## 5 Discussion
In the low-difficulty movements, we observed a statistically significant increase in the average shoulder abduction angle during'standing arm abduction' when AR feedback was provided (\(p\) = 0.04). Conversely,'standing arm raise overhead', another low-difficulty movement, did not show a significant difference with AR feedback. We interpret this by suggesting that the'standing arm raise overhead' movement might inherently push individuals towards their maximum range of motion, thereby limiting the additional benefit of visual feedback. In contrast, for'standing arm abduction', the AR feedback likely provided salient visual cues regarding the target angle, effectively guiding participants to achieve a wider range of motion. Extending our analysis to the medium-difficulty movements, we observed a similar pattern. The'standing trunk lateral flexion' exercise showed a statistically significant increase in the average trunk lateral flexion angle with the application of AR feedback (\(p\) = 0.02). This aligns with the findings from the low-difficulty'standing arm abduction', suggesting that the visual cues provided by AR feedback effectively facilitated a greater range of motion in lateral trunk bending. Conversely, the'standing diagonal raise with a medicine ball' did not exhibit a significant difference, likely due to the inherent limitations in the range and radius of trunk rotation involved in this movement, thus limiting the potential impact of AR feedback on this specific aspect of motion. The high-difficulty movements presented a unique set of demands, requiring both stable weight-bearing on the prosthetic limb and precise control of the sound limb. Notably, within this category, the'standing knee flexion to maximum height' movement demonstrated a significant increase in hip flexion angle with AR feedback (\(p\) = 0.03). This finding echoes the results from the low- and medium-difficulty movements where AR feedback enhanced the range of motion, indicating its potential effectiveness in guiding a larger hip flexion range in this challenging exercise as well. In contrast, the'standing forward lunge with dumbbells' and'stepping sideways and extending arms laterally' did not show discernible differences in the range of motion with or without AR feedback. For the'standing single-leg lateral raise', while a slight increase in the average value was noted, the inherent difficulty of lifting the sound leg laterally while weight-bearing on the prosthesis might explain why a more substantial change was not observed, possibly because participants were already operating near their maximal achievable range. In summary, while AR feedback did not consistently increase the joint range of motion across all exercises, statistically significant increases were noted specifically in standing arm abduction, standing trunk lateral flexion, and standing knee flexion to maximum height. This suggests that the effect of AR feedback on range of motion is likely contingent upon the nature of the exercise and the demands of the movement. For example, AR feedback may be particularly beneficial in guiding a greater range of motion in exercises with simpler, more defined paths. Conversely, its impact might be less pronounced in more complex movements or those where individuals already exhibit a full range of motion. Consequently, the implementation of AR feedback in rehabilitation training may necessitate the development of tailored feedback approaches that take into account the specific exercise and the intended joint movements. Beyond the effects on movement accuracy and range of motion, a particularly compelling finding of this study is the statistically significant higher subjective satisfaction reported by lower limb amputees who utilized AR feedback. This encompassed aspects such as the enjoyment of training, motivation levels, perceived exercise effectiveness, and perceived accuracy of movement.