Physiological Responses and Perceived Exertion During Robot-Assisted and Body Weight-Supported Gait After Stroke

A State-of-the-Art of Exoskeletons in Line with the WHO's Vision on Healthy Aging: From Rehabilitation of Intrinsic Capacities to Augmentation of Functional Abilities

The global aging population faces significant health challenges, including an increasing vulnerability to disability due to natural aging processes. Wearable lower limb exoskeletons (LLEs) have emerged as a promising solution to enhance physical function in older individuals. This systematic review synthesizes the use of LLEs in alignment with the WHO's healthy aging vision, examining their impact on intrinsic capacities and functional abilities. We conducted a comprehensive literature search in six databases, yielding 36 relevant articles covering older adults (65+) with various health conditions, including sarcopenia, stroke, Parkinson's Disease, osteoarthritis, and more. The interventions, spanning one to forty sessions, utilized a range of LLE technologies such as Ekso®, HAL®, Stride Management Assist®, Honda Walking Assist®, Lokomat®, Walkbot®, Healbot®, Keeogo Rehab®, EX1®, overground wearable exoskeletons, Eksoband®, powered ankle-foot orthoses, HAL® lumbar type, Human Body Posturizer®, Gait Enhancing and Motivation System®, soft robotic suits, and active pelvis orthoses. The findings revealed substantial positive outcomes across diverse health conditions. LLE training led to improvements in key performance indicators, such as the 10 Meter Walk Test, Five Times Sit-to-Stand test, Timed Up and Go test, and more. Additionally, enhancements were observed in gait quality, joint mobility, muscle strength, and balance. These improvements were accompanied by reductions in sedentary behavior, pain perception, muscle exertion, and metabolic cost while walking. While longer intervention durations can aid in the rehabilitation of intrinsic capacities, even the instantaneous augmentation of functional abilities can be observed in a single session. In summary, this review demonstrates consistent and significant enhancements in critical parameters across a broad spectrum of health conditions following LLE interventions in older adults. These findings underscore the potential of LLE in promoting healthy aging and enhancing the well-being of older adults.

Correlations between aerobic exercise time during physiotherapy and characteristics of patients with subacute stroke: A pilot cross-sectional study

BACKGROUND

The amount of aerobic exercise time (AET) is an important factor for improving physical function in patients with stroke. However, there is a lack of evidence regarding the factors for AET during physiotherapy, particularly in stroke patients.

OBJECTIVE

To investigate the correlation between AET during physiotherapy and characteristics of patients with subacute stroke.

METHODS

In this cross-sectional study, 61 hospitalized subacute stroke patients (age = 72 (11) years, (median (interquartile range)) were enrolled and their exercise intensity was measured by wearable sensors (Mio Alpha 2) worn during physiotherapy sessions. All patients were divided into two groups, non-ambulatory group (functional ambulation classification (FAC); 0-2) and ambulatory group (FAC; 3-5). The correlations between AET and patient characteristics were assessed in each group.

RESULTS

There was no significant difference in AET between the ambulatory and non-ambulatory groups (9 (12) min vs 5 (10) min, p = .27, respectively). There was a significant correlation between AET and the functional independent measures (FIM) motor score in the ambulatory group (r = 0.52, p = .005), and between AET and the FIM cognitive score in the non-ambulatory group (r = 0.44, p = .008).

CONCLUSION

Correlations between AET and patient characteristics were different according to ambulation capacity in patients with subacute stroke.

Rethinking the tools in the toolbox

The commentary by Dr. Labruyere on the article by Kuo et al. (J Neuroeng Rehabil. 2021; 18:174) posits that randomized trials evaluating the comparative efficacy of robotic devices for patients with neurological injury may not be needed. The primary argument is that researchers and clinicians do not know how to optimize training parameters to maximize the benefits of this therapy, and studies vary in how they deliver robotic-assisted training. While I concur with the suggestion that additional trials using robotic devices as therapeutic tools are not warranted, an alternative hypothesis is that future studies will yield similar equivocal results regardless of the training parameters used. Attempts are made to detail arguments supporting this premise, including the notion that the original rationale for providing robotic-assisted walking training, particularly with exoskeletal devices, was flawed and that the design of some of the more commonly used devices places inherent limitations on the ability to maximize neuromuscular demands during training. While these devices arrived nearly 20 years ago amid substantial enthusiasm, we have since learned valuable lessons from robotic-assisted and other rehabilitation studies on some of the critical parameters that influence neuromuscular and cardiovascular activity during locomotor training, and different strategies are now needed to optimize rehabilitation outcomes.

Robot-assisted gait training: more randomized controlled trials are needed! Or maybe not?

I was encouraged by the recent article by Kuo et al. entitled “Prediction of robotic neurorehabilitation functional ambulatory outcome in patients with neurological disorders” to write an opinion piece on the possible further development of stationary robot-assisted gait training research. Randomized clinical trials investigating stationary gait robots have not shown the superiority of these devices over comparable interventions regarding clinical effectiveness, and there are clinical practice guidelines that even recommend against their use. Nevertheless, these devices are still widely used, and our field needs to find ways to apply these devices more effectively. The authors of the article mentioned above feed different machine learning algorithms with patients’ data from the beginning of a robot-assisted gait training intervention using the robot Lokomat. The output of these algorithms allows predictions of the clinical outcome (i.e., functional ambulation categories) while the patients are still participating in the intervention. Such an analysis based on the collection of the device’s data could optimize the application of these devices. The article provides an example of how our field of research could make progress as we advance, and in this opinion piece, I would like to present my view on the prioritization of upcoming research on robot-assisted gait training. Furthermore, I briefly speculate on some drawbacks of randomized clinical trials in the field of robot-assisted gait training and how the quality and thus the effectiveness of robot-assisted gait training could potentially be improved based on the collection and analysis of clinical training data, a better patient selection and by giving greater weight to the motivational aspects for the participants.

Efficacy of an exoskeleton-based physical therapy program for non-ambulatory patients during subacute stroke rehabilitation: a randomized controlled trial

BACKGROUND

Individuals requiring greater physical assistance to practice walking complete fewer steps in physical therapy during subacute stroke rehabilitation. Powered exoskeletons have been developed to allow repetitious overground gait training for individuals with lower limb weakness. The objective of this study was to determine the efficacy of exoskeleton-based physical therapy training during subacute rehabilitation for walking recovery in non-ambulatory patients with stroke.

METHODS

An assessor-blinded randomized controlled trial was conducted at 3 inpatient rehabilitation hospitals. Patients with subacute stroke (< 3 months) who were unable to walk without substantial assistance (Functional Ambulation Category rating of 0 or 1) were randomly assigned to receive exoskeleton-based or standard physical therapy during rehabilitation, until discharge or a maximum of 8 weeks. The experimental protocol replaced 75% of standard physical therapy sessions with individualized exoskeleton-based sessions to increase standing and stepping repetition, with the possibility of weaning off the device. The primary outcome was walking ability, measured using the Functional Ambulation Category. Secondary outcomes were gait speed, distance walked on the 6-Minute Walk Test, days to achieve unassisted gait, lower extremity motor function (Fugl-Meyer Assessment), Berg Balance Scale, Patient Health Questionnaire, Montreal Cognitive Assessment, and 36-Item Short Form Survey, measured post-intervention and after 6 months.

RESULTS

Thirty-six patients with stroke (mean 39 days post-stroke) were randomized (Exoskeleton = 19, Usual Care = 17). On intention-to-treat analysis, no significant between-group differences were found in the primary or secondary outcomes at post-intervention or after 6 months. Five participants randomized to the Exoskeleton group did not receive the protocol as planned and thus exploratory as-treated and per-protocol analyses were undertaken. The as-treated analysis found that those adhering to exoskeleton-based physical therapy regained independent walking earlier (p = 0.03) and had greater gait speed (p = 0.04) and 6MWT (p = 0.03) at 6 months; however, these differences were not significant in the per-protocol analysis. No serious adverse events were reported.

CONCLUSIONS

This study found that exoskeleton-based physical therapy does not result in greater improvements in walking independence than standard care but can be safely administered at no detriment to patient outcomes. Clinical Trial Registration The Exoskeleton for post-Stroke Recovery of Ambulation (ExStRA) trial was registered at ClinicalTrials.gov (NCT02995265, first registered: December 16, 2016).

Towards a Clinical Decision-Making Algorithm Guiding Locomotor Therapy Modality in Subacute Stroke: An Exploratory Study

OBJECTIVES

To propose a clinical decision-making algorithm guiding modality choice and transition from the Lokomat® robotic to body-weight supported treadmill training in subacute stroke, due to current evidence being limited, making clinical decisions difficult.

MATERIALS AND METHODS

For 10 adult patients with subacute stroke completing Lokomat® therapy, physiotherapist clinical judgement regarding body-weight supported treadmill training readiness and the following objective measurements were collected; Functional Ambulation Category; sit to stand/standing ability; Lokomat® settings; maximal active hip and knee flexion in standing; and gait biomechanics during body-weight supported treadmill training. Based on observed patterns a proposed clinical decision-making algorithm was developed.

RESULTS

Clinical judgement deemed four of 10 participants ready to transition to body-weight supported treadmill training. Unlike participants judged not ready, these participants had: a) a Functional Ambulation Category of 1; b) independence with sit to stand and standing with even weight bearing; c) Lokomat®: Body-Weight Support <30%, Guidance Force <30-35%, speed >2.0kph; d) >45° standing active hip and knee flexion; e) no significant issues with physiological stepping in treadmill training or only requiring assistance from one therapist to achieve this.

CONCLUSION

Participants judged ready for transition from the Lokomat® to body-weight supported treadmill training presented with increased independent functional ability, more challenging Lokomat® settings, greater active volitional lower-limb control, and less issues with physiological stepping in treadmill training, than those participants judged not ready. Results were translated into a proposed clinical decision-making algorithm guiding transition from the Lokomat® to body-weight supported treadmill training, to be further tested in clinical trials.

Motor Cortical Activation Assessment in Progressive Multiple Sclerosis Patients Enrolled in Gait Rehabilitation: A Secondary Analysis of the RAGTIME Trial Assisted by Functional Near-Infrared Spectroscopy

This study aimed to determine cortical activation responses to two different rehabilitative programs, as measured through functional near-infrared spectroscopy (fNIRS). As a secondary analysis of the RAGTIME trial, we studied 24 patients with progressive multiple sclerosis (MS) and severe disability who were randomized to a regimen of robot-assisted gait training (RAGT) or overground walking (OW). Cortical activation during a treadmill walking task, assessed through fNIRS recordings from the motor and premotor cortexes (M1/PM), was calculated as the area under the curve (AUC) of oxyhemoglobin for each hemisphere and the total area (Tot-Oxy_AUC). Gait speed, endurance, and balance were also measured, along with five healthy control subjects. At baseline, Tot-Oxy_AUC during walking was significantly increased in MS patients compared to healthy people and was significantly higher for those with more severe disabilities; it was also inversely correlated with physical performance. After rehabilitation, significant opposite variations in Tot-Oxy_AUC were observed, with activity levels being increased after OW and decreased after RAGT (+242,080 ± 361,902 and −157,031 ± 172,496 arbitrary units, respectively; p = 0.002), particularly in patients who were trained at a lower speed. Greater reductions in the cortical activation of the more affected hemisphere were significantly related to improvements in gait speed (r = −0.42) and endurance (r = −0.44). Cortical activation, assessed through fNIRS, highlighted the brain activity in response to the type and intensity of rehabilitation.

The Metabolic Cost of Exercising With a Robotic Exoskeleton: A Comparison of Healthy and Neurologically Impaired People

While neuro-recovery is maximized through active engagement, it has been suggested that the use of robotic exoskeletons in neuro-rehabilitation provides passive therapy. Using oxygen consumption (VO₂) as an indicator of energy expenditure, we investigated the metabolic requirements of completing exercises in a free-standing robotic exoskeleton, with 20 healthy and 12 neurologically impaired participants (six with stroke, and six with multiple sclerosis (MS)). Neurological participants were evaluated pre- and post- 12 weeks of twice weekly robotic therapy. Healthy participants were evaluated in, and out of, the exoskeleton. Both groups increased their VO₂ level from baseline during exoskeleton-assisted exercise (Healthy: mean change in VO₂ = 2.10 ± 1.61 ml/kg/min, p =< 0.001; Neurological: 1.38 ± 1.22, p = 0.002), with a lower predicted mean in the neurological sample (-1.08, 95%CI -2.02, -0.14, p = 0.02). Healthy participants exercised harder out of the exoskeleton than in it (difference in VO₂ = 3.50, 95%CI 2.62, 4.38, p =< 0.001). There was no difference in neurological participants' predicted mean VO₂ pre- and post- 12 weeks of robotic therapy 0.45, 95%CI -0.20, 1.11, p = 0.15), although subgroup analysis revealed a greater change after 12 weeks of robotic therapy in those with stroke (MS: -0.06, 95%CI -0.78, 0.66, p = 0.85; stroke: 1.00, 95%CI 0.3, 1.69, p = 0.01; difference = 1.06, p = 0.04). Exercise in a free-standing robotic exoskeleton is not passive in healthy or neurologically impaired people, and those with stroke may derive more benefit than those with MS.

The Value of High Intensity Locomotor Training Applied to Patients With Acute-Onset Neurologic Injury

Long-standing research in animal models and humans with stroke or incomplete spinal cord injury (iSCI) indicate that specific physical training variables, such as the specificity and amount of practice, may influence neurologic recovery and locomotor function. More recent data highlight the contributions of exercise intensity, as estimated indirectly by cardiovascular exertion, as potentially more important than previously considered. The effects of exercise intensity are well described in neurologically intact individuals, although confusion regarding the definitions of intensity and safety concerns have limited its implementation during physical rehabilitation of patients with neurologic injury. The purpose of this review is to delineate some of the evidence regarding the effects of exercise intensity during locomotor training in patients with stroke and iSCI. We provide specific definitions of exercise intensity used within the literature, describe methods used to ensure appropriate levels of exertion, and discuss potential adverse events and safety concerns during its application. Further details on the effects of locomotor training intensity on clinical outcomes, and on neuromuscular and cardiovascular function will be addressed as available. Existing literature across multiple studies and meta-analyses reveals that exercise training intensity is likely a major factor that can influence locomotor function after neurologic injury. To extend these findings, we describe previous attempts to implement moderate to high intensity interventions during physical rehabilitation of patients with neurologic injury, including the utility of specific strategies to facilitate implementation, and to navigate potential barriers that may arise during implementation efforts.

Clinical assessment, management, and rehabilitation of walking impairment in MS: an expert review

INTRODUCTION

One of the most common and life-altering consequences of Multiple Sclerosis (MS) is walking impairment. The distance, speed, and Gait pattern functions are components of the International Classification of Functioning, Disability, and Health (ICF) and are also predictors of dependency in terms of daily living activities in patients with MS (pwMS).

AREAS COVERED

This article provides an overview of walking impairment in pwMS, with focus on the assessment of gait and the rehabilitation approaches.

EXPERT OPINION

The authors recommend that pwMS undergo gait assessment integrating the ICF perspective using validated clinical outcome measures that cover spatiotemporal gait parameters. Moreover, assessment of walking speed with short walking capacity tests such as the timed 25-foot walk (T25FW) or the 10-m walk test (10 MWT) and tests for walking distance with middle distance tests such as the 2-min walk test (2MWT) and the 6-min walk test (6MWT). This review further highlights strategies that may restore walking function including pharmacological symptomatic treatment and non-pharmacological rehabilitation approaches such as exercise and task-specific training providing an appraisal of mobility targeted therapies to be considered when planning multidisciplinary comprehensive-care of pwMS. Finally, new and novel strategies such as motor imagery and rhythmic auditory stimulation have been developed to improve walking speed and distance in pwMS.

Augmented Performance Feedback during Robotic Gait Therapy Results in Moderate Intensity Cardiovascular Exercise in Subacute Stroke

BACKGROUND

Low cardiovascular fitness is common poststroke. Conventional subacute stroke rehabilitation does not meet Australian National Stroke Guidelines for cardiovascular exercise, particularly in mobility-dependent patients. Walking robotics can potentially achieve recommended cardiovascular exercise with these patients.

AIM

The primary aim was to determine whether sustained moderate intensity cardiovascular exercise can be achieved using 3 Lokomat Augmented Performance Feedback activities in mobility-dependent adults with subacute stroke. Secondary aims were to assess if cardiovascular workload was influenced by the activity completed, participants motivation or enjoyment, or changes in Lokomat settings.

METHODS

Ten patients with subacute stroke (mean (SD) age: 63.4 (13) years) participated in 6x20-minute Lokomat study sessions. Each study session involved a warm-up and 3x5-minute APF activities presented in a random order. Metabolic data were collected using the COSMED-K5. Participants rated their perceived exertion on the BORG CR10 scale and Lokomat settings of body-weight support, guidance force, and speed were recorded.

RESULTS

Moderate intensity cardiovascular exercise was achieved and maintained over the 15 minutes of exercise, objectively demonstrated by a mean (SD) Metabolic Equivalent Task of 3.1 (1.3), and mean (SD) oxygen consumption of 8.0 (3.8) ml/kg/min, estimated as 52% VO₂max. This was subjectively confirmed by exertion scores between 3 and 5. The cardiovascular workload was not affected by which activity was completed, participant motivation or enjoyment, or significant progression of Lokomat settings between study sessions.

CONCLUSIONS

Mobility-dependent patients with subacute stroke can achieve sustained moderate intensity cardiovascular exercise on the Lokomat when using APF activities.

Clinical non-superiority of technology-assisted gait training with body weight support in patients with subacute stroke: A meta-analysis

BACKGROUND

Technology-assisted gait training (TAGT) with body weight support (BWS) has been designed to provide high numbers of repetitions during stepping practice, but its benefits have been inconclusive.

OBJECTIVE

We evaluated the superiority of TAGT over conventional overground training (COT) to judge the clinical benefits.

METHODS

We searched PubMed, Embase and Web of Science databases from their earliest record to July 1, 2019 and included randomized controlled trials of TAGT with BWS, such as robot-assisted gait training and body weight-supported treadmill training, for treating walking disability in patients within 6months after stroke. We conducted a meta-analysis of the outcomes motor impairment, mobility capacity, walking speed, endurance and fitness, balance, and activities of daily living as well as subgroup analyses of initial ambulatory ability and stroke duration.

RESULTS

Among 14robotics and 10body weight-supported treadmill studies included for review, 23studies involving 1452participants contributed to the meta-analysis. We found no significant standardized mean differences between TAGT and COT (P>0.05) across all outcome categories in the robotics subgroup, the body weight-supported treadmill subgroup, or both subgroups combined, for both the short and long term. Further subgroup analyses also revealed non-significant standardized mean differences (P>0.05) across all outcomes in the subgroups initially ambulatory, non-ambulatory, or stroke duration less than 3 months.

CONCLUSIONS

TAGT with BWS was not superior to COT in improving post-stroke recovery in patients with subacute stroke. Strategies other than simply increasing the repetitions by external assistance may be considered to augment the treatment effects of TAGT.

Physiological responses and perceived exertion during robot-assisted treadmill walking in non-ambulatory stroke survivors

PURPOSE

To examine physiological responses and perceived exertion during robot-assisted treadmill walking in non-ambulatory stroke survivors; compare these outcomes with aerobic exercise recommendations; and investigate the effect of robotic assistance.

MATERIALS AND METHODS

Twelve non-ambulatory stroke survivors (67 ± 11 years-old, 84 ± 38 d post-stroke) participated. Subjects walked three times 20 min (1 session/day) in the Lokomat: once with conventional exercise parameters, once with 60% robotic assistance and once with 100% robotic assistance. Gas exchange and heart rate were monitored continuously. Perceived exertion was assessed every 3 min during walking.

RESULTS

During conventional robot-assisted treadmill walking, net perceived exertion (0-14 scale) significantly increased between minute 6 (median = 2, interquartile range = 4) and 18 (median = 5, interquartile range = 4). Net physiological responses did not significantly change over time. Throughout exercise, percentage of predicted heart rate reserve was significantly below the 40% threshold (medians: 11-14%) and percentage of predicted maximum heart rate reached the 55% threshold (medians: 59-60%). Perceived exertion reached the 11-point threshold halfway. Net physiological responses and perceived exertion did not significantly differ between 60% and 100% robotic assistance.

CONCLUSIONS

The assistance level that non-ambulatory stroke survivors require at their highest tolerable walking speed seems too high to sufficiently stress the cardiorespiratory system during robot-assisted treadmill walking.Implications for rehabilitationThe exercise intensity of 20-minute conventional robot-assisted treadmill walking can be low, and might be too low to challenge the cardiorespiratory system of non-ambulatory stroke survivors.Lowering the level of robotic assistance from 100% to 60% does not seem to increase the exercise intensity of 20-minute robot-assisted treadmill walking.

Beyond therapists: Technology-aided physical MS rehabilitation delivery

In the last decade, rehabilitation technology has been developed, investigated, and entered specialized clinical settings. In this chapter, we first discuss the potential of rehabilitation technology to support the achievement of key factors in motor recovery, such as delivering massed practice with good movement quality but also question task-specificity and cognitive motor control mechanisms. Second, we discuss available technology-supported rehabilitation methods for improving gait, balance and fitness, and upper limb function. Finally, we discuss considerations in relation to the professional workforce in order to deliver optimal rehabilitation.

Robot-assisted gait training is not superior to intensive overground walking in multiple sclerosis with severe disability (the RAGTIME study): A randomized controlled trial

Background:

Rehabilitation may attenuate the impact on mobility of patients with progressive multiple sclerosis (MS) and severe gait disabilities.

Objective:

In this randomized controlled trial, we compared robot-assisted gait training (RAGT) with conventional therapy (CT) in terms of gait speed, mobility, balance, fatigue and quality of life (QoL).

Methods:

Seventy-two patients with MS (expanded disability status scale score 6.0–7.0) were randomized to receive 12 training sessions over a 4-week period of RAGT ( n = 36) or overground walking therapy ( n = 36). The primary outcome was gait speed, assessed by the timed 25-foot walk test. Secondary outcome measures were walking endurance, balance, depression, fatigue and QoL. Tests were performed at baseline, intermediate, at the end of treatment and at a 3-month follow-up.

Results:

Sixty-six patients completed the treatments. At the end of treatment with respect to baseline, both groups significantly improved gait speed ( p < 0.001) and most secondary outcomes without between-group differences. Outcome values returned to baseline at follow-up.

Conclusions:

RAGT was not superior to CT in improving gait speed in patients with progressive MS and severe gait disabilities where a positive, even transitory, effect of rehabilitation was observed.