The Optical Target Speed of the Body Tracking Test (BTT). The Test Condition for the BTT-No.2

To evaluate dynamic postural control, the Body Tracking Test (BTT) was developed. This paper investigated the optical target speed. The subject standing on the stabilometer was asked to track a moving optical target displayed on the screen by his/her bodily movement. Stabilometric data were recorded and computer-analyzed. The horizontal or vertical span of the target was 15 cm. The optical target moved in a horizontal or vertical manner. The movement of the optical target was programmed by controlled triangular waves. The sampling time was 50 mseconds for a total of 60 seconds. The subject stood erect on the stabilometer with feet together and the display screen was placed at eye level.In the horizontal BTT, the gain for target and tracking was 1.8. In the vertical BTT, the gain for target and tracking was 1.6.Fifty healthy young adult volunteers (male 24, female 26) were tested. The mean age was 23.6 (19-34). They were examined in groups of five by target movement speed.We established the optical target speed at 0.025-0.4 Hz. Total distance of bodily movements was adjusted by body weight.To compare the results of each scale, the total distance of bodily movements was divided by total target movement.This ratio was named "Index of BTT movement". At 0.025 Hz, the index of BTT movement was at a maximum, while at 0.4 Hz, the index of BTT movement was almost 1.0.However at 0.4 Hz, the bodily movement became a fixed rhythmical movement. With a slow amplification such as 0.025 Hz, a larger adjustment was made accordingly amplification. Therefore, it was considered appropriate to use 0.125 Hz to obtain stable stabilometric data.