Saskia Baltrusch

196 Chapter 7 are often much more variable in terms of technique and frequency. Additional research is needed to assess the effect of the exoskeleton on metabolic cost when performing demanding tasks for a longer period of time in a realistic setting. Also, we did not measure muscle activity around the knee joint, which could have been interesting in relation to knee loading. The results, however, show that the work generated around the knee joint when wearing the exoskeleton did not change. This indicates that the muscles did not generate more work when using the exoskeleton and hence muscle activity probably would not change either. However, this may miss for example co-contraction. Another limitation is the fact, that the effect of wearing the exoskeleton might be small in people with higher body mass than the participants tested. Besides, artefacts due to skin movement could have influenced kinematic outcomes. However, it is unlikely that these skin movements and the resulting errors are different between conditions. Hence, a measurement error due to skin movement acting as a confounding factor is highly unlikely. Our results cannot be generalized to other exoskeletons, as the effect of wearing an exoskeleton depends on the specific design characteristics of the device. The variation in individual behaviour highlights that different strategies can be used to exploit the effects of the exoskeleton and reduce metabolic cost. More insight into these different strategies and potential relations with participant characteristics might help to understand low back problems and further optimize trunk exoskeletons. However, the current sample is too small to allow further subgroup analyses. 5 Conclusion The findings presented in this study demonstrate the potential of the SPEXOR exoskeleton to decrease metabolic costs of lifting and by that reducing the risk of getting fatigued during repetitive lifting. This effect can be explained by the exoskeleton taking over muscular work generated in the hip and the L5S1 joint, reduced back muscle activity, while on average movement strategy remains unchanged. As such, the SPEXOR exoskeleton may contribute to preventing work-related low back pain for people executing highly demanding tasks, such as repetitive lifting.