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.

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.

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.

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.

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.

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.

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.

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.

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.

Evaluation of two posture survey instruments for assessing computing postures among college students.

OBJECTIVE: To determine agreement between two posture assessment survey instruments and which, if any, were correlated with experiencing upper extremity musculoskeletal symptoms. METHODS: Thirty undergraduate participants had three postural assessment surveys completed, one each for three separate 7-day data collection periods during a semester. Two observation assessment tools were used, a modified Rapid Upper Limb Assessment (mRULA) for computer users for the right and left limbs and the University of California Computer Use Checklist. Concurrently, upper extremity musculoskeletal symptom experience paired to each postural assessment was measured. Lin's concordance correlation coefficient evaluated survey agreement and multi-level statistical models described associations between survey responses and symptoms. RESULTS: There was no agreement between the two postural assessment tool scores (p> 0.85). In adjusted models, the UC Computer Use Checklist was positively associated with symptoms occurrence (OR=1.4, 90% CI 1.2-1.6 for any symptoms; OR=1.3, 90% CI 1.0-1.6 for moderate or greater symptoms). Associations with mRULA scores were inconsistent in that they were sometimes protective and sometimes indicators of risk, depending on the covariates included in the models. CONCLUSION: The mRULA for computer users and the UC Computer Use Checklist were independent of each other; however, due to the inconsistent associations with symptoms we cannot conclude one instrument is superior to the other. Our data do suggest the UC Computer Use Checklist demonstrates a traditional relationship with symptoms, where increasing scores signifiy greater risk. We observed a nontraditional relatioship with symptoms for the mRULA for computer users that needs to be further examined. This is a pilot study and, thus, findings should be interpreted as exploratory. Associations observed in the current study will be used to test hypotheses in the cohort study recently conducted.

Accessibility of radiology equipment for patients with mobility disabilities.

OBJECTIVE: The purpose was to evaluate accessibility of typical radiology platforms by participants with mobility disabilities. BACKGROUND: These patients have difficulty using radiology equipment and have an increased risk of falling. METHODS: This field study evaluated three common types of radiology platforms - X ray, computed tomography (CT) scan, and fluoroscopy - by 20 patients/participants with mobility impairments who used walking aids. The participants were required to get onto the equipment, simulate a typical radiological procedure, and get off. Each participant then watched a video of his or her own session and answered questions. Four researchers independently reviewed the videotapes and identified accessibility and safety barriers. RESULTS: Overall, the CT scan platform was the easiest to use and the fluoroscopy platform the most difficult, primarily because of platform height differences. Sitting up on the Xray table was rated as difficult by most participants, primarily because of a lack of hand-holds and the surface pad not being fixed in place. Maintaining a position on the fluoroscopy platform while it rotated from horizontal to vertical was difficult and frightening for most participants. CONCLUSION: Some radiology platforms are difficult to use and are perceived to be less safe for patients with mobility disabilities. The interaction of patient disability and equipment design can impose substantial physical demands on medical personnel. Recommendations for improved design are provided to enhance radiology platform accessibility and safety. APPLICATION: The findings may be applicable to the design of a wide range of medical patient platforms.

Effect of wrist posture on carpal tunnel pressure while typing.

Long weekly hours of keyboard use may lead to or aggravate carpal tunnel syndrome. The effects of typing on fluid pressure in the carpal tunnel, a possible mediator of carpal tunnel syndrome, are unknown. Twenty healthy subjects participated in a laboratory study to investigate the effects of typing at different wrist postures on carpal tunnel pressure of the right hand. Changes in wrist flexion/extension angle (p = 0.01) and radial/ulnar deviation angle (p = 0.03) independently altered carpal tunnel pressure; wrist deviations in extension or radial deviation were associated with an increase in pressure. The activity of typing independently elevated carpal tunnel pressure (p = 0.001) relative to the static hand held in the same posture. This information can guide the design and use of keyboards and workstations in order to minimize carpal tunnel pressure while typing. The findings may also be useful to clinicians and ergonomists in the management of patients with carpal tunnel syndrome who use a keyboard.

A three-dimensional anthropometric solid model of the hand based on landmark measurements.

Hand anthropometry data are largely based on measurements of the hand in an outstretched hand posture and are, therefore, difficult to apply to tool gripping hand postures. The purpose of this project was to develop a representative, scalable hand model to be used with 3-D software drawing packages to aid in the ergonomic design of hand tools. Landmarks (66) on the palmar surface of the right hand of 100 subjects were digitised in four functional hand postures and, from these, 3-D surface models of a mean, 25th and 75th% hand were developed. The root mean square differences in hand length between the hand model and the digitised data for the 25th, 50th and 75th percentile hand were 11.4, 3.2 and 8.9 mm, respectively. The corresponding values for hand breadth were 2.0, 0.4 and 1.4 mm. There was good agreement between distances on the digitised hand and the hand model. The application of this research includes improved ergonomic hand tool design through the use of hand anthropometry reference values developed from the general population using grasping hand postures.

A randomized controlled trial of chair interventions on back and hip pain among sewing machine operators: the los angeles garment study.

OBJECTIVE: Determine whether an adjustable chair with a curved or a flat seat pan improved monthly back and hip pain scores in sewing machine operators. METHODS: This 4-month intervention study randomized 293 sewing machine operators with back and hip pain. The participants in the control group received a placebo intervention, and participants in the intervention groups received the placebo intervention and one of the two intervention chairs. RESULTS: Compared with the control group, mean pain improvement for the flat chair intervention was 0.43 points (95% CI = 0.34, 0.51) per month, and mean pain improvement for the curved chair intervention was 0.25 points (95% CI = 0.16, 0.34) per month. CONCLUSIONS: A height-adjustable task chair with a swivel function can reduce back and hip pain in sewing machine operators. The findings may be relevant to workers who perform visual- and hand-intensive manufacturing jobs.

MMP-1, IL-1beta, and COX-2 mRNA expression is modulated by static load in rabbit flexor tendons.

Tendon cells respond to their mechanical environment by synthesizing and degrading the surrounding matrix. This study examined how expression of genes associated with tendon degeneration is affected by static loads. Forty flexor tendons from 10 New Zealand White rabbits were harvested and secured in a tissue loading system. A static load of 0, 2, 4, or 6 MPa was applied to tendons for 20 h. MMP-1, IL-1beta, COX-2, GAPDH, and 18s mRNA expression was measured by qRT-PCR. MMP-1 expression in tendons loaded to 6 MPa was significantly increased 259% compared to tendons loaded to 4 MPa. Relative to a 0 MPa load, IL-1beta expression was inhibited with load at 4 MPa (48%) while COX-2 expression was increased at 6 MPa (219%). A polynomial regression analysis found a significant positive correlation between creep and expression of MMP-1 (R(2) = 0.53, p < 0.001) and IL-1beta (R(2) = 0.55, p < 0.001). The results of this study indicate that moderate load inhibits IL-1beta and high load stimulates COX-2 relative to stress shielding. MMP-1 expression is up-regulated with high loads compared to moderate loads. The correlation between creep and expression suggests that the pathway for MMP-1 and IL-1beta expression, leading eventually to tendon degeneration, may be regulated by the biomechanical factor creep.

Evaluation of gene expression through qRT-PCR in cyclically loaded tendons: an in vivo model.

An in vivo rabbit animal model for the tendinopathy, epicondylitis, was used to examine the effects of repetitive load on the expression of various genes associated with matrix remodeling. Following 80 h of cumulative load, tissue from the distal and proximal regions of the flexor digitorum profundus tendon was collected. Quantitative RT-PCR was used to asses mRNA levels of collagenase-1 (MMP-1), stromelysin (MMP-3), vascular endothelial growth factor (VEGF), connective tissue growth factor (CTGF), cyclooxygenase-2 (COX-2), interleukin-1beta (IL-1beta), type III collagen (COL-III) and fibronectin (FBRN). No significant differences in expression levels were found between loaded and unloaded limbs at either region of the tendon. The findings were unexpected as the same model has already demonstrated an increase in the density of cells staining for VEGF and CTGF. Different regulatory mechanisms between mRNA and protein expression or localized changes missed due to homogenization of the tissue samples, may explain the discrepancy in findings.