重心動揺の正常範囲について

THE NORMAL RANGES OF DISPLACEMENT IN THE CENTER OF GRAVITY OF THE BODY

　Ⅰ．緒言

　人の重心の動きをディジタル量として表現したり，その特徴を正確に分析することは従来きわめて困難であつたが，電子計算機の導入により各種の分析法が可能になつた。

　生体で重心動揺の正確な値を知るには，重心の位置の測定と，重心の動きを構成する3つの成分すなわち直立時人体の左右方向への動き（X軸成分），前後方向への動き（Y軸成分）および上下方向への動き（Z軸成分）を正確に記録することが必要である。前者については，通常身長と体重より重心の高さを推定する方法がとられる。後者については，何らかの手段で各成分を記録する訳であるが，直立静止時にはZ軸成分がX軸成分やY軸成分に比較してきわめて小さいので，通常X軸成分とY軸成分について記録されている。

The displacement of the body's center of gra-vity in normal subjects was calculated by using a computer under the following four conditions:

1. In normal standing position.

2. The head tilted towards the right, left, downward or upward.

3. Mann's position with the right foot or the left foot forward.

4. Standing on a platform that may be tilted 15°forward, backwards, and towards the right or left.

The values obtained in this way were compared to those of normal standing with the eyes opened or closed. The results showing their interrelation-ship are illustrated in the schemata.

The same method was applied to seek the ratio of Y-component to X-component of displacement and to comparisons of values obtained by the eyes opened or closed which made it possible to comprehend the characteristics of the body bala-nce.

The following results were obtained:

1. The relative of displacement in the center of gravity of the body: Standing with the feet together with eyes open,the sway of the body anteriorly and posteriorly was more prominent than that to the sidway; with the eyes closed the direction of the sway became reversed.

With Mann's position the values obtained by holding either the right or the left foot forward were greater with the eyes opened than closed.

2. The ratio of the Y-component to X-compo-nent in displacement:

Standing with the feet together the body sway was larger towards the lateral direction than the other, similar to that of the Mann's position with the eyes closed.

With the tilting platform there was no signifi-cant difference in the values obtained with the eyes, either, opened or closed.

3. The ratio of values with the eyes opened to those of closed:

There was no significant difference in the X-component relative to the position of the head. With Mann's position, a normal range bordering on the larger upper limit was obtained with the right foot forward. In the Y-component ratio there was a characteristic smaller range.