Design of a passive chairless chair and evaluating its performance based on heart rate and energy expenditure

The purpose of this research is to design, construct, and evaluate the performance of a passive chairless chair composed of a series of links and tensile and torsional springs, intended to assist with repeated and prolonged sit-to-stand movements, particularly in industrial and medical environments. Performance validation and feasibility assessment of the exoskeleton were conducted with five healthy participants. During the experiments, each participant's heart rate was recorded under two conditions-using and not using the device-and at two different seat heights, while performing continuous sit-to-stand motions. Device performance was evaluated using two parameters: heart rate variation and the Physiological Cost Index (PCI), calculated for participants during the tests. The results demonstrated that using the device significantly reduced the increase in heart rate (by an average of 5 beats/min at a 57 cm seat height and 2.6 beats/min at a 62 cm seat height) and the PCI value (by an average of 0.35 beats/cycle at 57 cm and 0.17 beats/cycle at 62 cm), subsequently lowering users' energy expenditure compared with not using the device.