Stability of the human body investigated by sway magnetometry.

A new technique using a pre-calibrated magnetometer has been used to investigate the stability of the human body. Transducer coils were attached to a belt which was worn by the subject. Sway was measured over 30 s periods with eyes open and eyes closed. For 10 normal subjects, the mean sway speed was 3.6 +/- 0.9 mm/s with eyes open, and 5.3 +/- 1.5 mm/s with eyes closed. The mean ratio for eyes open to eyes closed was 0.68 +/- 0.10. The test was simple to perform and gave reproducible results.