Usability

The SUS score for each participant ranged from 52.5 to 87.5 (see Fig. 2A) and the average score was 75.4. In the QUEST questionnaire, satisfaction with each technical feature of the device ranged from 3.86 to 4.71, with an average score across all participants and all features of 4.1 (see Fig. 2B). Ease of transport, satisfaction with donning/doffing and satisfaction with the level of gained independence obtained the lowest median scores in the personalized questionnaire (see Additional file 1: Fig. S1).

Fig. 2

Usability questionnaires. A System Usability Scale. SUS scores for each participant and mean across participants show usability of the Myosuit above average. Each colour represents one participant. The grey bar represents the mean across participants. B Quebec User Evaluation of Satisfaction with assistive Technology. High satisfaction with most of the technical features of the Myosuit is shown. Individual results for each participant are reported using different colours

Performed activities

Three out of the seven participants reported to use the Myosuit mainly outdoors, while three participants used the Myosuit almost solely inside their houses (see Fig. 3A). Only one participant reported to frequently use the Myosuit both outdoors and at home, as well as at a physiotherapy center. None of the participant regularly used the Myosuit at work or at a gym.

Fig. 3

Location and purpose of use of the Myosuit. Subjects were asked to report how often they used the Myosuit A in different locations and B for different activities. The Myosuit were mostly used outdoors for walking either alone or with a physiotherapist. Most of the participants frequently used the Myosuit at home for exercising alone or with a physiotherapist. Only one participant uses the Myosuit frequently for activities of daily living. Each colour represents one participant. The thick black line indicates the median, and the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers extend to the most extreme data points not considered outliers. PT physiotherapist, ADLs activities of daily living

Inside the house, the Myosuit was exclusively used for exercising, either alone or with a physiotherapist remotely (see Fig. 3B). Outdoors the Myosuit was mainly used for exercising, either alone or with a physiotherapist. Three participants used the Myosuit outdoors for leisure activities (e.g., walking) with a family member, for social activities in the community (e.g., geocaching) or for activities of daily living (e.g., shopping).

Frequency and time of use

IMU data from participant P2 were not properly recorded due to technical issues of the device and hence could not be used for further analysis. Four out of the six participants for which data were available used the device on average approximately once per week (see Table 2). Greater use of the device was recorded for two participants, which used the device on average approximately five times per week. We did not find a notable difference on the average duration of the sessions between participants (median of 46.1 min). Although session’s duration was similar, participant performed considerably different number of steps (range from 252.1 to 4256.7 steps).

Table 2 Participants’ activity levelQualitative analysis

Three themes were identified during thematic analysis: (1) usability; (2) personal experience; and (3) context of use. Within each theme, codes were grouped, and multiple subthemes were identified (see Fig. 4). In this section we report exemplary statements for each theme, taken directly from the interview transcripts, using the wording from the participants (additional quotes in Additional file 1: Table S3).

Fig. 4

Thematic analysis results. Three themes were identified during thematic analysis: (1) Usability; (2) Personal experience; and (3) Context of use. Each theme is divided into subthemes and codes

Usability

This theme discusses the usability of the Myosuit in terms of (i) satisfaction towards the technical features of the device and (ii) factors that limit its use in daily life settings. Furthermore, (iii) user suggestions on how to improve the usability of the device were included within this theme.

All participants considered the Myosuit compact and were satisfied with its dimension and weight. The backpack was not perceived as heavy while walking but rather disturbing when sitting for a prolonged time and using the car. Similarly, comfort at the interface was maintained during walking but was mentioned as problematic during long sitting periods.

“The backpack is not perceived as disturbing weight. Once you have it on and turn the Myosuit on, that's not anymore. So, from the outside, it may seem that it's way too heavy, but this is not the case at all.” (Participant P2)

“[The straps of the Myosuit] tie you up pretty much when you have to sit somewhere longer.” (Participant P1)

The Myosuit was described as easy to control and all participants could operate it independently.

“There [operating the device] I'm mostly independent. I can make the settings alone.” (P7)

Users were satisfied with the support provided by the Myosuit, especially in term of increased safety and confidence while walking. However, since the robot does not support hip and knee flexion, participants struggled performing some activities of daily living, such as stairs climbing, as they could not independently reach enough foot clearance. In this regard, support to additional joint movements was desired. Participants expressed disappointment with the fasteners around the thigh and the shank.

“I don't really like Velcro fasteners for myself personally. They get trapped everywhere, right?” (Participant P4)

The donning process was mentioned by most of the participants as the main limitation of the Myosuit. Most participants could either not go through it independently or the time required for it was too long. The three participants that considered themselves satisfied with the donning process could do so in less than 5 min, compared to the other users that took up to 15 min.

“It's hard for me to be able to use the Myosuit on a regular basis. Because I always depend on someone. And that's frustrating in a certain way. If I put on the Myosuit on myself and don't need someone for it, then I would go walking [alone] with the walker too.” (Participant P1)

Limited time availability and exhaustion after a working day were also broadened up as explanations for the limited frequency of training with the Myosuit. Additionally, preserved abilities to ambulate inside the household without any assistive device limited use of the Myosuit during activities of daily living at home.

“I'm still working 100%. For me, normal everyday life is already extremely exhausting. It's practically a matter of time, too” (P4)

“At home in the house I don't use it. I just try the stuff I can still do without [the Myosuit]. My legs are still enough at home.” (P5)

User suggestions on how to improve the usability of the Myosuit were collected during the study. The most frequent answers related to the wish for a simpler design in terms of easier-to-don exosuit, and new features such as a touch screen controller or the possibility to control the device using a smartphone or a smartwatch. Some participants described very futuristic designs.

“The ideal device would be normal pants with the technology inside.” (Participant P2)

Personal experience

This theme describes the aspects that motivated participants to use the Myosuit while having it at their disposal at home. Particularly, we discussed (i) the goals set by the users and (ii) the perceived benefits.

Three main goals set by the users were identified. Firstly, participants that primarily used the Myosuit outdoors aimed at improving their walking abilities in terms of walking speed and distance covered. This would allow them to perform once again activities that were prevented by their lower-limb weakness. Secondly, participants used the Myosuit to improve their walking pattern and, thirdly, to delay the progression of their disease.

“My goal is to walk longer distances so I can go hiking in the mountains again.” (Participant P5)

“The goal is simply to improve the gait pattern so that I walk easier and better.” (Participant P3)

“I want to try to keep this walking ability, but also the strength in the legs. Because I'm going worse and worse all the time and if this "worsening" is slowed down, then I'm benefiting from it.” (Participant P6)

Participants were also motivated to continue using the Myosuit by the positive benefits and results that they experienced. We distinguished between physical and psycho-social benefits. Furthermore, we divided physical benefits into restorative (or therapeutic) and assistive benefits depending on whether they were mentioned to persist after removing the Myosuit or not, respectively. In fact, all participants explicitly expressed their excitement towards preserved improvements for a couple of days after a robotic-assisted training.

Restorative benefits included reduced tiredness and fatigue, improved walking pattern, greater stability, reduced pain and increased strength and endurance. One participant mentioned improved bladder function and, consequently, improved quality of sleep.

“I was almost not able to carry a cup of tea from the kitchen to the dining table at first. I spilled the tea because I wasn't stable enough from the pelvis and even jerked in the movements. And now I can transfer a cup of tea on my own [without the Myosuit], simply because the stability of the pelvis improved.” (Participant P1)

“It prevents me from getting pain in joints that are loaded incorrectly or also muscles.” (Participant P3)

Assistive effects included the possibility to walk longer and faster, reduced need to concentrate on the walking task and increased safety.

“[Without the Myosuit] I am very much slower when I move. With the Myosuit I'm always quicker at the destination.” (Participant P7)

“I sometimes block out my surroundings because I'm just concentrated on walking. And with the Myosuit is usually not as strong as without.” (Participant P6)

Most participants did not experience any social benefits. Two participants mentioned increased family interaction and participation in the community. Participants perceived psychological and emotional benefits in terms of increased life satisfaction and, in general, positivity connected to the possibility of being more active.

“I did not notice improvements within the society. I have such a good environment.” (Participant P2)

“Social is going again in the wood with my husband and moving outside with others clearly.” (Participant P5)

Context of use

This theme discusses how context of use influenced user experiences with the Myosuit. Specifically, we considered (i) home, (ii) physiotherapy center and (iii) the community as physical environments to which an exosuit could be exposed.

No need to commute and the possibility to integrate the training in the daily schedule at will (without ahead planning) were mentioned as factors that increased the frequency and time of training. However, the latter advantage vanished if assistance from another person was needed to don the device.

“You can individually incorporate it into your day. It has the advantage that I can train more often then, not just once a week. You can use Myosuit when it's convenient.” (Participant P3)

“I don't think it's an advantage now that I have it at home. Because if I don't automatically have someone to help me. It takes a lot more organization as if I have a fixed appointment.” (Participant P1)

In this regard, being at a physiotherapy center was considered an advantage, together with the possibility to receive expert’s feedbacks and corrections.

“I appreciate doing it with therapeutic support because I have to concentrate so much on the movements, that I often don't notice if I'm moving in the wrong way. And with a therapist, they can correct you. Which is also motivating, of course.” (Participant P6)

All participants highlighted the importance of being properly introduced to the device to use it efficiently and independently at home. Being correctly introduced to the Myosuit was extremely important not only for the user but for the physiotherapist too. Participants experienced situations in which the physiotherapist was either unable to deal with the device or preferred to stick to conventional therapy.

“He didn’t know what exercises he was supposed to do with me because he doesn't have the experience with devices like that, so he asked me to train without it.” (Participants P2)

Finally, the community showed a positive attitude towards the Myosuit in many circumstances. Participants reported interest and curiosity in the community, which could become annoying in case of excessive questioning. With respect to this, being conspicuous in the community was discussed but did not represent a problem for any of the users, apart from the same one participant that preferred to hide in the society not to receive questions.

“When walking around, then of course one is a certain eye-catcher, in a way. But that's totally fine for me. Because also with my wheelchair, even when I'm walking, I am always visible.” (Participant P6)

“Then of course everyone comes and wants to know how it works. You can't go anywhere without being addressed. And that takes longer. It's also really tedious for my family.” (Participant P4)