James Albers

Biomechanical Assessment of Three Rebar Tying Techniques

The National Institute for Occupational Safety and Health (NIOSH) conducted a study of ironworkers to evaluate their risk for developing back and hand injuries from hand-tying reinforcing steel bar and to investigate whether power tying tools can be an effective intervention for the prevention of work-related musculoskeletal disorders. A field investigation of biomechanical loading when using 3 techniques to tie together rebar was conducted. Researchers measured employees ‘ wrist and forearm movement with goniometers and videotaped and analyzed trunk postures. Manually tying rebar at ground level involved sustained deep trunk bending and rapid, repetitive, and forceful hand-wrist and forearm movements. Using a power tier significantly reduced the hand-wrist and forearm movements and allowed the ironworkers to use one free hand to support their trunk posture while tying. Adding an extension handle to the power tier allowed the ironworkers to tie rebar while standing erect, minimizing sustained trunk flexion.

Investigating reduced bag weight as an effective risk mediator for mason tenders.

Masonry workers face some of the highest physical demands in the construction industry where large bags of masonry material weighing 42.7 kg are commonly handled by mason tenders who mix the mortar, distribute mortar and bricks/blocks, and erect/dismantle scaffolding throughout the day. The objective of this study was to determine the effectiveness of using half-weight bags (21.4 kg) on reducing the biomechanical loading, physiological response, and perceived exertions. Ten male subjects performed asymmetric lifting tasks simulating unloading bags from a pallet. Muscle activity, trunk kinematics, heart rate, blood pressure and subjective rating data were collected. Spine loads were predicted from a well-validated EMG-assisted model. Bag weight, lift type, bag height at origin, and asymmetry at destination significantly impacted the spine loads. While there was a 50% reduction in bag weight, the peak loads for the half-weight bags were only 25% less than the more available full-weight bags (a reduction of about 320 N of shear and 1000 N of compression). Lifts allowing movement of the feet reduced the loads by about 22% in shear and 27% in compression compared to constrained postures. Interestingly, cumulative spine loads were greater for the lighter bags than the heavy bags ( approximately 40%). The subjective ratings of exertion and risk were significantly lower for the lighter bags. RELEVANCE TO INDUSTRY: The reduction in peak spine loading for the half-weight bags, particularly at the higher heights and when the feet were allowed to move could significantly reduce the injuries of masonry workers. However, there were trade-offs with cumulative loads that may minimize the reduced risk. Overall, given the limited amount of time lifting bags, the reduction of peak loads.

Finger Tendon Travel Associated with Sequential Trigger Nail Gun Use.

OCCUPATIONAL APPLICATIONS This article reports a method for assessing finger tendon motion associated with the use of a sequential actuation trigger pneumatic nail gun. The two-stage actuation process of the sequential actuation trigger reduces risk of nail puncture injury from unintended nail discharge (relative to the higher risk of the contact actuation trigger). However, widespread adoption of the sequential actuation trigger nail gun throughout the construction industry has been hindered by beliefs about productivity and musculoskeletal concerns about the repetitive trigger actuation and finger motion for each nail fired. Though existing guidelines for finger tendon travel exposure are not well established, predictions derived with the present method combined with productivity standards suggest insufficient evidence to contradict the safety-based recommendation to adopt the sequential actuation trigger trigger. TECHNICAL ABSTRACT Background: Pneumatic nail guns used in wood framing are equipped with one of two triggering mechanisms. Sequential actuation triggers have been shown to be a safer alternative to contact actuation triggers because they reduce traumatic injury risk. However, the sequential actuation trigger must be depressed for each individual nail fired as opposed to the contact actuation trigger, which allows the trigger to be held depressed as nails are fired repeatedly by bumping the safety tip against the workpiece. As such, concerns have been raised about risks for cumulative trauma injury, and reduced productivity, due to repetitive finger motion with the sequential actuation trigger. Purpose: This study developed a method to predict cumulative finger flexor tendon travel associated with the sequential actuation trigger nail gun from finger joint kinematics measured in the trigger actuation and productivity standards for wood-frame construction tasks. Methods: Finger motions were measured from six users wearing an instrumented electrogoniometer glove in a simulation of two common framing tasks—wall building and flat nailing of material. Flexor tendon travel was calculated from the ensemble average kinematics for an individual nail fired. Results: Finger flexor tendon travel was attributable mostly to proximal interphalangeal and distal interphalangeal joint motion. Tendon travel per nail fired appeared to be slightly greater for a wall-building task than a flat nailing task. The present study data, in combination with construction industry productivity standards, suggest that a high-production workday would be associated with less than 60 m/day cumulative tendon travel per worker (based on 1700 trigger presses/day). Conclusion and Applications: These results suggest that exposure to finger tendon travel from sequential actuation trigger nail gun use may be below levels that have been previously associated with high musculoskeletal disorder risk.

Equipment Interventions to Improve Construction Industry Safety and Health: A Review of Case Studies

A review was conducted of 153 case studies of construction equipment interventions, representing

Hand/Arm Forces with Pneumatic Nail Gun Actuation Systems

6.55 million (2016 USD) of equipment purchases incentivized through the U.S. state of Ohio Bureau of Workers’ Compensation (OBWC) Safety Intervention Grant (SIG) program. The source data were drawn from the applications and final reports of employers who received grants between 2003 and 2016. Outcomes were reductions in safety hazards, cumulative trauma disorder risk factors, and a score assessing quality of the intervention evaluative experience as determined through a framework developed by the authors. Items relating to the quality of the evaluative experience were manually extracted from the case study documentation. When aggregated by type of construction equipment, the risk factor reduction and evaluative quality scores were variable within and between equipment types. Equipment for cable pulling, used in the electrical trades, and skid steer attachments for concrete breaking (hydraulic breakers) both emerged as interventions ranked highly for reducing risk factors and for the evaluative quality of their case studies. Other intervention equipment types that ranked highly in both risk factor reduction and evaluative quality were concrete sawing equipment, trailers with hydraulic tilting/ramps, powered hand tools, and man lifts (boom lifts).

An ergonomic education and evaluation program for apprentice carpenters

A biomechanical model is presented to estimate cumulative user hand/arm force associated with two pneumatic nail gun trigger systems. The contact actuation trigger (CAT) can fire a nail when the user holds the trigger depressed first and then “bumps” the nail gun safety tip against the workpiece. With a full sequential actuation trigger (SAT) the user must press the tip against the workpiece prior to activating the trigger. The SAT is demonstrably safer in reducing traumatic injury risk, but increases the duration (and magnitude) of tip force exertion. Time integrated hand force was calculated for a single user from measurements of the tip contact force with the workpiece and transfer time between nails as inputs to a quasi-dynamic model of nailing in two task orientations. Application of the model shows the hand/arm force dependence upon the orientation of the workpiece in addition to the trigger system. Based on standard time allowances from work measurement systems (i.e. MTM - 1) the model results suggest that efficient application of tip contact force with the SAT would reduce total hand/arm force exertion attributable to this trigger system for this user. The present model is useful for considering differences in cumulative hand/arm force exposure between the SAT and CAT systems and the user perceptions and practices that result from these differences.