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workers, building, architect

NORA Manufacturing Sector Strategic Goals

92700BH - Prevention of Musculoskeletal Disorders Among Forklift Operators

Start Date: 10/1/2005
End Date: 9/30/2009

Principal Investigator (PI)
Name: Thomas Waters
Phone: 513-533-8147
Organization: NIOSH
Sub-Unit: DART
Funded By: NIOSH

Primary Goal Addressed

Secondary Goal Addressed

Attributed to Manufacturing


Project Description

Short Summary

This study will determine if forklift operators are at increased risk of back and neck pain due to driving forklift vehicles backward at work. A cross-sectional epidemiological study will be conducted to compare neck and back disorder rates for forklift operators with those of a non-exposed control group of production workers. The magnitude and duration of back and neck twisting will be measured and back and neck disorder rates will be determined through a questionnaire. Findings from this study will provide the impetus for forklift manufacturers to develop improved forklift cab designs and for companies to purchase them. The project addresses the NORA MSD cross-sector strategic goal of conducting valid, reliable, comprehensive exposure assessment in multi-factorial environments (SG1) and the intermediate goal of developing methods for measuring biomechanical exposures (IG1.1).


The goal of this study is to determine the extent to which forklift operators may be at increased risk of neck and back pain due to the extreme twisted trunk and neck postures and exposure to whole body vibration required during typical operation of a forklift vehicle. To achieve this goal, a cross-sectional research study design will be used in which a cohort of exposed forklift operators will be compared to an age and gender matched cohort of non-exposed production workers. Primary exposure variables will consist of measurement of the axial static neck and trunk rotation postures, whole body vibration (WBV), and duration of exposure to these factors. To control for possible confounders, data will also be collected on other physical and non-physical work factors that may contribute to risk of reporting back or neck pain, such as individual factors, psychosocial factors, and work organizational factors. Health outcome variables will include the prevalence of neck and lower back pain among study participants and pain and discomfort in other body parts. Logistic regression analysis will be used to determine the extent of the association between exposure and health outcomes.

The study will measure exposure to extreme back and neck postures among forklift operators and compare their back pain incidence rates to study participants in the non-exposed control group. Since exposure to whole body vibration has also been shown to be a risk factor for back pain, vibration levels at the seat will also be measured in order to control for exposure to WBV. The exposed group (i.e., those who operate forklifts) will be stratified on exposure, such that operators with both low and high levels of exposure to extreme postures plus vibration will be recruited into the study. One-year prevalence rates and the corresponding 95% confidence intervals of neck and lower back pain will be calculated for both exposure and comparison groups for the outcome variables. Summary statistics will be calculated for all variables and logistic regression analyses will be conducted to calculate odds ratios and the corresponding 95 confidence intervals for both neck and lower back pain, adjusting for all confounders. Crude and adjusted estimates (for potential confounders) will be computed (see statistical analysis plan and sample size calculations below.) In 2006, two different wearable posture measurement systems were developed and tested to measure the extent of neck and trunk twisting among forklift operators. There was a delay in conducting the full study due to these difficulties. We anticipate that the full data collection will be completed in FY2007, as planned.


Project objectives include:

• To determine the amount of time spent by forklift operators in non-neutral neck and lower back postures during a typical work day.

• To determine the prevalence of lower back and neck disorders among forklift operators.

• To determine the extent of exposure to organizational stressors, among forklift operators.

• To determine the level of magnitude and cumulative exposure to whole-body vibration among forklift operators during a typical workday.

Mission Relevance

Forklifts are widely used in manufacturing, service, and warehousing enterprises, with an estimated 1.2 million workers operating as many as 800,000 forklifts in the U.S. alone (Swartz, 1998). Forklift drivers often are required to operate the forklift in a reverse direction when transporting a load due to visual obstruction of the load in the front of the forklift, in many cases, for great distances. Operating a fully loaded forklift in the reverse direction creates two significant hazards. First, the operator is exposed to severe static musculoskeletal stress to the neck and trunk due to extreme twisting for extended periods of time that could significantly increase the risk of a work-related neck or back disorder. Second, the operators' field of view in the direction of movement is significantly reduced, sometimes by more than 90 degrees, when the operator is turned facing the back of the forklift during operation. A meta-analysis of existing studies revealed that there was a significant relationship between forklift operation and low back pain (meta-odds = 2.125), but the studies were unable to determine the relative contribution of risk associated with extreme postures and vibration resulting from operation of a forklift. Findings from this study will provide the impetus for forklift manufacturers to investigate research and development of improved forklift technology, including developing and evaluating new forklift cab designs that will allow the operator to drive the forklift without exposure to awkward trunk and neck postures and will reduce the risk of collision due to restricted field of view during operation. This project specifically addresses the NORA manufacturing sector Strategic Goal 3 (09PPMNFSG3): Reduce the number of musculoskeletal disorders among manufacturing sector workers, and Strategic Goal 9 (09PPMNFSG9): Enhance the state of knowledge related to emerging risks to occupational safety and health in manufacturing and the NORA transporation sector Strategic Goal 2 (09PPTWUSG2): By 2016, reduce incidence and severity of work-related musculoskeletal disorders (WMSD) among workers in the TWU sector. Finally, the project addresses the Musculoskeltal Disorders Cross-sector Strategic Goal 1 (09PPMSDSG1) (Exposure): Valid, reliable, comprehensive exposure assessment in multi-factorial environments with special emphasis on Intermediate Goal IG1.1 (09PPMSDIG1.1) (Biomechanical): Valid, reliable, comprehensive methods for measuring biomechanical exposures associated with MSDs.