Visualization of Exercise Intensity During Walking Using Walk-training Robot having Photoplethysmographic Sensor

This paper reports on a method to visualize exercise intensity, a crucial indicator in gait rehabilitation, using a photoplethysmography (PPG) sensor integrated into a walk-training robot. Improving endurance is known to be effective in preventing and alleviating physical frailty in the elderly, with aerobic exercise being particularly suitable. However, it is challenging for individuals to subjectively determine if they are engaging in aerobic exercise during their workout. To address this, we aim to visualize exercise intensity based on objective indicators by integrating a pulse sensor into the walk-training robot and calculating exercise intensity from the pulse rate during walking. The PPG sensor is integrated inside the handle of the walk-training robot. We calculate exercise intensity using the pulse rate at rest and during walking, along with age, based on the Karvonen formula. We compared the results with a medically certified reference device in stationary, handle-shaking, and walking conditions. In a walking test lasting approximately three minutes, we confirmed that the average pulse rate error compared to the reference device was within 1 bpm. Using this sensor-integrated walk-training robot, we demonstrated the visualization of exercise intensity during walking.