WEYRICH, A. S., S. P. MESSIER, B. S. RUHMANN, and M. J. BERRY. Effects of bat composition, grip firmness, and impact location on postimpact ball velocity.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 199–205, 1989. The purpose of this investigation was to examine the effects of bat composition (aluminum and wooden), impact location [center of percussion (COP), center of gravity (COG), and end of the bat (E)], and grip firmness [tight (T) and no tension (NT)] on postimpact ball velocity. With the bats placed alternately in NT and T conditions, baseballs were delivered at a speed of 27.1 m · s-1from a pitching machine positioned 1.5 m from the bat. Highspeed photography (400 fps) was performed using a Locam camera positioned 7.54 m from and perpendicular to the principal plane of ball movement. A three-way ANCOVA revealed significant (P< 0.01) differences in postimpact ball velocity between the three impact locations, with the COP yielding the greatest values, followed by the COG and E. Moreover, there was a significant (P<0.01) grip vs bat interaction. A simple-effects procedure revealed the following results: 1) the T grip produced greater (P<0.01) velocities than the NT grip across the aluminum (Al) bat; 2) there was no difference (P>0.01) between the T and NT grips across the wooden (W) bat; 3) the W bat produced greater (P<0.01) velocities than the Al bat across the NT grip; and 4) there was no difference (P>0.01) between the Al and W bats across the T grip. It was concluded that: ball-bat contact at the COP produces the greatest postimpact ball velocity of the three impact locations studied; a T grip enhances postimpact ball velocity relative to a NT grip, especially when using an Al bat; and postimpact ball velocity produced by W and Al bats favors W bats.