Saskia Baltrusch

190 Chapter 7 Positive and negative joint work at the knee during picking up and putting down the box, did not change when wearing the exoskeleton (Figure 7a). Total positive and negative joint work at the hip and L5S1 (generated by muscles and exoskeleton) also did not show significant differences between control and exoskeleton conditions (Figure 7b-c). Average positive and negative work generated by the exoskeleton (exowork) at the hip joint amounted to 13 joules (3.4) and -15 joules (-3.3), respectively. Despite the significant amount of work done by the exoskeleton, we did not find a significant difference in positive and negative muscle work (muswork) when wearing the exoskeleton, compared to the control condition for unloaded and loaded phases (Figure 7b). At the L5S1 joint, average positive and negative work generated by the exoskeleton (exowork) was 24 joules (4.5) and -24 joules, (-4.5), respectively. This resulted in a significant decrease in muscle-generated negative and positive work (muswork) in the exoskeleton condition in the unloaded phase (-51.47 joules (31.84) vs. -99.45 joules (55.81); p=0.02 and 48.51 joules (29.29) vs. 88.42 joules (29.29); p=0.02; Figure 7c). Muscle work in the loaded phases did not show significant differences.