Saskia Baltrusch

207 Chapter 8 recurrent low back pain. We recruited employees working in the luggage handling sector and operators working on the assembly lines, respectively. This research complied with the tenets of the Declaration of Helsinki and was approved by the medical ethical committee of VU medical center (VUmc, Amsterdam, The Netherlands, NL57404.029.16). Informed consent was obtained from each participant. 2.2 Quantitative method For the quantitative analysis we assessed self-efficacy by using the Modified Spinal Function Sort (M-SFS), a valid and reliable picture-based questionnaire that can be used in patients with chronic musculoskeletal disorders [28]. It consists of 20 daily activities (see Appendix 2 for task description), that involve loading of the spine. The respondents are asked to estimate their physical capacity in regard to their low-back pain by rating the different activities on a scale from 1 (“able”) through 2, 3 and 4 (“restricted”) to 5 (“impossible”). From this scale a total score is calculated such that high values indicate high self-efficacy (with a max of 80) and low values indicate low self-efficacy ( with a min of 0). A M-SFS score <56 is hypothesized to be predictive for non-return to work in patients with musculoskeletal disorders [29]. Participants Data for this study were obtained from a subgroup of participants that were included in a larger study on the effects of a passive exoskeleton on functional performance [16]. From that population, employees who had a history of low-back pain were included in this study. The final group had an average pain level of 3 (2-5) on a scale from 0=no pain to 10=maximum pain. The 19 participants selected for this study included 8 luggage handlers, 8 operators and 3 people from non-load handling occupations. Data from two participants had to be discarded from the analysis, since these participants failed to understand instructions. Procedure To assess a potential change in self-efficacy with using the exoskeleton, participants were asked to fill in the M-SFS at three different time points: 1) At the beginning of the session (BASE condition), 2) after they received a verbal 8