# Long-Term Effects of a Soft Robotic Suit on Gait Characteristics in Healthy Elderly Persons  
[PERSON]  
1 School of Engineering, Yanbian University, Yanji 133002, China; [EMAIL_ADDRESS] (S.J. ); [EMAIL_ADDRESS] (D.Z. ); [EMAIL_ADDRESS] (C.J.) 1  
[PERSON]  
2 School of Mechanical Engineering and Automation, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, China 2* 2* 2* 2  
[PERSON]  
1 School of Engineering, Yanbian University, Yanji 133002, China; [EMAIL_ADDRESS] (S.J. ); [EMAIL_ADDRESS] (D.Z. ); [EMAIL_ADDRESS] (C.J.) 2  
[PERSON]  
1 School of Engineering, Yanbian University, Yanji 133002, China; [EMAIL_ADDRESS] (S.J. ); [EMAIL_ADDRESS] (D.Z. ); [EMAIL_ADDRESS] (C.J.) 1  
[PERSON]  
3 Faculty of Engineering, Kyushu University, Fukuoka 8190395, Japan 3* 3  
their design and implementation should be solved. 1. Joint misalignment between exoskeleton and wearer may result in resistive force [17] and, consequently, may result in increase of energy expenditure. 2. Rigid frames may constrain the motion range of the lower limb of the wearer [18], while conducting daily physical activities requires a sufficient motion range. 3. A massive power supply system is required for generating a large assistive force. This places additional payload on the wearer and also may lead to increased energy expenditure. 4. The procedures of mounting and removing an exoskeleton are complicated, even impossible in some cases without the help of a fully-trained assistant. Such issues perhaps are problematic when using exoskeletons in daily physical activities. To avoid the limitations of exoskeletons, soft robotic devices have been researched for lower limb assistance, among which typical ones include [PERSON] et al. 's soft orthosis for ankle assistance [19; 20], [PERSON] et al. 's soft exosuit for ankle assistance [21], [PERSON] et al. 's multi-joint soft exosuit for gait assistance [22; 23], and our soft wearable robotic suit for hip assistance [24; 25]. In such devices, exact joint alignment between wearer and device is not necessary. Additionally, because of the adoption of soft materials, wearers can walk with almost no kinematic constraints, and they can conduct interactions with devices in a biomechanically-compatible and safe way [26]. Moreover, a smaller and lighter power supply system can be applied because they usually provide relatively less assistive power compared with exoskeletons. Specifically, in previous works [24; 25], the author and his colleagues have presented a soft robotic suit, as shown in Figure 1, for walking assistance for elderly persons in daily physical activities. The device provides a small, yet effective assistive force for hip flexion. In addition, its weight is light, and it provides an almost full lower limb motion range for wearers. It has been reported [24] that, as an immediate effect on nine 74.2 \(\pm\) 3.7 year-old elderly persons, the device significantly reduced energy expenditure in level walking with an average of 5.9% and significantly increased the walk ratio, which is a normalized measure of step length (i.e., stride length divided by cadence) [27], with an average of 8.9% in the condition of the device worn and powered on (PON) compared with the condition of worn, but powered off (POFF). It has also been reported [25] that energy expenditure was significantly reduced by 6.5% for inclined walking in the PON condition compared with the POFF condition. One of the major aims of walking assistive devices should be to provide gait training and rehabilitation for elderly persons by repeated use of the device. However, most of the existing research only focuses on immediate effects of the devices, e.g., the differences between the POFF condition and the PON condition. There is limited research indicating the long-term effects, e.g., the differences of the POFF condition between the initial state and the state of after long-term repeated use, and only a few reports are available in the literature [28].