INTRODUCTION

Individuals with Parkinson disease (PD) develop gait impairments and balance problems over time that interfere with their participation in meaningful activities in their homes and communities.1 Interventions that promote motor learning to optimize functional mobility in individuals with neurologic impairments often provide high repetition, task-oriented movement training.2,3 As examples, repetitive practice of stepping through treadmill walking or external cueing techniques improves walking performance in PD populations.4 However, many individuals cannot regularly exercise due to barriers including lack of access to exercise facilities, physical impairments, and low motivation (apathy).5,6

Robotic devices deliver high repetition task-specific training to promote motor learning, while reducing the need for manual assistance or cueing by therapists.7 Clinical trials of robotic-assisted treadmill training in PD demonstrated significant improvements in gait speed, functional mobility, walking endurance, freezing of gait (FOG), and quality of life.8-16 While people with PD (PwPD) accepted and benefited from the training, the robots used in these studies are large, heavy, and stationary (ie, Lokomat, G-ECOSYSTEM) that are cost prohibitive for most people and require extensive training before they can be used independently.

The Honda Walking Assist (HWA) device (Honda R&D Co Ltd, Wako, Japan) is a lightweight and portable single-joint robotic exoskeleton device (EXOD).17,18 Worn around the user’s waist and thighs, internal motors assist hip flexion during swing initiation and hip extension during stance walking phases (Figure 1). The device calibrates leg movements to spatial and temporal cadence targets to promote symmetrical walking patterns.19 Advantages of lightweight, wearable robotics over stationary robotic systems include easy donning and doffing, greater ease of use, and free movement in the home and community, thereby yielding greater walking practice.20

Figure 1:

Honda walking assist device.

Laboratory-based studies in healthy adult and neurological populations to examine the effects of gait training using EXODs with hip assistance, including the HWA device, have demonstrated improved gait spatiotemporal parameters and endurance.20-25 Healthy elderly and middle-aged adults showed temporary improvements in stride length, gait speed, and energy costs wearing the HWA compared with unassisted walking.21,22 Long-term HWA usage in individuals with stroke improved gait parameters during unassisted walking.20,23 Individuals with moderately advanced PD (n = 12) showed immediate improvements in gait speed, step length, and hip flexion and extension excursion while walking with the HWA device and improved walking endurance during unassisted walking after 10 half-hour sessions of gait training with the HWA device in the home setting.25 The mechanical assistance given by the HWA may provide (1) temporal (rhythmic tactile stimulus on leg) and spatial (attentional stimuli to increase step amplitude) external cues and (2) force assistance to increase hip mobility and ameliorate lower extremity muscle strength and power deficits26 that improve gait in people with mild to moderate PD.27,28 Thus, EXOD interventions may help overcome exercise barriers due to lack of access to exercise facilities by allowing in home gait training, physical impairments by providing lower extremity step cueing and mechanical assistance, and low motivation by making walking more comfortable and less effortful, thereby improving home and community mobility for daily life activities and the quality of life in PwPD.29,30

The primary purposes of this study were to determine the immediate effect of EXOD usage on gait speed and the effect of an 8-week robotic-assisted gait training (RAGT) intervention on gait speed while walking unassisted in the home and the community, and secondarily to determine the safety of EXOD usage in individuals with PD. We hypothesized that gait endurance, gait parameters, and perceived ease of walking would improve when (1) wearing the EXOD compared with unassisted walking over 1 session and (2) when walking unassisted after the RAGT intervention compared with before the intervention, and that (3) participants in the RAGT group would be able to walk safely with the EXOD.

METHODS

The study was approved by the Institutional Review Board of The Ohio State University and was registered at ClinicalTrials.gov (NCT03751371). A blinded, randomized controlled trial design was utilized to assess preliminary efficacy of the EXOD in individuals with idiopathic PD (Figure 2). Randomization allocation was 1:1 and stratified by Hoehn and Yahr (H&Y) stages 1-3.31 Each stratum randomization scheme was generated in permutated blocks of varying size to ensure a balance in the randomization among stage. Individuals randomized into the RAGT group performed outcome measures with and without the EXOD (hypothesis 1) and then received training with the EXOD in their homes or surrounding communities twice weekly for 8 weeks. The control (CON) group completed baseline outcome measures without the EXOD only and then continued with their usual care, daily activities, and ongoing exercise regimens. At 8 weeks, both groups underwent postassessment (hypothesis 2). The randomization scheme was overseen by biostatisticians using the randomizeR package version 1.4.2 in R 3.5.1 (Vienna, Austria).32 Trial assessors were blinded to group allocation and administered assessments that were collected without the EXOD. Assessors who obtained outcomes completed with the EXOD were not blinded.

Figure 2:

Study flow sheet. CON, control; EXOD, exoskeleton device; RAGT, robotic-assisted gait training.

Participants

Adults with idiopathic PD were recruited from central Ohio. Inclusion criteria were age 50 to 90 years, ambulation without assistance (H&Y stages 1-3), and on stable PD medication doses for 4 weeks prior to the study. Exclusion criteria were presence of other significant cardiac, neurologic, or orthopedic problems that affect gait; weight exceeding 220 lb and height exceeding 6′8″; electronic medical devices embedded in the body; participation in physical therapy; and inability to understand instructions as assessed by inappropriate or lack of responses to simple commands.

Exoskeleton Device

The EXOD, provided by Honda R&D Americas, Inc, weighs 5.95 lb and has 2 motors that run on a single rechargeable battery. The device has Food and Drug Administration clearance for people with stroke with gait deficiencies and has established safety and feasibility in healthy older adults and people with stroke.20-23 Hip joint angle and torque output are monitored using angle and current sensors. Assist torque is transmitted to the user’s thighs via thigh frames. When the user initiates walking, the EXOD automatically adjusts leg movements to reach target walk ratios (step length/cadence) by increasing hip flexion and/or extension using power supplied by the device.

A trained physical therapist (PT) properly sized and placed the EXOD around the participants’ waist and bilateral thighs and adjusted device settings. Flexion or extension assistance levels were adjusted to maximize the participants’ gait endurance and to promote a symmetric gait pattern based on tablet feedback provided by the EXOD. The PT applied a gait belt to ensure participant safety during walking.

Procedures

The PT investigators obtained demographic information and assessed outcome measures, and a neurologist administered the Unified Parkinson Disease Rating Scale (UPDRS) Part III—Motor Scale1 to determine H&Y stage in the investigators’ laboratory. Participants were instructed to take PD medications about 1 hour before assessments.

Hypothesis 1: Immediate Effect of EXOD

Gait endurance was measured with the 6-minute walk test (6MWT), a reliable and valid measure in the PD population.33,34 Participants were instructed to “walk as far as you can in 6 minutes.” Gait parameter measurements were speed, stride length, swing time, double support time, and coefficients of variation. These were collected during the first straight pass of the 6MWT for 50 ft using portable wearable sensors on each lower extremity (LEGSys, Biosensics, Newton, Massachusetts).35,36 Participants’ perceived ease of walking defined as how easy it felt to walk during the 6MWT was indicated on a visual analog scale (100-mm line with anchors “Not at all easy” and “Extremely easy”). Gait assessments were conducted in the RAGT group first during unassisted walking, followed by assisted (ie, wearing the EXOD) walking, with 15-minute rests between tests. CON group participants never used the device.

Hypothesis 2: Effect of RAGT Intervention

Gait assessments (6MWT, gait parameters) were obtained first without wearing the EXOD, followed by wearing the EXOD in the RAGT group, whereas they were obtained only without the EXOD in controls. All participants completed the Stanford Self-Efficacy for Measuring Chronic Disease 6-Item Scale37 questionnaire to measure participants’ confidence in performing daily activities, and the Freezing of Gait Questionnaire.38 Both the Stanford Self-Efficacy for Measuring Chronic Disease 6-Item Scale and the Freezing of Gait Questionnaire have good reliability and validity in individuals with PD.38,39 To determine changes in activity levels, all participants wore activity monitors (PAMSys, Biosensics, Newton, Massachusetts) to quantitatively measure physical activity and recorded daily activities in an activity log for 5 consecutive days during weeks 1 and 8. Participants continued to fill out activity logs in weeks 2 through 7 to compare general activity levels between groups. To monitor safety during the study period participants were asked to record any falls (ie, events that caused the person to rest inadvertently on the ground or floor) or other adverse events that occurred. All outcome measures were repeated after the 8-week intervention period for both groups.

Hypothesis 3: Safety

Safety during walking was assessed using counts of observed episodes of loss of balance (LOB), defined as a change in posture requiring the examiner walking with the participant to use the gait belt and/or manual assistance to prevent a fall. Safe walking was defined as no increase in incidences of LOB during walking with the EXOD as compared with unassisted walking. Longer-term safety of EXOD use was defined as no increase in incidences of falls throughout the intervention timecourse. Safety was also assessed as 80% of participants and greater in the RAGT group attaining a safe gait.

Intervention

RAGT group participants received PT supervised, home and community-based (ie, outside home and/or within surrounding community) walking training wearing the EXOD twice a week for 45 to 60 minutes for 8 weeks. Participants were cued to take larger and more symmetrical steps by the device’s assistance. The default device settings were used initially (2 Nm of flexion and extension assist bilaterally) and were adjusted as necessary (0 for no assist to 4 Nm) to promote a symmetrical, safe stepping pattern with primary goals to increase step length and foot clearance. Hip flexion assist was gradually increased by 0.5 Nm on the side that demonstrated a shorter step length until symmetry was achieved or maximum assist was reached. If maximum hip flexion assist was reached and a continued step length asymmetry was observed, hip extension assist on the contralateral limb was increased. Participants performed primarily forward walking during each intervention session (30-45 minutes) with an average of approximately 15 minutes of each session focused on multidirectional stepping, turning, and other challenging balance and motor control tasks during gait, with rests as needed. Because of the heterogeneity of the home/community environment and participant severity of symptoms, standardization of sessions was limited; however, consistency was attempted when possible. Environment (home vs community), home layout and size, weather, and the participant’s endurance influenced the training activities. Typical sessions in the community included outdoor forward walking over sidewalks and uneven ground including inclines, curbs, or grass. Emphasis during outdoor training was on endurance, speed, step length symmetry, and cadence. Examples of indoor community sessions included walking around a track at a fitness center, an open gym at a fitness center or church, or hallways, ramps, and stairs at a participant’s place of work. Indoor activities inside participants’ homes were focused on multidirectional walking (backward, side stepping), walking over various surfaces (hardwood, carpet, etc), obstacle negotiation, turns, and stair negotiation. The EXOD settings were modified to facilitate the goal of the activity, such as increasing hip extension cues during backward walking. To address freezing, the timing of flexion and extension assist in the EXOD was adjusted during activities that typically caused freezing episodes for the participant. Participants wore a gait belt with primarily standby assistance provided by the therapist with occasional contact guard assist during more challenging activities or fatigue, or minimal assistance in the event of LOB. The PT monitored participants’ heart rates and Ratings of Perceived Exertion (Borg RPE) to maintain a moderate intensity (RPE 13-16) for better intervention compliance and comparison across groups. Participants were progressed by increasing distance or time spent walking while maintaining EXOD settings as long as step symmetry and foot clearance was achieved. Participants were instructed to continue usual activities and to inform investigators of changes (eg, medications, starting new exercise programs, or physical therapy) made during the intervention period. The participants never wore or used the EXOD without therapist supervision.

Analysis

A priori power analyses predicted that 23 participants randomized to the RAGT group would have at least 80% power to detect a difference of 0.61 standard deviations in gait speed using a 2-sided paired t test with type I error rate of 0.05 for hypothesis 1, and 18 participants per group would detect a difference of 0.96 standard deviations in gait speed after week 8 (hypothesis 2) using a 2-sided t test with type I error rate of 0.05 (PASS 15, Kaysville, Utah).

For hypothesis 1, the primary analysis compared the difference in gait speed with/without the EXOD in the RAGT group only using a 2-sided paired t test at the 0.05 significance level. Secondary outcomes gait endurance, gait parameters (stride length, swing time, double support time, and coefficients of variation), and perceived ease of walking for hypothesis 1 were analyzed similarly using appropriate methods for paired data. For hypothesis 2, the primary analysis assessed the effect of treatment on gait speed at 8 weeks using a linear regression model that included an indicator of treatment, stage, and baseline gait speed. This analysis followed intention to treat principles to preserve the balancing properties of randomization.40,41 For analysis, H&Y stages 1 and 2 were combined because there was only 1 participant enrolled in stage 1. The test of treatment effect was 2-sided and at the 0.05 significance level. Post hoc subanalyses were performed to determine whether participant gait parameter responses to the intervention differed according to the participants’ baseline fall history status or to their baseline disease severity. The effect was estimated per a 5 unit increase in their baseline UPDRS motor scores, which is the minimal clinically important difference in the UPDRS motor scale.42 Participants who reported 1 fall and greater during the previous 6 months at baseline were designated as “fallers.” Secondary outcomes for hypothesis 2 were assessed similarly to the primary outcome using appropriate generalized linear models. This resulted in 11 separate models—1 for each secondary outcome. Data (incidences of LOB and falls) were analyzed using descriptive statistics for hypothesis 3. All analyses were done using SAS 9.4 (Cary, North Carolina).

RESULTS Participants

Between April 2019 and July 2021, 107 individuals were assessed for eligibility (Figure 3). Reasons for exclusion included not meeting criteria (n = 36), living outside of 1-hour driving distance from research laboratory (n = 11), and losing interest or not following up (n = 14). Forty-six participants were enrolled; 1 individual was withdrawn prior to randomization due to meeting exclusion criteria that was not disclosed during screening. Forty-five participants were randomized to RAGT (n = 23) or CON (n = 22) groups. Five participants (3 RAGT, 2 CON) did not complete the study due to a laboratory shutdown caused by COVID-19 pandemic (n = 3), an unrelated hospitalization (n = 1), and dropping out to receive physical therapy (n = 1).

Figure 3:

CONSORT diagram. PT, physical therapist; RAGT, robotic-assisted gait training.

Baseline participant characteristics are summarized in Table 1. Group characteristics were comparable, except that more CON group participants were male. There were 22 fallers and 20 nonfallers, (RAGT fallers = 11, nonfallers = 9; CON fallers = 11, nonfallers = 11).

Table 1. - Participant Characteristics Characteristic Levels RAGT, Median (Q1, Q3) CON, Median (Q1, Q3) Age, y 72 (65.21, 78.56) 72 (65.51, 77.03) Assistive device use No 15 (65%) 14 (64%) Yes 8 (35%) 8 (36%) Number of falls in past 6 mo 1 (0.00, 3.00) 1 (0.00, 2.00) Hoehn & Yahr stage Stage 1 1 (4%) 0 (0%) Stage 2 18 (78%) 18 (82%) Stage 3 4 (17%) 4 (18%) Sex Female 10 (43%) 2 (9%) Male 13 (57%) 20 (91%) Years since diagnosis 5 (3.00, 7.00) 5 (3.50, 10.00) Years since symptom onset 8 (6.00, 11.00) 8 (6.00, 16.00)

Abbreviations: CON, control group; Q1, quartile 1; Q3, quartile 3; RAGT, robotic-assisted gait training group.

Hypothesis 1: Immediate Effect of EXOD Analysis

At baseline, there were no significant differences in gait speed, or any secondary gait measures, when participants assigned to the RAGT group (n = 23) walked with EXOD assist compared with without the device (Table 2). Gait-related measures did not change significantly on first trial wearing the EXOD, though some measures worsened slightly in some participants.

Table 2. - Baseline Gait Measures With and Without Exoskeleton Devicea Comparison (With to Without Device) Mean Difference 95% CI P Gait speed, m/s −0.08 −0.16 to 0.01 0.0726 Stride length, cm −3.55 −8.90 to 1.81 0.1834 Stride length CV 0.00 −0.02 to 0.02 0.7064 Swing time, s −0.72 −1.87 to 0.43 0.0856 Swing time CV 0.00 −0.01 to 0.02 0.7026 Double support time, s 1.39 −0.89 to 3.67 0.2199 Double support time CV −0.01 −0.05 to 0.03 0.6821 6MWT, m −19.32 −41.4 to 2.80 0.0837 6MWT ease −0.04 −0.87 to 0.79 0.9144 6MWT loss of balance, log mean −0.26 −0.70 to 0.18 0.2284

Abbreviations: CI, confidence interval; CV, coefficient of variation; 6MWT, 6-Minute Walk Test.

an = 23.

Hypothesis 2: Effect of RAGT Intervention Analysis

No significant differences were noted in gait speed or the secondary outcome measures between RAGT and CON groups after the intervention period (Table 3, see Table, Supplemental Digital Content 2, available at: https://links.lww.com/JNPT/A460, Outcome Measure Unadjusted Means), except for instances of LOB during the 6MWT for the RAGT group compared with the CON group. In general, changes in outcomes were in the positive direction, including increases in speed, stride length, and the 6MWT distance.

Table 3. - Mean Adjusted Outcome Measures at the End of Intervention for the RAGT Compared With the CON Group Outcome Adjusted Mean CON Adjusted Mean RAGT Difference 95% CI P Gait speed, m/s 1.27 1.29 0.02 −0.10 to 0.14 0.7869 Stride length, cm 132.65 133.35 0.70 −9.03 to 10.43 0.8849 Stride length CV 0.07 0.07 −0.01 −0.05 to 0.03 0.7247 Swing time, s 41.77 41.42 −0.35 −1.34 to 0.64 0.4784 Swing time CV 0.06 0.05 −0.01 −0.03 to 0.02 0.5124 Double support time, s 16.57 17.18 0.60 −1.34 to 2.55 0.5328 Double support time CV 0.23 0.19 −0.05 −0.14 to 0.05 0.3150 6MWT, m 419.61 428.79 9.18 −26.1 to 44.45 0.6007 6MWT ease 7.45 6.30 −1.15 −2.49 to 0.19 0.0894 6MWT LOB (log rate) −2.00 −3.83 −1.83 −2.94 to −0.72 0.0019 FOGQ 9.24 8.89 −0.36 −2.21 to 1.50 0.7001 SSE 7.98 7.91 −0.06 −0.85 to 0.72 0.8705

Abbreviations: CI, confidence interval; CON, control group; CV, coefficient of variation; FOGQ, Freezing of Gait Questionnaire; LOB, loss of balance; RAGT, robotic-assisted gait training group; 6MWT, 6-Minute Walk Test; SSE, Stanford Self-Efficacy for Measuring Chronic Disease 6-Item Scale.

Baseline fall history status was not related to the participants’ responses to the intervention for any outcomes. Participants with higher baseline UPDRS motor scores had significantly greater improvement in stride length during unassisted walking following the intervention than those with lower scores (mean difference: 3.22, 95% confidence interval: 0.05-6.40; P = 0.04, Figure 4).

Figure 4:

Mean difference in stride length per 5 unit increase in UPDRS-motor score among RAGT group. Participants with higher symptom severity at baseline showed a greater increase in stride length during unassisted walking following the intervention than those with lower scores. In contrast, participants in the control (CON) group with higher symptom severity at baseline showed a decline in stride length after the 8-week period. CON, control; RAGT, robotic-assisted gait training; UPDRS, Unified Parkinson Disease Rating Scale.

Because of a combination of activity monitor technical problems and participants’ lack of compliance wearing activity monitors during weeks 1 and 8 of the study, there were insufficient data for valid statistical analysis of electronically monitored activity data. Data gathered from activity diaries indicated that the majority of participants in both groups engaged primarily in light activity (eg, taking a walk or slow bicycle ride) across the day and very few engaged in moderate- (eg, doing laundry, yard work) or heavy- (eg, running, chopping wood) level activity. Reported activity levels did not change in either group across the 8 weeks.

Hypothesis 3: Safety Analysis

All RAGT group participants were able to use the EXOD safely. There were no adverse events reported related to the study or EXOD usage. There were no differences in incidences of LOB between groups and while wearing the EXOD during gait testing (see Supplemental Digital Content 2, available at: https://links.lww.com/JNPT/A460).

DISCUSSION

This randomized controlled trial examined the short- and long-term impact of using a single-joint EXOD on improving unassisted and assisted mobility in individuals with mild to moderate PD. In contrast to robotic treadmill systems, the lightweight and portable EXOD used in this study offered the unique opportunity to study the effects of RAGT delivered in the home and community environment. While we demonstrated the safety of EXOD usage during home physical therapy, there was no significant immediate effect of EXOD usage or an 8-week RAGT intervention on the primary outcome gait speed. These findings suggest that the RAGT intervention may not be an effective intervention for gait training in the early-stage PD population. However, participants with greater disease severity demonstrated greater improvements in stride length after RAGT, suggesting that the intervention may be better suited for individuals with greater mobility impairments.

EXOD use did not immediately change the RAGT group participants’ gait measures or perceived ease of walking compared with unassisted walking. The novelty of the device may have resulted in cautious mobility. While participants briefly practiced walking with the EXOD prior to testing, longer practice sessions wearing EXODs, supervised by PTs, may be needed to improve self-efficacy and walking performances prior to testing and independent use. It is possible that the greater differences in immediate gait measure findings compared with ours reported by Kawashima et al25 may be because their gait measures were an average of the initial 6 trials and participants were tested after wearing the device with assistance turned off before testing them with the assistance turned on, resulting in increased exposure and practice using the EXOD. All RAGT participants could walk safely wearing the device, which supports the safety of device usage in early PD disease stages (H&Y 1-3).

Following the 8-week RAGT intervention, there were no significant changes in the participants’ perceived ease and ability to walk unassisted. Greater reduction in LOB occurrences during the 6MWT for the RAGT group compared with the CON group is likely explained by a few participants who had particularly high numbers of LOB. The lack of significant findings may be due to the high variability in the participants’ performances on outcome measures, as indicated by wide confidence intervals. Although most participants were classified as being in H&Y stage 2, we observed a wide range of performances among this group, possibly because we used the original H&Y stages, which lacks the 2.5 rating included in a modified version.43 Future studies with larger sample sizes and randomization using the modified H&Y stages could address this problem. Alternatively, the lack of effect may be that the intervention was not long or frequent enough.44-46 Although the 8-week intervention reflects a typical duration for home health physical therapy, some studies reported improvements with exoskeletons using 20 to 25 sessions.44-46 Another possibility is that the RAGT intervention is not effective in the PD population.

Disease severity, but not fall history status, was found to influence participants’ responses to the intervention. Participants with greater disease severity had greater increase in stride length during unassisted walking postintervention than those with less disease severity. Some participants demonstrated minimal gait deficits and therefore had little room for improvements. Although disease severity did not impact gait speed, improved stride length is a major goal of gait training in PwPD that has important implications for gait endurance and fall risk.47,48 In support of our finding of greater disease severity having a positive influence on intervention response, the study by Kawashima et al25 had a higher percentage of participants with moderate disease (H&Y 3) in the EXOD group compared with the CON group and reported a significant increase in distance and calculated gait speed for the 3-minute walk test (3MWT) in the EXOD group compared with no change in controls.25 Other possible factors that may have contributed to the improved gait endurance reported in the study by Kawashima et al compared with this trial were the ability to implement continuous overground walking outdoors (without constraints of indoor space within homes), over a longer intervention period (3 months), and better control of exercise/activity levels in the CON group.25 However Kawashima et al reported no significant changes in the 10-m walk test, while the 3MWT distance significantly improved, thereby causing the calculated gait speed on the 3MWT to be increased.25 Thus, the use of the 3 MWT by Kawashima et al versus the 6 MWT and the use of calculated gait speed using the 3MWT versus gait speed measurement over shorter distance using LEGSys may underlie the differences in our findings. Based on our findings, PD researchers designing future EXOD studies should consider enrolling participants with moderate to severe disease severity (H&Y 2.5-4). The lack of influence for fall history status on the intervention response may be that some participants with greater gait impairments and/or who experienced previous falls reduced their walking and/or implemented compensatory strategies (eg, assistive device use) to prevent falls and therefore were classified as “nonfallers.” An inverted U curve relationship found between fall frequency and disease severity that was mediated by activity levels in PwPD supports this idea.49

Limitations

A limitation of our study is the participant heterogeneity given the relatively low sample size, which likely contributed to the negative findings regarding primary measure gait speed improvements. Disruptions in recruitment and follow-up of participants due to COVID-19 pandemic restrictions were partially responsible for lower participant numbers. In addition, the high proportion of early-stage participants with minimal gait impairments likely lessened the room for improvements. Based on our findings, we calculate that for 80% power with type I error rate of 0.05 and with a standard deviation of 0.31, there would need to be 91 evaluable participants per group to detect a 0.13 m/s change in gait speed at week 8, an amount that was reported as a substantially meaningful change for gait speed in older adults.50

Gait training activities were individualized to accommodate each participant’s physical abilities and his or her specific home and community environments (eg, size of space, inclines, obstacles, access to outdoors). These accommodations introduced some variation in the dosages and complexities of the interventions delivered. However, these accommodations were necessary for greater transfer of training effects into their daily lives. A HWA device–specific limitation was torque restriction. The device stops providing assist when the motors reach a heat threshold, which frequently occurred with longer times walking, higher environmental temperatures, and participants’ higher gait speed or size. More consistent assist provided throughout each session may have produced a larger effect. While many participants in the RAGT group reported improved ease and ability to walk, and/or family members noticed improvements in their walking, we did not systematically collect qualitative data about participants’ and caregivers’ perceptions of the intervention’s effects on their walking. It is possible that ease of walking could change over a training period because of better fitness and not because of the device use. Because there was no active treatment control (eg, equally dosed gait training without EXOD but with a 6-lb weighted belt), we cannot distinguish the EXOD effect from the RAGT treatment effect. However, hypothesis 1 results suggest that the immediate effect of EXOD use on gait parameters is minimal. The small improvements in gait parameters observed after RAGT treatment may be due to increased levels of walking as they correspond with effects seen after comparable amounts of nonrobotic conventional gait training in PwPD.51,52 Future studies may wish to consider including the Functional Gait Assessment and/or the Timed Up and Go as recommended by the PD EDGE for their ability to measure functional mobility in this population.

CONCLUSIONS

This study demonstrates that it is feasible and safe for PTs to perform gait training using a robotic EXOD in the homes and the communities of PwPD. When initiating EXOD device usage with PwPD, PTs should provide gait training to allow them to become comfortable and confident walking with the device before testing or to ensure safe walking with the device prior to independent use. The RAGT program used in this mostly low impairment population of PwPD may not be effective enough and/or may not have been sufficiently dosed to see a positive treatment effect. RAGT may be more beneficial in individuals with PD in H&Y stages 2.5 and greater who have gait and balance deficits. Thus, researchers designing studies examining the effects of robotic EXODs on gait and mobility in PwPD should consider disease severity when selecting participants. Future studies should also explore the effects of single-joint versus multijoint EXOD usage on gait in PwPD.

ACKNOWLEDGMENTS

The authors thank Jessica Donovan, Dori Walterhouse, Dr Barbara Changhizi, Alex Janis, Steven Ciolek, Madison Blake, Marielle Lynch, Sara McKeeman, Anna Weibel, Julia Goodwin, and Nathan O’Malley for their assistance on data collection and analysis. They also thank The Michael J. Fox Foundation, Honda Research and Development, and people with PD who supported this project.

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