Inspection methods for stabilometry differ between Japan and overseas countries. In Japan, the closed parallel feet position is used, whereas various positions are used abroad, such as with feet parallel to each other at some distance and with each foot placed at 30° with heels in contact with each other. Further, arm postures include arms extended laterally, the folded arms posture, and others. In the present study, we performed stabilometry tests using various feet positions. Participants were 64 healthy subjects (males, 42; females, 22; mean age, 33.5 years) without a history of vertigo or balance disorders. Stabilometry with the closed parallel feet position and each foot placed at 30° was recorded with eyes open and eyes closed for 60 seconds each. Many parameters were low with each foot placed at 30° compared to the closed parallel feet position. Further, there was a significant difference (p<0.01) in total length (cm) with eyes open and eyes closed, and a significant decrease in area (cm2) with eyes open (p<0.05) and with eyes closed (p<0.01). Using the velocity of 8 directions, we obtained a ratio of left-right/anterior-posterior vector, with the closed parallel feet position found to be significantly higher (p<0.01) than with each foot placed at 30° both with eyes open and eyes closed. These results indicate that the closed parallel feet position is an unstable posture associated with more sway than each foot placed at 30°. Therefore, the closed parallel feet position may be more suitable for clinical use because it allows the detection of minute changes in the center of posture.
