Zero gravity is a specific position derived from NASA research into postures that minimise physical stress during launch. In a riser recliner, it means the backrest is reclined to approximately 120 to 130 degrees, the footrest is raised so the feet are at approximately heart level, and the knees are bent at around 90 degrees. This minimises lumbar disc pressure, encourages venous return from the lower legs, and distributes body weight evenly across the contact surface.

In zero gravity: lumbar spinal pressure decreases compared to both upright sitting and fully flat recline; leg swelling reduces as feet are elevated to heart level; the heart works slightly less hard as blood circulates without pumping against gravity to the lower limbs; and pressure on the sciatic nerve is typically reduced. For users with lower back pain, leg swelling, or heart conditions, these are meaningful physical benefits.

Full recline means the backrest is flat with the footrest raised to match. Zero gravity is not the same as full recline — in zero gravity the backrest is at 120 to 130 degrees, not flat. The specific angle combination creates the beneficial distribution of forces. A named zero gravity preset button on the remote activates this configuration directly.