動作スピードを変化させた立ち上がり動作における運動戦略の検証  [in Japanese] Effect of movement speed on the biomechanics of rising strategies from a chair  [in Japanese]

【目的】動作スピードを変化させた立ち上がり動作の殿部離床時点における身体重心と支持基底面との位置関係から,その運動戦略型を検証する。【対象】健常成人18名(男性9名,女性9名。平均年齢23歳)。【方法】座面高は被験者の下腿長とし足部の位置は任意として起立させた。動作スピードは自然な速さで起立,できるだけ速くまたはゆっくりの3条件とした。床反力計を含むVICON動作解析システムにて計測し下肢関節角度変位や身体重心(以下CM)位置を算出した。【結果】殿部離床時点のCM位置関係に各条件間で有意差があった。一方,CM進行最大速度との相関関係には有意差は認められず,運動戦略は3型に分類された。【考察】殿部離床時点のCM-支持基底面位置関係には,動作スピードに応じた速度依存性があると考えられた。しかし,被験者ごとの型分類からは,選択される運動戦略は一貫していなかった。これらから必ずしもスピードに応じて戦略を変えるのではなく,その個人ごとに固定した運動戦略を用いていることが示唆された。

The purpose of this study was to examine the rising strategies from chair that when the motion speed was changed. Eighteen healthy adults aged 19 to 33 years (mean 23ys) participated. The body's center of mass (CM) location and velocity were computed for rising from chair made at three movement speeds (natural, fast, slow) with the aid of a motion analysis system (VICON). The time when the subject lost contact with the chair were detected from two force-platforms output. The rising strategies was identified by the CM-base of support (BOS) distance. Horizontal component of CM momentum and the CM-BOS distance were significant for all speeds conditions. The displacement of the CM was positioned more anteriorly at lift-off during slow chair rises. As the speed of chair-rise increases, the CM was positioned more posteriorly at lift-off. However, correlation of the CM-BOS distance with CM momentum was no significant. So the type of strategies characterized by the CM-BOS distance. Three types of strategies were identified, 'representative', 'N-F type', 'N-S type'. In latter two types, it seems not to have separated with Natural, Fast or Slow condition even if the movement speed changed. The results of the study suggested that a linear relation might not necessarily exist to the relation between the rising strategies and CM-BOS distance.