Sharon Chiou

Effect of Boot Weight and Sole Flexibility on Gait and Physiological Responses of Firefighters in Stepping Over Obstacles

Objective: The authors investigated the effect of boot weight and sole flexibility on spatiotemporal gait characteristics and physiological responses of firefighters in negotiating obstacles. Background: Falls and overexertion are the leading causes of fire ground injuries and fatalities among firefighters. There have been few in-depth studies conducted to evaluate the risk factors of falls and overexertion associated with firefighter boots. Method: For the study, 13 female and 14 male firefighters, while wearing full turnout clothing and randomly assigned boots, walked for 5 min while stepping over obstacles. The independent variables included boot weight, sole flexibility, gender, and task duration. Spatiotemporal measures of foot trajectories and toe clearance were determined. Minute ventilation, oxygen consumption, carbon dioxide production, and heart rate were measured. Results: Increased boot weight was found to significantly reduce trailing toe clearance when crossing the 30-cm obstacle. Significant increases in lateral displacement of the foot were found near the end of the 5-min walk compared with the beginning of the task. Increased boot weight significantly increased oxygen consumption. There were significant decreases in oxygen consumption for more flexible soles. Conclusion: Firefighters were more likely to trip over obstacles when wearing heavier boots and after walking for a period of time. Boot weight affected metabolic variables (5% to 11% increases per 1-kg increase in boot weight), which were mitigated by sole flexibility (5% to 7% decrease for more flexible soles). Application: This study provides useful information for firefighters and boot manufacturers in boot selection and design for reducing falls and overexertion.

Assessment of perceived traumatic injury hazards during drywall hanging

Abstract Workers who handle massive and bulky drywall sheets are at a high risk of traumatic injuries. The objective of this study is to identify the drywall handling tasks and activities which are directly perceived as hazardous by workers. A questionnaire survey was conducted for the study. In the questionnaire, three hanging tasks were included: (1) hanging drywall on the ceiling; (2) hanging drywall on the upper half of the wall; and (3) hanging drywall on the lower half of the wall. Each of the three tasks was divided into 10 to 12 constituent activities. Supportive elevated equipment was also evaluated. Workers were instructed to rate the drywall-hanging tasks/activities and elevated equipment in regard to fall potential, perceived physical stress, and risk of being struck by or against objects, using a seven-point scale (1=hardly at all to 7=a great deal). Results from this study indicate that all the ratings of fall potential, perceived physical stress, and risk of being struck by or against objects while hanging drywall on the ceiling were greater than while performing the other two tasks. Activities involving lifting/carrying/holding drywall sheets were rated as most physically stressful. Workers perceived greatest physical stress and fall potential when wearing stilts as compared to using ladders or scaffolds. The findings of this study provide detailed information directly from the workers about the hazards associated with drywall hanging. Results from this study will assist in focusing future research efforts on the most hazardous tasks and activities of drywall hanging. Relevance to industry Construction workers who perform drywall installation have high occupational incident rate for traumatic injury. Handling massive and bulky drywall sheets increases the potential for physical stress, falls and struck by and against objects. A questionnaire was designed to collect injury information directly from construction workers who performed drywall hanging and to identify perceived hazards associated with drywall hanging. Prior to this study, there has been little substantive research to evaluate the excessive stresses imposed on this workforce.

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.

Physiological Effects of Boot Weight and Design on Men and Women Firefighters

The purpose of this study was to determine the effects of two leather (L1, L2) and two rubber (R1, R2) boots on firefighters’ metabolic and respiratory variables during simulated firefighting tasks. Twenty-five men and 25 women, while wearing full turnout clothing, a 10.5-kg backpack, gloves, helmet, and one of four randomly assigned pairs of firefighter boots, walked for 6 min at 3 mph (4.8 km/hr) on a level treadmill while carrying a 9.5-kg hose and climbed a stair ergometer for 6 min at 45 steps per min without the hose. Minute ventilation ( E), absolute and relative oxygen consumption ( and ml.kg.min-1, respectively), CO2 production (), heart rate (HR), and peak inspiratory (PIF) and expiratory (PEF) flow rates were measured, and an average of the breath-by-breath data from minute 6 was used for analysis. During treadmill exercise, a 1-kg increase in boot weight caused significant (p < 0.05) increases in E (9%), (5 – 6%), (8%), and HR (6%) for men, whereas a 1-kg increase caused significant increases in (3 – 4.5%) and (4%) for women. During stair ergometry, a 1-kg increase in boot weight caused significant increases in E(~3%), relative (~2%), (3%), and PIF (~4%) in men and women (p < 0.05) and a significant increase in absolute (~3.5%) in men only. Mean increases in metabolic and respiratory variables per 1-kg increase in boot weight were in the 5 to 12% range observed previously for men during treadmill walking but were considerably smaller for women. Mean increases in oxygen consumption during stair ergometry were statistically significant but were smaller in the current study than previously observed and may not be practically significant. There was no significant effect of boot design in addition to boot weight for either mode of exercise.

Analysis of musculoskeletal loadings in lower limbs during stilts walking in occupational activity.

Construction workers often use stilts to raise them to a higher level above ground to perform many tasks, such as taping and sanding on the ceiling or upper half of a wall. Some epidemiological studies indicated that the use of stilts may place workers at increased risk for knee injuries or may increase the likelihood of trips and falls. In the present study, we developed an inverse dynamic model of stilts walking to investigate the effects of this activity on the joint moments and musculoskeletal loadings in the lower limbs. The stilts-walk model was developed using the commercial musculoskeletal simulation software AnyBody (version 3.0, Anybody Technology, Aalborg, Denmark). Simulations were performed using data collected from tests of four subjects. All subjects walked without or with stilts through a 12-m straight path. The moments of the knee, hip, and ankle joints, as well as forces in major muscles or muscle groups in the lower limbs, for stilts walking were compared with those for normal walking. Our simulations showed that the use of stilts may potentially increase the peak joint moment in knee extension by approximately 20%; induce 15% reduction and slight reduction in the peak joint moments in ankle plantar flexion and hip extension, respectively. The model predictions on the muscle forces indicated that the use of stilts may potentially increase loadings in five of eight major muscle groups in the lower extremities. The most remarkable was the force in rectus femoris muscle, which was found to potentially increase by up to 1.79 times for the stilts walking compared to that for the normal walking. The proposed model would be useful for the engineers in their efforts to improve the stilts design to reduce musculoskeletal loadings and fall risk.

Human responses to augmented virtual scaffolding models.

This study investigated the effect of adding real planks, in virtual scaffolding models of elevation, on human performance in a surround-screen virtual reality (SSVR) system. Twenty-four construction workers and 24 inexperienced controls performed walking tasks on real and virtual planks at three virtual heights (0, 6 m, 12 m) and two scaffolding-platform-width conditions (30, 60 cm). Gait patterns, walking instability measurements and cardiovascular reactivity were assessed. The results showed differences in human responses to real vs. virtual planks in walking patterns, instability score and heart-rate inter-beat intervals; it appeared that adding real planks in the SSVR virtual scaffolding model enhanced the quality of SSVR as a human – environment interface research tool. In addition, there were significant differences in performance between construction workers and the control group. The inexperienced participants were more unstable as compared to construction workers. Both groups increased their stride length with repetitions of the task, indicating a possibly confidence- or habit-related learning effect. The practical implications of this study are in the adoption of augmented virtual models of elevated construction environments for injury prevention research, and the development of programme for balance-control training to reduce the risk of falls at elevation before workers enter a construction job.

Assessment of perceived traumatic injury hazards during drywall taping and sanding

The objective of this study was to identify the drywall finishing tasks which are directly perceived as hazardous by workers. A questionnaire survey was conducted to evaluate workers’ perceived injury hazards (physical stress, fall potential, and struck by/against an object) for six finishing tasks (4 taping and 2 sanding tasks) and three items of elevated support equipment. Thirty experienced drywall finishers participated in this study. The ratings of perceived physical stress and fall potential varied significantly among the six tasks (both p values <0.05). Subjects perceived greater physical stress for the two drywall sanding tasks than the four taping tasks. Sanding skimmed drywall without the use of pole sanders, in particular sanding ceiling joints, nails, and corners was rated most stressful. Wrists/hands and shoulders were identified as the most affected body part subject to physical stress during drywall taping and sanding. Tasks performed with the use of stilts were rated as having greater fall potential than those without using stilts. The activity of putting on stilts and getting up on them was most likely to cause loss of balance. Results from this study provide information directly from experienced workers to help identify hazardous tasks and activities associated with drywall finishing. The findings will assist in focusing future research efforts on the most hazardous tasks and activities of drywall finishing. Construction workers who perform drywall installation, including taping and sanding drywall sheets, have the highest incidence/injury rate compared to any other workforce. Taping and sanding drywall sheets increases the potential for physical stress, falls and struck by and against objects. A questionnaire was designed to collect injury information directly from painters who performed drywall taping/sanding and to identify perceived hazards associated with drywall taping and sanding. Prior to this study, there has been little substantive research to ergonomically evaluate the excessive stresses and potential injuries imposed on this workforce.

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.

EVALUATION OF A COMPUTER-SIMULATION MODEL FOR HUMAN AMBULATION ON STILTS

Stilts are elevated tools that are frequently used by construction workers to raise workers 18 to 40 inches above the ground without the burden of erecting scaffolding or a ladder. Some previous studies indicated that construction workers perceive an increased risk of injury when working on stilts. However, no in-depth biomechanical analyses have been conducted to examine the fall risks associated with the use of stilts. The objective of this study is to evaluate a computer-simulation stilts model. Three construction workers were recruited for walking tasks on 24-inch stilts. The model was evaluated using whole body center of mass and ground reaction forces. A PEAK™ motion system and two Kistler™ force platforms were used to collect data on both kinetic and kinematic measures. Inverse- and direct-dynamics simulations were performed using a model developed using commercial software — ADAMS and LifeMOD. For three coordinates (X, Y, Z) of the center of mass, the results of univariate analyses indicated very small variability for the mean difference between the model predictions and the experimental measurements. The results of correlation analyses indicated similar trends for the three coordinates. Plotting the resultant and vertical ground reaction force for both right and left feet showed small discrepancies, but the overall shape was identical. The percentage differences between the model and the actual measurement for three coordinates of the center of mass, as well as resultant and vertical ground reaction force, were within 20%. This newly-developed stilt walking model may be used to assist in improving the design of stilts.