Lumbago is caused when the load adds to the flexible intervertebral disk between vertebras that compose the lumbar vertebra and the intervertebral disk transforms. A typical method for measuring the intervertebral disk load is an invasive method to inserting the electrode to measure internal pressure into there directly. In this study, the intervertebral disk load is estimated by noninvasive method of measuring the shape of lumbar vertebra indirectly with three dimensional motion analysis system and signal processing. Under assumption that vertebra is rigid body, lumbar vertebra is approximated in the circular arc by using three dimensional position coordinate of vertebras, and the average gap between vertebras is estimated. Then it is evaluated as intervertebral disk load. Therefore, proposal method is safe. Moreover, intervertebral disk load can be estimated while moving. In this paper, proposal method is explained in detail, the experiment to estimate the intervertebral disk load in static postures is conducted, and it compares with the typical method. As a results it is shown that the proposal method is effective.
