Testing the shock protection performance of Type I construction helmets using impactors of different masses

BACKGROUND

Wearing protective helmets is an important prevention strategy to reduce work-related traumatic brain injuries. The existing standardized testing systems are used for quality control and do not provide a quantitative measure of the helmet performance.

OBJECTIVE

To analyze the failure characterizations of Type I industrial helmets and develop a generalized approach to quantify the shock absorption performance of Type I industrial helmets based on the existing standardized setups.

METHODS

A representative basic Type I construction helmet model was selected for the study. Top impact tests were performed on the helmets at different drop heights using two different impactor masses (3.6 and 5.0 kg).

RESULTS

When the helmets were impacted with potential impact energies smaller than the critical potential impact energy values, there was a consistent relationship between the peak impact force and the potential impact energy. When the helmets were impacted under potential impact energies greater than the critical potential impact energy values, the peak impact forces increased steeply with increasing potential impact energy.

CONCLUSION

A concept of safety margin for construction helmets based on potential impact energy was introduced to quantify the helmets' shock absorption performance. The proposed method will help helmet manufacturers improve their product quality.

Application of polyethylene air-bubble cushions to improve the shock absorption performance of Type I construction helmets for repeated impacts

BACKGROUND

The use of helmets was considered to be one of the important prevention strategies employed on construction sites. The shock absorption performance of a construction (or industrial) helmet is its most important performance parameter. Industrial helmets will experience cumulative structural damage when being impacted repeatedly with impact magnitudes greater than its endurance limit.

OBJECTIVE

The current study is to test if the shock absorption performance of Type I construction helmets subjected to repeated impacts can be improved by applying polyethylene air-bubble cushions to the helmet suspension system.

METHODS

Drop impact tests were performed using a commercial drop tower test machine following the ANSI Z89.1 Type I drop impact protocol. Typical off-the-shelf Type I construction helmets were evaluated in the study. A 5 mm thick air-bubble cushioning liner was placed between the headform and the helmet to be tested. Helmets were impacted ten times at different drop heights from 0.61 to 1.73 m. The effects of the air-bubble cushioning liner on the helmets' shock absorption performance were evaluated by comparing the peak transmitted forces collected from the original off-the-shelf helmet samples to the helmets equipped with air-bubble cushioning liners.

RESULTS

Our results showed that a typical Type I construction helmet can be subjected to repeated impacts with a magnitude less than 22 J (corresponding to a drop height 0.61 m) without compromising its shock absorption performance. In comparison, the same construction helmet, when equipped with an air-bubble cushioning liner, can be subjected to repeated impacts of a magnitude of 54 J (corresponding to a drop height 1.52 m) without compromising its shock absorption performance.

CONCLUSIONS

The results indicate that the helmet's shock absorbing endurance limit has been increased by 145% with addition of an air-bubble cushioning liner.

Biomechanical assessment while using production tables on mast climbing work platforms

The objective of this study was to assess the impact of using alternative mast climbing work platform (MCWP) designs on trunk motion and postural stability with masonry workers while performing bricklaying and stepping down tasks using a conventional MCWP setting (i.e. with a step deck) as well as two types of production tables (straight- and L-shaped). The trunk angles and postural sway parameters of twenty-five masonry workers were recorded for the following tasks: (1) standing on a simulated MCWP and laying bricks on an adjacent wall, and (2) stepping down onto the step deck to get into position for doing the bricklaying task. Results indicated that the use of the L-shaped production table resulted in the lowest trunk ranges of motion and significantly reduced the workers' trunk angles in all three planes when compared to both the straight-shaped production table and the conventional approach of not using a production table. Data showed that both body sway velocity and area were significantly reduced when using either one of the production tables. The use of production tables significantly reduced impact sway forces when workers stepped from the main platform to the step deck. The use of production tables on MCWPs improved workers' postures and overall stability, which could reduce the risk of injury.

Evaluation of the shock absorption performance of construction helmets under repeated top impacts

It is accepted in industries that an industrial helmet should be disposed of when it is subjected to a significant impact. There is no scientific evidence that supports this well-accepted belief. The current study was intended to evaluate the shock absorption performance of industrial helmets under repeated impacts. Common industrial or construction helmets are categorized as Type I according to ANSI Z89.1 and they are designed to mainly protect top impacts. A representative basic Type I construction helmet model was selected in the study. Helmets were repeatedly impacted ten times using a commercial drop tower tester with an impactor (mass 3.6 kg) at different drop heights from 0.30 to 2.03 m. A total of 80 impact trials were performed in the study. The relationships of the transmitted force with the drop height and with impact number were analyzed. A new parameter - the endurance limit - was proposed to evaluate the shock absorption performance of a helmet. The helmets were observed to experience cumulative structural damage with increasing impact number, resulting in a degrading shock absorption performance, when being impacted repeatedly with magnitudes greater than the endurance limit. Repeated impacts with magnitudes smaller than the endurance limit did not cause measurable cumulative structural damage to the helmets in our study.

Evaluation of postural sway and impact forces during ingress and egress of scissor lifts at elevations

Workers are at risk when entering (ingress) or exiting (egress) elevated scissor lifts. In this study, we recorded ground impact forces and postural sway from 22 construction workers while they performed ingress and egress between a scissor lift and an adjacent work surface with varying conditions: lift opening designs, horizontal and vertical gaps, and sloped work surfaces. We observed higher peak ground shear forces when using a bar-and-chain opening, with larger horizontal gap, with the lift surface more than 0.2 m below the work surface, and presence of a sloped (26°) work surface. Similar trends were observed for postural sway, except that the influence of vertical distance was not significant. To reduce slip/trip/fall risk and postural sway of workers while ingress or egress of an elevated scissor lift, we suggest scissor lifts be equipped with a gate-type opening instead of a bar-and-chain design. We also suggest the lift surface be placed no more than 0.2 m lower than the work surface and the horizontal gap between lift and work surfaces be as small as possible. Selecting a non-sloped surface to ingress or egress a scissor lift is also preferred to reduce risk.

An improved finite element modeling of the cerebrospinal fluid layer in the head impact analysis

The finite element (FE) method has been widely used to investigate the mechanism of traumatic brain injuries (TBIs), because it is technically difficult to quantify the responses of the brain tissues to the impact in experiments. One of technical challenges to build a FE model of a human head is the modeling of the cerebrospinal fluid (CSF) of the brain. In the current study, we propose to use membrane elements to construct the CSF layer. Using the proposed approach, we demonstrate that a head model can be built by using existing meshes available in commercial databases, without using any advanced meshing software tool, and with the sole use of native functions of the FE package Abaqus. The calculated time histories of the intracranial pressures at frontal, posterior fossa, parietal, and occipital positions agree well with the experimental data and the simulations in the literature, indicating that the physical effects of the CSF layer have been accounted for in the proposed modeling approach. The proposed modeling approach would be useful for bioengineers to solve practical problems.

Accelerated Evaluation of Automated Vehicles Safety in Lane-Change Scenarios Based on Importance Sampling Techniques

Automated vehicles (AVs) must be thoroughly evaluated before their release and deployment. A widely used evaluation approach is the Naturalistic-Field Operational Test (N-FOT), which tests prototype vehicles directly on the public roads. Due to the low exposure to safety-critical scenarios, N-FOTs are time consuming and expensive to conduct. In this paper, we propose an accelerated evaluation approach for AVs. The results can be used to generate motions of the other primary vehicles to accelerate the verification of AVs in simulations and controlled experiments. Frontal collision due to unsafe cut-ins is the target crash type of this paper. Human-controlled vehicles making unsafe lane changes are modeled as the primary disturbance to AVs based on data collected by the University of Michigan Safety Pilot Model Deployment Program. The cut-in scenarios are generated based on skewed statistics of collected human driver behaviors, which generate risky testing scenarios while preserving the statistical information so that the safety benefits of AVs in nonaccelerated cases can be accurately estimated. The cross-entropy method is used to recursively search for the optimal skewing parameters. The frequencies of the occurrences of conflicts, crashes, and injuries are estimated for a modeled AV, and the achieved accelerated rate is around 2000 to 20 000. In other words, in the accelerated simulations, driving for 1000 miles will expose the AV with challenging scenarios that will take about 2 to 20 million miles of real-world driving to encounter. This technique thus has the potential to greatly reduce the development and validation time for AVs.

Finite element simulations of the head-brain responses to the top impacts of a construction helmet: Effects of the neck and body mass

Traumatic brain injuries are among the most common severely disabling injuries in the United States. Construction helmets are considered essential personal protective equipment for reducing traumatic brain injury risks at work sites. In this study, we proposed a practical finite element modeling approach that would be suitable for engineers to optimize construction helmet design. The finite element model includes all essential anatomical structures of a human head (i.e. skin, scalp, skull, cerebrospinal fluid, brain, medulla, spinal cord, cervical vertebrae, and discs) and all major engineering components of a construction helmet (i.e. shell and suspension system). The head finite element model has been calibrated using the experimental data in the literature. It is technically difficult to precisely account for the effects of the neck and body mass on the dynamic responses, because the finite element model does not include the entire human body. An approximation approach has been developed to account for the effects of the neck and body mass on the dynamic responses of the head-brain. Using the proposed model, we have calculated the responses of the head-brain during a top impact when wearing a construction helmet. The proposed modeling approach would provide a tool to improve the helmet design on a biomechanical basis.

Gap Acceptance During Lane Changes by Large-Truck Drivers-An Image-Based Analysis

This paper presents an analysis of rearward gap acceptance characteristics of drivers of large trucks in highway lane change scenarios. The range between the vehicles was inferred from camera images using the estimated lane width obtained from the lane tracking camera as the reference. Six-hundred lane change events were acquired from a large-scale naturalistic driving data set. The kinematic variables from the image-based gap analysis were filtered by the weighted linear least squares in order to extrapolate them at the lane change time. In addition, the time-to-collision and required deceleration were computed, and potential safety threshold values are provided. The resulting range and range rate distributions showed directional discrepancies, i.e., in left lane changes, large trucks are often slower than other vehicles in the target lane, whereas they are usually faster in right lane changes. Video observations have confirmed that major motivations for changing lanes are different depending on the direction of move, i.e., moving to the left (faster) lane occurs due to a slower vehicle ahead or a merging vehicle on the right-hand side, whereas right lane changes are frequently made to return to the original lane after passing.

Can hepatitis B virus DNA in semen be predicted by serum levels of hepatitis B virus DNA, HBeAg, and HBsAg in chronically infected men from infertile couples?

Hepatitis B virus (HBV) in semen is important for father-to-child transmission of HBV and has adverse effects on sperm quality. However, risk factors associated with HBV in semen remain unclear. Serum HBV DNA and hepatitis B e antigen (HBeAg) levels may pose a risk on HBV in semen. This study aims to examine whether serum HBV DNA, HBeAg, and hepatitis B surface antigen (HBsAg) level were associated with HBV DNA in semen. 151 male patients chronically infected with HBV from infertile couples were included. Serum HBsAg and HBeAg were determined using an electrochemiluminescence immune assay (ECLIA). Serum and seminal plasma HBV DNA were detected by the QIAGEN Real-Time HBV DNA assay. Of 151 patients, 143 (94.7%) were serum HBV DNA-positive and 65 (43.0%) were seminal plasma HBV DNA-positive. Serum HBV DNA and HBeAg level of seminal plasma HBV DNA-positive patients were significantly higher (p < 0.001) as compared with those of seminal plasma HBV DNA-negative patients, HBsAg level of seminal plasma HBV DNA-positive patients was significantly lower (p < 0.001) compared with that of seminal plasma HBV DNA-negative patients. The best serum HBV DNA, HBeAg, and HBsAg value for discriminating between seminal plasma HBV DNA-positive and HBV DNA-negative patients were ≥6.9 log10 IU/mL (sensitivity 100.0%, specificity 90.7%), >14.8 S/CO (sensitivity 96.9%, specificity 81.5%), and <1791.5 S/CO (sensitivity 81.5%, specificity 81.2%), respectively. The combination of serum HBV DNA and HBeAg had high diagnostic sensitivity (100.0%) and specificity (95.4%) for the presence of HBV DNA in semen. As such, these serum markers especially the combination of HBV DNA and HBeAg are useful predictors of the presence of HBV DNA in semen in HBV chronically infected men from infertile couples.

Assessment of fall-arrest systems for scissor lift operators: computer modeling and manikin drop testing

OBJECTIVE

The current study is intended to evaluate the stability of a scissor lift and the performance of various fall-arrest harnesses/lanyards during drop/fall-arrest conditions and to quantify the dynamic loading to the head/ neck caused by fall-arrest forces.

BACKGROUND

No data exist that establish the efficacy of fall-arrest systems for use on scissor lifts or the injury potential from the fall incidents using a fall-arrest system.

METHOD

The authors developed a multibody dynamic model of the scissor lift and a human lift operator model using ADAMS and LifeMOD Biomechanics Human Modeler. They evaluated lift stability for four fall-arrest system products and quantified biomechanical impacts on operators during drop/fall arrest, using manikin drop tests. Test conditions were constrained to flat surfaces to isolate the effect of manikin-lanyard interaction.

RESULTS

The fully extended scissor lift maintained structural and dynamic stability for all manikin drop test conditions. The maximum arrest forces from the harnesses/lanyards were all within the limits of ANSI Z359.1. The dynamic loading in the lower neck during the fall impact reached a level that is typically observed in automobile crash tests, indicating a potential injury risk for vulnerable participants.

CONCLUSION

Fall-arrest systems may function as an effective mechanism for fall injury protection for operators of scissor lifts. However, operators may be subjected to significant biomechanical loadings on the lower neck during fall impact.

APPLICATION

Results suggest that scissor lifts retain stability under test conditions approximating human falls from predefined distances but injury could occur to vulnerable body structures.

Estimation of the kinetic energy dissipation in fall-arrest system and manikin during fall impact

Fall-arrest systems (FASs) have been widely applied to provide a safe stop during fall incidents for occupational activities. The mechanical interaction and kinetic energy exchange between the human body and the fall-arrest system during fall impact is one of the most important factors in FAS ergonomic design. In the current study, we developed a systematic approach to evaluate the energy dissipated in the energy absorbing lanyard (EAL) and in the harness/manikin during fall impact. The kinematics of the manikin and EAL during the impact were derived using the arrest-force time histories that were measured experimentally. We applied the proposed method to analyse the experimental data of drop tests at heights of 1.83 and 3.35 m. Our preliminary results indicate that approximately 84-92% of the kinetic energy is dissipated in the EAL system and the remainder is dissipated in the harness/manikin during fall impact. The proposed approach would be useful for the ergonomic design and performance evaluation of an FAS. STATEMENT OF RELEVANCE: Mechanical interaction, especially kinetic energy exchange, between the human body and the fall-arrest system during fall impact is one of the most important factors in the ergonomic design of a fall-arrest system. In the current study, we propose an approach to quantify the kinetic energy dissipated in the energy absorbing lanyard and in the harness/body system during fall impact.

Fall arrest characteristics of a scissor lift

PROBLEM

Census of Fatal Occupational Injuries (CFOI) data indicate 306 aerial lift fatalities between 1992-2003. Seventy-eight of these fatalities specifically involved scissor lifts. Members of standards committees have requested that NIOSH conduct research to determine the effects of safety-control practices related to using fall-protection systems for scissor lifts.

METHOD

This research examined the structural and dynamic stability of a scissor lift subjected to fall arrest forces. This was accomplished by conducting drop tests from a scissor lift. Anchorage locations evaluated included manufacturer-supplied anchorage points on the scissor lift platform as well as mid-rail and top-rail locations.

RESULTS

Preliminary drop tests determined that a 2400 lb maximum arrest force (MAF) could be generated by dropping 169 lb through a fall height of 36" using Nystron rope as a lanyard. The scissor lift maintained structural and dynamic stability for all drop tests when fully extended and on an incline.

DISCUSSION

Anchoring a fall arrest system to either the mid-rail or top-rail is not a recommended practice by the scissor lift manufacturer. Anchor points are provided on the platform floor of the scissor lift for this purpose. However, our results demonstrate that the mid-rail and top-rail absorb substantial energy from an arrested fall and may have potential as appropriate anchorage points.

IMPACT TO INDUSTRY

Employers and workers should consider implementing fall arrest systems when using scissor lifts as part of their overall risk mitigation plan for fall injury prevention.

Effects of foot placement on postural stability of construction workers on stilts

Stilts are elevated tools that are frequently used by construction workers to raise workers 18-40 inches above the ground. The objective of this laboratory study was to evaluate the potential loss of postural stability associated with the use of stilts in various foot placements. Twenty construction workers with at least 1 year of experience in the use of stilts participated in this study. One Kistler force platform was used to collect kinetic data. Participants were tested under six-foot-placement conditions. These 6 experimental conditions were statically tested under all combinations of 3 levels of elevation: 0'' (no stilts), 24'' stilt height and 40'' stilt height. SAS mixed procedure was used to evaluate the effect of different experimental conditions. The results of the multivariate analysis of variance (MANOVA) and repeated measures of univariate analyses of variance (ANOVAs) demonstrated that stilt height, foot-placement direction, and foot-placement width all had significant effects on the whole-body postural stability. This study found that the higher the stilts were elevated, the greater the postural instability. A stance position with one foot placed forward of the other foot produced greater postural instability than a position with the feet parallel and directly beneath the body. This study found that placement of the feet parallel and directly beneath the body, with the feet positioned a half shoulder width apart, caused a greater amount of postural sway and instability than one and one-and-half shoulder width. This study also found that construction workers using the stilts could perceive the likely postural instability due to the change in foot placements.

Kinematics and kinetics of gait on stilts: identification of risk factors associated with construction stilt use

This study investigated kinematics and kinetic strategies and identified risk factors associated with gait on stilts. A six-camera motion-analysis system and two force platforms were used to test 20 construction workers for straight walking or turning, with or without carrying tools while wearing safety shoes or stilts at different heights. The results indicated that gait on stilts is characterised by increases in stride length, step width and the percentage of double support period, decreases in cadence, minimum foot clearance and a weaker heel-strike and push-off. Stilts place greater joint loadings on lower extremities to compensate for the added weight and limitation in joint mobility. Smaller foot clearances found for gait on stilts constitute an increased risk for tripping over obstacles. Workers may need to avoid prolonged use of stilts to alleviate stresses on the joints. This study was conducted to determine to what extent stilts alter the gait strategies and to explain the compensatory movements. Prior to this study, there has been little substantive research to evaluate the stresses and potential injuries associated with stilts.

Aerial lift fall injuries: a surveillance and evaluation approach for targeting prevention activities

PROBLEM

Work on aerial lift platforms exposes workers to fall hazards. The objective of this study was to identify the most common injury scenarios and determine current research gaps for addressing fall incidents associated with aerial lifts.

METHODS

Three databases were searched: Census of Fatal Occupational Injuries (CFOI), NIOSH Fatality Assessment and Control Evaluation (FACE) reports, and OSHA Incident Investigation Records.

RESULTS

The majority of falls/collapses/tipovers were within the height-category of 10-29 feet. Tipovers comprised 44-46% of boom-lift falls and 56-59% of scissor-lift falls. Constructing and repairing activities were most commonly associated with fall/collapse/tipover incidents.

DISCUSSION

CFOI and OSHA/FACE show convergent data, suggesting similar scenarios for aerial lift tipovers.

IMPACT ON INDUSTRY

The analysis provides the aerial lift industry information to prioritize their efforts on aerial lift design.

The role of adrenomedullin and its receptor system in cardiovascular calcification of rat induced by Vitamin D(3) plus nicotine

Adrenomedullin (ADM) is a potent vasodilatory peptide which regulates blood pressure, cell growth and bone formation. Our work was aimed to explore the production of ADM, changes and pathophysiological significance of ADM mRNA and ADM receptor components--calcitonin receptor like receptor (CRLR) and receptor activity modifying proteins (RAMPs) mRNA in calcified myocardium and aorta of rats induced by Vitamin D3 plus nicotine. Contents of ADM in plasma, myocardium and aorta were measured by radioimmunoassay (RIA). The amount of ADM, CRLR and RAMPs mRNA was determined by semi-quantitative RT-PCR. The calcium content and alkaline phosphatase activity in myocardium and aorta of rats were measured. The results showed that the contents of calcium in calcified myocardium and aorta were increased by 3.5- and 6-fold (all P < 0.01), respectively, and alkaline phosphatases activity in calcified myocardium and aorta were increased by 66.5 and 82.7% (all P < 0.01 ), respectively, compared with control. Contents of ADM in plasma, myocardium and aorta were increased by 58% (P < 0.01), 14.3% (P < 0.01) and 27.8% P < 0.05). Furthermore, it was found that the amount of ADM, CRLR and RAMP2 mRNA in calcified myocardium was elevated by 90.6, 157.5 and 119.6% (all P < 0.01), RAMP3 mRNA was decreased by 14.1% (P < 0.01), respectively, compared with control. The amount of ADM, CRLR, RAMP2 and RAMP3 mRNA in calcified aorta was elevated by 37.7% (P < 0.01), 41.4% (P < 0.01), 60.1% (P < 0.05) and 13% P < 0.01), respectively, compared with control. The elevated level of CRLR and RAMP2 mRNA were in positive correlation with that of ADM mRNA (r = 0.992 and 0.882, respectively, P < 0.01) in calcified myocardium. The elevated level of CRLR and RAMP3 mRNA were also in positive correlation with that of ADM mRNA (r = 0.727, P < 0.05 and 0.816, P < 0.01, respectively) in calcified aorta. These results demonstrated that calcified myocardium and aorta generated an increased amount of ADM, up-regulated gene expressions of ADM, CRLR and RAMP2 mRNA. While the alteration of RAMP3 mRNA in calcified myocardium and aorta was different. These suggested that ADM and its receptor system might involve in the regulation of calcification in heart and aorta.

Traumatic injury among drywall installers, 1992 to 1995

This study examined the traumatic-injury characteristics associated with one of the high-risk occupations in the construction industry--drywall installers--through an analysis of the traumatic-injury data obtained from the Bureau of Labor Statistics. An additional objective was to demonstrate a feasible and economic approach to identify risk factors associated with a specific occupation by using an existing database. An analysis of nonfatal traumatic injuries with days away from work among wage-and-salary drywall installers was performed for 1992 through 1995 using the Occupational Injury and Illness Survey conducted by the Bureau of Labor Statistics. Results from this study indicate that drywall installers are at a high risk of overexertion and falls to a lower level. More than 40% of the injured drywall installers suffered sprains, strains, and/or tears. The most frequently injured body part was the trunk. More than one-third of the trunk injuries occurred while handling solid building materials, mainly drywall. In addition, the database analysis used in this study is valid in identifying overall risk factors for specific occupations.

Misclassification of physical work exposures as a design issue for musculoskeletal intervention studies

OBJECTIVES

This study determined the impact of misclassification due to using job titles as surrogate variables for physical work exposures to assess confounding in a study of the preventive effect of back belts on back injury. The authors present retail merchandise data that quantify misclassification from residual confounding by physical work exposures on injury rate ratios when available administrative job titles are used.

METHODS

Job title and direct observation data on 134 workers were used to calculate the percentage to which the job-title-adjusted rate ratio for back injury accounts for confounding by the true physical work exposures, awkward postures, and heavy weight handling. Workers' compensation data, an estimate of the effect of back belts from the literature, and the percentage of adjustment of the rate ratio due to the job title variable were used to calculate the magnitude of bias from the rate ratio adjusted for job title.

RESULTS

The job title variable was found to have sensitivities of 97% and 85% and specificities of 68% and 58% for awkward postures and heavy weight handling, respectively. The magnitude of confounding bias remaining for the back-injury rate ratio when the job title surrogate was used was 24% for postures and 45% for heavy weight handling.

CONCLUSIONS

The administrative job title performed poorly in this setting; residual confounding was sufficient to bias the rate ratio from 2.0 to 1.3. The effect of additional sources of misclassification and the need for better exposure measures than job title are discussed.

Ergonomic exposure assessment: an application of the PATH systematic observation method to retail workers. Postures, Activities, Tools and Handling

This study examined biomechanical stressor variables (physical work exposures) in relation to job title, gender, and back-belt status in 134 retail store workers. The principal concerns were to quantitatively describe physical work exposures and to determine the degrees to which these quantitative variables correlated with job title and with the use of back belts. An additional objective was to assess the inter-rater reliability of the observation method. The systematic observation method employed was based on a modification of the PATH (Postures, Activities, Tools, and Handling) measurement method. Chi-square analysis indicated that the frequencies of bent or twisted postures followed the pattern of unloaders > stockers > department managers. For weight handled per lift, lower, or carry, the pattern was unloaders > department managers > stockers. The mean lifting frequencies per hour were 35.9 for department managers, 48.8 for stockers, and 137.4 for unloaders. Back-belt-wearing percentages were higher for unloaders (63%) compared with stockers (48%) and department managers (25%). Back-belt-wearing workers had higher levels of biomechanical stressor variables, including arm position, twisting, weight handled, and number of lifts per hour. Kappa statistics ranged from 0.5 to 0.63, a level of adequate or good reliability beyond chance. The method employed in this study is applicable in studies that require only fairly crude distinctions among biomechanical stressor variables. Nevertheless, this level of distinction may be sufficient when implementing intervention studies and control strategies for many material-handling-intensive jobs.

The impact of keyboard design on comfort and productivity in a text-entry task

Concerns have arisen that the keyboard is a causal factor in the development of work-related musculoskeletal disorders (WRMDs) among video display terminal (VDT) operators. A number of alternative keyboard designs have been developed with altered geometry in an effort to improve comfort in keyboard operation. However, few data are available to substantiate whether these new keyboard designs are actually effective in reducing discomfort and musculoskeletal problems in users. The purpose of this study was to provide data on the efficacy of certain alternative keyboard design features (e.g. splitting the keyboard in half, and laterally inclining the keyboard halves) in reducing fatigue and musculoskeletal discomfort among keyboard operators. The study also explored the effects of these design features on performance. Fifty subjects performed a text-entry task for one day on a standard keyboard, then were assigned to one of five keyboard conditions for an evaluation period of two days (i.e. 10 subjects/condition). Outcome measures included performance (i.e. keystrokes/h, errors/h) and self-report measures of discomfort and fatigue. The results indicated an initial decline in productivity when subjects began typing on two of the alternative keyboards, but these productivity losses were recovered within the two-day evaluation period. The results also indicated no significant differences between keyboard conditions in discomfort and fatigue. These results suggest a minimal impact of the keyboard design features examined in this study on productivity, comfort and fatigue, at least after two days of exposure.

An exploratory study of the relationship between biomechanical factors and right-arm musculoskeletal discomfort and fatigue in a VDT data-entry task

The relationship of key force and keystroke rate with right-arm musculoskeletal discomfort and fatigue was explored in a video-display-terminal (VDT) data-entry task. Forty-three data transcribers entered bogus data from tax forms at a VDT for one workday with their right hand. Peak key force and keystroke rate were monitored on a continuous basis. Self-ratings of right-arm discomfort and fatigue were assessed at periodic intervals. Stepwise regression analyses indicated that both lower key forces and lower keystroke rates were associated with higher ratings of right-elbow discomfort. In addition, lower key forces were associated with higher ratings of right-hand discomfort and lower keystroke rates were associated with higher ratings of right-shoulder discomfort and fatigue. The amount of variance accounted for by these models ranged from 7 to 24%. These results appear to be contrary to conventional biomechanical models that postulate a positive association between key force, keystroke rate and musculoskeletal discomfort in VDT work. Further laboratory and field research under controlled conditions is needed to clarify the direction and extent of the cause-and-effect relationship between biomechanical factors and musculoskeletal discomfort in VDT data-entry work.

Chylous ascites: report of one case

Chylous ascites is rare if found in the pediatric age group, and is usually of unknown etiology or comes from congenital anomalies of the lymphatic system. A 3.2 kg male newborn was born at 36-week gestation by Cesarean section prompted by fetal distress. Distended abdomen was noted after birth and abdominal ultrasound revealed significant ascites. Repeated paracenteses were done to relieve the respiratory distress, and a milky ascitic fluid with specific gravity of 1.031, WBC 1.32 x 10(4)/mm3 (lymphocytes predominant), and triglycerides 812 mg/dl was noted at the third tapping after feeding with normal infant formula. The lipoprotein electrophoresis of the ascites showed great increase in proportion of chylomicron to 19.05%. Pregestimil was given, and the ascites gradually subsided. The patient was discharged on the 13th day after birth. His growth was normal at one-month follow up without recurrence of ascites.