Maintain your core with the Ergo Sit from Theragear. Much like a balance ball, the Ergo Sit cushion makes you sit up straight while working your abs. The air-filled Ergo Sit cushion is an innovative way to improve posture and promote better balance. Sitting on it encourages upright posture, which means less stress on your spine. Strengthen back and abdominal muscles while working at your computer, or put the Ergo Sit on the floor to exercise your legs and feet. Use the round side forward for active sitting and the thigh-support forward for more stable sitting.