified that wrist position provides the accurate measurements of human body conditions. Hence in this paper, wrist watch is developed as distembot system. Initially, distembot system is designed and fabricated using Fused Deposition Modelling (FDM) technology. Then, temperature sensor and pulse sensor amped heart rate sensor are employed in the system to measure temperature, pulse rate and respiratory rate of a person. The distembot system is interfaced with respective sensors using ESP32 module. Network Time Protocol (NTP) is adopted to synchronize the clock over a network and OLED is interfaced with the system to display the measurements. The digital values of various measurements are extracted from the device using Wi-Fi module. The results suggested that proposed system is performing effectively to monitor the human health conditions in a repeated span of time.

BIOMECHANICAL EVALUATION OF PNEUMATIC SLEEVE ORTHOSIS FOR LOFSTRAND CRUTCHES.

Crutch walking, especially when using a swing-through gait pattern, is associated with high, repetitive joint forces, hyperextension/ulnar deviation of the wrist, and excessive palmar pressure that compresses the median nerve. To reduce these adverse effects, we designed a pneumatic sleeve orthosis that utilized a soft pneumatic actuator and secured to the crutch cuff for long-term Lofstrand crutch users. Eleven able-bodied young adult participants performed both swing-through and reciprocal crutch gait patterns with and without the custom orthosis for comparison. Wrist kinematics, crutch forces, and palmar pressures were analyzed. Significantly different wrist kinematics, crutch kinetics, and palmar pressure distribution were observed in swing-through gait trials with orthosis use (p<0.001, p=0.01, p=0.03, respectively). Reductions in peak and mean wrist extension (7%, 6%), wrist range of motion (23%), and peak and mean ulnar deviation (26%, 32%) indicate improved wrist posture. Significantly increased peak and mean crutch cuff forces suggest increased load sharing between the forearm and cuff. Reduced peak and mean palmar pressures (8%, 11%) and shifted peak palmar pressure location toward the adductor pollicis denote a redirection of pressure away from the median nerve. In reciprocal gait trials, non-significant but similar trends were observed in wrist kinematics and palmar pressure distribution, whereas a significant effect of load sharing was noticed (p=0.01). These results suggest that Lofstrand crutches modified with orthosis may improve wrist posture, reduce wrist and palmar load, redirect palmar pressure away from the median nerve, and thus may reduce or prevent the onset of wrist injuries.

Investigating Wrist Joint Position Sense and Hand Functions in Children With Polyarticular Juvenile Idiopathic Arthritis With Wrist Involvement.

Comparing the wrist joint position sense and hand functions between children with juvenile idiopathic arthritis (JIA) and healthy controls, and determining possible relationships between these parameters in children with JIA were the aims of this study. Twenty children with polyarticular JIA with wrist involvement (JIAWrist+), 20 children with other subtypes of JIA without wrist involvement (JIAWrist-), and 20 healthy controls were included. Wrist joint position sense was evaluated by measuring joint repositioning error. Hand functions were assessed by using the Purdue Pegboard test, hand grip strength, pinch strength, and Duruoz Hand Index. Joint position sense and hand functions were diminished in the JIAWrist+ group compared with healthy control group (P < .05). Few moderate relationships were detected between hand functions and wrist joint position sense (P < .05). Improving proprioceptive acuity by appropriate training methods may have a role in enhancing hand functions.

Wrist Proprioception in Adults with and without Subacute Stroke.

Proprioception is critical to motor control and functional status but has received limited study early after stroke. Patients admitted to an inpatient rehabilitation facility for stroke (n = 18, mean(±SD) 12.5 ± 6.6 days from stroke) and older healthy controls (n = 19) completed the Wrist Position Sense Test (WPST), a validated, quantitative measure of wrist proprioception, as well as motor and cognitive testing. Patients were serially tested when available (n = 12, mean 11 days between assessments). In controls, mean(±SD) WPST error was 9.7 ± 3.5° in the dominant wrist and 8.8 ± 3.8° in the nondominant wrist (p = 0.31). In patients with stroke, WPST error was 18.6 ± 9° in the more-affected wrist, with abnormal values present in 88.2%; and 11.5 ± 5.6° in the less-affected wrist, with abnormal values present in 72.2%. Error in the more-affected wrist was higher than in the less-affected wrist (p = 0.003) or in the dominant (p = 0.001) and nondominant (p &lt; 0.001) wrist of controls. Age and BBT performance correlated with dominant hand WPST error in controls. WPST error in either wrist after stroke was not related to age, BBT, MoCA, or Fugl-Meyer scores. WPST error did not significantly change in retested patients. Wrist proprioception deficits are common, bilateral, and persistent in subacute stroke and not explained by cognitive or motor deficits.

Dynamic Model Informed Human Motion Prediction Based on Unscented Kalman Filter

Human motion prediction is the foundation stone of human–robot collaboration in intelligent manufacturing. The nonlinear and stochastic nature of human motion has made it challenging to predict the motion accurately. Many recent deep-learning-based approaches, e.g., convolutional neural networks or recurrent neural networks (RNNs), have been applied to address this challenge. On the other hand, existing works tend to ignore the importance of human dynamics in motion prediction, especially the effect of muscle force on the motion. This article proposes a novel dynamic model informed motion prediction method. It utilizes an unscented Kalman filter (UKF) to predict the state of the future arm dynamic model such that the future motion of the human arm can be obtained. In particular, the arm dynamic model is developed based on Lagrangian mechanics and represented by differential equations. Embracing the future muscle force predicted by RNN into the differential equations, such a dynamic model is capable of explicitly establishing the intrinsic relation between the future muscle force and the corresponding future arm motion. UKF is leveraged to predict the future joint position and velocity of the human arm based on the dynamic model. Experiments on three motion datasets validate that the proposed prediction method, compared with the traditional RNN-based prediction using skeleton vectors, significantly improves the prediction accuracy regarding elbow and wrist positions.

Carpal tunnel volume distribution and morphology changes with flexion-extension and radial-ulnar deviation wrist postures.

Non-neutral wrist postures have been reported to cause decreased carpal tunnel volume (CTV) contributing to impingement of the median nerve and development of carpal tunnel syndrome. Recent analysis found CTV did not change with ±20° flexion-extension (FE), however, CTV decreased with ulnar deviation over the range of -5° to 15° radial-ulnar deviation (RUD). These findings suggest CTV may be too coarse of a measure to reflect the effects of slight non-neutral postures, or that volume is conserved and redistributed due to changes in tunnel morphology with posture. The objective of this study was to assess volume distribution along the length of the carpal tunnel and to quantify regional morphology changes with deviated wrist postures in both FE and RUD. Analysis was performed on a dataset of computed tomography scans collected on ten cadaveric specimens (5 male, 5 female, mean age = 80.7 ± 10.9 years) over a range of FE and RUD postures. The carpal tunnel of each scan was divided into four quartiles of equal length along the tunnel to quantify volume distribution. Volume within the carpal tunnel was seen to redistribute with both FE and RUD. Decreased volume in the distal aspect of the tunnel with flexion and proximal aspect of the tunnel with ulnar deviation may contribute to localized compression of the medial nerve. Measures of mean cross-sectional area, width and depth by quartile provided an indication of the morphology changes associated volume redistribution. Morphology analysis also revealed twisting between the proximal and distal aspects of the tunnel which increased with flexion and ulnar deviation and may further contribute to strain on the median nerve.

Upper Limb Kinematics of Handwriting among Children with and without Developmental Coordination Disorder.

Background: Children with developmental coordination disorder (DCD) often experience difficulties with handwriting legibility and speed. This study investigates the relationship between handwriting and upper limb kinematics to characterize movement patterns of children with DCD and typically developing (TD) children. Methods: 30 children with and without DCD matched for age, gender, and parent education were compared across handwriting abilities using a standardized handwriting assessment of both copied and dictated tasks (A-A Handwriting). The 3D motion capture system (Qualysis) was used to analyze upper limb kinematics and characterize movement patterns during handwriting and contrasted with written output. Results: Children with DCD wrote fewer legible letters in both copying and dictation. Children with DCD also showed poor automatization of key writing concepts. Atypical wrist postures were associated with reduced legibility for children with DCD (F (1,27) 4.71, p = 0.04, p-η2 = 0.15); whereas for TD children, better legibility was associated with greater variations in movement speed, particularly of the wrist (rho = −0.578, p < 0.05). Conclusion: Results reflect different movement parameters influencing handwriting in children with DCD. An improved understanding of the movement characteristics during handwriting of these children may assist intervention design.

Prevalence status and associated factors of wrist postural injury in the Chinese occupational population.

This study investigated the prevalence of wrist injuries in 15 industries and different types of work in China. Study on the associated factors of wrist injuries provides a scientific basis for prevention and treatment of wrist diseases in occupational workers. A cross-sectional study of musculoskeletal symptoms of related practitioners in 15 industries, including automobile manufacturing, was conducted to retrieve worker demographic information, working wrist posture, and pain conditions. Multivariable binary logistic regression analyses were performed to identify factors associated with work-related musculoskeletal disorders (WMSDs). The prevalence of wrist injuries among the study population was 13.2%. Toy manufacturing, animal husbandry, automobile manufacturing, shoe manufacturing, and biopharmaceutical manufacturing had the highest wrist injury rates at 29.1, 19.1, 14.9, 14.9, and 14.0%, respectively. Among the types of jobs, enamel workers (63.0%), butchers (43.6%), combers (32.5%), welders (31.3%), and scaffolders (26.5%) had the highest prevalence rates. Based on the final multivariate logistic regression analysis: female [odds ratios (OR) = 1.24; 95% confidence interval (CI), 1.15-1.35], 6-10 years of service (OR = 1.11; 95% CI, 1.03-1.18), >10 years of service (OR = 1.15; 95% CI, 1.06-1.25), frequent upward and downward flexion in wrist posture at work (OR = 1.81; 95% CI, 1.84-2.11), and frequent wrist placement on the edge of angular objects increased the OR of injury (OR = 1.52; 95% CI, 1.44-1.61). Need to squeeze objects tightly while working (OR = 1.72; 95% CI, 1.57-1.89), prolonged wrist flexion (OR = 1.86; 95% CI, 1.75-1.97), and work hand position above the shoulder for prolonged periods (OR = 1.11; 95% CI, 1.04-1.19) also suggested the relationship between these factors and the higher prevalence of wrist injury in the workers. The associated factor was physical activity (OR = 0.86; 95% CI, 0.80-0.94). This study suggested the relationship between these factors and the higher prevalence of wrist injury in the toy manufacturing, animal husbandry, automobile manufacturing, and shoe-making industries, enamel workers, butchers, and combers. And are work types that require special attention. Females, working age, physical activity, and abnormal posture of the wrist were factors significantly associated with WMSDs.

ANALISIS POSTUR KERJA DENGAN METODE WORKPLACE ERGONOMIC RISK ASSESMENT PADA OPERATOR MESIN BUBUT MANUAL PADA PT YOGYA PRESISI TEHNIKATAMA INDUSTRI

PT Yogya Presisi Tehnikatama Industri is a company engaged in manufacturing such as making molds, industrial machinery spare parts, automotive and plastic injection. The problem that occurs in this company is that there is activity on the lathe operator that has the potential to cause fatigue and pain complaints such as Musculoskeletal Disorders in workers, the results of filling out the NBM Questionnaire found that there were complaints on the back with a percentage of 56.25%, right forearm 62.5 %, 56.25% left thigh, 50% left knee, 50% right thigh, 68.78% right calf, 87.5% right ankle, and 87.5% right foot. So companies need to do an analysis related to posture of workers. One technique or method that can analyze work posture is the WERA (workplace ergonomic risk assessment) method.As for based on the analysis, the suggestions for improvement given are that the shoulders form a moderate position of less than 60o with more pauses, the wrists form an angle of less than 50° with repetitions of 0 to 10 times per minute, on the neck in a position of 10°-20° with movement increased pause. On the operator's back with a position of 0°-20° with 4-8 repetitions per minute, on the leg factor in a normal upright position, with a duration of less than 4 hours, on the contact stress factor the suggestion given is to improve the posture on the worker's wrist earlier. If it's more than 50o, it's best if the wrist posture is less than 50o. Meanwhile, from the results of data processing, a comparison of the final working posture scores obtained in the posture before the proposal was 39 for facing activities, and 38 for drilling and drilling activities included in the MEDIUM category. While the WERA score after the proposal is 26, which is included in the LOW category.&#x0D;

Sensor-Based Motion Tracking System Evaluation for RULA in Assembly Task.

Industries need a mechanism to monitor the workers' safety and to prevent Work-related Musculoskeletal Disorders (WMSDs). The development of ergonomics assessment tools helps the industry evaluate workplace design and worker posture. Many studies proposed the automated ergonomics assessment method to replace the manual; however, it only focused on calculating body angle and assessing the wrist section manually. This study aims to (a) propose a wrist kinematics measurement based on unobtrusive sensors, (b) detect potential WMSDs related to wrist posture, and (c) compare the wrist posture of subjects while performing assembly tasks to achieve a comprehensive and personalized ergonomic assessment. The wrist posture measurement is combined with the body posture measurement to provide a comprehensive ergonomics assessment based on RULA. Data were collected from subjects who performed the assembly process to evaluate our method. We compared the risk score assessed by the ergonomist and the risk score generated by our method. All body segments achieved more than an 80% similarity score, enhancing the scores for wrist position and wrist twist by 6.8% and 0.3%, respectively. A hypothesis analysis was conducted to evaluate the difference across the subjects. The results indicate that every subject performs tasks differently and has different potential risks regarding wrist posture.

Passive wrist deviation to increase the ultrasound identified procedural safe zone in carpal tunnel syndrome: A retrospective cohort study.

Carpal tunnel syndrome (CTS) is the most common peripheral nerve entrapment syndrome. Although prior studies have explored the anatomic changes of the median nerve and carpal arch with different wrist deviations and positionings, the change in safe zone distance between the median nerve and ulnar artery with ulnar or radial wrist deviations has not been adequately investigated. To identify the optimal wrist positioning that increases the safe zone distance between the median nerve and ulnar artery using ultrasound in patients with CTS. Retrospective cohort study. Quaternary medical center multidisciplinary outpatient hand clinic. Twenty five patients (41 wrists) with clinical CTS who received an electrodiagnostic study (EDX) to evaluate CTS within 1 year prior to enrollment. Ultrasound-identified safe zone distance measurements were obtained in each patient between the ulnar aspect of the median nerve and the radial aspect of the ulnar artery with the wrist in neutral radial-ulnar deviation as well as in passive ulnar and radial deviation. The ultrasound-identified safe zone distance with the wrist in each of the three positions. The interstructural safe zone distance was significantly greater when measured in the ulnarly deviated position (1.08 cm) compared with either the neutral (0.61cm, p < .001) or radially deviated positions (0.52 cm, p < .001). Interstructural safe zone distance did not differ between those with normal, mild, moderate, or severe classifications of pathology, or between dominant and nondominant limbs. This study demonstrates that the ultrasound-measured interstructural safe zone distance was significantly greater in the ulnarly deviated position than in either the neutral position or radially deviated position. These findings may lead to improvement in the safety of ultrasound-guided injections.

A comparative study of the efficacy and functionality of 10 commercially available wrist-hand orthoses in healthy females during activities of daily living.

Optimal wrist/hand function facilitates the performance of activities of daily living (ADL), which are associated with independent living and increased quality of life. Rheumatological, musculoskeletal, and neurological conditions or injuries can negatively impact hand/wrist function, with wrist-hand orthoses (WHOs) being prescribed to control motion and improve wrist alignment whilst enhancing hand/wrist functionality. The objective of this follow-up study was to quantify and assess the efficacy and functionality of 10 commercially available WHOs during five ADLs. Randomised comparative functional study of the wrist/hand with and without WHOs. Ten right-handed healthy female participants with no underlying condition or pain affecting the wrist/hand that could influence their ability to undertake ADLs. The primary outcome was ascertaining the impact of each WHO during five ADLs. Movement was quantified in sagittal, coronal, and transverse planes with and without WHO use. The resting position, maximum mean flexion, extension, pronation, supination, and radial and ulnar deviation attained were quantified, with the time spent in wrist flexion, wrist flexion and ulnar deviation, wrist extension >15°, and radial deviation recorded. Finally, the time to complete each task was compared between conditions. At rest, four WHOs maintained the desired sagittal plane wrist position, with only one preventing radial deviation with variation observed in the transverse plane. All WHOs reduced mean maximum flexion, with only 10 out of 50 tests (20%) showing a successful restriction of flexion (p < 0.05) and 14 out of 50 (28%) showing a reduction of the time spent in flexion (p < 0.05). In 42 out of 50 tests (84%), the wrist was extended >15° for a significant amount of time (p < 0.05), with the wrist in radial deviation in 98% for a significant amount of time (p < 0.001). The wrist was flexed and in ulnar deviation for a significant time for 6 out of 50 tests (12%, p < 0.05), whilst all WHOs impacted transverse movement, with 27% reducing it significantly, and all tasks took a longer time to complete, with 46% taking a significantly longer time (p < 0.05). The WHOs did not control movement sufficiently to successfully manage any condition requiring motion restriction associated with pain relief and were found to increase the time to complete the ADLs. Multifactorial design aspects influenced functionality, and there is a clear need for WHO redesign.

Effects of multidirectional elastic tape on forearm muscle activity and wrist extension during submaximal gripping in individuals with lateral elbow tendinopathy: A randomised crossover trial

BackgroundLateral elbow tendinopathy is associated with changes to forearm muscle activity and wrist posture during gripping. Multidirectional elastic tape is thought to exert a deloading effect on underlying musculotendinous structures, which could potentially alter muscle activity or wrist posture. MethodsThis single-blinded randomised crossover trial compared the immediate effects of tensioned multidirectional elastic tape, untensioned control tape, and no tape, in individuals with lateral elbow tendinopathy. Muscle activity of extensor carpi radialis longus and brevis, extensor carpi ulnaris, and extensor digitorum and wrist extension angle were recorded during a submaximal gripping task. Muscle activity was normalised to the maximum amplitude recorded during maximal grip. Change scores were calculated (post-condition minus baseline). Repeated-measure analyses of variance were used to examine between-condition differences. Findings27 participants (16 males, mean age (SD): 48.6 (11.9) years) underwent all conditions. Extensor digitorum muscle activity was reduced during the multidirectional elastic tape, compared to control tape and no tape (MD −5.6% [95%CI: −9.9 to −1.3], MD −5.8% [95%CI: −10.2 to −1.4], respectively). Extensor carpi ulnaris muscle activity was reduced during the multidirectional elastic tape, compared to the control tape (mean difference [MD] −3.2% [95%CI: −5.3 to −1.1]), but increased during the control tape, compared to the no tape (MD 2.9% [95%CI: 0.8 to 5.0]). No differences were observed in extensor carpi radialis brevis or longus muscle activity, or extension wrist angle between conditions. InterpretationA decreased in extensor carpi ulnaris and extensor digitorum muscle activity during multidirectional elastic tape may be evidence of a deloading effect during submaximal gripping.

The effect of rigid tape on wrist postures during tree planting

Taping has been suggested to reduce the incidence of tendinopathy in tree planters. However, the ability of taping to reduce wrist postures during planting has not yet been formally evaluated. The primary aim was to test the effect of rigid taping on wrist postures during tree planting tasks. Eleven tree planters planted up to 50 trees in three conditions: no-tape (NT), tape-on-the-dorsum-of-the-hand (T1) and tape-on-the-thumb (T2) in a randomised cross-over, within-participant, repeat-measures design. Electrogoniometers (EG) recorded continuous wrist postures. Digital video recordings were used to segment EG traces of each planting cycle (one planted tree) into 4 kinematically distinct Phases. The tree and shovel wrist were analysed separately. Tree-wrist peak ulnar deviation and frequency of shovel-wrist awkward frontal plane postures were significantly reduced in the T2 condition. Taping may be effective at reducing non-neutral postures and should be researched further to determine its effectiveness in reducing tree planting injuries. Practitioner summary: The effect of rigid taping on wrist postures during tree planting has not yet been formally evaluated. A randomised cross-over, within-participant, repeat measures design was used to evaluate the effect of rigid taping on wrist postures during planting. Thumb rigid taping appeared to reduce wrist range of motion during planting. KEY POINTS Taping of the thumb reduced peak ulnar deviation of the tree wrist and frequency of awkward frontal plane postures of the shovel wrist. While taping of the dorsum of the hand appeared to be more restrictive, it did not significantly reduce wrist movement; this is likely because only its effect on sagittal plane posture was assessed which had a higher variance. Upon application, tape appeared to restrict voluntary movement patterns, decreased voluntary grip force exertion and physically restrain wrist movement. Overall, rigid tape was found to be an acceptable intervention for the tree planting occupation, with financial costs and perceived effort identified as the primary barriers to acceptability.

Video-Based Automatic Wrist Flexion and Extension Classification

A computer vision method was developed to automatically measure wrist flexion and extension from a 2-D video for occupational health and safety research. Marker-less tracked skeletal joints of the elbow, wrist, and hand estimated the wrist flexion/extension angle between the hand and forearm. Based on the estimated angles, wrist posture was classified as flexion (palmar bending), neutral (no bending), or extension (dorsal bending) for each cycle of hand movement. Applying to a set of laboratory videos of a simulated repetitive motion task, we demonstrated the feasibility of using this algorithm for assessing the state of hand activities during manual work. Tested on 1464 frames from 61 recorded videos for 16 participants, the algorithm achieved an average performance of 72.40% correct, per-class accuracy. The sensitivity and specificity for flexion were 66.16% and 91.47%, respectively. The sensitivity and specificity for extension were 77.12% and 89.72%, respectively. This compared favorably against a previously reported consistency rate of 57% between human analyst estimates and wrist electrogoniometer measured wrist flexion/extension angles. We also applied this technique to 262 video frames of hand flexion instances selected from industrial field video data. For these videos, the average correct per-class accuracy was 76.03% in comparison to human observers. The sensitivity and specificity for flexion were 69.23% and 94.17%, respectively, and the sensitivity and specificity for extension were 91.95% and 80.57%, respectively.

Surgically Implanted Electrodes Enable Real-Time Finger and Grasp Pattern Recognition for Prosthetic Hands.

Currently available prosthetic hands are capable of actuating anywhere from five to 30 degrees of freedom (DOF). However, grasp control of these devices remains unintuitive and cumbersome. To address this issue, we propose directly extracting finger commands from the neuromuscular system. Two persons with transradial amputations had bipolar electrodes implanted into regenerative peripheral nerve interfaces (RPNIs) and residual innervated muscles. The implanted electrodes recorded local electromyography with large signal amplitudes. In a series of single-day experiments, participants used a high speed movement classifier to control a virtual prosthetic hand in real-time. Both participants transitioned between 10 pseudo-randomly cued individual finger and wrist postures with an average success rate of 94.7% and trial latency of 255 ms. When the set was reduced to five grasp postures, metrics improved to 100% success and 135 ms trial latency. Performance remained stable across untrained static arm positions while supporting the weight of the prosthesis. Participants also used the high speed classifier to switch between robotic prosthetic grips and complete a functional performance assessment. These results demonstrate that pattern recognition systems can use intramuscular electrodes and RPNIs for fast and accurate prosthetic grasp control.

A Novel PPG-FMG-ACC Wristband for Hand Gesture Recognition

Wrist-based hand gesture recognition has the potential to unlock naturalistic human-computer interaction for a vast array of virtual and augmented reality applications. Photoplethysmography (PPG), force myography (FMG), and accelerometry (ACC) have generally been proposed as isolated single sensing modalities for gesture recognition, but any of these alone is inherently limited in the amount of biological information it can collect during finger and hand movements. We thus propose a novel, wrist-based, PPG-FMG-ACC combined sensing approach based on a multi-head attention mechanism fusion convolutional neural network (CNN-AF) for gesture recognition. Nine subjects performed twelve hand gestures involving various wrist and finger postures. Experimental results showed that multi-modal fusion improved classification performance significantly ( p 0.01) compared to any single sensing modality, and the F1-score of the combined PPG-FMG-ACC approach was 40.1% higher than PPG alone, 27.4% higher than ACC alone, and 11.9% higher than FMG alone. To the best of our knowledge, this paper is the first to combine wrist-based PPG, FMG, and ACC signals for hand gesture recognition. These results could serve to inform wrist-based gesture recognition design (e.g., via a smartwatch) and thus expand the capabilities of intuitive and ubiquitous human-machine interaction.