John A. Miles

Ergonomics in Agriculture: Workplace Priority Setting in the Nursery Industry

Although agriculture is generally recognized as the nations most hazardous industry and displays high rates of musculoskeletal disorders with evidence to suggest that ergonomic risk factors are involved, there is very little history of application of ergonomic approaches in agricultural workplaces. A three-year National Institute for Occupational Safety and Health-supported study has been initiated in California nurseries to describe and design engineering interventions for priority musculoskeletal disorders. In this article are reported the results of the projects initial workplace job task screening for ergonomic risk factors and associated musculoskeletal disorder reports to define landmark ergonomic risk factors for the nursery industry and select priority job tasks for intervention.

Priority risk factors for back injury in agricultural field work: vineyard ergonomics

ABSTRACT With support of a NIOSH Community Partners grant, the authors reviewed data from three cooperating vineyard companies in Napa and Sonoma Counties, finding both high rates of evidence of musculoskeletal disorders (MSDs) and identifying priority MSD hazards for intervention. Data from OSHA 200 injury report logs identified 29 reported MSDs and 435 lost workdays in a working population of 194 in a 30-month period. The majority of these (20) involved backstrain. High risk job tasks were identified, including: employer-identified tasks, analysis of injury reports, and ergonomics risk factor checklist survey of task work. Triangulating across these three data groups resulted in identification of high priority tasks, including: hand harvest work, hand pruning, and weeding using shovels. Priority risk factors for back injury in these jobs were: repetitive lifting of heavy loads, repetitive exertion of force by the trunk and upper extremities, and repetitive or sustained awkward postures of the trunk (including full stoop and twisting with loads).

High Risk Tasks for Musculoskeletal Disorders in Agricultural Field Work

Agricultural work involves heavy physical exertion and is characterized by evidence of high rates of musculoskeletal disorders. Currently ergonomics is a low priority for injury and illness prevention in agriculture. However, based on costs and incidence rates ergonomics risk factors should rank among the highest farm safety priorities. Analysis of field work jobs by the University of California with support from NIOSH yield an industry generalizable set of high risk tasks which should have high intervention priority. These are: repetitive and awkward forward flexion, repetitive lifting and carrying heavy loads, and highly repetitive hand work.

Ergonomics Interventions in the Manual Harvest of Wine Grapes

Winegrape operations, especially at harvest, produce a high incidence of work-related musculoskeletal disorders, predominantly involving back injury. The Agricultural Ergonomics Research Center of the University of California initiated a study of vineyard operations and recruited four cooperating growers representing 191 permanent workers. The goal was to develop, field-test, and evaluate interventions to reduce ergonomics risk factors for WRMSDs during winegrape harvest. We assessed pre- and post-intervention injury records and other indicators of musculoskeletal symptoms to monitor the impact of interventions on involved workers, and used biomechanical, metabolic, and postural analyses to evaluate the effectiveness of various approaches for handling cut grapes during vineyard harvest. We introduced a smaller, lighter tote bin with improved handles, reducing the average full bin load from 25.5 kg to 20.9 kg. The proportion of workers reporting pain lasting more than a week dropped from 61% to 26%. Biomechanical and metabolic assessments indicated reduced risk for WRMSDs. We are currently field-testing a conveyor system to reduce the height at which the bins are dumped.

Influence of Suspension, Tires, and Shock Absorbers on Vibration in a Two-horse Trailer

Combinations of vehicle suspensions (leaf-spring and torsion-bar), tires bias-ply (311 kPa), normal-pressure (344 kPa) and low-pressure (172 kPa) radials, and shock absorbers were evaluated for smoothness of ride and common frequencies of vibration using a two-horse, bumper-pull, tandem-axle, forward-facing trailer. Accelerations on the x-axis (dorsal-ventral, upward-downward) were measured on each wheel and each corner of the trailer while the trailer was driven over fourteen 25-mm-diameter cables spaced at 4.8-m intervals at three speeds (40, 56, and 72 km/h). Twelve combinations of suspension, tires, and shock absorbers were tested in all. Initially, five steel barrels filled with 1 000 kg of water (total mass) were positioned in the trailer to mimic the body masses of two horses. The leaf-spring suspension with low-pressure radial tires and without shock absorbers provided the smoothest ride in terms of the lowest root mean square (rms) accelerations (P < 0.05), but the leaf-spring suspension combined with bias-ply tires and without shock absorbers also had similarly low rms accelerations. The torsion-bar suspension combined with normal-pressure radial tires was the roughest (in terms of rms accelerations) combination tested. Generally, the addition of shock absorbers did not improve ride quality in terms of x-axis acceleration. Several combinations of suspension and tires (leaf-spring suspension with bias-ply, low-pressure and normal-pressure radials, and the torsion-bar suspension with normal-pressure radials) were chosen to test with four live horses riding in the trailer (horses were transported two at a time). Root mean square acceleration values (x-axis only) were measured on the left and right front trailer subframe, the left front hoof and left trunk of one horse, and the right front hoof and right trunk of another while the trailer was driven over smooth and rough roads. The leaf-spring suspension with low-pressure radial tires provided the smoothest ride. Horses traveling on the right side of the trailer experienced more vibration than horses on the left side of the trailer, perhaps because of the poor conditions of asphalt roads near the shoulders.

Airship Logging: Parameters Affecting Load Factors

ABSTRACT A helicopter logging operation was studied to evaluate some parameters which affect load factors. Estimates of log weights had considerable error. Estimates of lift capacity appeared to be accurate and the weights of limbs and trim on the logs were negligible, as were the incremental forces required to break the logs free of the ground. Readings from the helicopters load indicator were precise but biased.

Reducing Wrmsd Risk Factors and Symptoms in Plant Nurseries through Material Handling Modifications

University of California researchers developed new handles for lifting and carrying plants in nursery containers that resulted in significantly reduced exposures for work-related musculoskeletal disorders. Data are reported on risk factor exposure improvements and the incidence of related musculoskeletal symptoms following an extended field trial.

Modeling the Obstacle Performance of Cable-Towed Vehicles

Abstract The forces required to pull wheeled vehicles over idealized terrain obstacles were studied. Scale models and computer simulations were used to evaluate the peak forces for single-axle vehicles equipped with rigid wheels and pneumatic tires. A scale model of a rimless spoke wheel was also tested. The results from the rigid wheel and pneumatic- tired simulations approximated those for the scale models. The rimless spoke wheel model required relatively high towing forces. The computer results indicated that towing forces could be reduced by a factor of three in some situations by using low pressure tires instead of rigid wheels. Even with low pressure tires, it is not possible to pull vehicles over obstacles larger than approximately 1/5 of the wheel diameter, if towing forces are not to exceed the vehicle weight.

Evaluation of the NAGCAT Tractor Guidelines

This study aims to build upon the North American Guidelines for Childrens Agricultural Tasks (NAGCAT) project by providing a field test of the NAGCAT tractor guidelines. Several tractor dealers and farmers offered their tractors for the study in California and Wisconsin; for a total of 86 tractors. A unique photographic technique provided 3-D digital mock-ups of the tractors, which facilitated the evaluation of reach and visual abilities of adolescents using anthropometric data. Force requirements were captured using a digital force gauge and compared to existing force requirements and databases. The results indicate, in general, that hand-operated controls tend to be out of reach for both genders with the exception of steering wheels. The worst controls were hand throttle levers. On the other hand, foot-operated controls yielded higher reachable percentages for both genders, while steering wheels showed a medium range of reachable percentages. In general, youth operators showed relatively restricted fields of vision compared to the adults, and their fields of vision decreased as obstacles were closer to the tractor. The results also showed that foot-operated controls require more strength than the recommended levels. In the meantime, the recommended physical strengths of children surpassed the activation forces for hand-operated controls. This result suggests that youth operators would be very likely exposed to muscle fatigue in the leg due to the frequent use of foot clutches and brakes during tractor operation. The study showed that the demarcation of the NAGCAT by the size of the tractor is not significant for the majority of controls.

Ergonomic Evaluation of California Winegrape Trellis Systems

The winegrape industry suffers from high incidence rates of work related musculoskeletal disorders (MSDs). Pruning of dormant vines requires long periods of highly repetitive and physically demanding work that increases risk for MSDs. The purpose of this study is to quantify risk factors associated with the development of musculoskeletal injuries to the wrist and lower back while pruning five commonly used winegrape trellis systems. Eleven subjects (10 male, 1 female) participated in this study. Subjects performed a simulated pruning task as wrist and trunk postures and psychophysical data were gathered. The results showed significant differences among the trellis systems. Compared to the other systems, the vertical shoot positioned (VSP) was determined to be most optimal in terms of decreasing relative MSD risk. These results will assist vineyards in selecting suitable trellis systems that may improve worker health.