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This study compares human climbing performance, including climbing speed and movement and force patterns, between rail- and rung-climbing styles for a moderate aerial ladder slope (52.5°). Hand and foot movements and forces were recorded for 9 male and 10 female firefighters as they ascended and descended a 3.4-m ladder using elevated handrails (rail-climbing) or rungs (rung-climbing) for hand support. The results indicated that climbers used three or more points of contact 54% of the time for rung-climbing and 100% of the time for rail-climbing. Furthermore, rail-climbing was 10% faster than rung-climbing. In rail-climbing, the lateral hand forces were mostly directed away from the body; while during rung-climbing, they were alternated in lateral and medial directions. Overall, the results suggested that rail-climbing provides better control over body positioning and faster climbing speed. Furthermore, the continuous contact of both hands in rail-climbing may reduce the fall risk by facilitating the recovery from a slip or perturbation.

This study investigated the effects of aerial ladder rung spacing on firefighter climbing biomechanics. Ten female and 9 male firefighters ascended and descended instrumented ladders with rungs spaced at 356 mm (current design) and 305 mm in a laboratory setup. The climbing tests were performed at five ladder slope and handrail conditions: 30° with low (305 mm) and high (914 mm) handrails, 52.5° with and without a low handrail, and 75° without a handrail. Foot and hand forces and body movements were recorded and used to calculate joint moments of the upper and lower body. Reduced rung spacing resulted in reduced foot forces, reduced hand forces, and reduced ankle transverse moment. It was also associated with increased climbing speed for female climbers, and increased ankle vertical overshoot. The results indicate that reduced rung spacing on aerial ladders may lead to lower biomechanical stress; better climbing efficiency and safety; and reduced climbing speed disparity across sexes.

A leading cause for extension ladder fall incidents is a slide-out event usually related to suboptimal ladder inclination. An improved ladder positioning method or procedure could reduce the risk of ladder stability failure and the related fall injury. The objective of the study was to comparatively evaluate the effectiveness of a multimodal angle indicator with other existing methods for extension ladder angular positioning. Twenty experienced and 20 inexperienced ladder users participated in the study. Four ladder positioning methods were tested in a controlled laboratory environment with 4.88 m (16 ft) and 7.32 m (24 ft) ladders in extended and retracted positions. The positioning methods included a no-instruction method, the current standard anthropometric method, and two instrumental methods – a bubble level indicator, and a multimodal indicator providing direct feedback with visual and sound signals. Performance measures included positioning angle and time. The results indicated that the anthropometric method was effective in improving the extension ladder positioning angle (p < 0.001); however, it was associated with considerable variability and required 50% more time than no-instruction. The bubble level indicator was an accurate positioning method (with very low variability), but required more than double the time of the no-instruction method (p < 0.001). The multimodal indicator improved the ladder angle setting as compared to the no-instruction and anthropometry methods (p < 0.001) and required the least time for ladder positioning among the tested methods (p < 0.001). An indicator with direct multimodal feedback is a viable approach for quick and accurate ladder positioning. The main advantage of the new multimodal method is that it provides continuous feedback on the angle of the device and hence does not require repositioning of the ladder. Furthermore, this indicator can be a valuable tool for training ladder users to correctly apply the current ANSI A14 standard anthropometric method in ladder angular positioning. The multimodal indicator concept has been further developed to become a hand-held tool in the form of a smart phone application.

This study evaluated the effect of an extension ladder "walk-through" top design on kinetic and kinematic behaviors and the outward destabilizing forces induced on the ladder during transitioning at elevation. Thirty-two male participants performed stepping tasks between a ladder top and a roof at simulated elevation in a surround-screen virtual-reality system. The experimental conditions included a "walk-through" and a standard ladder top section supported on flat and sloped roof surfaces. Three force platforms were placed under the ladder section and in the roof to measure propulsion forces during transitions. A motion measurement system was used to record trunk kinematics. The frictional demand at the virtual ladder base was also calculated. The results indicate that under optimal ladder setup (angle 75.5 °), the frictional demand at the ladder base remains relatively small for all experimental conditions. Also, the "walk through" ladder top eased the ladder-to-roof transitions but not the roof-to-ladder transitions.

The risk of falls from height on a construction site increases under conditions which degrade workers' postural control. At elevation, workers depend heavily on sensory information from their feet to maintain balance. The study tested two hypotheses: "sensory enhancement"--sub-sensory (undetectable) random mechanical vibrations at the plantar surface of the feet can improve worker's balance at elevation; and "sensory suppression"--supra-sensory (detectable) random mechanical vibrations can have a degrading effect on balance in the same experimental settings. Six young (age 20-35) and six aging (age 45-60) construction workers were tested while standing in standard and semi-tandem postures on instrumented gel insoles. The insoles applied sub- or supra-sensory levels of random mechanical vibrations to the feet. The tests were conducted in a surround-screen virtual reality system, which simulated a narrow plank at elevation on a construction site. Upper body kinematics was assessed with a motion-measurement system. Postural stability effects were evaluated by conventional and statistical mechanics sway measures, as well as trunk angular displacement parameters. Analysis of variance did not confirm the "sensory enhancement" hypothesis, but provided evidence for the "sensory suppression" hypothesis. The supra-sensory vibration had a destabilizing effect, which was considerably stronger in the semi-tandem posture and affected most of the sway variables. Sensory suppression associated with elevated vibration levels on a construction site may increase the danger of losing balance. Construction workers at elevation, e.g., on a beam or narrow plank might be at increased risk of fall if they can detect vibrations under their feet. To reduce the possibility of losing balance, mechanical vibration to supporting structures used as walking/working surfaces should be minimized when performing construction tasks at elevation.

Falls from elevation continue to be the most serious hazard for the workers in construction. Simple and cost effective technical approaches to improve workers' balance on sloped roofs and deformable/unstable platforms have potential to reduce the risk of falls. This study evaluated the effectiveness of simple vertical structures as visual references (cue) for balance improvement. Twenty-four construction workers were tested while standing on sloped and deformable surfaces at elevation and performing undemanding visual tasks with vertical structures positioned at different proximal locations. Workers' balance performance was assessed by sway parameters calculated from the center-of-pressure movement collected with a force platform. The study results indicate increased instability on the sloped and deformable surfaces at elevation, and show that a simple vertical structure, e.g., a narrow bar, can serve as a visual cue and assist workers' balance. Workers' balance improved linearly with cue proximity in the tested distance range both on the sloped and the deformable surfaces. At a moment of instability, workers can redirect their attention to a proximal structure, available in the line of sight, to assist balance control. These findings may be useful in modifying elevated work environments and construction procedures to improve workers' postural balance during various construction phases.

The study evaluated the effects of shoe style on workers' instability during walking at elevation. Twenty-four construction workers performed walking tasks on roof planks in a surround-screen virtual reality system, which simulated a residential roof environment. Three common athletic and three work shoe styles were tested on wide, narrow and tilted planks on a simulated roof and on an unrestricted surface at simulated ground. Dependent variables included lateral angular velocities of the trunk and the rear foot, as well as the workers' rated perceptions of instability. The results demonstrated that shoe style significantly affected workers walking instability at elevated work environments. The results highlighted two major shoe-design pathways for improving walking balance at elevation: enhancing rear foot motion control; and improving ankle proprioception. This study also outlined some of the challenges in optimal shoe selection and specific shoe-design needs for improved walking stability during roof work. The study adds to the knowledge in the area of balance control, by emphasising the role of footwear as a critical human-support surface interface during work on narrow surfaces at height. The results can be used for footwear selection and improvements to reduce risk of falls from elevation.

Understanding roof-work-related risk of falls and developing low-cost, practical engineering controls for reducing this risk remain in high demand in the construction industry. This study investigated the effects of the roof work environment characteristics of surface slope, height, and visual reference on standing balance in construction workers. The 24 participants were tested in a laboratory setting at 4 slopes (0 degrees, 18 degrees, 26 degrees, and 34 degrees), 2 heights (0, 3 m), and 2 visual conditions (with and without visual references). Postural sway characteristics were calculated using center of pressure recordings from a force platform. Workers' perceptions of postural sway and instability were also evaluated. The results indicated that slope and height synergistically increased workers' standing postural instability. Workers recognized the individual destabilizing effects of slope and height but did not recognize the synergistic effect of the two. Visual references significantly reduced the destabilizing effects of height and slope. Actual and potential applications of this research include the use of temporary level work surfaces and proximal vertical reference structures as postural instability control measures during roofing work.

Falls remain a leading cause of unintentional injury mortality nationwide [corrected].Among workers, approximately 20% of fall injuries involve ladders. Among construction workers, an estimated 81% of fall injuries treated in U.S. emergency departments (EDs) involve a ladder. To fully characterize fatal and nonfatal injuries associated with ladder falls among workers in the United States, CDC's National Institute for Occupational Safety and Health (NIOSH) analyzed data across multiple surveillance systems: 1) the Census of Fatal Occupational Injuries (CFOI), 2) the Survey of Occupational Injuries and Illnesses (SOII), and 3) the National Electronic Injury Surveillance System-occupational supplement (NEISS-Work). In 2011, work-related ladder fall injuries (LFIs) resulted in 113 fatalities (0.09 per 100,000 full-time equivalent [FTE] workers), an estimated 15,460 nonfatal injuries reported by employers that involved ≥1 days away from work (DAFW), and an estimated 34,000 nonfatal injuries treated in EDs. Rates for nonfatal, work-related, ED-treated LFIs were higher (2.6 per 10,000 FTE) than those for such injuries reported by employers (1.2 per 10,000 FTE). LFIs represent a substantial public health burden of preventable injuries for workers. Because falls are the leading cause of work-related injuries and deaths in construction, NIOSH, the Occupational Safety and Health Administration, and the Center for Construction Research and Training are promoting a national campaign to prevent workplace falls. NIOSH is also developing innovative technologies to complement safe ladder use.

Objective: The study objectives were to identify factors affecting extension ladders’ angular positioning and evaluate the effectiveness of two anthropometric positioning methods. Background: A leading cause for extension ladder fall incidents is a slide-out event, usually related to suboptimal ladder inclination. An improved ladder positioning method or procedure could reduce the risk of ladder stability failure and the related fall injury. Method: Participants in the study were 20 experienced and 20 inexperienced ladder users. A series of ladder positioning tests was performed in a laboratory environment with 4.88-m (16-ft) and 7.32-m (24-ft) ladders in extended and retracted positions. The setup methods included a no-instruction condition and two anthropometric approaches: the American National Standards Institute A14 and “fireman” methods. Performance measures included positioning angle and time. Results: The results indicated that ladder setup method and ladder effective length, defined by size and extended state, affected ladder positioning angle. On average, both anthropometric methods were effective in improving extension ladder positioning; however, they required 50% more time than did the no-instruction condition and had a 9.5% probability of setting the ladder at a less-than-70° angle. Shorter ladders were consistently positioned at shallower angles. Conclusion: Anthropometric methods may lead to safer ladder positioning than does no instruction when accurately and correctly performed. Workers tended to underperform as compared with their theoretical anthropometric estimates. Specific training or use of an assistive device may be needed to improve ladder users’ performance. Application: The results provide practical insights for employers and workers to correctly set up extension ladders.

Objective: This study determined the most favorable strategy for carrying scaffold end frames while minimizing the risk of injuries from being struck by an object, falling, and overexertion. Background: Scaffold erectors are at risk of high exposure to the aforementioned hazards associated with the dynamic human-scaffolding interface and work environments. Identifying an optimal work strategy can help reduce risk of injuries to the worker. Method: Three carrying methods, four types of work surfaces, two weights of scaffold frames, and three directions of stepping movement were tested in a laboratory with 18 construction workers. Results: The effects of carrying method on postural instability and task difficulty rating were significant for handling the 22-kg end frame. Response time, postural instability, and perceived task difficulty rating were significantly reduced when the 9-kg end frame was used as compared with the 22-kg frame. Conclusion: The symmetric side-carrying method was the best option for handling 22-kg scaffold end frames. A 9-kg end frame (e.g., made of reinforced lightweight materials) has the potential to reduce injury risk among scaffold handlers during their scaffold erection and dismantling jobs. Application: Scaffold erectors may want to adopt the symmetric side-carrying method as the primary technique for handling the 22-kg scaffold end frame, which is currently the one most used in the industry.

The study compared human perceptions of height, danger, and anxiety, as well as skin conductance and heart rate responses and postural instability effects, in real and virtual height environments. The 24 participants (12 men, 12 women), whose average age was 23.6 years, performed "lean-over-the-railing" and standing tasks on real and comparable virtual balconies, using a surround-screen virtual reality (SSVR) system. The results indicate that the virtual display of elevation provided realistic perceptual experience and induced some physiological responses and postural instability effects comparable to those found in a real environment. It appears that a simulation of elevated work environment in a SSVR system, although with reduced visual fidelity, is a valid tool for safety research. Potential applications of this study include the design of virtual environments that will help in safe evaluation of human performance at elevation, identification of risk factors leading to fall incidents, and assessment of new fall prevention strategies.