An Evaluation of the NIOSH Lifting Equation: A Psychophysical and Biomechanical Investigation
Using the results of psychophysical and biomechanical experiments, NIOSH (National Institute for Occupational Safety and Health) Recommended Weight Limit (RWL), the Lifting Index (LI), the form of the asymmetry multiplier, and the criterion for compression force were investigated. Analysis of the results indicated a significant difference between the NIOSH RWL and the reported Maximum Acceptable Weight of Lift (MAWL). Contrary to the NIOSH lifting equation, the form of the asymmetry multiplier was found to be non-linear. The overall average of peak compression force on the L5/S1 was 3685 N. Fifty-eight percent of all compression forces reported in the biomechanical experiment were found to exceed the suggested 3400 N set by NIOSH guidelines. These results support previous research findings on the validity of NIOSH guidelines.
Safe Lifting in Patients with Chronic Low Back Pain: Comparing FCE Lifting Task and Niosh Lifting Guideline
Introduction: Both the floor-to-waist lifting task of the Isernhagen Work Systems Functional Capacity Evaluation (IWS FCE) and recommended weight limit (RWL) of the NIOSH produce safe lifting weights and are used world-wide nowadays. It is unknown whether they produce similar safe lifting weights. Aim of this study was to compare FCE performance on the floor-to-waist lifting task and RWL of the NIOSH lifting guideline for this task, in patients with chronic low back pain (CLBP). Methods: Ninety-two patients performed the FCE lifting task. RWL was calculated for this task. Performance was compared with RWL. A lifting index was calculated by dividing performance by RWL. Differences between groups with a lifting index ≤1, 1–3, and >3 were calculated for pain intensity, scores on the Roland Morris Disability Questionnaire (RMDQ) and work status. Results: Men lifted on average 32.5 kg (SD 15.4) and women 18.8 kg (SD 7.8). RWL for this task was 12.8 kg. Mean difference between performance and RWL was 15.0 kg (SD 14.7; range −8.8 to 59.2). The Roland Morris Disability score of patients with a lifting index ≤1 was significantly lower than patients with a lifting index 1–3 and >3. No difference in pain intensity and work status was found between groups. Conclusion: It was concluded that performance on the FCE floor-to-waist lifting task and RWL of the NIOSH for this task produce different safe lifting weights in individual patients with CLBP, which may result in contradictory recommendations about need for rehabilitation and return to work.
The microscale obstacle-resolving meteorological model MITRAS v2.0: model theory
Abstract. This paper describes the developing theory and underlying
processes of the microscale obstacle-resolving model MITRAS version 2. MITRAS
calculates wind, temperature, humidity, and precipitation fields, as well as
transport within the obstacle layer using Reynolds averaging. It explicitly
resolves obstacles, including buildings and overhanging obstacles, to
consider their aerodynamic and thermodynamic effects. Buildings are
represented by impermeable grid cells at the building positions so that the
wind speed vanishes in these grid cells. Wall functions are used to calculate
appropriate turbulent fluxes. Most exchange processes at the obstacle
surfaces are considered in MITRAS, including turbulent and radiative
processes, in order to obtain an accurate surface temperature. MITRAS is also
able to simulate the effect of wind turbines. They are parameterized using
the actuator-disk concept to account for the reduction in wind speed. The
turbulence generation in the wake of a wind turbine is parameterized by
adding an additional part to the turbulence mechanical production term in the
turbulent kinetic energy equation. Effects of trees are considered
explicitly, including the wind speed reduction, turbulence production, and
dissipation due to drag forces from plant foliage elements, as well as the
radiation absorption and shading. The paper provides not only
documentation of the model dynamics and numerical framework but also a solid
foundation for future microscale model extensions.
