This case study investigates, characteristics of time dependent changes in performance and throwing motion, and possible parameters of the changes caused by prolonged periods of fielding infield fungoes. A fungo is a ball tossed into the air by the batter, hit as it comes down, and is used for base ball fielding practice.
One college baseball player, who is an infielder, participated in this study. We carried out 10 sessions of fungo drills with one minute break between each session. One session included a fungo every 17 seconds for 5 minutes. We analyzed 10 throwing motions for each session with the three-dimensional motion analysis.
The characteristic changes over time are as follows. In performance, ball velocity decreased significantly, whereas throwing angle increased considerably. In throwing motion, there is a significant decrease in pelvic rotation angle at the instant of maximum shoulder external rotation (MER) and at ball release (REL), shoulder abduction angle at the instant of stride foot contact (SFC), MER, and REL, the amount of angle variation of forward trunk tilt during the acceleration phase, and the moving speed of the middle point of both greater trochanters during the step phase and throwing phase. There is also a great increase in the maximum backward angle in the throwing phase of shoulder horizontal abduction and pelvic rotation. Furthermore, knee and hip joint angles of the stride leg at SFC, trunk twist angle at SFC, MER, and REL, and the amount of angle variation of shoulder horizontal adduction in the acceleration phase increased significantly.
Based on the above results, the following changes were noted in throwing motion 1) from using the step speed to expanding motion range of joints, 2) to “relying-on-the-arm" movements due to the decrease in the pelvic forward rotation angle caused by the knee extensions, 3) with tendencies for distance throw, and 4) movement changes which may become a risk factor for shoulder throwing injuries.
