Dr Laudner is from the School of Kinesiology and Recreation, Illinois State University, Normal, and Mr Sipes is from the Physical Education Department, Eastern Illinois University, Charleston, Ill.
The authors have no financial or proprietary interest in the materials presented herein.
The study was funded by a grant from the National Federation of State High School Associations. The authors thank Anthony Holman and the Illinois High School Association for their help with this project.
Address correspondence to Kevin G. Laudner, PhD, ATC, School of Kinesiology and Recreation, Illinois State University, Campus Box 5120, Normal, IL 61790; e-mail: firstname.lastname@example.org.
In the 1970s, the first aluminum baseball bat was introduced to improve bat durability due to the occurrence of wood bat breakage. Advancements in aluminum bat construction led to the use of other alloy bat composites, including titanium, graphite, carbon fiber, fiberglass, and synthetic fiber, which were constructed to be lighter and stronger than their predecessors. Along with these advances in bat construction, many individuals speculated that non-wood bats produced greater offensive statistics, giving batters an unfair advantage due to increased ball exit speeds after contact.1–3
Although past research has reported mixed results when comparing ball exit speeds between wood and non-wood bats,1–5 there was clearly a rise in offensive statistics during the 1990s when the non-wood bats hit their pinnacle in terms of construction advancement.6 These higher offensive statistics, along with several studies showing faster ball exit speeds,1–3 began a debate about the safety of the position players, primarily pitchers who were closest in proximity to the batter. Past research has shown pitchers to have the highest absolute number of game-related injuries due to batted balls (29.5%).7 Boden et al8 studied high school and collegiate baseball players during a 21-year period and found that being struck by batted balls was the most common reason for catastrophic injury to pitchers (34.2%).
Debates over the potential advantages and dangers of using non-wood bats eventually led the National Collegiate Athletic Association (NCAA) to place restrictions on the ball exit speed that each bat could produce.9 Such restrictions on the manufacture of non-wood bats have resulted in a subsequent decrease in run production and are believed to produce durable non-wood bats that perform more like wood bats.6 However, despite these manufacturing restrictions, pitchers continue to sustain injuries caused by batted balls.7
Despite the long debate about the safety and advantage of using non-wood bats, there are currently no data comparing the injury rates or offensive production statistics of wood versus non-wood bats. As such, the purpose of this study was to determine whether differences exist in the injury rates sustained during high school baseball games played with non-wood bats compared with those played with wood bats. Furthermore, the authors of this study compared offensive game statistics between both types of bats and also determined the incidence of wood bat breakage. The authors hypothesized that non-wood bats, compared with wood bats, would produce a statistically higher incidence of injuries and would increase offensive game statistics. Identification of differences in injury rates, offensive statistics, and wood bat breakage rates may provide some clarity regarding the debate about non-wood baseball bat use.
Materials and Methods
Thirty-two high school varsity baseball teams from various athletic conferences in Illinois voluntarily agreed to participate in this study during the 2007 baseball season. Each team was required to use wood bats for all conference games and non-wood bats for all nonconference games.
Several instruments were used in this study, including an injury report form, a game statistics form, and a bat usage form. The injury report form consisted of eight injury-related questions to determine the type, mechanism, and extent of all injuries sustained by fielders (ie, pitchers, catchers, infielders, outfielders) during the season. Specific questions addressed the position of the injured player, whether the injury required the player to be removed from the game, how much time was lost from competition due to the injury, the specific anatomical structure injured, the specific type of injury, the mechanism of injury, the type of bat used, and the type of care provided for the injury. Although coaches completed the survey questions regarding type and extent of injury, these factors were determined by qualified medical personnel (eg, certified athletic trainer, medical doctor) associated with the baseball team and then relayed to the coach.
The game statistics form consisted of date, type of game (ie, conference or nonconference), total number of at-bats, hits, and runs scored. In addition, data recorded on the game statistics form included whether an injury was sustained, whether fielders were hit by a batted ball, the game duration (defined as the number of minutes from the first pitch of the game until the final out at the end of the game), and the number of broken bats. The bat usage form was used to determine the specific date, the number of players using a bat, and the total number of at-bats for each bat.
All teams participating in this study used bats that were ball exit speed ratio (BESR) certified9 as mandated by the National Federation of State High School Associations (NFHS). The BESR limits bat diameter to 2.625 inches, a weight-to-length unit differential of no greater than 3 units, maximum ball exit speeds that mimic those of wood bats, and standardized moment-of-inertia requirements.9 These restrictions are believed to produce non-wood bats that perform more like the top models of wood bats.9
All participating teams agreed to use wood bats for all conference games and non-wood bats for all nonconference games. At the conclusion of each game, coaches recorded several pieces of game-related data and submitted these data to the investigators of this study. These recordings included a game statistics report for every game, an injury report for all games that resulted in an injury, and a bat usage report for all games in which a wood bat was used. Specific game-related injury data, such as diagnosis of injury and length of time lost from competition were not recorded and returned until this information was known. All participating coaches provided informed written consent as mandated by the university’s institutional review board prior to participation, and follow-up e-mail reminders were sent periodically throughout the season.
Once submitted, data were imported into the SPSS software package for statistical analysis (version 11.5, SPSS Inc, Chicago, IL). A chi-square analysis was used to examine the significance of any difference in the injury rates, due to batted balls, among games played with non-wood bats and games played with wood bats. The incidence rate of injury for both wood and non-wood bats were calculated as the number of batted ball injuries × 1000 per total number of exposures. Relative risk (RR) was then calculated to compare the incidence of injury between bat types. Level of significance was set at α<0.05 a priori. Dependent t tests were used to determine significance of the offensive statistics (hits per game, runs per game, game duration). Because multiple tests were calculated, α1 was adjusted using a Bonferroni’s correction (P < .05/3, or P < .017) to protect against Type I error.
Wood bat data were recorded by each of the 32 teams. However, only 11 teams submitted both wood and non-wood bat data (wood = 143 games; non-wood = 144 games). As such, only the data submitted by these 11 teams were used for comparison of injuries and offensive statistics during wood and non-wood bat games (Table). Wood bat data from all 32 teams were used to determine bat breakage rates.
Table: Descriptive Injury and Offensive Statistics for Games Played with Non-Wood and Wood Bats
There were 2 injuries resulting from a batted ball during the non-wood bat games and 1 injury of a similar nature during the wood bat games. The incidence rate of injury when using non-wood bats was 0.43 injuries per 1000 at-bats (95% CI, 0.02–9.28). In baseball games using wood bats, the incidence of injury was 0.22 injuries per 1000 at-bats (95% CI, 0.0009–54.43). These data produced no observed statistically significant difference in the number of injuries sustained between non-wood and wood bat games (χ2 = 0.29; P = .59; RR = 1.91; 95% CI, 0.18–20.13). The results of the 2 batted ball injuries when using non-wood bats were minor contusions sustained by pitchers to the upper leg and forearm and did not result in either pitcher being removed from the game. A similar result occurred for the one batted ball injury sustained when using a wood bat, as the pitcher received a minor contusion to the knee. The 3 other injuries reported that were not related to a batted ball consisted of 1 chronic rotator cuff strain and 2 fractured jaws caused by an athlete being hit by an errant throw and the other athlete being hit by a wild pitch.
Offensive game statistics showed no statistical difference in the number of runs scored per game (P = .03) with non-wood bats compared with wood bats. However, games using non-wood bats had a significantly greater number of hits per game (2.3 more hits per game; P = .005) and a longer game duration (12.4 minutes longer per game; P = .009).
Among the wood bat data for all 32 teams, 368 broken bats were reported during a total of 13,009 at-bats. This resulted in an incidence of breakage of 28.3 bats for every 1000 at-bats. As such, a wood bat was used for an average of 35.5 at-bats before breakage.
Controversy continues to mount regarding the safety and advantages of using non-wood baseball bats. Many individuals have criticized non-wood bats for increased ball exit speeds and the perceived increase in injuries and offensive production. Unfortunately, previous research regarding exit speeds has used various methods, leading to contradicting results and an increased confusion about what is best for athletes.1–5 Regardless, the results demonstrate that non-wood bats do not have a statistically higher prevalence of injuries compared with wood bats. However, non-wood bats did produce more hits per game and a longer game length. Furthermore, wood bats tended to break on a semi-frequent basis.
Several studies have shown that prior to bat limitation standards, non-wood bats used by various levels of baseball players produced higher ball exit speeds than wood bats.2,3 These studies reported ball exit speeds of approximately 4 to 9 mph faster when using non-wood bats. Such increases in ball exit speed have been speculated to partially result from stored energy in the bat being transferred to the ball.10 As a ball contacts a bat, the ball compresses, resulting in lost internal friction.11 However, in a hollow bat, such as non-wood bats, the bat also compresses on impact (trampoline effect), decreasing the lost energy and benefits from the stored energy that is then returned to the ball.10 Despite these findings and theories, subsequent research has reported conflicting results indicating that hollow wood bats do not display a similar trampoline effect.12 As such, Weyrich et al5 and Hester and Koenig4 have performed similar studies examining ball exit speeds using stationary bats and found no difference among the various bat types.
Although the study did not examine ball exit speeds, the results demonstrated a significantly higher number of hits per game when compared with wood bats. However, there was no difference in the number of batted ball injuries between bats. The lack of significance in batted ball injuries may partially be explained by the increased use of non-wood bats. More specifically, it is conceivable that the more these non-wood bats are used, the more accustomed pitchers and position players become in the high exit speeds and the subsequent decrease in reaction time necessary for batted balls. This lack of significance may also be explained by the study’s relatively small sample size and the overall few total injuries.
With discrepancies between ball exit speed studies and research examining the trampoline effect of bats, speculation arose that non-wood bats could be swung at faster speeds than wood bats due to a different weight distribution, thereby producing greater ball exit speeds.2,3 Wood bats tend to have heavier barrels, thereby increasing the torque necessary to accelerate the bat. Therefore, a decreased linear bat velocity would result in a decreased ball exit speed.13 Fleisig et al14 supported these results, stating that the moment of inertia of a bat is directly related to bat velocity; the authors recommended regulating this factor to minimize bat velocity and subsequent ball exit speeds.
Due to the increases in offensive statistics and the speculation of increased risk of injury during the mid-to-late 1990s, the NCAA was compelled to place restrictions on the construction of non-wood bats. The NFHS quickly adopted these restrictions, which included limiting bat diameter, weight-to-length differential, moment-of-inertia, and ball exit speed.9 These restrictions seemed to address all previous concerns regarding non-wood bats, potentially producing non-wood bats that could perform more like wood bats. Although there has been an observable decrease in offensive production in NCAA baseball games,6 Dick et al7 showed that there was no significant change in injury rates when comparing the prevalence of injury prior to and several years following the mandated restrictions. Although the study did not look at injury rates when using non-wood bats prior to the BESR certification, the results suggest that BESR-certified bats do not produce a significantly greater amount of batted ball injuries than do wood bats. However, the non-wood bats did produce more hits per game and a longer game duration, which may have been a direct correlation of the increased hits per game.
Bat breakage has always been a concern among athletic directors, coaches, and players. Many coaches and administrators argue that the use of wood bats is not cost feasible for some athletic programs and, therefore, non-wood bat use is the only alternative. The study’s results suggest that wood bats tend to break every 35.5 at-bats; however, the authors did not assess the breakage or crack rate of the non-wood bats used in this study.
The authors acknowledge a few limitations in their study design. The sample size was relatively small given the overall number of teams who were recruited to provide both non-wood and wood game data. As such, the statistically insignificant findings may be a characteristic of the insufficient sample size. Furthermore, this study was conducted using only high school baseball players. The use of non-wood bats at higher levels of competition, such as the collegiate level and other adult leagues, may produce different results due to higher bat swing velocities, therefore creating faster ball exit speeds. In addition, because all of the bats used for this study were BESR certified, games that do not regulate the specific characteristics of the non-wood bats to perform similarly to their wood counterparts may produce more injuries and even greater offensive statistics. There also may have been confounding factors between the conference and nonconference games, such as extra-inning and slaughter rules, as well as familiarity of wood bat usage among players. These factors should be considered when interpreting the study’s results. However, regarding player familiarity with wood bats, the participating teams frequently used wood bats during practices prior to wood bat games, although the exact usage was not recorded for this study. Finally, the frequency of non-wood bat breakage was not assessed. These bats may have a tendency to dent or deform due to repeated use or use in extreme weather and should be considered when contemplating the expense of different types of bats.
The results of this study indicate that few injuries are reported among high school baseball players regardless of the type of bat used. The study’s results also demonstrate that using non-wood bats during high school baseball games does not produce a statistically significant greater number of batted ball injuries compared with wood bats, although a relatively small sample size was used for analysis. As such, with respect to the limitations of the study, the risk of potentially catastrophic and fatal injuries due to batted balls needs to be further addressed to ensure the safety of all participants. However, the results demonstrate that regardless of the type of bat used, few injuries occurred during high school baseball games. Games using non-wood bats did produce more hits per game and a longer game duration. Finally, wood bats had a fairly common incidence of breakage. This study may provide further insight into the controversy over the use of non-wood baseball bats, but more research is necessary to fully comprehend the advantages and disadvantages of non-wood bats.
- Bryant FO, Burkett LN, Chen SS, Krahenbuhl GS, Lu P. Dynamic and performance characteristics of baseball bats. Res Q. 1977;48:505–509.
- Crisco JJ, Greenwald RM, Blume JD, Penna LH. Batting performance of wood and metal baseball bats. Med Sci Sports Exerc. 2002;34:1675–1684. doi:10.1097/00005768-200210000-00021 [CrossRef]
- Greenwald RM, Penna LH, Crisco JJ. Differences in batted ball speed with wood and aluminum baseball bats: A batting cage study. J Appl Biomech. 2001;17:241–252.
- Hester LR, Koenig K. Performance measurement of baseball bats. Journal of the Mississippi Academy of the Sciences. 1993;38(2):7–10.
- Weyrich AS, Messier SP, Ruhmann BS, Berry MJ. Effects of bat composition, grip firmness, and impact location on postimpact ball velocity. Med Sci Sports Exerc. 1989;21:199–205.
- Gardiner A. CWS “good baseball” replaces “gorilla ball.”; USA Today. June16, 2005;C9.
- Dick R, Sauers EL, Agel J, et al. Descriptive epidemiology of collegiate men’s baseball injuries: National Collegiate Athletic Association Injury Surveillance System, 1988–1989 through 2003–2004. J Athl Train. 2007;42:183–193.
- Boden BP, Tacchetti R, Mueller FO. Catastrophic injuries in high school and college baseball players. Am J Sports Med. 2004;32:1189–1196. doi:10.1177/0363546503262161 [CrossRef]
- National Collegiate Athletic Association. National Collegiate Athletic Association Standard for Testing Baseball Bat Performance. Indianapolis, IN: National Collegiate Athletic Association; 2006.
- Cross R. Impact of a ball with a bat or racket. American Journal of Physics. 1999;67:692–702. doi:10.1119/1.19354 [CrossRef]
- Russell DA. Physics and acoustics of baseball and softball bats. http://www.kettering.edu/~drussell/bats.html. Published 2002. Updated September 10, 2008. Accessed July 27, 2009.
- Nathan AM, Russell DA, Smith LV. The physics of the trampoline effect in baseball and softball bats. Engineering of Sport. 2004;2:38–44.
- Nicholls RL, Elliott BC, Miller K. Impact injuries in baseball: Prevalence, aetiology and the role of equipment performance. Sports Med. 2004;34:17–25. doi:10.2165/00007256-200434010-00003 [CrossRef]
- Fleisig GS, Zheng N, Stodden DF, Andrews JR. Relationship between bat mass properties and bat velocity. Sports Engineering. 2002;5:1–8. doi:10.1046/j.1460-2687.2002.00096.x [CrossRef]
Descriptive Injury and Offensive Statistics for Games Played with Non-Wood and Wood Bats
|NON-WOOD BATS||WOOD BATS|
|TOTAL||AVERAGE PER GAME||TOTAL||AVERAGE PER GAME|
|Fielders struck by hit ball||2||0.014||1||0.007|
|No. of injuries||5||0.03||1||0.007|
|Duration of game (minutes)a||18,050||125.4||16,159||113|