Towards a Healthier Workplace: How Flexos, an Active and Bilateral Shoulder Exoskeleton, Provides Support in Weight-Lifting and Carrying Tasks

The wide adoption of occupational shoulder exoskeletons in industrial settings remains limited. Passive exoskeletons were proved effective in a limited amount of application scenarios, such as (quasi-)static overhead handling tasks. Quasi-active devices, albeit representing an improved version of their passive predecessors, do not allow full modulation of the amount of assistance delivered to the user, lacking versatility and adaptability in assisting various dynamic tasks. Active occupational shoulder exoskeletons could overcome these limitations by controlling the shape of the delivered torque profile according to the task they aim to assist. However, most existing active devices lack compactness and wearability. This prevents their implementation in working environments. In this work, we present a new active shoulder exoskeleton, named Active Exo4Work (AE4W). It features a new flexible shaft-driven remote actuation unit that allows the positioning of the motors close to the wearer’s center of mass while it maintains a kinematic structure that is compatible with the biological motion of the shoulder joint. in vitro and in vivo experiments have been conducted to investigate the performance of AE4W. Experimental results show that the exoskeleton is kinematically compatible with the user’s workspace since it does not constrain the natural range of motion of the shoulder joint. Moreover, this device can effectively provide different types of assistance while the user executes various dynamic tasks, without altering perceived comfort.

Assessment of muscular effort in workers performing an actual use-case manual material handling with and without the assistance of Bazar robot

Detection of Occupational Physical Activities using a Smart Textile System

We recorded whole scalp magnetoencephalographic (MEG) signals simultaneously with the surface electromyogram from upper and lower limb muscles of six healthy right-handed adults during voluntary isometric contraction. The 15- to 33-Hz MEG signals, originating from the anterior bank of the central sulcus, i.e., the primary motor cortex, were coherent with motor unit firing in all subjects and for all muscles. The coherent cortical rhythms originated in the hand motor area for upper limb muscles (1st dorsal interosseus, extensor indicis proprius, and biceps brachii) and close to the foot area for lower limb muscles (flexor hallucis brevis). The sites of origin corresponding to different upper limb muscles did not differ significantly. The cortical signals preceded motor unit firing by 12-53 ms. The lags were shortest for the biceps brachii and increased systematically with increasing corticomuscular distance. We suggest that the motor cortex drives the spinal motoneuronal pool during sustained contractions, with the observed cortical rhythmic activity influencing the timing of efferent commands. The cortical rhythms could be related to motor binding, but the rhythmic output may also serve to optimize motor cortex output during isometric contractions.

Muscle fatigue is less studied in dynamic tasks than in isometric contractions. We analysed muscle activity (sEMG) parameters (Median Frequency and Root Mean Square) during 4 sets of dynamic (15 curls/30s) and static (30s hold at 90° elbow) tasks with a 4kg dumbbell, with rest decreasing from 90 to 30s. sEMG data from 8 upper-limb muscles were collected from healthy participants (19–39 years, 5 females). Perceived exertion (Borg RPE) recorded in all and pre/post task MVC were in 6 participants. Borg RPE significantly increased from set 1 to set 4 (8±1.7; P<0.0001), with MVC decreasing by 24.1% post-fatigue, indicating our protocol induced fatigue. Significant MDF decreases and RMS increases (P<0.0001) were observed. MDF/RMS gradients varied across and within muscles, revealing three fatigability levels and varied fatigue onset. Curl-cycle analysis highlighted phase-specific activation changes, with synergistic muscles showing divergent patterns, reflecting heterogeneous neural control. We developed an indexing method integrating MDF (frequency shifts reflecting motor-unit recruitment/de-recruitment) and RMS (amplitude changes indicating recruitment). This categorizes fatigue states into four quadrants, capturing fatigue progression across tasks and muscles. It offers a simplified clinical tool, providing a holistic view of muscle activity, simplifying interpretation, minimizing misinterpretation risks, thus enhancing visualization of fatigability. This method elucidates compensatory neural mechanisms more effectively than traditional sEMG analysis. Fatigability, defined by MDF/RMS gradients, clarifies fibre-specific effects and neural dynamics. Future work will explore the source of inter-muscular variability extending it to pathological populations. Thus, enhancing understanding of fatigue mechanisms while offering tools for clinical and sports applications.

Biomechanical analysis of risk factors for work-related musculoskeletal disorders during repetitive lifting task in construction workers

Background: Aim of the study is to assess the upper limb and core muscle strength in physiotherapy student aged 20-25 years.Methods: A observational study was carried out among 150 undergraduate physiotherapy students both males and females under the age group 20-25 years including final years and interns. A study was conducted by using modified push up test (females), standard push up test (males), hand grip strength using Jamar hand dynamometer and 1 min plank test to assess upper limb and core muscle strength respectively.Results: The results showed that most of the female physiotherapy students have a weak upper limb and core muscle strength compared to males.Conclusions: To conclude most of the female physiotherapy students have a weak upper limb and core muscle strength compared to male physiotherapy students. This is one of the factors that leads to musculoskeletal pain and work-related musculoskeletal disorders in physical therapy profession.

The evidence for neural mechanisms underpinning rapid strength increases has been investigated and discussed for over 30 years using indirect methods, such as surface electromyography, with inferences made toward the nervous system. Alternatively, electrical stimulation techniques such as the Hoffman reflex, volitional wave, and maximal wave have provided evidence of central nervous system changes at the spinal level. For 25 years, the technique of transcranial magnetic stimulation (TMS) has allowed for noninvasive supraspinal measurement of the human nervous system in a number of areas such as fatigue, skill acquisition, clinical neurophysiology, and neurology. However, it has only been within the last decade that this technique has been used to assess neural changes after strength training. The aim of this brief review is to provide an overview of TMS, discuss specific strength training studies that have investigated changes, after short-term strength training in healthy populations in upper and lower limbs, and conclude with further research suggestions and the application of this knowledge for the strength and conditioning coach.

In the Philippines, fishing industry is one of the most important sectors, considering it as one of the top fishing producing countries. In fish ports, workers are involved in carrying different weights of loads that may lead to Work-Related Musculoskeletal Disorders (WMSDs). This study aims to establish a basis for WMSDs on porters in fish ports and intends to examine the prevalence, severity, and significant factors that may cause their existence. The body regions with high prevalence of self-reported symptoms were the ankle/feet, hips/buttocks, and shoulder body regions. The Binary Logistic Regression models showed that there is a relationship between prevalence of symptoms of WMSDs and the significant factors. The factors found to be significant were ‘cigarette smoking’, ‘number of banyeras carried’, ‘assistance from coworkers’, ‘weight of load’, ‘workspace’, and ‘conflicts at work’. Based on the results of the study, recommendations were developed to reduce the prevalence of WMSDs among the porters.

BackgroundNeuromuscular fatigue induced by contractile activity can lead to prolonged depression of muscle forces evoked through low frequency electrical stimulations, termed prolonged low‐frequency force depression (PLFFD). PLFFD is assessed as the ratio of forces evoked from low (e.g., 10 Hz) and high (e.g., 50 Hz) frequency stimulations, which has been examined most often using isometric contractions. However, fatigue is task specific, and it is unknown if PLFFD induced via dynamic contractions is accurately characterized using isometric torque, as it is not influenced by the velocity or power components of dynamic movements.Objectives and HypothesesOur primary objective was to compare isometric and dynamic PLFFD following a concentric fatiguing task in healthy young adults. We hypothesized that both isometric and dynamic PLFFD will be impaired following the task but dynamic PLFFD will be reduced to a greater extent.MethodsYoung (18‐35 years) males (n=5) and females (n=1) performed a prone, knee straight (180°) concentric plantar flexion fatiguing task (Humac Norm). The task involved maximal velocity isotonic‐like contractions at a resistance of 15% maximal voluntary contraction (MVC) through a 30° ankle range of motion (90° to 120° plantar flexion) until a 75% reduction in peak power. To assess PLFFD, contractions were electrically evoked at 10 Hz and 50 Hz via tibial nerve stimulation using a current that elicited maximal isometric 50 Hz torque. Isometric (joint ankle 90°) and isotonic (5% MVC load) PLFFD were assessed as the ratio of 10 to 50 Hz for peak torque and peak power, respectively. Recovery of isotonic and isometric PLFFD (Figure 1), MVC, and voluntary peak power (5% MVC load) was evaluated at 0‐, 2.5‐, 5‐, 10‐, 20‐, and 30‐minutes post task failure.ResultsOn average (±SD), participants performed 151 ±47 contractions, which resulted in an ~74% reduction in peak power. Isometric (~6%) and isotonic (~8%) 10:50 Hz ratios were similarly reduced following task failure (Figure 2). However, at 2.5‐ and 5‐minutes, isotonic PLFFD was further reduced (~15% and ~21%, respectively), but isometric PLFFD remained relatively unchanged (~0% and ~5%, respectively). By 10 minutes of recovery, isotonic and isometric PLFFD were reduced compared to baseline, which remained until the 30 minute time point (~31% and ~20%, respectively). Voluntary peak power was reduced more than isometric MVC at task failure (~44% vs. ~29%), but both recovered similarly by 30 minutes (~8% vs. ~13%).ConclusionsThis preliminary analysis observed that PLFFD assessed using isometric and isotonic contractions are similarly reduced following task failure; however, differences in the degree of depression may exist throughout 30 minutes of recovery, particularly within the early (<10 minutes) phase. These results demonstrate that PLFFD can be assessed using isotonic contractions, which may have implications for better understanding fatigue responses during dynamic tasks.

Background: Work-related Musculoskeletal Disorders (WRMSDs) are highly prevalent among equipment operators in the mining industry, particularly in underground coal mining. The multifaceted nature of risk factors contributing to WRMSDs necessitates a robust and accurate predictive model to assess the likelihood of these disorders among operators. Methodology: This study presents a novel Artificial Neural Network (ANN)-based predictive model developed to estimate the prevalence of WRMSDs among seated vehicle operators. Key input variables include demographic and ergonomic factors such as age, Body Mass Index (BMI), years of experience, posture scores (REBA), frequency-weighted Root Mean Square (RMS) acceleration, and Vibration Dose Values (VDV). Data on WRMSDs prevalence and severity were collected using the standard Nordic Musculoskeletal Questionnaire (NMQ). Results: The analysis demonstrated a strong positive correlation between the severity of WRMSDs and the identified risk factors. The optimal ANN configuration included hidden layers with sizes [5, 10, 15], learning rates [0.01, 0.1, 0.2], and class weights [1, 1], [0.5, 1.5], and [1, 2]. The model's performance was validated using 12 unseen datasets, achieving excellent predictive accuracy (0.975 ± 0.014), precision (0.805 ± 0.083), recall (1.000 ± 0.000), F1 score (0.890 ± 0.053), and AUC-ROC (0.996 ± 0.005) (mean ± standard deviation). Conclusion: This ANN-based model offers a powerful tool for predicting WRMSDs across different body regions of seated vehicle operators. Its ability to incorporate diverse input factors will support the implementation of targeted occupational health and safety interventions, particularly for shuttle car operators and other mining professionals at high risk of WRMSDs. Major Findings: The study developed an ANN-based model to predict WRMSDs prevalence among seated vehicle operators in underground mining, incorporating demographic and ergonomic factors. The model achieved high predictive accuracy, with a strong correlation between WRMSDs severity and identified risk factors.

Overhead working tasks are usually associated with a higher incidence of work-related musculoskeletal disor-ders (WRMDs) at the level of the shoulder and neck. Shoulder exoskeletons effectively reduce shoulder muscle activity during overhead work. Neck support's development and validation, on the other hand, has not equally advanced yet. Also, a limited amount of occupational neck support devices, which yield sim-ilar characteristics and limitations, are commercially available. Hence, a new neck support that possesses the characteristic to be fully adjustable and compatible with a previously developed shoulder exoskeleton has been designed and characterized. Preliminary results of a pilot study, conducted to investigate the effectiveness of the neck support during the execution of an overhead handling task, indicate that the novel neck support can reduce neck muscle activity up to 81%. Moreover, the combination of a neck support with a shoulder exoskeleton during overhead work may elicit a synergistic effect between the devices in terms of reduction of shoulder muscle activity.

Whole-body vibration and upper limb vibration (ULV) continue to gain popularity as exercise intervention for rehabilitation and sports applications. However, the fatiguing effects of indirect vibration stimulation are not yet fully understood. We investigated the effects of ULV stimulation superimposed on fatiguing isometric contractions using a purpose developed upper limb stimulation device. Thirteen healthy volunteers were exposed to both ULV superimposed to fatiguing isometric contractions (V) and isometric contractions alone Control (C). Both Vibration (V) and Control (C) exercises were performed at 80% of the maximum voluntary contractions. The stimulation used was 30 Hz frequency of 0.4 mm amplitude. Surface-electromyographic (EMG) activity of the Biceps Brachii, Triceps Brachii and Flexor Carpi Radialis were measured. EMG amplitude (EMGrms) and mean frequency (MEF) were computed to quantify muscle activity and fatigue levels. All muscles displayed significantly higher reduction in MEFs and a corresponding significant increase in EMGrms with the V than the Control, during fatiguing contractions (p < 0.05). Post vibration, all muscles showed higher levels of MEFs after recovery compared to the control. Our results show that near-maximal isometric fatiguing contractions superimposed on vibration stimulation lead to a higher rate of fatigue development compared to the isometric contraction alone in the upper limb muscles. Results also show higher manifestation of mechanical fatigue post treatment with vibration compared to the control. Vibration superimposed on isometric contraction not only seems to alter the neuromuscular function during fatiguing efforts by inducing higher neuromuscular load but also post vibration treatment.

High proprioceptive sensitivity is an important factor in the efficiency of technical elements and athletic performance in many sports. However, proprioceptive control of the positions of upper limb segments and muscle effort in wrestlers has hardly been investigated. The purpose of this article was to study the reproduction accuracy of hand position and muscle effort during discrete contraction and relaxation of the forearm muscles in sambo athletes. Materials and methods. The research involved young sambo wrestlers (n = 10) and nonathletes (control, n = 15). We evaluated the reproduction accuracy of forearm pronation/supination angles (20, 50 and 80°) using a PABLO Handsensor (Tyromotion, Austria) and the accuracy of isometric muscle contraction during static pronation/supination, using a stationary hand joystick, in the ascending and descending directions of effort development (0, 20, 50 and 80 % of the maximum effort) according to the level of electromyographic activity of forearm pronators and supinators (Trust-M functional electrical stimulation system, Neurocore, Russia). Results. We found that proprioceptive control of forearm position accuracy and static effort during the contraction of forearm pronators and supinators did not differ between wrestlers and non-athletes. However, the absolute reproducibility error of 50 and 80 % of muscle effort during discrete relaxation of the pronators was lower (p &lt; 0.01) in wrestlers than in non-athletes. Moreover, in the general sample, effort reproduction accuracy at pronators’ discrete contraction was higher than at discrete relaxation, which indicates a deficit of proprioceptive control of muscle effort during relaxation. Thus, exercising upper limb muscles in sambo improves proprioceptive control of discrete muscle relaxation. Further studies should determine the role of the established phenomenon in the effectiveness of wrestling skills and sports results.

Work-related musculoskeletal disorders (WMSDs) in the Philippines has become an ordeal in the manufacturing industry. WMSDs are injuries in both muscle and skeletal systems of the body caused by repetitive tasks, prolonged and strenuous range of actions done by most people. Workers experiencing various WMSDs are associated with increased absenteeism, less productivity, and physical and psychological stress. The study aims to identify and analyze statistically significant variables contributing to work-related musculoskeletal disorders, particularly postural related considerations in the lower back, experienced by machinists in a steel manufacturing company. Through correlation and multiple regression analysis, results showed that Height (p-value = 0.001), Weight (p-value = 0.001), Noise (p-value = 0.000), Temperature (p-value = 0.002), Load Weight (p-value = 0.014), BMI (p-value = 0.047), Sleep Quality (p-value = 0.044) and Workload (p-value = 0.007) contributes to the WMSDs experienced by the machinists. Recommendations such as medical examinations, worker's education in the use of PPEs, suitable ventilations, adequate working space, and worker's physical fitness is expected to minimize the risk of WMSDs among workers.