Usability Test for Motion Tracking Gait Assistive Walker

Ⅰ. Introduction

Older adults who have experienced falls have decreased location and physical mobility due to the fear of falling and limited walking ability and depend on others for their daily life activities (Lee et al, 2009; Kyeoung MJ,2022). Gait assistive devices are designed to alleviate the impact of mobility limitations, enhance independence, and promote greater freedom and independent living. They are necessary for seniors and individuals with mobility impairments to facilitate a more active and independent lifestyle while reducing the burden of therapy and care (Arefin et al, 2020; Dong CP, 2021). In particular, introducing gait assistive devices early during the initial stage of walking training or when independent walking is difficult can increase the base of support (BOS) while standing, induce symmetrical weight load on the lower extremities, and improve gait stability.

The most commonly used gait assistive devices in everyday life include canes, crutches, and walkers. Among them, walkers have the advantage of providing stability by securing a wide BOS and minimizing skewed gait by allowing the use of the assistive device with both hands. However, using walkers with both hands limits the swinging of the arms when walking, preventing the natural gait pattern (Liu 2009), and excessive weight support of walkers can reduce the effect of limb muscle strengthening and cause secondary musculoskeletal damage to the wrists (Bradley and Hernandez, 2011). Visintin and Barbeau (1994) reported that the reduction in the arm-swinging motion while walking with gait-assistive devices is a factor that interferes with the normal gait pattern, and Bateni and Makio (2005) reported that the free movement of the upper extremities should be considered in training for the normal gait pattern when applying gait-assistive devices because the motion of lifting the walker and pushing it forward can potentially disturb the center of mass.

Mobility and maneuverability are necessary to avoid multiple obstacles while moving in a narrow, complex space. However, while conventional walkers provide high structural safety, they have limitations in terms of mobility and maneuverability. Sufficient space is needed to change the direction when walking with a walker, and the user must lift the body of the walker and slightly change the direction in several steps. Such a directional change is a challenging task for older adults with insufficient muscle strength of the lower limbs and reduced concentration and cognitive function, and falls may occur while changing directions.

Therefore, we developed a motion-tracking gait-assistive walker (MTGAW) that reduces the fall-inducing factors of gait-assistive devices identified in previous research and clinical practice, and clinical specialists, including physiotherapists and occupational therapists, evaluated the usability of the walker. Functional satisfaction and improvement areas were determined through the usability evaluation and interviews, which will be reflected in the promotion for of commercialization of the walker in future product development.

Ⅱ. Methods

1. Participants

Thirty-seven physiotherapists and occupational therapists at C Hospital in C City participated in the usability evaluation. All participants were fully informed and understood the purpose and characteristics of this study and voluntarily agreed to participate in the usability evaluation. The usability evaluation involved individual interviews to assess satisfaction with 19 items across four areas and identify areas for improvement after the participants directly used the prototype. The general characteristics of the participants are shown in (Table 1).

Table I.

General characteristics of the participants(n = 37)

2. MTGAW (Motion Tracking Gait Assistive Walker)

An MTGAW was developed to assist older adults with mobility and individuals with a disability who have difficulty walking independently. It consists of a motion intent detection unit and a Mecanum wheel-based driving unit (Fig. 1). The motion intent detection unit is equipped with two independent wire displacement sensors and is connected to the straps worn on the top of both femurs of the user. The wires coil and shorten when the user moves forward and loosen and lengthen when the user moves backward. When the user rotates to the right, the right wire lengthens while the left shortens, and when the user rotates to the left, the left wire lengthens while the right shortens. The motion intent detection unit detects the user's motion intention based on the length displacement of the wire according to the above lower limb motions. The Mecanum wheel-based driving unit is designed to move while tracking the user's motion in forward, backward, and rotational directions by using the Mecanum wheel drive according to the user's motion intention input from the motion intent detection unit. In addition, each Mecanum wheel is equipped with a shock absorber and designed to withstand the pressure of the user's weight of up to 200 kg.

Figure 1.

Setting for the motion tracking gait assistive walker

Ⅲ. Results

1. Results of Satisfaction Survey

This study investigated the satisfaction on 19 items across four areas: six items on safety, six items on maneuverability, five items on usability, and three items on management. All items were measured on the following 5-point scale: 1 = Very unlikely, 2 = Unlikely, 3 = Neutral, 4 = Likely, and 5 = Very likely. Table II shows the results of the satisfaction survey.

Table II.

Results of Satisfaction survey(n = 37)

2. Results of in-depth Interview

Table III shows the main results of the in-depth interview on the four areas.

Table III.

Main results of the in-depth interview(n= 37)

Ⅳ. Discussion

Gait-assistive devices are used to improve independent mobility and prevent falls in older adults and individuals with a disability (Arefin et al, 2020). These devices are selected according to the user's level of balancing ability and whether the assistive device can be grasped using one or both upper limbs (Bruun, 1986; Wu et al, 2010; Hassan et al, 2014; Wilson et al, 2019). Walkers have limited location mobility compared with crutches or canes; however, they provide optimal stability with a wide BOS and help minimize users’ anxiety (Oh et al, 2022). However, both upper limbs are required to operate a walker, and incorrect use (e.g., relying on the walker for excessive weight support by using the upper limbs that hold the walker) can interfere with weight transfer to the lower limbs (Melis et al, 1999; Edelstein 2019). Moreover, prolonged, incorrect walker use can result in the user having an inappropriate gait pattern (Bateni and Maki, 2005; Bradley and Hernandez, 2011).

Therefore, we developed an MTGAW that compensates for the shortcomings of conventional walkers. The MTGAW detects gait intention through the wire displacement sensor connected to the user's lower extremities to track and assist the user's walking and allows unrestricted motion of the upper extremities. Additionally, the walker is equipped with Mecanum wheels and has been designed to enable front-back and left-right movements and in-situ rotation motion tracking of the user. While the MTGAW has been developed to address the known shortcomings of walkers, it is necessary to examine the currently developed prototype's stability, safety, and effectiveness before making it available to older adults and individuals with a disability. Accordingly, this study also involved the evaluation of the developed prototype's usability by clinical experts, including physiotherapists and occupational therapists.

The usability evaluation showed that the MTGAW's detection technology for user motion intention allowed free movement of the hands while walking, thereby providing psychological stability and preventing falls. Another advantage of the walker reported was that the tracking function for the left-right directional change and in-situ rotation motions is essential for everyday life at home, which is not provided in existing gait-assistive devices or walking rehabilitation robots. As such, high satisfaction levels were reported in the four areas. Nevertheless, a few areas for improvement were identified, namely, improvements to reduce the discomfort caused by a slow speed, safety measures to prevent posterior falls, and a function to adjust the height and width of the walker according to the user's body. Speed adjustment should be possible since the current fixed slow speed can further increase fall risk, and improvements are needed to enable the adjustment of the height and width of the product to tailor it to the user's body to prevent tripping on the product when walking. In particular, using the harness used in the study by Visintin and Barbeau (1994) instead of a Velcro-type strap worn on the thighs to connect the body to the wire displacement sensor for motion tracking will be more effective for weight support and enhancing a psychological sense of safety.

Ⅴ. Conclusion

In this study, a usability evaluation, including a satisfaction survey and an interview, was conducted by physiotherapists and occupational therapists to identify the areas of improvement for the MTGAW developed for walking assistance for older adults and individuals with a disability. The survey showed overall high satisfaction levels on 19 items across four areas, and several improvement points were suggested in the interviews. This study constitutes a significant contribution to the field of domestic rehabilitation robotics in Korea. It offers a promising avenue for addressing the shortcomings of existing walking assistive devices. While the MTGAW compensated for the shortcomings of conventional walkers, suggestions were received to ensure safety measures to prevent posterior falls, ameliorate the discomfort caused by the slow speed, and add the height and width adjustment function to customize the walker to the user's body. In the future, an improved MTGAW that reflects the clinician-recommended needs derived from this study should be developed, and for its commercialization, a follow-up study should be performed to analyze the walker’s clinical effectiveness in older adults and individuals with a disability who require walking assistance.

Acknowledgments

This research was supported by "Regional Innovation Strategy (RIS)" through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE) (2021RIS-001).

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