ZEPU-AI5 Strength Training Study (ZEPUAI5RCT)

Walking impairment due to neurological and orthopedic conditions significantly limits independence and functional mobility, making lower-limb strength training a key focus of rehabilitation. Robotic-assisted rehabilitation systems have shown promising results in improving strength and functional outcomes in high-income countries; however, their feasibility, safety, and efficacy remain underexplored in low- and middle-income settings. In Bangladesh, the ZEPU-AI5 lower-limb strength training and evaluation robot is a novel technology that has not yet been systematically evaluated in this population.

The ZEPU-AI5 is a computer-controlled electromechanical rehabilitation device consisting of a rigid main frame, a motor-driven walking training table, bilateral robotic mechanical legs aligned with the patient's hip and knee joints, adjustable foot pedals, thigh and calf fixation straps, and a body-weight support suspension system. The walking platform supports up to 135 kg, with continuously adjustable body-weight unloading from 0-80 kg, allowing progressive loading according to patient tolerance and recovery stage. Prior to training, individualized calibration is performed by measuring thigh and calf lengths to align the robotic joints with the participant's anatomical hip and knee axes, with bilateral symmetry adjustment available when needed.

The system provides programmable control over hip joint angles (30°-50°) and knee joint angles (50°-80°) in 1° increments, with gait offset parameters adjustable by ±10 units to allow individualized correction of abnormal gait patterns. Walking speed is adjustable from 0.1 to 3.5 km/h, allowing graded progression from slow assisted stepping to higher-speed gait training.

At study entry, participants will undergo a face-to-face interview to gather clinical and sociodemographic data using a semi-structured, pre-tested questionnaire. Weight and height will be measured to calculate Body Mass Index (BMI). All participants will be allocated a study ID, and assessments will be conducted at the Robotic Rehabilitation Center, Department of Physical Medicine and Rehabilitation, Bangladesh Medical University.

Inclusion criteria

• Lower-limb motor dysfunction due to one of the following: (a) stroke (onset 2-24 months), (b) incomplete spinal cord injury (neurological level T12 or below, ASIA Impairment Scale C or D), or (c) orthopedic surgery (e.g., knee/hip replacement) with persistent gait impairment more than 3 months post-surgery
• Age greater than 18 years and up to 60 years
• Medically stable and able to provide informed consent
• Able to meet device anthropometric criteria for use of the ZEPU-AI5 system

Exclusion criteria

• Complete spinal cord injury with inability to bear any weight
• Severe cognitive impairment (Mini-Mental State Examination score less than 24) preventing safe participation
• Severe spasticity of the lower limbs (Modified Ashworth Scale greater than 3)
• Unstable fractures, severe hip/knee contractures (greater than 30 degrees fixed flexion), or severe osteoarthritis requiring imminent surgery
• Uncontrolled cardiac arrhythmia, pacemaker incompatibility, or any implanted electronic device incompatible with the robot's sensors
• Pregnancy