Hemodynamics of Active Ankle Motion in a Seated Position Using a Soft Robotic Wearable Actuator: A Comparative Study of Exercise Protocols and Cycles

This study evaluates a soft robotic wearable device, equipped with a Hyper-extension Pneumatic Actuator (HPA), to prevent deep vein thrombosis (DVT). We investigate the hemodynamic efficacy of a novel "Combined" exercise protocol, which strategically integrates the high-load advantage of resistance exercise with the wide range of motion from induced exercise, all delivered by a single soft actuator system. The effects of four distinct exercise modalities on key hemodynamic parameters, including time-averaged maximum blood flow velocity (TAMAX), were systematically evaluated in healthy participants. Results demonstrated that all active exercise modalities showed a strong tendency to augment blood flow velocity compared to rest (effect size r>0.8). Notably, the "Combined" protocol yielded a statistically significant increase in TAMAX compared to exercise without the device (p < .05). This enhancement is attributed to the protocol's ability to elicit high-quality, high-tension muscle contractions by balancing exercise load with a sufficient range of motion, thereby optimizing the muscle pump mechanism. These findings provide engineering guidelines for developing effective DVT prevention strategies, demonstrating that the intelligent integration of a control protocol—not just the hardware alone—is key to maximizing hemodynamic efficacy.