## 4 Discussion
The findings showed that the BSIE led to a lower mean (~40% (\(p<0.01\))) COP velocity during all three task portions. The trunk movement was also reflected in the whole-body stability measures, with a higher mean COP velocity occurring during retraction vs. bending. A 12% decrease in the maximum COP distance from the initial position during the transition portion was seen when the tasks were performed with the BSIE. Interestingly, the BSIE did not affect the mean COP during the performance of the asymmetric vs. symmetric postures. However, when the BSIE was not worn, the mean COP velocities in all three task portions were ~15-17% (\(p<0.01\)) higher during the asymmetric vs. symmetric postures. Fatigue is known to impact stability measures [39]. The presence of fatigue equally affected the mean COP velocity when the tasks were performed with and without the BSIE, with a similar rate of increase between the beginning and end conditions. However, the values without the BSIE at the end were almost twice those of when the tasks were performed with BSIE assistance. Thus, contrary to our hypothesis, using the BSIE led to more stable postures during the bending tasks, especially in the presence of asymmetric and fatiguing conditions. This study utilized a controlled experiment in which the study participants performed repeated cycles of trunk flexion. In addition, fatigued states were attained for all the participants through intermittent trunk flexion tasks involving static standing, bending/retraction, and sustained trunk flexion in symmetric and asymmetric postures. This was performed to understand the effects of using a BSIE on the muscle demands, kinematics, and stability. While we simulated realistic scenarios in a controlled fashion with standard body movements, real-world tasks may include much more variability in body movement. In such cases, we recommend that practitioners thoroughly evaluate the types of body movements, as well as the proportion (considering duration and frequency) of body postures, where a BSIE is designed to be beneficial (sustaining a posture with trunk flexion) across activities within tasks. While our study has shed light on diverse aspects of the physical demands concerning the spatial and temporal dimensions, it is essential to acknowledge certain limitations inherent in our research. Firstly, our participant group primarily consisted of young adults, and extending the investigation to encompass gender and anthropometric variations would enhance the study's applicability to a broader demographic. Another critical component is the variability introduced by different exoskeleton designs, ranging from soft to rigid and encompassing passive, active, and hybrid systems [40]. These structural and actuation differences among exoskeletons can significantly impact the observed variations in the physical-demand measures. As the BSIEs were helpful for reducing the leg demands during the repetitive trunk flexion-extension tasks, our future steps may compare the efficacies of BSIEs and their lower-limb counterparts that enable sitting/leaning postures to negate the need for trunk flexion-extension tasks [41]. Future work could delve into field evaluations, focusing on the muscle demands in the trunk musculature, such as the trapezius and oblique muscles, which are especially relevant for tasks involving asymmetric postures. Additionally, lower-body kinematics, stability measures based on the foot contact area derived from marker positions, and a comparative analysis between the demands imposed on wearers of BSIEs across newer and different types of these wearable assistive devices could be explored.