Redistributing Ground Reaction Forces During Squatting Using a Cable-Driven Robotic Device

Squatting is a dynamic task that is often done for strengthening and improving balance. Most squat training systems partially support body weight. However, one of the benefits of a squat exercise is efficiently distributing the body weight among the feet while maintaining stability. Several studies have shown how squatting and redistributing body weight among the feet can improve balance. The goals of this study are: (i) to show a robotic device that is transparent for studying human behavior during the squatting task, (ii) to investigate how ground reaction forces can be altered among the feet by applying a pelvic force during squatting. Seven able bodied adults underwent three squat conditions, squatting eight times per test. The first two conditions are a baseline set of squats followed by the third condition where participants received a constant lateral force on their pelvis. We use a cable-driven Robotic Upright Stand Trainer, RobUST, to deliver the lateral force on a pelvic belt. The lateral force was 5% of participants' body weight. Results show that a lateral force on the pelvis can significantly redistribute participants' ground reaction forces by increasing the symmetry index from 11.2% to 35.7% and increasing the lateral center of pressure amplitude from.07 to 0.18. The results also show that the pelvic lateral force did not add variability to the natural squat motion between repetitions, as measured by the coefficient of variability. These results are promising for future squat training paradigms to redistribute ground reaction forces and encourage specific weight distribution patterns.