Saskia Baltrusch

162 Chapter 6 for multiple testing were made by dividing α by the number of tests performed for each outcome within each group of tasks. General discomfort and User’s impression, are presented descriptively, since these parameters were only assessed in the Exoskeleton condition. All statistical analyses were performed using SPSS for Windows (IBM, SPSS Statistics 23.0, USA). 3 Results 3.1 Group characteristics The healthy group and the low-back pain group did not differ in age (44years vs. 43years), weight (87kg vs. 78kg) and height (180cm vs. 175cm). Eight of the 13 participants, allocated to the low back pain group, reported they had multiple inactive working periods due to sick leave related to their low-back problems in the past. In the healthy group, two participants reported to have been on sick leave due to low-back pain once. The current pain level of the low-back pain group at the start of the measurement was 4 (2-5) on a scale from 0=no pain to 10=maximal pain. In the healthy group only one participant reported to have current pain, with a value of 1. 3.2 Objective performance A significant increase in performance when wearing the exoskeleton was found for maximum number of lifts in 2 minutes (18lifts ± 6 vs. 20 lifts ± 6, p=0.000) and maximum static forward bending time (3.1mins ± 1.4 vs. 4.2mins ± 1.0, p=0.000) (Figure 2a). These tasks belong to the group of tasks in which we expected support by the exoskeleton. Performance in three tasks of the group in which we assessed the potential hindrance of the exoskeleton, slightly but significantly, decreased when wearing the exoskeleton: walking distance (475.1m ± 47.0 vs. 444.1m ± 42.4, p=0.000), stair climbing time (17.7s ± 3.0 vs. 19.1s ± 3.2, p=0.000) and wide stance distance (109.6cm ± 22.4 vs. 104.2cm ± 25.5, p=0.005). A main effect of group was only found for lifting, with greater performance in the healthy group, compared to the low-back pain group (16 lifts ± 2 vs. 23 lifts ± 2, p=0.003). Interaction effects between exoskeleton and allocated group were found for static forward bending (p=0.001) and wide stance (p=0.018) (Figure 2b). These interactions revealed that the increase