## 4 Discussion
### Sources of Error and Precautionary Steps  
There are four potential sources of error associated with the residual limb volume measurement procedure for the lower limb. First, the final volume measurement is extremely sensitive to subject or residual limb movement in a few measurement techniques including water displacement, contact probes, laser scanning, MRI, and ultrasound. Subject movement can be caused by several factors including a lengthy scanning time, the subject's inability to stand for an extended period, and the subject's inability to stand still. Second, when the researcher employs certain measuring procedures, there are errors due to the distortion of the residual limb's shape that happens when force is applied to the skin and creates a compression of the residual limb. These errors are presented by the anthropometric measurement, contact probes, and water displacement techniques. Third, the post-doffing effect also contributes directly to the source of error. All techniques except for SXCT and bioimpedance are susceptible to this error. After removing the prosthesis, the residual lower limb volume will have some changes in its volume. Slow-capturing residual limb volume measuring techniques will result in varying volume estimations. To minimisethe misinterpretation of volume readings, researchers need timing criteria for measuring the residual limb volume of the lower extremity. Lastly, device resolution and precision may also potentially lead to errors in measuring the residual lower limb volume. This type of error is caused by faulty equipment used by the researchers to measure the volume of the residual lower limb. The potential errors in various techniques may contribute to different interpretations of the residual limb volume even though researchers measure the identical residual limb subject. It is challenging to obtain the same residual limb volume across studies when utilising various measuring techniques, but to properly interpret the residual limb volume, researchers must evaluate whether the measurement technique's error was greater than the changes in the residual limb volume. It is a good research practise for researchers to compare or use many techniques in studies in order to identify the best approaches with the least amount of error, as demonstrated by [PERSON] et al. [32], [PERSON] et al. [33], [PERSON] et al. [30], [PERSON] et al. [21], [PERSON] et al. [28], [PERSON] et al. [37], and [PERSON] [31]. In previous studies, it is hypothesised that water displacement is the most accurate measuring technique [28; 29; 31; 32], but as other techniques have been developed, this water displacement technique cannot be set as the only gold standard in evaluating the other techniques. The water displacement technique is thought to have a large potential for error, especially when it involves repetitive sessions, since the researchers must ensure that the residual limb has the same level of immersion and knee flexion, and that the person cannot be moved while the measurement is being taken. In addition, as this technique is a contact measurement type, extra caution should be taken because surface tension between the residual limb and the water during immersion has a large potential for error. With the developed technology, laser scanner techniques are potentially seen to be more accurate in giving the volume of the residual limb compared to other techniques. Although the laser scanning approach has several limitations, the authors still consider it to be an effective measurement technique with less potential error because it is a fast-measuring technique. As stated by the authors, one of the issues with this laser scanning technique is related to subject movement rather than the interaction of the laser with soft tissue. Additionally, subject movement may contribute to issues in achieving the proper alignment of shapes from different scans.