Saskia Baltrusch

96 Chapter 4 3.1 Lifting Metabolic costs A main effect of exoskeleton use was found on metabolic costs during lifting for both, knee height (p=0.046) and ankle height (p=0.047, Figure 3). For lifting from knee height, post-hoc testing revealed a significant reduction in metabolic costs of 17% between Control condition and High-cam Exo condition (mean (sd): 3.09W/kg (0.92) vs. 2.56W/kg (0.52); p=0.012). For lifting from ankle height we found 16% decrease in metabolic costs between Control condition and High-cam Exo condition (mean (sd): 5.06W/kg (1.11) vs. 4.27W/kg (0.60); p=0.012). The 7% reduction in metabolic cost between Low-cam Exo and Control condition when lifting from knee height and 8% reduction when lifting from ankle height did not reach significance. Figure 3: Left: Metabolic costs of lifting from knee and ankle height. Values are normalized for bodyweight. N=11. Error bars indicate standard deviations. *Significant change in metabolic costs between control condition (without) and exoskeleton condition (low cam/ high cam). Kinematics With regard to movement strategies in lifting, the range of motion (ROM) in the joints analysed did not show a main effect of exoskeleton use (Figure 4). Still, a tendency to smaller range of motion in all joints was observed in the exoskeleton conditions when lifting from ankle height.