Repetitive Forces Research Articles

Validity of an expert-based job exposure matrix of hand-wrist physical exposures and their prospective associations with carpal tunnel syndrome.

Epidemiological studies of occupational risk factors for rare disorders require large study populations with adequate exposure estimates. Job exposure matrices (JEMs) linked to national information on standardized job titles may enable such large studies. We aimed to establish and validate a JEM for occupational hand-wrist exposures that could be linked to Danish national register data on job titles and hand-wrist disorders. We developed a JEM for hand-wrist repetition, force, vibration, and computer work in 96 job groups covering 91% of the 2227 occupational titles in the Danish version of the International Standard Classification of Occupation-88, and examined inter-rater reliability of five expert ratings. Poisson regression models were used to estimate incidence rate ratios for the association of carpal tunnel syndrome (CTS) with the level of repetitive movements, force, vibration, and hours of computer work described by the JEM, adjusted for relevant confounders. The JEM based on expert ratings had fair to good interrater reliability. The incidence of CTS increased with increasing levels of force, hand-wrist repetition, and vibration, Exposure-response patterns for repetition and vibration became less consistent after adjustment for force. The interaction between repetition and force was complex and did not support an overall positive interaction. Computer work was negatively associated with incident CTS. The JEM was able to identify known risk factors for CTS consistent with current evidence, and provided further associations on exposure-response patterns, mutual exposure adjustment, and interaction effects between repetition and force. The reliability of expert assessments of hand-wrist physical exposures was fair to good.

The Force of Repetition: Citiational Chains and Modern/Colonial Gender Violence

The Force of Repetition: Citiational Chains and Modern/Colonial Gender Violence

A novel centrifugal electrospinning design for preparing of high alignment β-phase PVDF nanofibers for high-performance piezoelectric nanogenerators

The effects of polyvinylidene fluoride (PVDF) wt. % and electric fields on the production of PVDF fibers using a novel centrifugal electrospinning design were investigated. High-quality, bead-free fibers with diameter of (0.55 ± 0.04) μm were successfully produced. Fibers with exceptionally high β-phase content of 96.1 % and piezoelectric coefficient, d33 of (−157 ± 5) pC N−1 were obtained using PVDF amount and electric field of 14.0 wt % and 400 V cm−1, respectively. Under 3.0 N repetitive vertical forces, the fabricated piezoelectric nanogenerator (PENG) exhibited impressive open-circuit voltage, short-circuit current and power density of (32.6 ± 0.7) V, (3.26 ± 0.07) μA and (15.4 ± 0.6) μW cm⁻2, respectively. The production of high and well aligned β-phase in the fibers indicated by good d33 values are the likely reasons for the excellent performance of the PENG. Ultimately, potential of the fabricated PENG as a self-power supply for low-energy electronic devices was demonstrated.

Understanding the Injury Mechanism in Hamate Hook Fractures by Investigating Fracture Morphologies: A Case Series Study.

Many studies have described hamate hook fractures resulting from direct force from sporting tools. However, several authors have reported fractures that did not occur during swing-related activities. This study aimed to understand the injury mechanism of fractures by investigating their morphologies. We selected patients with hamate hook fractures and collected data on computed tomography scans, injury causes, and how athletes handled sporting tools. We investigated 50 patients, and the study cohort included 32 patients who sustained injuries during sports: 24 during baseball (group A) and 8 during other sports (group B). Sixteen patients sustained injuries from falls (group C), and 2 had their hands crushed while using an industrial press machine (group D). In group A, most patients had a fracture line starting from the middle section of the radial side, accompanied by osteosclerotic changes in their lower hand. In group B, most patients had fracture morphologies similar to those of most patients in group A. The main morphology of fractures in group C was a transverse fracture at the base. Two patients in group D had minimal fragments at the tip of the hooks. Our results question the theory that most hamate hook fractures in athletes are caused by direct force exerted on the palm because the fracture morphology was different from that of patients injured by acute trauma from direct force. Instead, these fractures likely stem from an indirect mechanism involving repetitive force generated by the tendons and muscles acting on the hook.

PREVALENCE OF MUSCULOSKELETAL DISORDERS AMONG IT PROFESSIONALS IN TECHNOPARK THIRUVANANTHAPURAM

Musculoskeletal disorders or MSDs are soft tissue injuries caused by sudden or sustained exposure to repetitive motion, force, vibration and awkward positions. IT Professionals represent an occupational group where chances to develop MSDs are high because of their work pattern, in which they have fixed or constrained body position, continual repetition of movements, force concentrated on small parts of the body, like hand or wrist or a pace of work that does not allow sufficient recovery between movements. In India, many studies were done to evaluate the prevalence of MSDs among other occupational groups but not much among IT Professionals. This study has been carried out to determine the prevalence of Musculoskeletal Disorders (MSD) among IT Professionals. The study design was cross sectional with information technology (IT) Professionals working in Technopark Thiruvananthapuram as the study population. The sampling method used for the survey is the simple random sampling. Data was collected using a modified version of Dutch musculoskeletal questionnaire. Chi-square (χ2) test was applied for statistical significance and associations were assessed through p value with 95% confidence interval. Prevalence of work related MSD during last 12 months, was 36.57%. The common prevalence of work related MSD reported during last 12 months based on their body region were neck (83.42), shoulders (76.57%), and back (61.71%). There was a statistically significant difference in terms of experience, sitting for long period, using key board and working in the same posture for long period. There was no statistically significant difference in terms of age, BMI, gender, education. The study has concluded that MSD is prevalent among IT Professionals working in Technopark Thiruvananthapuram..

Prevalence of degenerative vertebral disc changes in elite female Crossfit athletes – a cross-sectional study

BackgroundCrossfit athletes consistently recruit or transfer high levels of repetitive forces through the spine, and MRI has documented a higher rate of intervertebral disc degeneration in athletes compared with matched controls. The aim of this study was to evaluate early degenerative spinal disc changes in elite female CrossFit athletes quantified by 3.0 Tesla magnetic resonance imaging (MRI) matched with female none-athletes.MethodsIn a cross-sectional single-center study 19 asymptomatic adult participants, nine German female elite Crossfit athletes and ten female participants underwent spinal MRI (3.0T). Demographic data, spinal clinical examination results and sport-specific performance parameters were collected prior to the MRI. The primary outcome was the prevalence of degenerative spinal disc changes. The secondary outcome was the grade of degeneration using Pfirrmann grading.ResultsA total of 437 discs underwent spinal MRI (3.0T). The prevalence of early degenerative disc disease was not increased. Pfirrmann degenerative grade did not show significant differences among groups.ConclusionAsymptomatic female elite Crossfit athletes do not show an increased prevalence of degenerative disc disease. Compared to a sex-matched control group, high training volume in Crossfit does not correlate to a higher incidence of degenerative disc changes in young females.

Black Transmission: Toward a Hieroglyph-Analysis

This meditation is an experimentation with Hortense Spiller’s concept of psychoanalytics. It considers the hieroglyph as a repetitive and enacted (but unrepresentable) force of historical trauma marking black bodies and passed between them generationally (much like the Lacanian object a). Reading the Lacanian pass and erotogenic zones as heuristic features of the hieroglyph, this meditation presents black nihilism as an analytic setting enabling the hieroglyph to speak its ineffable repetition, rather than just a repertoire of hedonistic pleasures and destructive behaviors as described in black optimism.

Investigating change of discomfort during repetitive force exertion though an exoskeleton cuff

This article investigates discomfort development for forces exerted repetitively and for extended durations through a rigid cuff.Three force patterns, chosen to mimic exoskeleton use, were applied to the thigh of 15 healthy participants for 30 min. Changes in perceived comfort and skin effects were recorded.Discomfort was detected at normal forces ranging from 40 to >230 N. Repetitive force application triggered discomfort after a median of 4.1 min (normal force only) and 5.4 min (normal and shear force) respectively. Discomfort increased over time but the repetitive force applications did generally not result in pain and there were no significant differences between repetitive loading patterns.Exoskeleton design and use should be informed by comfort thresholds specific to prolonged repetitive loading. Large interindividual differences in perception of discomfort limit the possibilities for generally applicable comfort thresholds. Further research is needed to investigate how patient groups perceive such repetitive loading.

Damage cause analysis of coating failure of pot roll for hot-dip aluminizing

Hot-dip aluminized steel is produced by immersing cold-rolled steel in a molten aluminum bath for a certain period. However, the pot rolls immersed in the aluminum bath suffer significant surface damage due to the reactions with the molten bath. This study identified the cause of surface damage of the stabilizer roll used for continuous hot-dip plating of aluminum at 660 °C. The damage was caused by molten Al infiltrating a defective structure with interconnected pores and splat boundaries. This molten Al dissolves the metal components of both the coating and substrate. As the lower part of the coating melts and liquefies, repetitive external frictional forces lead to the formation and growth of cracks in the upper coating. That eventually leads to the upper part of the coating partially or entirely detaching, resulting in surface defects in the form of pits. Possible ways to extend the lifetime of the port rolls to suppress such damage have been proposed.

Immature bovine cartilage wear is due to fatigue failure from repetitive compressive forces and not reciprocating frictional forces

Wear of articular cartilage is not well understood. We hypothesize that cartilage wears due to fatigue failure in repetitive compression instead of reciprocating friction. This study compares reciprocating sliding of immature bovine articular cartilage against glass in two testing configurations: (1) a stationary contact area configuration (SCA), which results in static compression, interstitial fluid depressurization, and increasing friction coefficient during reciprocating sliding, and (2) a migrating contact area configuration (MCA), which maintains pressurization and low friction while producing repetitive compressive loading in addition to reciprocating sliding. Contact pressure, sliding duration, and sliding distance were controlled to be similar between test groups. SCA tests exhibited an average friction coefficient of μ=0.084±0.032, while MCA tests exhibited a lower average friction coefficient of μ=0.020±0.008 (p<10-4). Despite the lower friction, MCA cartilage samples exhibited clear surface damage with a significantly greater average surface deviation from a fitted plane after wear testing (Rq=0.125±0.095 mm) than cartilage samples slid in a SCA configuration (Rq=0.044±0.017 mm, p=0.002), which showed minimal signs of wear. Polarized light microscopy confirmed that delamination damage occurred between the superficial and middle zones of the articular cartilage in MCA samples. The greatest wear was observed in the group with lowest friction coefficient, subjected to cyclical instead of static compression, implying that friction is not the primary driver of cartilage wear. Delamination between superficial and middle zones implies the main mode of wear is fatigue failure under cyclical compression, not fatigue or abrasion due to reciprocating frictional sliding.

Natural Phytic Acid-Assisted Polyaniline/Poly(vinyl alcohol) Hydrogel Showing Self-Reinforcing Features.

Polyaniline (PANi) hydrogels that combine advantages of hydrogels and conductive PANi have recently emerged in areas of wearable devices and personal healthcare. Nevertheless, their mechanical performance often gradually degrades after being used for a period, caused by destruction of the inner structures when external forces are applied. Inspired by biological structures with persistent durability, we develop here a phytic acid-assisted PANi/poly(vinyl alcohol) (PVA) hydrogel that shows self-reinforcing features. As a natural product holding plenty of phosphate groups, phytic acid (PA) plays two crucial roles when preparing this hydrogel: (1) aniline is salinized by PA in aqueous solution to promote in situ polymerization, making the resulting PANi conductive; (2) PA/PANi particles form hydrogen bonds with PVA, acting as stress concentration points to induce structure orientation. The optimal PVA/PA/PANi hydrogel displays dark green color with a uniform distribution of PA/PANi particles. After experiencing repetitive 4 × 100 stretching at a strain of 10%, the hydrogel exhibits an enhanced fracture strength (20.35 MPa), Young's modulus (22.66 MPa), and toughness (36.24 MJ·m-3) compared with the original hydrogel. This self-reinforcing feature is mainly attributed to the formation of anisotropic structures fixed by hydrogen bonds between PA/PANi particles and PVA chains upon repetitive external forces. Moreover, anisotropic structures can be disassembled by swelling the post-stretched hydrogel in water, and the swollen hydrogel shows similar self-reinforcing behaviors. The good mechanical durability and reusable characteristics make the PVA/PA/PANi hydrogel a reliable strain sensor. This work provides a structural growing-reviving approach for conductive hydrogels with persistent durability.

Multifunctional bilayer membranes composed of poly(lactic acid), beta-chitin whiskers and silver nanoparticles for wound dressing applications

Nanomaterial-based wound dressings have been extensively studied for the treatment of both minor and life-threatening tissue injuries. These wound dressings must possess several crucial characteristics, such as tissue compatibility, non-toxicity, appropriate biodegradability to facilitate wound healing, effective antibacterial activity to prevent infection, and adequate physical and mechanical strength to withstand repetitive dynamic forces that could potentially disrupt the healing process. Nevertheless, the development of nanostructured wound dressings that incorporate various functional micro- and nanomaterials in distinct architectures, each serving specific purposes, presents significant challenges. In this study, we successfully developed a novel multifunctional wound dressing based on poly(lactic acid) (PLA) fibrous membranes produced by solution-blow spinning (SBS) and electrospinning. The PLA-based membranes underwent surface modifications aimed at tailoring their properties for utilization as effective wound dressing platforms. Initially, beta-chitin whiskers were deposited onto the membrane surface through filtration, imparting hydrophilic character. Afterward, silver nanoparticles (AgNPs) were incorporated onto the beta-chitin layer using a spray deposition method, resulting in platforms with antimicrobial properties against both Staphylococcus aureus and Escherichia coli. Cytotoxicity studies demonstrated the biocompatibility of the membranes with the neonatal human dermal fibroblast (HDFn) cell line. Moreover, bilayer membranes exhibited a high surface area and porosity (> 80%), remarkable stability in aqueous media, and favorable mechanical properties, making them promising candidates for application as multifunctional wound dressings.

Risk Factors Associated with Musculoskeletal Disorders Among Professional Drivers in Asian Countries: A Systematic Review

Musculoskeletal disorders (MSDs) are injuries in the musculoskeletal system caused by sustained or sudden exposure to repetitive motion, vibration, force, and awkward positions. Professional drivers are one of the working populations with a high risk of developing MSDs. Several studies had examined the prevalence and risk factors (RFs) for MSDs among professional drivers. Thus, this systematic review aims to analyze the literature and report the risk factors associated with MSDs among professional drivers in Asian countries. Published literature was systematically searched through EBSCOhost, Web of Science, and OVID. Studies which met the inclusion criteria were methodologically appraised using the Appraisal Tool for Cross-Sectional Studies (AXIS). Based on the studies included, the RFs reported to be significantly associated with MSDs among professional drivers included physical RFs, individual RFs, and psychosocial RFs. There were some RFs that did not fall into the three categories. The most frequently and comprehensively investigated RFs were the physical RFs. In conclusion, there were various RFs associated with MSDs among professional drivers in Asian countries. Further studies should be conducted to understand MSDs among professional drivers in different contexts and circumstances. A holistic and multidisciplinary approach should be used to develop effective management and preventive techniques to address this common occupational problem affecting a large proportion of the working population.

Faktor yang Berhubungan dengan Keluhan Musculoskeletal Disorders pada Pekerja Batik Cap

Background: Musculoskeletal Disorders (MSDs) are soft tissue injuries caused by sudden or repetitive meovement, forces, vibrations, and awkward positions. Batik cap workers are at risk of developling musculoskeletal complaints because they work in a static position for a long time. The purpose of this study was determine the factors associated with the incidence of musculoskeletal complaints stamped batik workers. Method: This type of research is descriptive quantitative with a cross sectional approach using a total sampling method that is a number of 53 workers, the instruments used are measuring sheets observations and questionares. Data were analyzed using the chi-square test and fisher’s test. The research wa conducted in November-December 2022. Results: The conclution in this study is that the variables associated with musculoskeletal complaints were work posture (p=0.000), length of work (p=0.043), length of service (p=0.000), workload (p=0.019), age (p= 0.000). There was no relationship with the incidence of gender complaints (p=0.404), exercise habits (p=0.581), body mass index (p=0.898). Conclusion: The conclusion in this study is that there is a relationship between work posture, length of work, years of service, workload, age, and there is no relationship between gender, exercise habits, body mass index.

Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management.

Micro-traumatic posterior shoulder instability (PSI) is an often missed and misdiagnosed pathology presenting in tennis players. The aetiology of micro-traumatic PSI in tennis players is multifactorial, including congenital factors, loss of strength and motor control, and sport-specific repetitive microtrauma. Repetitive forces placed on the dominant shoulder, particularly combinations of flexion, horizontal adduction, and internal rotation contribute to the microtrauma. These positions are characteristic for kick serves, backhand volleys, and the follow-through phase of forehands and serves. The aim of this clinical commentary is to present an overview of the aetiology, classification, clinical presentation, and treatment of micro-traumatic PSI, with a particular focus on tennis players. 5.

Combining DNA scaffolds and acoustic force spectroscopy to characterize individual protein bonds

Single-molecule data are of great significance in biology, chemistry, and medicine. However, new experimental tools to characterize, in a multiplexed manner, protein bond rupture under force are still needed. Acoustic force spectroscopy is an emerging manipulation technique which generates acoustic waves to apply force in parallel on multiple microbeads tethered to a surface. We here exploit this configuration in combination with the recently developed modular junctured-DNA scaffold that has been designed to study protein-protein interactions at the single-molecule level. By applying repetitive constant force steps on the FKBP12-rapamycin-FRB complex, we measure its unbinding kinetics under force at the single-bond level. Special efforts are made in analyzing the data to identify potential pitfalls. We propose a calibration method allowing in situ force determination during the course of the unbinding measurement. We compare our results with well-established techniques, such as magnetic tweezers, to ensure their accuracy. We also apply our strategy to study the force-dependent rupture of a single-domain antibody with its antigen. Overall, we get a good agreement with the published parameters that have been obtained at zero force and population level. Thus, our technique offers single-molecule precision for multiplexed measurements of interactions of biotechnological and medical interest.

Development of a bioreactor for in-vitro compression cycling of tissue engineered meniscal implants

Injuries to the meniscus are common and can impair physical activities. Bioprinted meniscal tissue offers an attractive alternative to donor tissue for meniscal repair but achieving the strength of native tissue is a challenge. Here we report the development of a tissue engineering bioreactor designed to apply repetitive force which may lead to an increase in the compressive modulus and durability of bioprinted meniscal tissues. The modular bioreactor system is composed of a sterilizable tissue culture vessel together with a dock that applies and measures mechanical force. The culture vessel allows for simultaneous compression cycling of two anatomically sized menisci. Using a hybrid linear actuator with a stepper motor, the dock can apply up to 300 N of force at speeds up to 20 mm/s, corresponding to the upper limits of anatomical force and motion in the knee. An interchangeable 22 N load cell was mated between the culture vessel and the dock to log changes in force. Both the culture vessel and dock are maintained in a standard cell culture incubator to provide heat and CO2, while the dock is powered and controlled externally using a step motor drive and customized software.

Assessing the impact of critical risk factors on the development of musculoskeletal disorders: a structural equation modelling approach

Musculoskeletal Disorders (MSDs) have a significant impact on people’s lives as well as their workplaces, organizations, families, society, and national economy. Therefore, the main objective of this study is to investigate the impacts of different risk factors in developing MSD problems. Structural equation modelling has been used to examine the effects of different risk factors on developing MSD problems. Five hypotheses were developed for workplace, personal, biomechanical, psychosocial, and organisational risk factors to examine the positive relation with MSD problems generation. Results showed that biomechanical risk factors, including repetitive motion, vibration, force, posture, and deviation from neutral body alignment, have significant impacts on the development of MSD problems. Similar results were found for workplace, personal, psychosocial, and organisational risk factors. Therefore, either the single risk factor or collectively contributes significantly to MSD problems generation. Decision-makers can use this study to analyse the impacts of different factors on the generation of MSD problems within their industries or organizations. To the best of the author’s knowledge, this study is the first and foremost approach to determine the impacts of the critical risk factors on developing MSD problems through an organised and scientific approach.

Silicone breast implant rupture is more prevalent in the dominant limb side: A retrospective cohort study

Breast implant rupture is associated with multiple risk factors such as implant age, manufacturer, and a history of trauma to the breast. However, the exact mechanism of breast implant rupture remains unclear. We hypothesize that repetitive minor mechanical forces on the implant collectively play a significant role in the cascade that eventually leads to its rupture. Therefore, we expect a more significant cumulative effect on the breast implant in the dominant upper limb side. Thus, we aim to ascertain whether laterality in silicone breast implant rupture is associated with the dominant upper limb. A retrospective cohort study was performed on patients with silicone breast implants who underwent an elective breast implant removal or exchange. All patients had breast augmentations for cosmetic reasons. We collected data on implant rupture laterality and limb dominance together with known risk factors like patient age, implant age, implant pocket, and implant volume. A total of 154 patients with unilateral implant rupture were included in the study. Among patients with a dominant right limb (n=133), an ipsilateral rupture was found in 77 patients (58%) (p=0.036), while in patients with a left dominant limb (n=21), an ipsilateral rupture was found in 14 patients (67%), (p=0.036). The dominant limb was a significant risk factor for ipsilateral breast implant rupture. The prevailing theory that cyclic envelope movement carries an increased rupture risk is reinforced in this study. Extensive prospective studies are needed to clarify risk factors for implant rupture further.

Asphalt mixture force chains morphological characteristics and bearing capacities investigation using discrete element method

ABSTRACT Force chain morphological characteristics and bearing capacities can reflect the asphalt mixture’s skeleton external loading transfer behaviour. In this study, asphalt mixture discrete element models were established by the particle flow code in two dimensions (PFC2D) software. Force chains’ morphological characteristics and bearing capacities were evaluated by considering repetitive force chains (RFC). The results indicate that dense-graded asphalt concretes (AC) transfer external loading along the vertical direction, and force chains of stone mastic asphalt (SMA) and open-graded asphalt friction course (OGFC) have large expansion areas. AC-type asphalt mixtures form force chains easily with a shorter length and weak strength. Nominal maximum aggregate size (NMAS) has little influence on force chain alignment coefficient (FCAC) and force chain angle (FCA) distributions for AC, but it has stronger effects for SMA and OGFC. Whatever kinds of asphalt mixtures, with NMAS increase, the proportion of lower strength force chains will decrease gradually. The passing percentage of sieve size 2.36 mm (P2.36) needs to be limited within a certain range to ensure the asphalt mixture with the trapezoidal force chain shape for transferring the external loading better. For example, P2.36 needs to be restricted within 34% for AC16, and thresholds are 15% and 13% for SMA16 and OGFC16, respectively.