Bat design and ball exit velocity in baseball: Implications for player safety
R.L. Nicholls* , B.C. Elliott & K. Miller
University of Western Australia
Wooden bats have been used in baseball since the founding of the game in nineteenth-century America. These bats are still exclusively used by professional players, and in the Olympic Games and World Championships. More durable metal bats were introducted into baseball in 1972, and are used in most non-professional and youth baseball leagues.
Metal bats have been the subject of recent research as concerns arise over increasing ball exit velocity and player safety. The National Centre for Catastrophic Sports Injury Research ranked baseball ninth in nonfatal injuries to US collegiate athletes in 1997. However, baseball had the highest fatal injury rate of the 13 men’s sports surveyed (0.63 fatal injuries per 100,000 participants), exceeding that of gridiron and ice hockey (NCAA News, June 8, 1998). The US Consumer Product Safety Commission reported 14 fatalities in children from blunt impact by a baseball to the head or chest between April 1994 and April 1995 (Van Amerongen, Rosen, Winnik & Horwitz, 1997).
As the closest infielder to the hitter, the pitcher is at greatest risk of being injured by the batted-ball. In 1998, 375 Division I collegiate pitchers were struck by linedrives (hard-hit, low-trajectory balls). Such impact injuries comprise about 3% of all injuries to pitchers, and this rate has remained relatively constant since 1972 (Dick, 1999). However, increasing sophistication in metal bat design indicates the risk to pitchers may be greater when facing hitters using metal bats. ’Ball exit velocity (BBV) for balls hit with metal bats has been demonstrated higher than from wood bats (Bryant, Burkett, Chen, Krahenbuhl & Lu, 1977; Elliott, 1979). BBV values obtained from wood bats ranged between 39.62 - 44.17 m/s (143 - 159 km/h). At a distance of 16.46 m, minimum movement time for a pitcher to complete a protective motion against a linedrive is approximately 400 ms (Cassidy & Burton, 1989). This represents a ’safe’ BBV of approximately 42 m/s (151 km/h). Greenwald, Penna & Crisco (2001) quantified average ball exit velocity from metal bats as 47.61 m/s (171 km/h), with even high-school hitters achieving BBV exceeding 160 km/h. It is evident ball exit speeds from metal bats present a particular danger to the pitcher.
Differences in elastic or vibrational characteristics of the bat constituent material have been proposed as factors in the superior performance of metal bats (Ashley, 1991). However during a high-speed impact, the baseball may be in contact with the bat for as little as 2 ms (Greenwald, Penna & Crisco, 2001). Adair (1994) estimated the impulse generated by a ball striking a bat held firmly in the hands may take up to 8 ms to propagate from the point of impact in the barrel, to the hands, and back to the impact point - by which time the ball will have already departed. These findings suggest factors beside bat material properties may affect ball exit velocity.
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