Cantilever seat

A cantilever seat cushion for reducing lower back strain, comprising:

• (a) an inner pre-cut foam;
• (b) an air tight shell that surrounds the inner pre-cut foam, wherein the air tight shell is any type of fabric having an air tight backing material or laminated with an air tight material;
• (c) an air valve that adjusts an incline angle of the cantilever seat cushion by deflating or inflating the seat, wherein the incline angle of the cantilever seat cushion is in a range from 10 to 25 degrees,
• wherein said cantilever seat cushion has six surfaces and has a front side height (F) of 3 to 8 inches, a rear side height (R) of 1 to 4 inches, a depth (D) of 8 to 20 inches and a width size (W) of 10 to 26 inches,
• wherein the cantilever seat cushion is washable, and
• wherein the cantilever seat cushion creates four forces that act on a femur in each leg causing a femoral head in each leg to lift up the sitting bones off the seat and push the pelvis and the lumbar against a seat back cushion, said four forces are:
• (1) a moment of force caused by weight of hanging legs and feet that acts on the femoral head at a hip joint socket that pushes up the two sitting bones according to formula 1:
• VTL=2×VFL×DkL:DfL,
• VTL is moment of force acting on the femoral head at the hip joint socket,
• VFL is force perpendicular to the femur at the knee joint which is [leg weight]×[Cos Φ],
• Φ is inclined angle of the cantilever seat,
• DkL is distance from axis of knee to reference point on the femoral head at the hip joint, and
• DfL is distance from axis of the femoral head to reference point on the femur,
• (2) a corresponding force that pushes the femur at the hip joint socket against the seat back cushion according to formula 2:
• 2×HFL,
• HFL is corresponding force acting on the femur along incline surface of seat which is [Leg weight]×[Sin Φ],
• (3) a downward vertical force caused by weight of thighs on an incline surface that acts on a femoral head at a hip socket that pushes up two sitting bones according to formula 3:
• and
• VTT=2×VFT×DrC:DrF,
• VTT is moment acting on the femoral head at the hip joint socket,
• VFT is force perpendicular to the femur which is [thigh weight]×[Cos Φ],
• DrC is distance from CHM to reference point on the femur,
• CHM is center of hip mass as the mean position of entire hip mass distribution,
• Drf is distance from axis of the femoral head to reference point on the femur,
• (4) a corresponding force to the downward vertical force that pushes the femur at the hip joint against the seat back cushion according to formula 4:
• VCT=2×HFT,
• VCT is corresponding force pushing the femur at hip joint against seat back cushion,
• HFT is corresponding force acting on the femur along incline surface of seat which is [thigh weight]×[Sin Φ].