Abstract
In order to collect information concerned with the development of a measuring device for baseball pitching, pattern of motion and ball speed during a baseball pitch were estimated from acceleration measured at the wrist through multivariate analysis. The subjects were 26 college baseball players (eight pitchers, five catchers, nine infielders and four outfielders). Three accelerometers were attached to the wrist of each subject. The subjects then pitched fifteen times, with intensities ranging from weak to full, to a defensive net set up six meters distant. The accelerometers were arranged perpendicularly to each other on three axes : distal-proximal direction, ulnar-radial direction, and dorsalpalmar direction. The ball speed was measured with a laser device set between the subjects and the defensive net. The time of ball-release was detected using electrical conductive tape placed on the tip of each subjects index and middle fingers and the ball. After extracting the 18 parameters relating to amplitude and time that characterize the acceleration wave, the 26 subjects were classified into three groups-A, B and C-by cluster analysis, and ball speed was estimated in each group by multiple regression analysis. The estimation errors were 2.3 ± 1.8% in group A, 2.5 ± 2.3% in group B, 2.4 ± 2.4% in group C, and 3.4 ± 2.8% for all data. For estimating the ball speed, acceleration in the distal-proximal direction was more effective than that in the other two directions.
