Saskia Baltrusch

49 Chapter 3 1 Introduction Low-back pain is one of the major health problems, causing large-scale personal suffering [1], work absenteeism [2] and socioeconomic costs [3]. Affecting 60-80% of people at some point in their lifetime [4] and being one of the most common health reasons given for work loss [2,5,6] low-back injuries continue to be an occupational health problem. Despite increasing awareness of the need for prevention, the prevalence of musculoskeletal disorders (MSD) has not decreased [7]. With recent advances in technology interest has shifted from adaptions of the work environment or worker behavior, towards body worn assistive devices, also called (non-actuated) exoskeletons, which support the user when performing tasks that involve high back loads. To date, most devices that have been developed to reduce back loading and to prevent low-back pain are mainly in the experimental stage and are not used in practice yet. Several experimental studies found reduced low-back loading during lifting, bending and static holding tasks when using assistive devices that passively support the user’s trunk against gravity [8-12]. These studies have generally been performed using controlled manual materials handling tasks in artificial laboratory settings. Bosch et al., (2016) [9] assessed the effect of wearing the passive exoskeleton “Laevo” (Intespring, Delft, The Netherlands), which is commercially available and already used at different work sites, on discomfort and endurance time in forward bending work. They found lower discomfort in the lower back and an increase in endurance time when wearing the exoskeleton. A similar study was conducted by Graham et al., (2009) [10]. They performed one of the few studies to assess user acceptance in the field. Participants were wearing a personal lift assist device (PLAD) and performed an on-line assembly task at an automotive manufacturing facility. Participants reported no interference of the PLAD with the task and an offloading of their back. Despite the problem of pressure points at legs and shoulder, the device reached high user acceptance. However, the tasks performed in the above studies mainly required static holding of a forward bent trunk posture. In contrast, most physically demanding jobs, such as warehousing, construction work or healthcare comprise combinations of many different tasks besides lifting, such as carrying, walking and working in 3