1セグメントモデルを用いて投球時の外反ストレスを推定する方法論

抄録

The purpose of this study was to test the validity of using a one- and a two-segment models for determining elbow joint valgus stress during baseball pitching. The one-segment model consisted of a single segment representing the ball, hand and forearm together as a rigid segment. The two-segment model consisted of a distal segment representing the ball, hand and forearm together as a rigid segment and a proximal segment representing the upper arm. In addition, a three-segment model, which is the most widely and frequently used model for determining the valgus stress of baseball pitching, was defined to provide a reference value for testing the validity of the fewer segment models. The three-segment model was comprised of a distal segment representing the ball and hand together as a rigid segment, a mid-segment representing the forearm and the proximal segment representing the upper arm. Fourteen university students with the baseball experience were asked to throw a baseball with their maximum effort and a motion capture analysis system (VICON, Oxford Metrics) was used to measure the motions of the segments. The result showed that the maximum values of the valgus stress determined with one- and two-segment models (approx. 64 Nm for fast balls) were significantly greater than the corresponding value determined with three-segment model (47 Nm), but the correlations among the three models were found to be significantly high (r > 0.83, p < 0.01). These findings suggest that the fewer segment models can be used to compare the magnitude of valgus stress among subjects and among pitches for evaluation of risk of elbow injuries.