# Development and Biomechanical Evaluation of a Back Exoskeleton to Support Lifting Tasks
## 1 Introduction
Passive exoskeletons are generally lightweight, cost-effective, and maintenance-friendly, making them suitable for tasks requiring lower assistance. In contrast, active exoskeletons can generate higher levels of support and allow precise, time-dependent force control, making them more adaptable to dynamic and demanding applications [15]. Advancements in exoskeleton technology have enabled the development of support systems that dynamically adjust their support characteristics based on the user's movements and external conditions [16]. To achieve this, various sensors, such as capacitive force cells and inertial measurement units, are required to detect the interactions between the user, exoskeleton, and environment. By utilizing sensor data as input for the control strategy, adaptive exoskeletons offer enhanced usability and versatility across a broader range of tasks compared to passive systems. This optimization maximizes the exoskeleton's potential while improving user comfort and productivity. However, these benefits come at the cost of increased complexity in development, maintenance, design, and energy consumption, emphasizing the need to carefully consider context-specific requirements and constraints [17]. Considering the working conditions of nurses and care workers in hospitals, healthcare facilities, or home care settings, exoskeletons must meet specific requirements to ensure safe and effective use during patient interactions. To accommodate the high range of motion required for lifting tasks, these systems should be lightweight and non-restrictive, minimizing interference with natural movements. Since nurses often work in confined spaces while lifting or transferring patients, wearable exoskeletons must be designed to fit closely with the wearer and remain unobtrusive [18]. Given these constraints, fabric-based exosuits are well-suited for prolonged wear in dynamic care environments due to their flexibility and comfort. However, caregiving tasks frequently involve handling heavy loads, making it essential to integrate rigid components for structural support and load-bearing capabilities. This is particularly important in active exoskeletons, where actuation mechanisms must provide the necessary assistance while adapting to various tasks [19]. In order to combine the advantages of lightweight passive exoskeletons with the adaptability of active systems, a compact active exoskeleton was developed, featuring an efficient and straightforward control strategy specifically tailored to assist lifting motions. This paper outlines the design of a newly developed exoskeleton aimed at supporting the lower back during lifting activities and presents an evaluation of its biomechanical impact. To assess the biomechanical effects, we analyzed the hip and leg kinematics and muscle activation in healthy participants while performing lifting tasks with and without the activated exoskeleton. The objective of this study was to examine variations in joint kinematics and muscle activity between the two experimental conditions. We hypothesized that the joint angle trajectories would remain unchanged due to the biomimetic design and highly dynamic actuation system. In contrast, we expected a reduction in muscle activation when using the exoskeleton, as the applied assistive force should alleviate the muscular strain during lifting.