Text

Introduction: Technical measurements are becoming increasingly important for quantifying physical workloads due to their objectivity. However, to date there are only a few approaches to evaluate the continuously recorded measurement data. There is a lack of suitable evaluation systems, particularly with regard to the evaluation of physical stress in specific regions of the body. This article presents a measurement-based approach for quantifying and evaluating the strain on the lumbar spine, which was applied to a specific practical example to evaluate the potential relief provided by an unloading aid during baggage handling at an airport.

Methods: Risk factors for the development of MSDs in the lumbar spine include high levels of exertion, awkward postures, and repetitive activities. These are measured using kinematic and kinetic parameters. In the example, 5 volunteers were equipped with a whole-body motion capture system (Awinda, Movella) and insoles for recording vertical ground reaction forces (Loadsol, Novel) and data were recorded during a work shift.

The kinematic assessment index (KAIx) and the daily dose of lumbar compression force at L5-S1 (DoseCF) were used to assess lumbar loading. The KAIx measures the proportion of time spent in non-recommended postures and movements, while the DoseCF is based on the continuously determined compression force using the biomechanical model “The Dortmunder”. To assess the daily exposure of the lumbar spine, the measured parameters are cumulated over a work shift and assigned to the following four risk categories (RC) according to the MEGAPHYS risk concept (1: low risk to 4: high risk).

Results: The range limits between the RCs were derived from measured exposure data from 196 real workplaces and their plausibility was checked at real workplaces with activities of different exposure intensities. In relation to a day shift, a KAIx <5% is assigned to RC1 and a KAIx ≥22% to RC4. The DoseCF assigns women a value <0.4 kNh to RC1 and ≥3.5 kNh to RC4. For men, a DoseCF <0.8 kNh is assigned to RC1 and ≥4.5 kNh to RC4.

Baggage handling at the airport is characterised by an alternation of very high work intensity during unloading the cargo containers and low intensity during waiting for the next flight and its cargo containers. For the day shift, a KAIx of 11.8% was determined without unloading aid and a KAIx of 11.5% with unloading aid, which corresponds to a slightly increased risk (RC2). The DoseCF is significantly reduced from 8.8 kNh by the unloading aid to 5.7 kNh, which is nevertheless both classified as RC4.

Discussion: The measurement data underlines the importance of the waiting times between the cargo containers as a recovery phase for the employees. In both cases, the load intensity is high, but this is reduced with the unloading aid. The workplace analysis helped the airport to decide on the introduction of the unloading aid.

The measurement-based approach enables a more precise risk assessment, but more measurement data and epidemiological studies are required to validate or adjust the range limits of the risk categories. The method is particularly suitable for scientists and ergonomics experts but can also be used in a simplified form by operational practitioners.