9 June 2026
15
min read
Feasibility and Safety of a Powered Exoskeleton for Balance Training for People living with Multiple Sclerosis. A Single-Group Preliminary Study (RAPPER III)
A preliminary clinical study demonstrating that powered robotic exoskeleton-assisted balance rehabilitation is feasible, safe, and potentially beneficial for improving mobility and quality of life in people living with Multiple Sclerosis.
A preliminary clinical study demonstrating that powered robotic exoskeleton-assisted balance rehabilitation is feasible, safe, and potentially beneficial for improving mobility and quality of life in people living with Multiple Sclerosis.
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Updated:
9 June 2026
Abstract
Objective
The aim of this study was to evaluate the feasibility, usability, safety, and potential health benefits of using an exoskeleton device for the rehabilitation of people living with Multiple Sclerosis.
Design
Single-group preliminary study.
Subjects
Eleven adults living with Multiple Sclerosis were recruited with Expanded Disability Status Scores that ranged from 6 to 7.5 (mean age 54.2 years (11.8)).
Methods
Individual participants undertook a balance rehabilitation exercise program using the Rex Rehab robotic exoskeleton device. Each participant undertook 4 x 45-60 minute supervised, balance exercise sessions. Primary outcomes measured were: 1) Number of participants who completed the trial protocol safely, and 2) Number and nature of Adverse Events reported. Secondary outcomes assessed mobility; balance; spasticity; sleep; functional independence; quality of life and device satisfaction.
Results
10 out of 11 participants completed the trial protocol safely. Four adverse events were recorded (one serious) all of which were deemed to be unrelated to the trial.
Secondary outcomes showed allied improvements in balance, joint mobility, spasticity and quality of life. All participants found the device acceptable to use.
Conclusion
These results suggest it is feasible and safe to use the Rex Rehab exoskeleton device to assist with balance rehabilitation for people living with Multiple Sclerosis.
Key Words: Feasibility, Safety, Balance, Multiple Sclerosis, Rehabilitation, Robotic Exoskeleton Device, Abdominal Muscles, Mobility
Lay abstract
Multiple sclerosis (MS) is a chronic neurological disease that can lead to symptoms including muscle weakness and balance issues. The incidence of falls in people living with MS (PwMS) is three times higher than that in older people. To try to reduce this vulnerability to falls, this study aimed to evaluate the feasibility, safety, and potential health benefits of using an exoskeleton device for a balance exercise programme. 11 PwMS undertook 4 x 45-60 minute supervised, balance exercise sessions using the exoskeleton. Feasibility and safety were assessed by identifying the number of participants who completed the trial safely; consideration of any issues experienced during the trial and how these were resolved. 10 participants completed the trial (1 withdrew due to their MS) and only 4 issues were reported, all of which were unrelated to the trial. Some participants also experienced improvements in balance, mobility and quality of life.
Introduction
Multiple sclerosis (MS) is a common neurological disorder characterised by an autoimmune response causing inflammation and demyelination of nerve cells within the brain and spinal cord (1). Approximately, 80% of people living with MS (PwMS) experience gait and mobility impairments, while 75% suffer from balance disorders (2). Balance impairment may be related to a variety of factors including muscle weakness, in-co-ordination, sensory disturbances, spasticity and cerebellar symptoms (3).
While it is recognised that many PwMS have poor balance that is associated with falls (4), there is a growing body of research evidence, which identifies the many benefits of exercise, including better balance (5-7). However, given that balance issues like increased postural sway (8) have been identified as contributory risk factors for falls, it is important to find ways that PwMS can exercise safely and effectively. Rehabilitation using assistive technology has been identified as one effective means of addressing this problem (9).
Building on a preliminary study that used the current Rex Rehab exoskeleton device for people with spinal cord injury (10), this study aimed to assess the feasibility and safety of using the same exoskeleton device (11), to support a balance rehabilitation program for PwMS.
Feasibility was assessed in the relatively broad manner adopted by other stage 1 trials (12-13), which have addressed aspects of process, management, scientific outcome and resources.
Safety was assessed by comprehensively documenting the number and nature of adverse events and how effectively the trial team identified, managed and resolved them (Table 1). Secondary objectives sought to determine whether there may be health benefits associated with undertaking a balance exercise treatment intervention supported within a Rex Rehab exoskeleton. Alongside this, we sought simple feedback comments from participants about their experiences of the trial.
Methods
The study utilised a prospective, open label, single arm, non-randomized design, and was approved by the East of England-Cambridgeshire and Hertfordshire Health Research Authority Ethics panel (REC reference: 16/EE/0553) IRAS reference: 219334. The trial was registered with CTN: NCT05102682 via ClinicalTrials.gov and with the National Institute for Health and Care Research reference: NEUR 33236. Organizational registration via East Kent University Hospitals NHS Foundation Trust Research and Innovation ref: 2016/NEURO/10. (A copy of the Protocol, participant consent and information sheets are provided in Supplemental material files). An outline of the study components is provided in a flow chart (Figure 1).

Setting and Participants
The trial was conducted in an Outpatient setting on a University campus. Participants self-referred following an advertisement placed with MS services, charities, East Kent Neuro-rehabilitation Unit and social media platforms. All applicants were screened by questionnaire on the telephone against the trial inclusion and exclusion criteria identified in Table 2. Eleven individuals enrolled from April to July 2017 and provided written informed consent on trial entry.
Equipment
A Rex Rehab exoskeleton was used, supplied by Rex Bionics Ltd. PO Box 316-063. Auckland 0760, New Zealand.
Study Outcomes
All outcome measurements were performed by the same neuro-physiotherapist at the beginning and end of the intervention period and training sessions were spaced at 1 week intervals, which enabled ample recovery time between sessions.(18)
The primary feasibility measurement outcomes were:
Proportion of individuals who were eligible for inclusion following screening process
Number of participants who completed the trial
Dropout Rate – percentage of participants who dropped out of the trial
Time taken for an individual to transfer into the Rex device
Level of assistance required with the transfer
Time taken to complete sit to stand inside the device
The primary safety outcomes were:
Number of Adverse Events recorded
The severity and nature of Adverse Events reported
An Adverse event (AE) is defined as an event associated with a medical device that led to death or serious injuries of a patient, or may lead to such if the event recurs (19).
The secondary outcome measures were the Berg Balance Scale (BBS) (20), Modified Ashworth Scale (MAS) (17), Modified Falls Efficacy Scale (MFES) (21), Multiple Sclerosis Impact Scale (MSIS-29) (22), Health related Quality of Life Scale EQ-5D-5L (23), Psychosocial Impact of Assistive Devices Scale (PIADS) (24), Activities-Specific Balance Confidence Scale (ABC) (25), Multiple Sclerosis Walking Scale (MSWS-12) (26), Arm Activity Measure (ArmA) (27), Epworth Sleepiness Scale (28), and the Visual Analogue Scale for Pain (VAS) (29). Passive joint range of motion (ROM) for ankles, knees and hips was measured using a standard goniometer and standard principles for joint measurement were followed (30). For all outcome measures used, standard procedures were followed which included the use of a standard chair (for example, as defined in the BBS scale) and standard plinth, which were adjusted as deemed suitable by the trial team. This enabled standardisation of all testing measurements across all testing sessions. All participants recruited were living with chronic advanced MS and presented with a variable degree of paresis. A decision was made to have a detailed functional assessment taken instead of using the Medical Research Council Muscle Power Scale (31), which is an impairment focused scale. Further information on mobility; walking aids; ataxia; relevant anti-spasticity medication and ongoing treatment is presented in Table 2. Outcome measure questionnaires were presented in the same order across all participants. A 15 minute interview was conducted 10 days post-trial with participants and their care-giver if available to gain feedback on individual experiences. Interviews were audio recorded and transcribed by the interviewer.
Intervention
The balance exercise program was designed to focus on strengthening leg extensor and abdominal muscles, recommended as important for PwMS (32-331). The program also included a focus on maintaining an optimal upright posture, when standing in the Rex and performing dynamic balance exercises (34), [See Appendix 1 for exercise programme]. Given the absence of Cochrane guidelines (35) on the optimal type, duration, intensity and frequency of exercise training sessions for PwMS, the intervention was delivered in 4 exercise sessions (with data collected before and after). This number of sessions exceeded the single session applied in the previous SCI study (10) and was constrained by the resources to hand. The time schedule between each training session was an interval of one week. Spasticity was measured before the training intervention, at the beginning of session 3 and at the end of the fourth session. Individual participants were offered and supported with appointment times as flexibly as possible within the available weekend diary slots of the team. As spasticity can vary throughout the day for numerous reasons, when feasible, it is recommended that therapies take place at the same period of the day.
The Rex device used is a robust powered exoskeleton which covers the waist, pelvis and lower limbs of the individual (16 and Figure 2).

The individual user is supported securely within the device using a pelvic harness, thigh and calf cuffs, and an abdominal pad (Figure 3).

The Rex is designed for use in a clinical environment under the supervision of a Rex-trained clinician and is operated by a keypad and joystick.
Individuals transferred into the Rex with the appropriate level of assistance as risk assessed by the trial team. Optimal postural alignment and positioning of the individual within the device was ensured by the trial neuro-physiotherapist. Following a verbal briefing, the clinician then switched on the device and used the joystick to bring the individual up from a sitting to standing position. From the standing position, the appropriate functionality mode was selected (e.g. move forward). The device was then operated via “hands on” assistance from the trial neuro-physiotherapist, which enabled the participant to relax their arms and concentrate on their posture. The trial neuro-physiotherapist always held onto the Rex device to stabilise it when moving, a technique termed “spotting” taught as part of the device training (16).
Statistical Analysis
Descriptive statistics are provided for the primary outcome measures and safety data (Table 1 - Adverse Events). Categorical variables were summarised by the number and percentage of responses in each category, whilst the mean and standard deviation were used to summarise continuous variables. Analyses of secondary outcome measures were conducted using paired t-tests to examine changes in scores from pre-trial to post-trial time points. The distribution of changes in scores was assessed visually and found to be approximately normally distributed for all outcomes. Where outcomes were measured on more than two occasions, two-way ANOVA was used for to compare between timepoints (with participant and time being the two factors). For the PIADS scale, measured once post-treatment, a one-sample t-test was used to indicate if the results varied significantly from zero, in relation to whether using the Rex device in the trial had a positive or negative impact on the rated domains. All statistical tests were performed with a two-sided 95% significance level. The software package Stata (Version 15.1) was used for all analyses.
Results
11 individuals were enrolled into the trial from a sample of 21 PwMS who were screened, which equates to 52%. Table 4 provides participant demographic data. The most common reason for exclusion at screening was when a potential participant’s calf muscle bulk exceeded 375 mm in circumference (this measurement is taken at a fixed point 80 mm below the knee), as identified in the Manual (16), which was identified on 6 occasions during screening. The other reasons were low blood pressure, back pain, history of osteoporotic fractures, short tibial length and sacral lesions.
Primary Outcome Measures
10 out of 11 participants (91%) completed the trial, and only one participant chose to withdraw due to a reported relapse of their MS. All 11 participants completed the transfer into the device with a mean time of 3 minutes 35 seconds. Five individuals managed to transfer into the exoskeleton device independently after instruction from the trial team. One required verbal support and supervision from the neuro-physiotherapist, 4 required “hands on” physical assistance from the neuro-physiotherapist and 1 required the assistance of 2 trained team members and the use of a hoist. All participants completed the sit to stand task within the device with assistance from the neuro-physiotherapist.
Adverse Events
A total of 4 AEs were recorded (Table 1), only 1 of which was categorised as serious, and none were directly attributable to the trial.
Secondary Outcome Measures
Tables 5, 6, 7, 8, 9 and 10 report the statistically significant changes between the baseline and post-trial measurements taken.
Passive Joint ROM (Table 5)
The mean left ankle inversion ROM reduced by 7 degrees and the mean right knee flexion increased by 9 degrees at the end of the trial.
Balance (Tables 6 and 7)
4 participants achieved a clinically significant improvement in balance over the course of the trial. This was determined by calculating whether a sufficient increase in points had been made by the individual relative to their initial BBS score (36) (Table 6).
MSIS-29 (Table 7)
There was a positive change for all but 2 participants in how MS was perceived to impact on their daily lives during the trial.
EQ-5D-5L (Table 7)
Scores increased over time by a mean of 0.17 units, with all but 3 participants reporting an improvement and none showing a decline.
Spasticity (Table 8)
Statistically significant reductions in spasticity were detected in the left ankle plantarflexors and dorsiflexors and right ankle dorsiflexors.
PIADS (Table 9)
Participants consistently reported that taking part in the trial had made a significant positive impact on the 3 individual components of competence, adaptability and self-esteem.
ABC/ArmA/VAS (Pain)/ESS/MSWS-12/MFES (Tables 7 and 10)
There was no significant change between timepoints for the ABC, ArmA, VAS pain, ESS scores, MSWS-12 and MFES during the trial.
The improvements observed above accorded with informal feedback from participants’ and, in some cases, their carers (See Appendix 2 for all feedback).
Discussion
The main findings from this study are that it is feasible and safe to use this exoskeleton to support and enable the performance of a balance exercise programme by PwMS provided that there is a specialist team with an advanced level of clinical knowledge and expertise available to support participants. Taken together and mindful of the criteria (37) on what constitutes a successful feasibility study, the outcomes showed that the intervention and assessment protocols were well-tolerated and not associated with any serious study-related adverse events.
There were only three minor adverse events and one serious adverse event, which were not directly related to the study, and which did not consume an excessive amount of unanticipated time or resource. Individuals diagnosed with relapsing remitting MS can experience a relapse at any time and taking part in a clinical research trial would not prevent such an event. This accounts for the first AE in Table 1. AEs two (suspected deep vein thrombosis) and three (back pain) were likewise un-associated with trial participation. Recording and resolving these AEs demonstrated the effectiveness of our risk assessment and safety monitoring process, given that they were quickly picked up when the participants arrived for their sessions. Direct access to the Principal Investigator within the team via telephone communication enabled swift access to expert knowledge and clinical decision making to establish the most appropriate and safe course of action to be taken. AE four involved a participant who reported that they had fallen at home. It is known that the incidence of falls is three times higher in PwMS compared to older people (38) and this context is relevant and can account for this incident alone. It is perhaps notable that none of these AEs were connected to the use of the device or exercise programme. We suggest that this was partly due to the advanced level of clinical expertise and specialism within the trial research team, which meant for example, that individual participants were optimally positioned within the exoskeleton by the trial neuro-physiotherapist and thereon kept under continuous, careful observation. An advanced level of expertise also enabled dynamic advanced risk assessment of participants, which enabled optimal safety throughout all trial exercise sessions.
We are aware of only one other feasibility and safety research trial which examined the use of a different powered exoskeleton for PwMS (13). This trial concluded that the exoskeleton used was feasible and safe for only 4 people out of the sample population of 13 participants. Conversely, our trial demonstrated that with an experienced trial team using the Rex exoskeleton, it was feasible for all 10 individuals to participate and complete the trial safely. Our result accords with those of two other studies that examined the feasibility and safety of two different exoskeletons for people with SCI (10, 39), with both studies reporting safe, study protocol completion. Future studies could also compare different training regimes with or without powered exoskeleton devices. In terms of changes and improvements in participant independence and required assistance during the exercise sessions, it could also be useful to consider including a broader outcome measure to detect and record these changes over the trial period in future research.
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