Regen is a robot-assisted device designed to help therapists and improve the quality of treatment. It works by replicating the movement of the therapist and providing assistance as needed for the patient. This study aims to assess the safety, feasibility, usability, and ability to Regen to replicate the movement pattern of therapist in young healthy adults during treadmill walking.

Physical therapy, despite its effectiveness, is a physically demanding profession that requires moderate to high physical and psychological work demands. A single session typically lasts close to an hour per patient, with a substantial portion dedicated to hands-on rehabilitation therapy, excluding assessment. Long sessions, repetitive manual motions, and awkward postures contribute to fatigue, risk of musculoskeletal strain, and limited treatment duration.

One of such physically demanding tasks in rehabilitation is gait training, which often requires therapists to provide continuous manual assistance to a patient's lower limbs during treadmill walking or overground training. This repetitive, non-ergonomic work not only accelerates therapist fatigue and low back pain but also restricts the number of gait cycles that can be practiced, thereby limiting patient outcomes. These challenges create a growing need for robotic technology that can share the physical workload while maintaining therapy quality.

Rehabilitation robotic technology ranges from exoskeletons to end-effector-based assisted training devices. These provide precision, repeatability, and adaptability beyond traditional therapy methods, while also providing sensory and motor feedback. Despite these advantages, current robotic devices still face significant barriers to widespread adoption. Most rehabilitation robots either provide fixed-repetitive motions, work on just one joint, or require extensive pre-programming, which limits adaptability and versatility to individual patient needs. Further, high equipment costs, the need for specialized staff training, and required adaptations to clinical infrastructure often limit their accessibility and scalability.

Regen offers a potential solution to these gaps. Regen is a medical robotic technology aimed at improving the strength and mobility of patients. This device consists of a human-interactive robot arm that connects patients via an arm or leg brace, providing therapeutic motions to patients. It works by replicating therapist-guided movements, extending therapy duration, and ensuring consistent motion delivery. Regen is unique in its "assist-as-needed" capability. This allows the therapist to directly teach and calibrate new trajectories for each user, set repetitions, and then run based on the patient's abilities. This adaptability not only supports patient progression but also enhances motivation for the patient. Thus, the system is more responsive to the real-world variability of therapy sessions.

Before such systems can be brought into clinical practice, it is essential to evaluate usability and validity. Usability assesses whether the system is acceptable, safe, and easy to use for both therapists and patients. Validity assesses the system's ability to accurately replicate therapeutic movement trajectories.

The primary aim of this study is to evaluate the feasibility and usability of Regen in young healthy adults. The secondary aim is to assess the validity of the device in replicating therapist-guided movement using a marker-based motion capture system. The investigators hypothesize that Regen is a safe, usable, and valid tool for delivering therapist-like rehabilitation movements.

Inclusion Criteria:

1. Healthy study participants: adults (18-50 years) who can walk independently on a treadmill for at least 6 minutes
2. Physical therapist (PT) with a license and experience in gait rehab (self-reported)

Exclusion Criteria:

(1) For healthy study participants:

1. Any neurological or orthopedic condition that can affect walking (Self-reported)
2. Uncontrolled cardiovascular or metabolic condition that can affect walking (Self-reported)
3. Current lower-limb pain or discomfort
4. Lower-limb surgery within the past six months
5. On medications that may impair balance (Self-reported)
6. Open wound in the lower limb

(2) For PT:

1. Not having license
2. No experience in gait rehab