Understanding contributing factors to exoskeleton use-intention in construction: a decision tree approach using results from an online survey.

Work-related musculoskeletal disorders (WMSDs) are a major health concern in the construction industry. Occupational exoskeletons (EXOs) are a promising ergonomic intervention to help reduce WMSD risk. Their adoption, however, has been low in construction. To understand the contributing factors to EXO use-intention and assist in future decision-making, we built decision trees to predict responses to each of three EXO use-intention questions (Try, Voluntary Use, and Behavioural Intention), using online survey responses. Variable selection and hyperparameter tuning were used respectively to reduce the number of potential predictors and improve prediction performance. The importance of variables in each final tree was calculated to understand which variables had a greater influence. The final trees had moderate prediction performance. The root node of each tree included EXOs becoming standard equipment, fatigue reduction, or performance increase. Important variables were found to be quite specific to different decision trees. Practical implications of the findings are discussed.Practitioner summary: This study used decision trees to identify key factors influencing the use-intention of occupational exoskeletons (EXOs) in construction, using online survey data. Key factors identified included EXOs becoming standard equipment, fatigue reduction, and performance improvement. Final trees provide intuitive visual representations of the decision-making process for workers to use EXOs.

Impact of Booster Breaks and Computer Prompts on Physical Activity and Sedentary Behavior Among Desk-Based Workers: A Cluster-Randomized Controlled Trial.

INTRODUCTION: The 15-minute work break provides an opportunity to promote health, yet few studies have examined this part of the workday. We studied physical activity and sedentary behavior among office workers and compared the results of the Booster Break program with those of a second intervention and a control group to determine whether the Booster Break program improved physical and behavioral health outcomes. METHODS: We conducted a 3-arm, cluster-randomized controlled trial at 4 worksites in Texas from 2010 through 2013 to compare a group-based, structured Booster Break program to an individual-based computer-prompt intervention and a usual-break control group; we analyzed physiologic, behavioral, and employee measures such as work social support, quality of life, and perceived stress. We also identified consistent and inconsistent attendees of the Booster Break sessions. RESULTS: We obtained data from 175 participants (mean age, 43 y; 67% racial/ethnic minority). Compared with the other groups, the consistent Booster Break attendees had greater weekly pedometer counts (P < .001), significant decreases in sedentary behavior and self-reported leisure-time physical activity (P < .001), and a significant increase in triglyceride concentrations (P = .02) (levels remained within the normal range). Usual-break participants significantly increased their body mass index, whereas Booster Break participants maintained body mass index status during the 6 months. Overall, Booster Break participants were 6.8 and 4.3 times more likely to have decreases in BMI and weekend sedentary time, respectively, than usual-break participants. CONCLUSION: Findings varied among the 3 study groups; however, results indicate the potential for consistent attendees of the Booster Break intervention to achieve significant, positive changes related to physical activity, sedentary behavior, and body mass index.

Developing a pooled job physical exposure data set from multiple independent studies: an example of a consortium study of carpal tunnel syndrome.

BACKGROUND: Six research groups independently conducted prospective studies of carpal tunnel syndrome (CTS) incidence in 54 US workplaces in 10 US States. Physical exposure variables were collected by all research groups at the individual worker level. Data from these research groups were pooled to increase the exposure spectrum and statistical power. OBJECTIVE: This paper provides a detailed description of the characteristics of the pooled physical exposure variables and the source data information from the individual research studies. METHODS: Physical exposure data were inspected and prepared by each of the individual research studies according to detailed instructions provided by an exposure subcommittee of the research consortium. Descriptive analyses were performed on the pooled physical exposure data set. Correlation analyses were performed among exposure variables estimating similar exposure aspects. RESULTS: At baseline, there were a total of 3010 participants in the pooled physical exposure data set. Overall, the pooled data meaningfully increased the spectra of most exposure variables. The increased spectra were due to the wider range in exposure data of different jobs provided by the research studies. The correlations between variables estimating similar exposure aspects showed different patterns among data provided by the research studies. CONCLUSIONS: The increased spectra of the physical exposure variables among the data pooled likely improved the possibility of detecting potential associations between these physical exposure variables and CTS incidence. It is also recognised that methods need to be developed for general use by all researchers for standardisation of physical exposure variable definition, data collection, processing and reduction.

Effect of font size and glare on computer tasks in young and older adults.

PURPOSE: At a fixed viewing distance (VD), reading speed increases with print size. It is not known if this holds for computer tasks when postures are not constrained. Reflective glare on a monitor may reduce productivity. The effects of both may be modified by age. We evaluated effects of age, font size, and glare on performance for visually demanding text-based tasks on a computer. METHODS: Nineteen young (18 to 35 years old) and eight older (55 to 65 years old wearing progressive lenses that correct for presbyopia) subjects participated in a study with two trial factors: font size (1.78, 2.23, and 3.56 mm) and glare (produced by bright light-emitting diode task light reflective off a matte liquid crystal display monitor). The monitor location was fixed but subjects were allowed to change their posture and move the chair. Subjects performed visual tasks that required similar visual skills to common tasks such as Internet use, data entry, or word processing. RESULTS: Productivity, accuracy, and VD increased as font size increased. For each 1-mm increase in font size, there was a mean productivity gain of 3 correct clicks/min and an improvement in accuracy of 2%. Font size increase also led to lowered perceived task difficulty. Adding reflective glare on the monitor surface led to a reduced VD but had no effect on productivity or accuracy. With visual corrections for presbyopia, age had no effect on these relationships. CONCLUSIONS: Productivity is improved when the font is increased from 1.78 or 2.23 to 3.56 mm for text-based computer tasks. The largest font size corresponds to a visual angle of font of 23.4 arcmin. This visual angle of font is above the high end of ISO recommendations (International Organization for Standardization, 1992, 2011). The findings may be useful for setting the font sizes for computers and for training office workers.

Booster Breaks in the workplace: participants' perspectives on health-promoting work breaks.

Increasing sedentary work has been associated with greater cardiovascular and metabolic risk, as well as premature mortality. Interrupting the sedentary workday with health-promoting work breaks can counter these negative health effects. To examine the potential sustainability of work-break programs, we assessed the acceptance of these breaks among participants in a Booster Break program. We analyzed qualitative responses from 35 participants across five worksites where one 15-min physical activity break was taken each workday. Two worksites completed a 1-year intervention and three worksites completed a 6-month intervention. Responses to two open-ended questions about the acceptance and feasibility of Booster Breaks were obtained from a survey administered after the intervention. Three themes for benefits and two themes for barriers were identified. The benefit themes were (i) reduced stress and promoted enjoyment, (ii) increased health awareness and facilitated behavior change, and (iii) enhanced workplace social interaction. The barrier themes were the need for (iv) greater variety in Booster Break routines and (v) greater management support. This study provides empirical support for the acceptance and feasibility of Booster Breaks during the workday. Emphasizing the benefits and minimizing the barriers are strategies that can be used to implement Booster Breaks in other workplaces.

Touch displays: the effects of palm rejection technology on productivity, comfort, biomechanics and positioning.

Direct touch displays can improve the human-computer experience and productivity; however, the higher hand locations may increase shoulder fatigue. Palm rejection (PR) technology may reduce shoulder loads by allowing the palms to rest on the display and increase productivity by registering the touched content and fingertips through the palms rather than shoulders. The effects of PR were evaluated by having participants perform touch tasks while posture and reaction force on the display were measured. Enabling PR, during which the subjects could place the palms on the display (but were not required to), resulted in increased wrist extension, force applied to the display and productivity, and less discomfort, but had no effect on the self-selected positioning of the display. Participants did not deliberately place their palms on the display; therefore, there was no reduction in shoulder load and the increased productivity was not due to improved hand registration. The increased productivity may have been due to reduced interruptions from palm contacts or reduced motor control demands.

Pooling job physical exposure data from multiple independent studies in a consortium study of carpal tunnel syndrome.

Pooling data from different epidemiological studies of musculoskeletal disorders (MSDs) is necessary to improve statistical power and to more precisely quantify exposure-response relationships for MSDs. The pooling process is difficult and time-consuming, and small methodological differences could lead to different exposure-response relationships. A sub-committee of a six-study research consortium studying carpal tunnel syndrome: (i) visited each study site, (ii) documented methods used to collect physical exposure data and (iii) determined compatibility of exposure variables across studies. Certain measures of force, frequency of exertion and duty cycle were collected by all studies and were largely compatible. A portion of studies had detailed data to investigate simultaneous combinations of force, frequency and duration of exertions. Limited compatibility was found for hand/wrist posture. Only two studies could calculate compatible Strain Index scores, but Threshold Limit Value for Hand Activity Level could be determined for all studies. Challenges of pooling data, resources required and recommendations for future researchers are discussed. PRACTITIONER SUMMARY: There is a need for standardised measures and measurement protocols of physical exposure for the upper extremity. This study may provide guidance for those planning to conduct an epidemiological study on quantified job physical exposures, or planning to merge physical exposure data from similar studies with some methodologic differences.

Follow-up of neck and shoulder pain among sewing machine operators: The Los Angeles garment study.

BACKGROUND: The aim of the present study is to explore factors affecting or modifying self-reported neck/shoulder pain in sewing machine operators. METHODS: We investigated self-report neck/shoulder pain in 247 workers who participated in a 4-month prospective intervention study for musculoskeletal disorders. All participants were immigrants. We examine the influence of individual and work-related factors on changes in neck/shoulder pain during follow-up employing linear mixed models with time-spline functions. RESULTS: We observed a dramatic decline (72%) in self-reported pain intensity in the first month of follow-up, followed by a small increase from the first to fourth month (4% per month). Workers who perceived and reported their physical workload as high or worked overtime experienced less overall pain reduction. Higher baseline pain intensity, being of Hispanic ethnicity (vs. Asian), and taking cumulative daily rest time during work of 35 min or more allowing for muscles to rest were associated with a larger pain reduction in the first month, but not thereafter. CONCLUSION: Our findings indicate that some work-related factors may be of clinical relevance for reducing neck/shoulder pain. Having lower physical workloads and less overtime work should be considered when treating patients or planning workplace interventions for managing work-related musculoskeletal disorders in this underserved immigrant population.

A randomized controlled trial evaluating an alternative mouse or forearm support on change in median and ulnar nerve motor latency at the wrist.

BACKGROUND: The purpose of this study was to determine the effects of an alternative mouse and/or a forearm support board on nerve function at the wrist among engineers. METHODS: This randomized controlled intervention trial followed 206 engineers for 1 year. Distal motor latency (DML) at baseline and follow-up was conducted for the median and ulnar nerves at the right wrist. RESULTS: One hundred fifty-four subjects agreed to a nerve conduction study at the beginning and end of the study period. Those who received the alternative mouse had a protective effect (OR = 0.47, 95% CI 0.22-0.98) on change in the right ulnar DML. There was no significant effect on the median nerve DML. The forearm support board had no significant effect on the median or ulnar nerve DML. CONCLUSIONS: In engineers who use a computer for more than 20 hr per week, an alternative mouse may have a protective effect for ulnar nerve function at the wrist. No protective effect of a forearm support board was found for the median nerve.

Cyclic loading inhibits expression of MMP-3 but not MMP-1 in an in vitro rabbit flexor tendon model.

BACKGROUND: Gene expression analysis is useful for assessing cellular behavior and may improve our understanding of the initial cellular response to mechanical load leading to tendon degeneration. This study assessed gene expression of MMP-1 and MMP-3, genes associated with matrix degradation, in tendons exposed to cyclic loads within physiologic range. METHODS: Six flexor tendons from each of ten New Zealand White rabbits were harvested and randomly assigned to one of the following six groups: load deprived for 18h; cyclically loaded for 18h to a peak stress of 2MPa; 3MPa; 4MPa; 5MPa; or snap frozen in liquid nitrogen. MMP-1, MMP-3 and 18s mRNA expression was measured by qRT-PCR. FINDINGS: No significant differences in MMP-1 mRNA expression levels were found between loading groups. MMP-3 expression was significantly inhibited (57%) in tendons cyclically loaded to a peak stress of 4MPa in comparison to load deprived tendons, however, when peak stress was increased to 5MPa, expression was no longer significantly lower compared to stress shielded tendons. INTERPRETATION: The results suggest a 'U' shape relationship between load and MMP-3 expression. The lack of change in MMP-1 expression with loading was unexpected as inhibition of MMP-1 in response to mechanical load has been demonstrated in previous studies. In conclusion, we demonstrate that MMP-3 expression is modulated by cyclic load and is sensitive to load magnitude. MMP-1 mRNA expression is not significantly modulated by cyclic load in this model.

Effect of repetition rate on the formation of microtears in tendon in an in vivo cyclical loading model.

We reported previously the formation of microtears in an in vivo loaded Flexor Digitorum Profundus (FDP) rabbit tendon with a repetition rate of 60 repetitions per minute and a peak force of 15% of maximum peak tetanic force for 80 cumulative hours. Tear area as a percent of tendon area, tear density (tears/mm(2)), and mean tear size (microm(2)) were higher in tendons from the loaded limb compared to the unloaded control limb. The purpose of the present study was to compare those results to results obtained with a repetition rate of 10 while maintaining the same peak force and force-time integral (n = 8). Due to a strain gradient between the inner and outer sides of the FDP tendon, microtears were quantified in four regions, two regions each along the inner and outer sides of the tendon. The tear area as a percent of total tendon area and the mean tear size were significantly greater in the loaded limb compared to the unloaded limb (p < 0.03). However, the effects were less than those observed at 60 repetitions/min. The higher repetition loading pattern resulted in an increase in tear measures in all four regions, while the lower rate produced changes only in the outer regions of the tendon. This finding may establish where the initial sites of damage occur in tendons that insert into bone in a similar arrangement as the FDP. The results suggest that repetition rate or number of loading cycles is associated with increased tendon microtears or fragility in a dose-response pattern.

A multi-method study evaluating computing-related risk factors among college students.

PURPOSE: To characterize undergraduate computer use using different data collection methods, emphasizing computing-related postures, use patterns and upper extremity musculoskeletal symptoms. SUBJECTS AND METHODS: In Spring, 2004, undergraduate students from a single dormitory at a private university agreed to complete a College Computing & Health Survey. For three separate data collection periods each lasting a week, we observed postures during computer once per period and continuously measured computer input device usage. During these three periods, students self-reported computer usage and symptoms 3-5 times daily. RESULTS: Thirty students participated and all completed the study. Eighty-six percent reported ever experiencing symptoms after computer work. There were no time-related trends across data collection periods for posture, symptoms, and computing activities and patterns. Typed work and communicating (when compared with playing games) were usually the predominant computing activities throughout the semester. There was significantly greater self-reported computer use than that directly measured (p<0.05). CONCLUSION: This is the first study that utilized several methods of exposure assessment to describe computing postures, use patterns and upper extremity musculoskeletal symptoms among a college student cohort. Epidemiological studies need to explore time-related changes such as time of day, weekday, and days into the semester to further understand symptoms, posture, and computer use changes.

VEGF, VEGFR-1, and CTGF cell densities in tendon are increased with cyclical loading: An in vivo tendinopathy model.

Tendon injuries can occur in athletes and workers whose tasks involve repetitive, high-force hand activities, but the early pathophysiologic processes of tendinopathy are not well known. The purpose of this animal study was to evaluate the effects of cyclical tendon loading on the densities of cells producing growth factors such as vascular endothelial growth factor (VEGF), its receptor, vascular endothelial growth factor receptor 1 (VEGFR-1), and connective tissue growth factor (CTGF) in the Flexor Digitorum Profundus (FDP) tendon at the epicondyle. The FDP muscles of nine New Zealand rabbits were electrically stimulated to contract repetitively for 80 h of cumulative loading over 14 weeks. The contralateral limbs served as controls. The tendons at the medial epicondyle insertion sites were harvested, and sections were immunostained with antibodies directed against VEGF, VEGFR-1, or CTGF. Positive-staining cells were counted in six regions of interest: three along the enthesis, and three corresponding regions 1500 microns distal to the enthesis. VEGF (p = 0.0001), VEGFR-1 (p = 0.046), and CTGF (p = 0.0001) cell densities were increased in the tendon of the loaded limb compared to the nonloaded limb. In addition, regional differences in VEGF, VEGFR-1, and CTGF cell densities were found. VEGF, VEGFR-1, and CTGF are increased in tendon experiencing cyclical loading and may play a role in the early vascular changes in the progression to tendinosis.

Evidence of tendon microtears due to cyclical loading in an in vivo tendinopathy model.

Tendon injuries at the epicondyle can occur in athletes and workers whose job functions involve repetitive, high force hand activities, but the early pathophysiologic changes of tendon are not well known. The purpose of this study was to evaluate early tendon structural changes, specifically the formation of microtears, caused by cyclical loading. The Flexor Digitorum Profundus (FDP) muscle of nine New Zealand White rabbits was stimulated to contract repetitively for 80 h of cumulative loading over 14 weeks. The contralateral limb served as a control. The tendon at the medial epicondyle insertion site was harvested, sectioned, and stained. Microtears were quantified, using image analysis software, in four regions of the tendon, two regions along the enthesis and two distal to the enthesis. The tear density (loaded: 1329+/-546 tears/mm(2); unloaded: 932+/-474 tears/mm(2)) and mean tear size (loaded: 18.3+/-6.1 microm(2); unloaded: 14.0+/-4.8 microm(2)) were significantly greater in the loaded limb (p<0.0001) across all regions compared to the unloaded contralateral limb. These early microstructural changes in a repetitively loaded tendon may initiate a degenerative process that leads to tendinosis.

Upper extremity mononeuropathy among engineers.

OBJECTIVES: The objectives of this study were to estimate the prevalence of mononeuropathy at the wrist among engineers who use computers and to identify associated risk factors. METHODS: This is a cross-sectional study of 202 engineers using questionnaires and electrophysiological nerve testing. The definition for median or ulnar mononeuropathy required the combination of distal upper extremity discomfort and abnormal distal motor latency. RESULTS: The prevalence of neuropathy at the wrist among engineers was 10.3% (right median), 3.4% (left median), 1.8% (right ulnar), and 2.9% (left ulnar). Logistic regression analysis identified three variables with positive associations (body mass index, hours of computer use, and antihypertensive medication) and three variables with negative associations (typing speed, driving hours, total break time). CONCLUSIONS: Mononeuropathies at the wrist occur among computer-using engineers and are related to a number of factors, including hours of computer use.

Entrapment neuropathies: pathophysiology and pathogenesis.

A number of theories of pathogenesis of entrapment neuropathy, due to repeated loading, have been proposed and these theories are being actively explored with animal models. Tubes placed loosely around peripheral nerves cause delayed onset, chronic pain and changes in nerve morphology including nerve sprouting. Balloons placed around or adjacent to the nerve and inflated to low pressures, rapidly produce endoneurial edema and a persistent increase in intraneural pressure. The same models demonstrate long-term changes such as demyelination and fibrosis. The applied pressure causes a decrement in nerve function and abnormal morphology in a dose-dependent manner that appears to be linked to the amount of endoneurial edema. A new model involving involuntary, repetitive fingertip loading for 6 h per week for 4 weeks has caused slowing of nerve function at the wrist similar to that seen in patients with carpal tunnel syndrome. These models have the potential to reveal the mechanisms of injury at the cellular and biochemical level and address questions about the relative importance of various biomechanical factors (e.g. peak force, mean force, force rate, duty cycle, etc.). In addition, these models will allow us to evaluate various prevention, treatment and rehabilitation protocols.

Exposure-response relationships for the ACGIH threshold limit value for hand-activity level: results from a pooled data study of carpal tunnel syndrome.

OBJECTIVES: This paper aimed to quantify exposure-response relationships between the American Conference of Governmental Industrial Hygienists' (ACGIH) threshold limit value (TLV) for hand-activity level (HAL) and incidence of carpal tunnel syndrome (CTS). METHODS: Manufacturing and service workers previously studied by six research institutions had their data combined and re-analyzed. CTS cases were defined by symptoms and abnormal nerve conduction. Hazard ratios (HR) were calculated using proportional hazards regression after adjusting for age, gender, body mass index, and CTS predisposing conditions. RESULTS: The longitudinal study comprised 2751 incident-eligible workers, followed prospectively for up to 6.4 years and contributing 6243 person-years of data. Associations were found between CTS and TLV for HAL both as a continuous variable [HR 1.32 per unit, 95% confidence interval (95% CI) 1.11-1.57] and when categorized using the ACGIH action limit (AL) and TLV. Those between the AL and TLV and above the TLV had HR of 1.7 (95% CI 1.2-2.5) and 1.5 (95% CI 1.0-2.1), respectively. As independent variables (in the same adjusted model) the HR for peak force (PF) and HAL were 1.14 per unit (95% CI 1.05-1.25), and 1.04 per unit (95% CI 0.93-1.15), respectively. CONCLUSION: Those with exposures above the AL were at increased risk of CTS, but there was no further increase in risk for workers above the TLV. This suggests that the current AL may not be sufficiently protective of workers. Combinations of PF and HAL are useful for predicting risk of CTS.

Ergonomic evaluation of ten single-channel pipettes.

UNLABELLED: Repetitive pipetting is a task that is associated with work-related musculoskeletal disorders of the hand and arm. OBJECTIVE: The purpose of this study was to evaluate the usability and ergonomic performance of commercially available pipettes as determined by user ratings and objective measurements. PARTICIPANTS: Participants were laboratory technicians and scientists at the Lawrence Berkeley National Laboratory with experience performing pipetting tasks. METHODS: Twenty-one experienced pipette users completed a standardized pipetting task with 5 manual and 5 electronic pipettes. After using each pipette, the user rated it for attributes of comfort and usability. RESULTS: Although no single pipette was rated significantly better than all of the others for every attribute tested, some significant differences were found between pipettes. The Rainin Pipet-Lite received the highest overall quality score among manual pipettes, while the Thermo Scientific Finnpipette Novus was the top-ranked electronic pipette. Features correlated with greater hand and arm comfort were lower tip ejection force, lower blowout force, and pipette balance in the hand. CONCLUSIONS: The findings, when considered with participant comments, provide insights into desirable pipette features and emphasize the value of user testing and the importance of the interactions between task, workplace layout, and pipette design.

The Booster Break program: description and feasibility test of a worksite physical activity daily practice.

OBJECTIVE: Work breaks are underutilized opportunities to promote health. The Booster Break program is a co-worker led physical activity group session devoted exclusively to standard 15-minute work breaks. The purpose of this study was to report the fidelity, attendance, feasibility, and sustainability of the Booster Break program and to explore its potential impact. PARTICIPANTS: The study site was a small business that provides legal and court reporting services to lawyers. The company's services include legal videography, litigation, records retrieval, and videoconferencing to civil attorneys. Established in 1973, the organization has 14 employees (8 women and 6 men), from 32 to 66 years of age. METHODS: For six months, this small business implemented the Booster Break program. Booster Break facilitators conducted the group sessions according to protocol, which included describing, cueing, and executing the physical activity sequence. RESULTS: During the six month period, 117 sessions were conducted. The average monthly attendance ranged from 76% to 86%. Participants significantly improved HDL cholesterol (p=0.04) and lost an average of 14 pounds. CONCLUSIONS: The Booster Break program is a feasible physical activity program for small business settings. The implications of the Booster Break program for future research in worksite settings are discussed.

Self-reported pain and physical signs for musculoskeletal disorders in the upper body region among Los Angeles garment workers.

Reports of pain and physical exam findings for musculoskeletal disorders (MSDs) are two common outcome measures independently used to assess work-related MSDs in the scientific literature. How these measures correlate with each other, however, is largely unknown. We recruited 520 sewing machine operators to describe the correlation between subjective self-reported pain and physical findings of MSDs in three upper body regions including the neck/shoulder, elbow/forearm, and hand/wrist. Self-reports of pain and physical findings resulted in different and partly non-overlapping classifications of subjects as MSD cases in our study. Both outcome measures were found to be consistently associated with 'having a medical history of MSDs', 'perceived physical exertion', 'perceived job insecurity' (neck/shoulder), being of older age (arm/forearm), and female gender (arm/forearm and hand/wrist); however, we observed inconsistency for the measures for a number of other job related factors such as 'operating a single machine' and 'number of work hours per week'. Because to date no agreed upon "gold standard" for diagnosing MSDs exists, our findings suggest that research results can be very different when using self-reported measures versus physical exam findings. Also, in order to evaluate the success of an intervention, screening, or surveillance program for work related MSDs, it is important to define clearly which outcome measure best to employ.