Effects of Changes in Bat Grip Position on Baseball Bat Swing Timing, Ground Reaction Force, and Muscle Activation Characteristics*

Abstract

This study aimed to clarify the eŠects of changing to a short bat grip position from the long bat grip position on baseball bat swing timing, peak ground reaction force with the front leg, and activation of the upper and lower limb muscles.Nine male college baseball players participated in this study. By using a batting simulator, the coincident timing task was to swing the bat coincidentally with the arrival timing of a moving target by using the long or short bat grip position. The batter performed 10 sets of four swings for a total of 40 swings for the coincident timing task. During the four swings, the batter swung the bat by using the long grip position in theˆrst, second, and fourth swings. Only in the third swing did the batter use the short grip position. The ground reaction force with the front leg was measured, and electromyograms of the upper and lower limb muscles were obtained during the coincident timing task.Our results indicated no signiˆcant diŠerences in absolute and variable timing errors between the long and short bat grip positions. In contrast, the constant timing error was signiˆcantly increased with the short bat grip position. Moreover, the time to peak ground reaction force and time to peak muscle activation of both the upper and lower limb muscles were signiˆcantly delayed when the short bat grip position was employed. Signiˆcant positive relationships were observed between the constant timing error and time to peak ground reaction force, which showed diŠerences between the second and third swings. No signiˆcant diŠerence in swing time was observed between the long and short bat grip positions.Theseˆndings indicate that changing to the short bat grip position from the long bat grip position will not improve the batter's swing timing. Furthermore, changing to the short bat grip position could delay the batter's swing timing, probably because the change causes a delay in swing preparation.

Examining Changes in Electromyography during Swing Performance in Various Strike Zone Locations of Collegiate Baseball Players

“…The swing time was defined as the time to peak ground reaction force to impact [19,24]. Results of this study showed the average percent activation of the stride leg during swing time of the VL close to 80% of MVIC, 40% of the BF, 80% of the MG, and 60% for the TA of their swing trials [18].The percent activation during the swing phase in our study was 160.321.9% for the H, 164.363.6% for MG, 20.393.6% for the VMO, and 20.334.1% for the TA. We chose to examine changes in electrical activity of both the vastus medialis and semitendinosus for their role in extending and flexing the knee respectively.…”

“…A study completed Ohta and Nakamoto 2015 [17] does not align with the results of our study. Investigators of this study wanted to examine differences in ground reaction forces and muscle activation characteristics of the stride leg vastus lateralis (VL), BF, and MG based on different bat grips in nine collegiate baseball players [18].Each participant swung a bat at a moving target to simulate a ball being thrown towards home plate. The swing time was defined as the time to peak ground reaction force to impact [19,24].…”

“…Participants that completed Ohta and Nakamoto's 2015 protocol initiated the swing with a batting simulator with a photoelectric tube system with a target running down a track and ending in the middle of home plate. This was designed to consider the reaction time of a batter before engaging in the swing [18].…”

“…Some of these distinguishing factors that enables athletes an increased likelihood of making contact with the ball include skill level, spatial accuracy of the bat, swing mechanics, and velocity of the bat approaching ball contact [2-14].The process of swinging a bat approaching ball contact requires distinct coordination of muscle activation for this task. In order to better understand the sequencing of this motion, a limited number of investigations examining electromyography have been conducted (EMG) [15][16][17][18][19].…”