Osaki Massage Chair The newest in zero-gravity massage chairs, designed with a set of S-tracks which contour your body for a consistent and lifelike massage. The Osaki OS-4000 is equipped with a computer body scan for the back and legs which adjusts to most body types, specializing on the neck, shoulder, and lumbar area. The Osaki OS-4000 is equipped with a computer body scan for the back and legs which adjusts to most body types, specializing on the neck, shoulder, and lumbar area.