Vern Putz-Anderson

Revised NIOSH equation for the design and evaluation of manual lifting tasks

In 1985, the National Institute for Occupational Safety and Health (NIOSH) convened an ad hoc committee of experts who reviewed the current literature on lifting, recommend criteria for defining lifting capacity, and in 1991 developed a revised lifting equation. Subsequently, NIOSH developed the documentation for the equation and played a prominent role in recommending methods for interpreting the results of the equation. The 1991 equation reflects new findings and provides methods for evaluating asymmetrical lifting tasks, lifts of objects with less than optimal hand-container couplings, and also provides guidelines for a larger range of work durations and lifting frequencies than the 1981 equation. This paper provides the basis for selecting the three criteria (biomechanical, physiological, and psychophysical) that were used to define the 1991 equation, and describes the derivation of the individual components (Putz-Anderson and Waters 1991). The paper also describes the lifting index (LI), an index of relative physical stress, that can be used to identify hazardous lifting tasks. Although the 1991 equation has not been fully validated, the recommended weight limits derived from the revised equation are consistent with or lower than those generally reported in the literature. NIOSH believes that the revised 1991 lifting equation is more likely than the 1981 equation to protect most workers.

Musculoskeletal disorders among visual display terminal users in a telecommunications company

The relationship between workplace factors and work-related upper extremity musculoskeletal disorders (UE disorders) was assessed in a cross-sectional study of 533 telecommunication employees utilizing video display terminals (VDTs). Cases of UE disorders were defined using symptom questionnaires and physical examinations. Data on demographics, individual factors (medical conditions and recreational activities), work organization and practices, and psychosocial aspects of work, including electronic performance monitoring (EPM), were obtained by questionnaire. Associations between workplace factors and UE disorders were assessed by multiple logistic models generated for each of the four UE areas (neck, shoulder, elbow, hand/wrists). One-hundred and eleven (22%) participants met our case definition for UE disorders. Probable tendon-related disorders were the most common (15% of participants). Probable nerve entrapment syndromes were found in 4% of participants. The hand/wrist was the area most affected, 12% of participants. The following variables had associations in the final models (p < 0.05) with at least one of the four UE disorders, although the strength of these associations were modest. Non-white race, a diagnosis of a thyroid condition (self-reported) use of bifocals at work, and seven psychosocial variables (fear of being replaced by computers, increasing work pressure, surges in workload, routine work lacking decision-making opportunities, high information processing demands, jobs which required a variety of tasks and lack of a production standard) were associated with UE disorders. This study indicates that work-related UE musculoskeletal disorders are relatively common among telecommunication workers who use VDTs, and adds to the evidence that the psychosocial work environment is related to the occurrence of these disorders.

Methods for Assessing the Physical Demands of Manual Lifting: A Review and Case Study from Warehousing

Assessment of the physical demands of potentially hazardous manual material handling (MMH) activities is fundamental to the prevention of disabilities from occupationally related low back pain, a problem costing the nation billions of dollars annually. Although there is a variety of ergonomic assessment methods available for assessing MMH activities, there is a lack of practical information to assist users in choosing the most appropriate assessment methods of a particular job. This article reviews currently available assessment methods and presents case study results of a physically demanding repetitive manual lifting job in two grocery warehouses. The case study will provide a framework for a comparison of the methods and a discussion of relevant application issues designed to assist users in selecting appropriate methods for assessing MMH jobs. Based on the results of the study, it is concluded that all of the ergonomic methods were in agreement that the job of grocery selector has a high level of risk for low back pain. Differences between the methods were noted, however, that should be considered when choosing a specific method for a specific application.

The NIOSH program for evaluating biomechanical hazards in the workplace

Twenty evaluations of reported biomechanical hazards were performed by the National Institue for Occupational Safety and Health (NIOSH) at the request of industrial workers or management over an 8-year period. The evaluations were part of the Hazard Evaluation and Technical Assistance (HETA) program authorized under the Occupational Safety and Health Act of 1970. A number of these evaluations are described here. Principles drawn from the field of ergonomics were used to evaluate whether a certain work activity has caused an observed incidence of cumulative trauma to the neuro-musculo-skeletal system. Procedures for conducting these ergonomic evaluations are reviewed, and the results are summarized. Recommendations are made for implementing control procedures, and the problem of obtaining reliable follow-up information is discussed. Project results suggest an encouraging degree of success in accomplishing prevention and control of biochemical hazards in the workplaces studied.

Vibration thresholds as a function of age and diagnosis of carpal tunnel syndrome : a preliminary report

To determine if vibration thresholds vary independently with age and carpal tunnel syndrome (CTS), 61 subjects, including 27 diagnosed with carpal tunnel-induced neuropathy, and 34 non-CTS controls, ranging in age from 20 to 65 years, were tested using the Optacon, a device used to assess vibration thresholds. No statistically significant interaction was found between the age and diagnosis factors. Results did confirm the findings of previous studies that vibration thresholds increased with age and that thresholds were elevated within the CTS group, compared to the controls. These results indicate that age-adjusted norms for vibration threshold data need to be developed. Without age-adjusted norms, screening programs for CTS that rely on vibration threshold data are likely to generate high levels of false positives, particularly for workers over 40 years of age.

Ergonomic Evaluation of Checkstand Designs in the Retail Food Industry: A Report Based on Expert Assessment

Abstract Increasing evidence suggests that musculoskeletal disorders are common in the U.S. retail food industry. Cashiers who use electronic scanners appear to be at especially high risk for upper extremity cumulative trauma disorders (CTDs). One potential source of biomechanical stress is the checkstand design. Checkstand design can greatly influence the cashiers posture and movement patterns during grocery checking tasks. It is hypothesized that designs which expose cashiers to stressful postures and unnatural movements may be associated with increased musculoskeletal complaints. The National Institute for Occupational Safety and Health (NIOSH) is conducting an industrywide study to evaluate the prevalence and possible causes of musculoskeletal disorders among retail food workers. An objective of this research is to evaluate the relationship between CTDs and different checkstand designs. This article describes initial activities to identify ergonomic stressors associated with five common checkstand ty...

Evaluation of the Impact of the Revised National Institute for Occupational Safety and Health Lifting Equation

Objective: The objective of this article is to evaluate the impact of the Revised National Institute for Occupational Safety and Health Lifting Equation (RNLE). Background: The RNLE has been used extensively as a risk assessment method for prevention of low back pain (LBP). However, the impact of the RNLE has not been documented. Methods: A systematic review of the literature on the RNLE was conducted. The review consisted of three parts: characterization of the RNLE publications, assessment of the impact of the RNLE, and evaluation of the influences of the RNLE on ergonomic standards. The literature for assessing the impact was categorized into four research areas: methodology, laboratory, field, and risk assessment studies using the Lifting Index (LI) or Composite LI (CLI), both of which are the products of the RNLE. Results: The impact of the RNLE has been both widespread and influential. We found 24 studies that examined the criteria used to define lifting capacity used by the RNLE, 28 studies that compared risk assessment methods for identifying LBP, 23 studies that found the RNLE useful in identifying the risk of LBP with different work populations, and 13 studies on the relationship between LI/CLI and LBP outcomes. We also found evidence on the adoption of the RNLE as an ergonomic standard for use by various local, state, and international entities. Conclusion: The review found 13 studies that link LI/CLI to adverse LBP outcomes. These studies showed a positive relationship between LI/CLI metrics and the severity of LBP outcomes.

Understanding and evaluating manual handling injuries: NIOSH research studies

This paper presents an overview of NIOSH research aimed at characterizing and identifying intervention strategies for reducing musculoskeletal injuries during manual handling activities. Surveillance and evaluative research projects are reviewed. Future research directions of the Institute are also discussed.