Introduction

Incomplete recovery is considered as one of the main causes for developing MSDs. This paper describes the further development and application of an assessment tool, Ergo-Index, which can be used to analyse different ways to perform a work task considering load ergonomics as well as time aspects. It can support decision making when choosing production methods and help reduce the physical load and the risk of MSDs in combination with good production economics.

Objectives

The objectives were to further develop the existing Ergo-Index by i) gaining data to understand how load level and loading time affect recovery need ii) modelling the recovery need, iii) refining the existing Ergo-Index model iv) testing and implementing the model and gathering examples in a database and v) disseminating the results.

Methods

An experimental study was carried out with 10 participants. over 16 sessions, each participant pushed a handle, in which static force and time were altered between the sessions. Subjectively rated Endurance time (ET) and Resumption time (T_res), defined as the time period needed after loading until the participant would resume the task if it was his job, was noted, as well as other parameters. Based on experimental data mathematical relationships were established, using regression analysis. A new version of the Ergo-Index was developed based on the results and results from literature. The new tool was coded as a simple Excel-program and applied to 10 typical work tasks in industry and evaluated using biomechanical and subjective methods.

Results

The main results were data for ET, T_res and Rating of perceived discomfort/fatigue and a new Ergo-Index model, which is described briefly in the conference paper. Some applied examples are illustrated in the presentation.

Discussion

Different types of fatigue and models are discussed, as well as issues when trying to model the complex phenomena of fatigue.

Conclusions

It is concluded that the recovery time can be modelled as a relationship between load level and loading time, and that the method has to be further used and validated.