Work-related falls from roofs remain a significant problem for workers in the construction industry. Knowledge about the main causative or initiating factors leading to fall incidents is desperately needed for fall prevention intervention. From biomechanical and psychophysiological perspectives the majority of occupational falls, including falls from roofs, can be regarded as loss-of-balance incidents. The primary objective of this paper is to summarize the current knowledge from multiple fields about factors that are related to the control of balance during roofing work. An extensive literature review identified a number of environmental, task-related and personal factors that degrade the control of balance and could be associated with the initiation of falls from roofs. These factors include visual exposure to elevation; unstable visual cues and inadequate visual information in the work environment; 'confined' and inclined support surfaces; unexpected changes in roof surface properties; load handling; physical exertion; fatigue; task complexity that diverts workers' attention; individual differences; work experience and training; and personal protective equipment. Current measures to reduce falls from roofs focus mainly on fall protection procedures, such as the use of covers, guardrails, safety nets, and personal fall-arrest systems, or the application of warning-line systems, safety monitoring systems, and fall protection plans. In many instances, these procedures are not practical for the industry and current regulations allow the use of alternative means of fall protection, such as slide guards. Future research on preventing falls from roofs should consider the main effects and interactions of the environmental, task-related and personal factors that affect the balance control of workers. Research-supported improvements in the visual and physical characteristics of the roof work environment, the construction materials and methods, and work procedures and practices may result in improved workers' balance control as well as overall safety performance, and would ultimately reduce incidents of falling from a roof.
The recent rapid adoption of insole pressure measurement systems for clinical and ergonomic evaluations of human gait has necessitated a comprehensive understanding of the accuracy and precision of such systems. Five bench experiments were performed to examine the Pedar and F-Scan in-shoe pressure measurement systems. The insoles examined were the Pedar Y-sized right insole and the F-scan insole trimmed to the size and shape of a Pedar Y-sized insole. Data were sampled at 50 Hz at different levels of applied pressure, calibration procedure, duration of pressure application, insole age of use and experiment day or week. The system accuracy was determined by the per cent error of measurement, the system precision by the 95% tolerance interval of the per cent error. The results show that system accuracy and precision varied among levels of applied pressure, calibration procedure, duration of pressure application and insole age of use. The Pedar system showed the greatest accuracy and precision when the insole was new and measurements were taken (1) after a system calibration as specified by the manufacturer, (2) in the 50 - 500 kPa pressure range and (3) within a few seconds after pressure was applied. Under this condition, the measurement error was in the range -0.6 to 2.7%, and the magnitude (upper bound minus lower bound) of the 95% tolerance intervals was from 13.5 to 18.7%. Measuring less than 35 kPa with the Pedar system is not recommended. To ensure the accuracy and precision of the F-Scan system, users are recommended to estimate the range of the applied pressure and then choose a similar pressure level for calibration. Under this condition, the measurement error was in the range 1.3 - 5.8% and the magnitude (upper bound minus lower bound) of the 95% tolerance intervals was estimated to be in the range 1.1 - 14.8%. When the calibration pressure was outside this range of applied pressure, the per cent errors were considerably higher, ranging from -26.3 to 33.9%.
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