**Author details**

of the first variant a mean for the JSI of 1.055 with a standard deviation of 0.32 was measured. According to this, the spread lets us expect that the JSI measurements lay at 1.055 ± 0.32. The maximum spread is approximately ±0.5. These results indicate that during the experiments different influencing factors like the grip and strength of fingers, posture of hand and fingers

26 Anatomy, Posture, Prevalence, Pain, Treatment and Interventions of Musculoskeletal Disorders

The literature review has shown that no digital hand models exist that are used for the simulation and analysis of influencing factors with respect to the pressure simulation. Either realistic skin deformation is simulated [13] or part models to study material investigation are used [9]. Here are no statements taken to the sensation of pressure. With the known hand models, a derating of the pressure distribution can be indeed proven; however, the inclusion of influences by [28] is ignored. With the help of the digital hand model, there is the ability to save subjects, expensive prototypes and pressure sensor mats in the development of handheld products. The hand model can develop proposals for the design in a short time, and reduces the pressure load objectively. The comparison between the pressure simulation and pressure measurement showed that correct pressure loads are determined with the linear approach of the hand model. The literature review shows, in this context, such as the work of [10] that a linear material behavior on skin tissue can be assumed. However, the linear material behavior is permitted only for a certain range of forces and demands, for example, for the fingers typing e-modules. This effort can be eliminated in a non-linear material behavior. Since in most cases, skin damage due to shearing arises, for further development the expansion of the model for simulation of shear stress is recommended. Other criticisms of the model include the fixing of the metacarpals in the room. These ensure that the palm is immobile. In addition, the palm consists of a plurality of muscles which alter the mobility of the metacarpal bone. The application displays a new approach to produce an impact analysis. The results of the impact analysis can be implemented directly in the CAD model and give a product which produces low and evenly distributed pressure distributions on the hand tissues for the simulated factors. The impact analysis gives findings about which factors have

In summary, regarding the literature on the measurement of hand stress can be said, that there is no work, which uses a sensor glove to measure strain variables from the JSI method [14]. Very often sensor gloves with force sensors are used to obtain an indication of the power level, without taking the hand posture into account. In some works, such as [22], for example, only the movement or the hand posture for motion capture is measured with the sensor glove. Then the measurement data scored with RULA, without taking forces into account. None of the sensor gloves aims solely the ergonomic quality of a hand-held product. The developed JSI-System give an effective tool for assessing the hand stress based on JSI method. In addition, the examiners do not always have the same expertise and experience regarding the hand ergonomics and therefore evaluate differently. Regarding the standardization of JSI, with the JSI-System arises a potential for application in the industry. The JSI-System

etc. have influences on hand stress.

an influence on the pressure distribution.

**5. Conclusion**

Aydin Ünlü\*, Peter Gust and Frank Mersch \*Address all correspondence to: aydin.unlu@outlook.com University Wuppertal, Germany
