Towards a measurement of active muscle control for lumbar stabilisation.

No measure described to date reflects the ability of muscles to stabilise the lumbar spine. A static model was developed in supine crook lying, to measure active rotatory control with trunk loading in the sagittal plane via low, unilateral leg load. The hypothesis was that excessive lumbar movement indicates an inability of the stabilising muscles to automatically co-ordinate appropriate muscle force to support the spine. A computerised sensor was developed to monitor lumbar positional change. A rotatory stability index was calculated from pressure variations on taking leg load. Preliminary trials showed that this static model identified individuals with poor active rotatory control. Further development of the measurement model is warranted.