## 4 Discussion  
An existing method that can be used to assist individuals with amputations with the management of their residual limbs' volume fluctuations is based on measurements of the volume of the limb. Bioimpedance is the most practical volume measurement technique for this purpose. Compared to the proposed method of this study, the disadvantage of bioimpedence is that it requires proper electrical contact between electrodes and the skin through the use of hydrogel. Moreover, this method is dependent on the cause of volume fluctuations as it measures variations in the fluid volume of the limb. Another existing method that can be utilized towards the goal of this study is to use the limb-socket interface pressure registered using load cells. The main disadvantages of this method compared to the one proposed in this paper are: it requires alterations of the prosthetic socket for sensor mounts; it increases the weight of the prosthetic system; and it is relatively expensive. Alternatively, the pressure map at the interface of the residual limb and the prosthetic socket can be obtained using computational methods. The con of this method compared to that of this study is that it requires precise measurements for each individual derived from scans of the limb. This makes the computational method relatively complex and expensive. The method proposed in this study is novel since, unlike most other methods, it is easily integrated within the user's prosthesis with minimal modifications. The sensory system requires one time installation and can be used seamlessly afterwards. Using this method, volume variations can be detected as the user carries out their daily activities using the prosthetic socket without a need for doffing the socket. This method is simple to use and does not require extensive calibration before use. Signals used in this method can be potentially acquired throughout extended periods of time. FSR signals are easy to process, making this method computationally efficient [28; 29]. Another advantage of this method is that it does not require direct contact with the skin and is less prone to errors due to environmental changes compared to some of the alternative methods. Moreover, this method, unlike some alternatives, does not depend on the reason of volume change. For instance, bioimpedance measures variations in the fluid volume of the limb rather than directly measuring the volume of the limb itself. One potential application of the proposed method is developing a smart volume adjustment system, e.g., using adjustable bladders inside prosthetic sockets [30]. The hypothesis used in this study, which guided the design choices such as the number and placement of the sensors, was based on the literature and the expertise of the Certified Prosthetist who collaborated in this work. [PERSON] et al. conducted a study that monitored distal positioning of the residual limb inside a prosthetic socket. In this study, they reported that a larger volume of the residual limb would cause a more proximal placement inside the socket, relieving some of the distal pressure [22]. Based on the results reported by [PERSON] et al. and the experience of the collaborating Certified Prosthetist, it was clear that the interface pressure at the distal location would provide information about fluctuations in the volume of the residual limb. Although the pressure in other areas of the limb-socket interface would also be affected by variations in the limb's volume, the distal pressure was expected to be more consistent amongst different individuals. A possible approach to investigate the feasibility of the proposed method could be to increase the number of sensors used in the three-ply phase. However, we used four sensors as it was already clear that the distal location was the most promising location for the goal of this study.