A multicenter prospective pilot study was conducted at the outpatient departments of rehabilitation medicine of 2 university hospitals and in 3 rehabilitation centers in the Netherlands. All centers were specialized in treatment of NMD. This study included 2 different cohorts; in one cohort, the ReVi app was applied as part of usual care at the Department of Rehabilitation Medicine at the Amsterdam UMC, location Amsterdam Medical Center (AMC). The other cohort consisted of patients using the ReVi app in the intervention group of an ongoing multicenter randomized controlled trial on the efficacy of a physical activity program, which combines the B-FIT aerobic exercise program and motivational interviewing coaching to improve physical fitness in people with NMD [16].

The medical ethics review committee of the AMC waived the need for medical ethical approval for the usual care cohort, and approved the study protocol of the randomized controlled trial (NL62104.018.17). All patients provided informed consent.

The inclusion criteria applied to both cohorts were (1) diagnosis of a slowly progressive NMD, (2) age ≥18 years, and (3) possession of a smartphone or tablet. Exclusion criteria were (1) contraindication for being physically active, (2) inability to follow verbal or written instructions, and (3) insufficient competence in the Dutch language. In addition, patients in the randomized controlled trial had to be motivated to improve their reduced physical fitness and were excluded if they had participated in an exercise program for a period longer than 4 weeks in the past 6 months. For the purpose of this study, we included only data of patients who completed at least 12 of the 48 possible training sessions, to ensure sufficient experience with the use of the ReVi app to evaluate its usability. We aimed to include a total of 30 patients in this study.

Physiotherapists were included in the study if they supervised at least 1 patient. Physiotherapists that were already exposed to the B-FIT training guide followed a half-day training course to refresh their knowledge on the use of the B-FIT training program and learn the use of the ReVi app. Physiotherapists that were not exposed to the B-FIT training guide followed a full-day training course to learn both the B-FIT training program and the use of the app. Furthermore, they received an instruction manual with a step-by-step guide on the use of the app.

The ReVi app (Amsterdam UMC) was built by a company (everywhereIM BV) specialized in the development of medical apps. The app was available for iOS and Android and it was developed in the Dutch language. An expert group consisting of physiotherapists, rehabilitation physicians, exercise physiologists, patients with different types of NMD, and representatives of the Dutch Society of Muscle Diseases and of the app builder actively participated in the development of the ReVi app. Expert group meetings were organized to discuss the aims of the app, to identify essential functionalities, and to provide feedback on so-called functional designs (on paper). The primary objective during this initial developmental phase was to create an app to assist a 16-week aerobic exercise regimen. If the study yields favorable results, the next developmental stage will be initiated to enhance the app’s functionality and further explore the possibilities for offering longer-term support to home-based aerobic exercise. The data protection officer of Amsterdam UMC (location AMC) was also involved in the app’s development process to ensure that personal data processing was organized in accordance with the General Data Protection Regulation (GDPR).

Descriptive statistics are used to present patient and physiotherapist characteristics. The data from the questions that were scored on a 5-point Likert scale were reduced by combining “agree” and “strongly agree” responses to form an “agree” category, and response options of “strongly disagree” and “disagree” were combined to form “disagree.” Frequencies were calculated on the basis of the total number of responses to each question on the usability questionnaire and expressed as percentages. Data analysis was performed using SPSS (version 28.0; IBM Inc).

Between January 2020 and November 2021, 23 patients started their exercise program as part of the usual care cohort, of which 20 patients were included in the study. Three patients were excluded because they executed less than 12 exercise sessions. Reasons included technical problems with the ReVi app (n=1), medical issues (n=1), and a lack of motivation (n=1). Nine other patients participating in the ongoing randomized controlled trial were also included and started between July 2021 and December 2021.

Patient characteristics are shown in Table 1. Twenty-three patients were treated at the outpatient clinic of the Department of Rehabilitation of the Amsterdam UMC (location AMC), supervised by 6 physiotherapists. The other 6 patients were treated by 4 physiotherapists at Rehabilitation Center Klimmendaal (Arnhem; n=2), Basalt Rehabilitation Center (Leiden; n=2), University Medical Center Utrecht (Utrecht; n=1), and Sint Maartenskliniek (Nijmegen; n=1). Twenty-eight patients trained based on heart rate and 1 patient based on the Borg scale. Twenty-seven patients performed the exercise program using a bicycle ergometer and 2 patients used a rowing ergometer.

This study provides insight into the usability of the ReVi app among people with NMD to support home-based aerobic exercise according to the B-FIT training program. The different components of usability, including efficiency, effectiveness, and satisfaction, were all judged as good by physiotherapists and patients, despite the occurrence of technical issues.

Patients were generally positive about the efficiency of the ReVi app due to its rapid learning curve and ease of use. Patients could independently work with the app based on the instructions that they received from their treating physiotherapist. Adequate instructions are known to be a key facilitator of patient engagement with mHealth apps [22]. With regards to its effectiveness, patients reported that the most important goals of the ReVi app were achieved: its use motivated them to complete the exercise program and helped them to exercise within their target intensity zones. These outcomes were supported by the findings that patients attended the majority of training sessions and spent most time within the target intensity zones. Patients were mostly satisfied with the use of the app, which concurs with other studies on apps supporting home-based physical exercise programs in amyotrophic lateral sclerosis, which is a rapidly progressive type of NMD [23], and a variety of other patient populations [24-26].

Physiotherapists were positive about the efficiency of the ReVi app. This was mainly due to the rapid learning curve and its ease of use; a half- or full-day training course was required for physiotherapists to learn how to work with the app and the B-FIT training guide, depending on prior experience with B-FIT. In terms of effectiveness, physiotherapists reported that the most important goals of the ReVi app were achieved. They found the app helpful when monitoring patients during their home-based program, mainly because it enabled them to provide feedback based on exercise data. They were generally satisfied with the use of the ReVi app and would recommend the use of the app to other physiotherapists.

While efficiency, effectiveness, and user satisfaction were overall judged as positive, one of the efficiency items was clearly judged as insufficient: 55% (n=16) of the patients and 90% (n=9) of the physiotherapists experienced technical issues. Most of these issues were solved, but in all cases, this required the help of a physiotherapist, researcher, or software developer. Technical issues are known to negatively impact usability and decrease adherence and engagement with mHealth tools [22]. They often cause patients to stop their mHealth interventions, leading to high dropout rates, and they are reported as a main barrier to further implementation of mHealth or eHealth apps [22,27]. This is consistent with our finding that the most important reason for discontinuation of the exercise program was when the ReVi app did not function well. Therefore, resolving technical issues is an important concern for further implementation of the ReVi app in clinical rehabilitation practice on a broader scale. This also underlines the importance of offering technical support when using mHealth tools such as the ReVi app [28]. Physiotherapists could play an important role in this, but that would require sufficient proficiency with mHealth. Moreover, considering the limited availability of physiotherapy personnel, it is essential for successful implementation of mHealth tools like the ReVi app to minimize technical issues and provide access to additional technical support for more complex problems.

The attendance rate, time within target intensity zones, and adverse events found in this study suggest that training in the home environment with the help of the ReVi app is a good alternative to center-based training. The attendance rate of 88% and time within target intensity zones of 76% are in line with adherence rates found in other studies evaluating aerobic exercise programs for NMD [29-37] that were mostly conducted in a hospital or rehabilitation center. Comparison of the attendance rate and time within target intensity zones between this study and past studies on exercise for NMD is hampered by incomplete or absent descriptions of adherence assessment methods in most other studies. In some studies, it is unclear if reported values are for attendance rates, the time spent within exercise zones, or training time. Moreover, some studies excluded patients who dropped out, leading to overestimated adherence. In this light, the attendance rate in our study may have been impacted by excluding patients who performed less than 12 exercise sessions and by the finding that some patients performed several training sessions without using the ReVi app. Despite these uncertainties, the attendance rate and time within target intensity zones found in our study seem to be in line with values reported in other aerobic exercise studies. The limited number of adverse events reported in this study also concurs with other studies on center-based aerobic exercise programs for NMD [32,38,39]. This further strengthens the notion that home-based aerobic exercise supported by the ReVi app may be considered a safe and feasible alternative for center-based exercise programs, which is in line with earlier research in telemonitoring of home-based exercise for amyotrophic lateral sclerosis [23].

Patients with a positive attitude toward the use of mHealth may have been more inclined to participate in this study, causing selection bias and limiting generalizability to people with NMD and less affinity for mHealth. Also, most patients trained under supervision of a physiotherapist experienced in treating patients with NMD, which limits generalizability of our results to other health care settings, such as primary care physiotherapy practices.

Implementation of mHealth, such as with the ReVi app, in rehabilitation care presents some major challenges, such as the comfort of patients and therapists with the use of technology, legal and ethical considerations regarding patient monitoring and the protection of privacy rights, and integration of mHealth tools into current working protocols [40,41]. Additionally, specific application design requirements have to be considered for NMD patients who experience reduced hand functionality due to muscle weakness. These requirements may include sufficiently large buttons and input fields. As a consequence of these challenges, the scientific literature on telerehabilitation in NMD patients is still limited [42,43]. To enable the broader implementation of mHealth in clinical practice, research is warranted into other facilitators of and barriers to the implementation of mHealth specific to neuromuscular rehabilitation.

The usability of the ReVi app in terms of perceived efficiency, effectiveness, and user satisfaction is high, despite the occurrence of technical issues. Combined with the high attendance rate and time spent within target intensity zones and low number of adverse events, the ReVi app can be considered a promising tool to support home-based aerobic exercise in rehabilitation practice for NMD. Further development of the ReVi app to resolve technical issues is warranted before broader implementation into clinical rehabilitation practice.