Abstract: An abdominal/back muscle member 19 tightly surrounds narrowed portions 172 and 182 of an upper and a lower body members 17 and 18 of a lumbar assembly of human lumbar model structure. Shoulders 173 and 183 are formed at the bounds of the narrowed portion 172 and 182 from the remaining upper and lower portions of the upper body member and the lower body member 17 and 18 with a radial height larger than the thickness of the abdominal/back muscle member 19 to form hood-like radial flanges protruding from the outer upper and lower edges of the muscle member. The hood-like radial flanges effectively prevent the upper and lower edges of the muscle 19 from going over the shoulders, even if the maximum vertical loading is applied to the structure.

Abstract: An abdominal/back muscle member 19 tightly surrounds narrowed portions 172 and 182 of an upper and a lower body members 17 and 18 of a lumbar assembly of human lumbar model structure. Shoulders 173 and 183 are formed at the bounds of the narrowed portion 172 and 182 from the remaining upper and lower portions of the upper body member and the lower body member 17 and 18 with a radial height larger than the thickness of the abdominal/back muscle member 19 to form hood-like radial flanges protruding from the outer upper and lower edges of the muscle member. The hood-like radial flanges effectively prevent the upper and lower edges of the muscle 19 from going over the shoulders, even if the maximum vertical loading is applied to the structure.

Abstract: The human lumbar model structure comprises a lumbar assembly and an abdominal/back muscle member. The lumbar assembly comprises an upper body member, an upper lumbar member, an annulus fibrosus member, a lower lumbar member, and a lower body member which are coaxially arranged around a common center axis and which are superposed vertically from top to bottom in this order. The abdominal/back muscle member is made of an elastic material and has a hollow cylindrical shape. The abdominal/back muscle member surrounds and elastically tightens the lumbar assembly over a center area around the annulus fibrosus member. The annulus fibrosus member comprises a thick cylindrical ring made of a hard elastic material and is tightly fitted into the upper and lower lumbar members with its inner cavity filled with a fluid as a nucleus pulposus member. A pressure sensor is arranged along the center axis of the lower lumbar member in direct contact with the nucleus pulposus member.