As the static balancing ability of the body is physiologically so complicated, that it is not easy to appraise it objectively and quantitatively. The aim of this study is to asses the motion of the gravity center of the body, using the body-balance analyzer (MGC-O1A, TOSHIBA), and to evaluate the validity of its use in the physical testing system.
The trace of the motion of the gravity center of 30 second duration, while the subject standing quietly on the sense-table with his eyes closed and his toes 60 degree opened, was drawn on the chart sheet and its length (L) was calculated electronically.
Preliminarily, 14 healthy men and women, whose ages ranged from 21 to 48 years old, were subjected to the test six times every day for ten consecutive days. The L values of 60 time measurements of each subject showed a slightly eccentric distribution with the coefficient variation of 20% on the average, but the coefficient variations of logarithmic value of L were small and they were between 2.4 and 6.0%. There was no significant difference between the L in the morning and that in the afternoon. Well-trained subjects seemed to show the smaller L values than the not-trained, but the latter some-times had little values, which might perhaps tell the existance of some predispositional ability for body balancing. Half of the subjects showed a“training effect”; L became smaller as the experimental day went on.
The L values of 2212 male and female subjects, age of those ranging from 19 to 83 years old, who performed the general physical testing, were then analyzed. The distribution of L was that of a “logarithmic normal”and it's geometric mean value was 210.8cm per 30 seconds, where the range of ± 1 S.D. was 149.0-298.3. It seemed that L increased with aging, only with a very low correlation coefficient (r : 0.14) . And there was no significant difference in L values between male and female. Although the multivariate analyses, in which L was set as the object variable, was performed, the correlation between L and the other physical abilities (muscular strength, power, agility, flexibility. and VO₂max) was very low (r : lower than 0.12) .