Dynamic sitting aids, like air-filled cushions, encourage postural shifts and activate trunk muscles, potentially mitigating musculoskeletal discomfort and preventing the onset of low back pain. However, evidence on optimal design and pressure is lacking. This project addresses these gaps by developing a portable cushion to reduce discomfort in high-risk office workers. A systematic, four-phase iterative approach optimized the cushion’s diameter, construction, and air fill. The resulting round cushion, with two layers of chambers at 21–25 kPa, promotes postural shifts and trunk muscle activation while maintaining comfort. Future research should evaluate its application and sustained benefits in diverse office environments.