A pilot randomized clinical trial evaluating robotic rehabilitation for stroke survivors with hemiplegia found that gait training with a wearable hip exoskeleton yielded significantly greater gains in walking distance and speed compared to conventional physiotherapy alone. Across twelve training sessions, participants in both intervention and control groups demonstrated statistically significant functional progress from baseline, but patients assisted by the robotic device covered greater distance during standardized walking assessments and executed timed mobility transitions faster than those in the control group.
Stroke represents a leading cause of long-term disability and the fifth leading cause of death globally, frequently leaving survivors with hemiplegic gait patterns marked by asymmetry, reduced velocity, elevated fall risks, and diminished quality of life. While gait rehabilitation relies heavily on repetitive, long-term exercise, conventional methods impose considerable physical burden on therapists and incur substantial economic costs. Wearable overground devices such as the Hip Exoskeleton Assistive robot provide an alternative to fixed robotic platforms by allowing patients to explore real environments with natural sensory inputs, though randomized clinical evidence assessing overground robotic efficacy versus standard physiotherapy remains limited.
The trial enrolled 24 participants selected from a screened cohort of 250 patients, adhering to CONSORT reporting standards and ethical clearance from Mashhad University of Medical Sciences. Eligible participants were in the subacute stage of ischemic or hemorrhagic stroke within three months of onset, exhibited stage 5 recovery on the Brunnstrom scale, possessed muscle strength grades of at least 3+ in the quadriceps and gluteus muscles, and scored above 24 on the Mini-Mental State Examination. Investigators excluded individuals with flaccid paralysis, prior walking incapacity, bilateral involvement, severe leg spasticity exceeding score 3 on the Modified Ashworth Scale, pusher syndrome, or unstable cardiopulmonary conditions.
Researchers allocated the 24 participants equally into intervention and control groups using a blocked randomization schedule comprising six blocks of four subjects. To minimize assessment bias, the trial maintained a single-blind structure wherein one physiotherapist administered the therapeutic protocols while an independent, blinded assessor conducted baseline and post-intervention evaluations. Both cohorts participated in 60-minute rehabilitation sessions conducted three times weekly over four consecutive weeks, totaling twelve sessions per participant.
Every session began with 30 minutes of identical baseline therapy for both groups, consisting of neuromuscular electrotherapy alongside conventional physical exercises. Electrotherapy applied functional electrical stimulation to the ankle dorsiflexor muscles for 15 minutes at a 40 Hz frequency with a 0.3 millisecond pulse duration, alternating stimulation and rest in a 1:1 ratio. Conventional exercises encompassed postural and balance training, weight shifting, joint stretching, and progressive muscle strengthening performed in two to three sets of 10 to 15 repetitions with manual therapist resistance.
The remaining 30 minutes of each session consisted of overground gait training, during which control patients walked with direct manual therapist support and verbal cueing for symmetry, while intervention patients walked assisted by the FUM-HEXA-IV robotic exoskeleton under therapist supervision. The wearable exoskeleton weighs approximately 5.5 kg and incorporates an active single hip joint actuated by a 160-watt Maxon motor and precision gearbox capable of delivering up to 16 N·m of flexion torque per hip. Integrated force sensors measure user-generated force to adapt assistive motion dynamically; the robot initiated movement if baseline force fell below a set threshold or assisted ongoing motion once the threshold was attained, with assistance programmed to decrease by 10% each session following the initial two full-power sessions as patient independence increased.
Investigators evaluated functional recovery using five validated clinical measurement tools before the first session and following the twelfth session. Walking capacity was measured using the 6-Minute Walk Test, dynamic balance and transitional speed via the Timed Up and Go test, dynamic gait abilities through the 10-item Functional Gait Assessment, static and dynamic balance using the 14-item Berg Balance Scale, and stroke-specific health outcomes across 49 items via the Stroke Specific Quality of Life questionnaire.
Statistical evaluation using two-way repeated measures analysis of variance revealed significant main effects of time across all measured outcomes, confirming post-intervention improvement in both study groups. A statistically significant main effect of group emerged for the 6-Minute Walk Test and the Timed Up and Go test, with the robotic intervention group achieving greater distances and faster completion times. For the Berg Balance Scale, a significant group-by-time interaction was identified, with Wilcoxon testing demonstrating marked post-test improvements in both cohorts, whereas between-group comparisons for the Functional Gait Assessment and Stroke Specific Quality of Life questionnaires did not reach statistical significance.
The authors contextualized these outcomes within the International Classification of Functioning, Disability and Health framework, noting that short-term robotic interventions appeared most effective at remediating immediate structural and functional movement impairments rather than broader social participation restrictions. The observed improvements in walking speed and distance align with prior findings in wearable robotics trials, while differences across studies regarding balance and quality-of-life measures highlight how variations in robotic design, assistance algorithms, patient recovery phases, and training dosage affect published results across the neurorehabilitation literature.
The investigators emphasized several methodological constraints, particularly the pilot trial sample size of 24 participants, the lack of post-intervention follow-up monitoring to assess long-term retention of mobility gains, and the inability to control for potential robotic placebo effects. Future investigations with larger cohorts, extended longitudinal tracking, and standardized assistance protocols will be necessary to confirm the durability of overground hip exoskeleton benefits in stroke rehabilitation programs.
Beyond general neurologic inclusion criteria, candidate selection depended on precise anthropometric and functional thresholds. Investigators required participants to measure between 160 and 190 centimeters in height and weigh between 50 and 100 kilograms to ensure proper mechanical fitting within the wearable exoskeleton frame. Enrolled patients possessed active knee and hip extension alongside preserved weight-bearing capability on the affected limb, demonstrated by minimum muscle strength grades of 3+ across the quadriceps and gluteus musculature. Researchers excluded individuals presenting with strokes caused by tumors or infections, flaccid paralysis, bilateral involvement, pre-stroke walking incapacity, or pusher syndrome, an impairment marked by active pushing away from the non-hemiparetic side. Following ethical clearance, the investigators formally registered the pilot trial with the Iranian Registry of Clinical Trials under identifier IRCT20210730052024N1.
Participant randomization relied on a blocked allocation sequence using six balanced four-subject permutations: AABB, ABAB, BAAB, BABA, BBAA, and ABBA. A research assistant, masked to baseline evaluations, selected six sequential numbers from a random number table to distribute patients into their designated treatment cohorts. To mitigate testing fatigue and potential learning effects, therapists randomized the order of functional assessments, dedicating the opening appointment to familiarizing participants with the testing environment and procedures. During overground training sessions, protocol guidelines placed no restrictions on arm positioning or hand usage, leaving individuals free to use their arms naturally while ambulating. Clinicians actively monitored patient comfort, pausing the gait protocol whenever participants required rest and routinely querying them regarding potential physical discomfort or pain.
Engineered at the Center of Advanced Rehabilitation and Robotics Researches at Ferdowsi University, the FUM-HEXA-IV robotic device couples two 70-watt brushless motors with an AG Harmonic Drive precision gearbox and a 160-watt Maxon EC90 actuator. The mechanical assembly attaches directly to each thigh with Velcro straps, delivering active hip flexion torque during walking. Integrated force sensors continuously register user effort to guide mechanical assistance. If a patient generates hip flexion force meeting a distinguished minimum threshold, the robot operates assistively to help complete the intended movement range up to 16 newton meters per joint. When patient torque falls short of this threshold, the system initiates joint motion independently, dynamically modulating subsequent torque according to the user’s physical engagement. The setup excluded donning and doffing time from the designated 30-minute training window.
Standardized clinical instruments guided outcome evaluation. Aerobic capacity was quantified by total meters covered during the six-minute walk test. The timed up and go test assessed positional balance by recording the seconds required for a seated participant to stand, walk three meters forward, turn, return to the chair, and sit down. Dynamic gait function was measured across the ten sections of the Functional Gait Assessment, each scored from zero to three points for a cumulative score up to 30. Functional balance was graded using the 14 tasks of the Berg Balance Scale, with scores ranging from zero to 56 points, while quality of life was surveyed using the 49 questions of the Stroke Specific Quality of Life questionnaire, spanning 49 to 245 points. Persian versions of these three assessment tools had all been validated in prior rehabilitation literature.
Sample size planning specified 12 participants per group to detect clinically important differences on the six-minute walk test with 80 percent power and a two-sided alpha of 0.05, assuming 20 percent attrition. Statistical computations in SPSS version 23 coded the cohorts as numeric indicators. When Shapiro-Wilk testing revealed non-normal distribution for walking distance, researchers transformed values into base-10 logarithms prior to analysis of variance. Baseline demographic balance was confirmed using independent t-tests for body mass index, Mann-Whitney tests for age and mental status scores, Pearson chi-square tests for categorical variables, and likelihood ratio testing for diabetes mellitus. Based on the measured results, the authors concluded that the hip exoskeleton can effectively improve walking capacity by more than 60 percent and gait velocity by 30 percent.
Subject of Research: Robotic hip exoskeleton assistance in stroke gait rehabilitation
Article Title: The effect of using the hip exoskeleton assistive (HEXA) robot compared to conventional physiotherapy on clinical functional outcomes in stroke patients with hemiplegia: a pilot randomized controlled trial
Article References: Mamipour, H., Hoseini, S. A., Negahban, H., Moradi, A., Hojjati, A., Rezaeitalab, F., Torshizian, M., Mehrali, A., Parsa, M., Kardan, I., Tabesh, H., Hassankhani, E. G., & Akbarzadeh, A. (2024). The effect of using the hip exoskeleton assistive (HEXA) robot compared to conventional physiotherapy on clinical functional outcomes in stroke patients with hemiplegia: a pilot randomized controlled trial. BMC Biomedical Engineering, 6(1), Article 7. https://doi.org/10.1186/s42490-024-00082-0
Image Credits: AI Generated
DOI: 10.1186/s42490-024-00082-0
Keywords: stroke rehabilitation, robotic gait training, hip exoskeleton, hemiplegia, walking recovery, physical therapy, biomechatronics, randomized controlled trial, effect, exoskeleton, assistive, HEXA
