From: Journal of Sport & Exercise Psychology Jul2007 Supplement, Vol. 29, pS92

In baseball hitting, a powerful bat swing needs to be produced by utilizing ground reaction force (GRF) and it should also be temporally coordinated relative to the flight of a pitch. Therefore, organizing a hitting movement to meet these task requirements is a key for a successful hitting performance. This leads to a presumption that a front-foot stepping motion adopted for utilizing GRF to produce power for a bat-swing motion should be temporally coordinated with respect to an oncoming pitch. The present study investigated the temporal organization of hitting movements by focusing on the timing of the stepping motion relative to the flight of pitches. Six participants hit pitches projected by a pitching machine with following task conditions: 1) hitting pitches traveling at a consistent speed and 2) hitting pitches traveling at fast/slow speeds, which were randomly delivered. The second condition was aimed at eliciting movement modulation to the difference in the pitches’ speeds. Ground reaction forces exerted by left and right feet during hitting movements was recorded by two force plates to measure the timing of the front-foot take-off and landing in the stepping motion. Hitting motions were also recorded by a high-speed camera for interpreting the change of GRF profile relative to the hitting movement. The comparison between the GRF profiles in the two task conditions revealed that the timing of the stepping motion and shifting weight forward for initiating the bat swing was modulated relative to the pitch’s speed. Temporal relation between successive motion phases was compensatory such that the early timing of landing the front foot relative to an oncoming pitch was followed by the late initiation of shifting weight onto the landed front foot, and vice versa. The timing variability in the successive motion phases progressively reduced up to the ball-bat contact. These results demonstrated the coordinative structure of the hitting movement for timing the bat swing relative to the pitch’s flight.