- 一般社団法人 日本体育学会
- 体育学研究 (ISSN:04846710)
- vol.61, no.2, pp.517-535, 2016 (Released:2016-12-14)
The purpose of this study was to clarify the profiles of lower limb and trunk motion during baseball pitching in relation to differences between the mound and the flat ground, and to determine the motion characteristics while pitching from the 2 locations. The subjects were 12 baseball pitchers (age 18.6±2.5 yr, height 173.4±6.5 cm, weight 74.7±11.0 kg) who belonged to high school or university baseball teams. Three-dimensional positions of 36 reflective markers attached to each subject were tracked by an optical motion capture system (Mac3D System) with 12 cameras. The ground-reaction forces (GRF) of the pivot and stride legs during pitching were determined using 2 multicomponent force plates. Pitching motion was divided into two phases: phase 1 was defined as the period from when the knee of the stride leg reached maximal height (MKH: 0%time) until the point when the stride foot made contact with the ground (SFC: 100%time), while phase 2 was defined as the period from the SFC until the point when the ball was released (REL: 200%time). Ball velocity was measured using a radar gun. The results were as follows: 1) The maximum and average ball velocities were significantly higher when pitching was performed from the mound than from the flat ground (p<0.05). 2) Hip/knee flexion angles and hip abduction/extension angular velocities on the pivot leg were significantly greater for mound pitching than for flat ground pitching, and the hip/knee extension angle and hip adduction/internal rotation/flexion angular velocities on the stride leg were significantly greater for the former (p<0.05). 3) The GRF of the stride leg was significantly greater for mound pitching than for flat ground pitching (p<0.01). 4) Upper torso and pelvis angle/angular velocities at SFC and the maximum pelvis, upper torso and trunk tilt angular velocities were significantly greater for mound pitching than for flat ground pitching (p<0.05). The present results indicate that baseball pitchers show biomechanical differences in the kinematic and kinetic profiles of the trunk and lower limbs when pitching from the mound in comparison with the flat ground, and that high school or collegiate baseball pitchers can increase their pitched ball velocity by using the height of the mound.