Submitted by: Mark McDowell, Ph. D., Michael V. Ciocco, Ph.D. & Bryan Morreale
In the past few years, there has been a composite bat construction revolution in the softball bat industry. While composite material bats have enabled softball bat performance to increase much to the delight of hitters, they can pose a significant safety risk to defensive players and especially the pitcher. A controlled experiment using two composite softball and two wooden softball bat models has been conducted in order to present experimental data on the field performance of various bat/ball combinations. Three types of softballs were used in this study; low-compression, cork-centered softballs, mid-compression polyurethane softballs and high-compression polyurethane softballs ranging from 1134 to 2389 N/0.64 cm (255 to 537 lbs/0.25 in) compression. Three experienced softball players were chosen as test subjects for this study. Initial batted-ball velocities ranged from 126.2 to 164.3 km/h (78.4 to 102.1 mph), corresponding to an available pitcher reaction time ranging from 0.456 to 0.350 seconds. The goal of this study is to present the potential safety and injury risks associated with using composite softball bats in the sport of softball.
Over the past few years, the sport of softball has undergone a revolution in bat construction. When the sport was originated, wood was the major construction material of softball bats. In the 1980s, softball bats constructed from aluminum-based materials were introduced followed by titanium-based bats in the mid-1990s. However, the excessive batted-ball velocities (BBV) resulting from the use of titanium-based bats led to them being declared illegal and unsafe by all of the major governing bodies of softball due to their increased injury potential. From the late 1990s to the present, bats constructed of composite materials are the most commonly used bats and have been responsible for countless injures and even fatalities in the sport (Dawson, R., 2003). Composite softball bats are currently being used at all levels of softball from fast pitch softball in the Olympics, collegiate and high school levels to the recreational weekday slow-pitch softball league. Although there are over 19 million softball players in the U.S. (Ramsey J. and Smith G., 2003), there is no national database on injuries and fatalities in the sport and this complicates the issue of establishing a national safety standard for the sport of softball.
The authors have conducted a batted-ball field test study using three different compression ranges of softballs in order to show the potential risks involved when using wood and composite softball bats by measuring the BBV for each of the bat/ball combinations and using these speeds to calculate the time a pitcher has to react to a batted-ball, which the authors call available pitcher reaction time (APRT).
A field study to analyze composite and wood softball bat performance using three different softball compression values was conducted. Three experienced softball players with an average height of 1.85 m (6 ft, 1 in) and weight of 99.8 kg (220 lbs) were chosen as subjects for this study and were required to record over twenty-five BBV measurements with each bat-ball combination over five test rounds. In each round, at least five recorded hits out of a maximum of seven from each tester was recorded in order to minimize fatigue. In addition, there was a mandatory minimum five-minute rest period between each round. In order to be considered a valid test, the standard deviation of the top five (20%) BBV readings from each bat-ball combination had to be within 3.9 km/h (2.4 mph) based on a statistical margin of error at the 95% confidence level.
All softballs were compression-tested according to the ASTM standard for ball testing (ASTM F 1888-02, 2002). Ball compression is defined as the amount of force necessary to compress a softball 0.64 cm (0.25 in) and is measured in N/0.64 cm (lbs/0.25 in). Three different softball models with compression values ranging from 1134 to 2389 N/0.64 cm (255 to 537lbs/0.25 in) were chosen for this study (sixty balls per model). All softballs were purchased from retail sporting goods stores and are listed in Table 1.
The composite bats chosen for the study were an 850 g (30 oz) EastonÒ Synergy+ and a 794 g (28 oz) MikenÒ Freak model. The wooden bats chosen were an 850 g (30 oz) TPSÒ and an 850 g (30 oz) BWPÒ Maple model. These bats were selected due to their popularity amongst recreational softball players and were purchased from retail sporting goods stores.
Batted-ball velocity measurements
A Jugs® professional radar gun having an accuracy to within 0.8 km/h (0.5 mph) was used to measure BBV. Before each round, the Jugs® radar gun was calibrated using a certified 98.2 km/h (61 mph) K-band tuning fork. Readings were taken approximately halfway between the batter’s impact point and the pitcher’s mound.
A Jugs® Professional softball pitching machine capable of accurately and reliably pitching a softball in the 26 to 40 km/h (16 to 25 mph) range through the hitting zone was used. This range was used in order to simulate the actual pitch speeds that occur in a slow-pitch softball game.
Available Pitcher Reaction Time: Using the fact the pitcher’s mound in slow-pitch softball is 15.24 m (50 ft) away from home-plate; the available pitcher reaction time (APRT) for a particular bat-ball combination can be calculated once the BBV is recorded. The APRT is a safety metric that can be used to determine if a bat-ball combination is considered safe or unsafe. As a general rule, the higher the BBV’s, the lower the APRT’s, and thus, the higher the risk of injury.
The initial BBV and APRT data is listed in Tables 2 through Table 6. The initial BBV using cork-centered, mid- and high-compression softballs using the wooden softball bats ranged from 126.0 to 136.8 km/h (78.3 to 85.0 mph), which translates into an available pitcher reaction time ranging from 0.456 to 0.421 seconds. The initial BBV using cork-centered, mid- and high-compression softballs using the composite softball bats ranged from 143.5 to 164.3 km/h (89.2 to 102.1 mph), which translates into an available pitcher reaction time ranging from 0.401 to 0.350 seconds. It should be noted that at the time of this study, the two largest softball associations, the United States Specialty Sports Association (USSSA) and the Amateur Softball Association (ASA) of America mandated that any bat achieving an initial BBV of 137.2 km/h (85.2 mph), which translates into an APRT of 0.420 seconds (USSSA, 2003), (ASA, 2003) is considered unsafe. Based on our data, the composite bats would be considered unsafe for all balls tested while the wooden softball bats would be considered safe for all balls tested.
Discussion and Implications
The main finding of this study is that unsafe batted-ball velocities were achieved using composite softballs bats. The initial BBV of the composite bats were as much as 27.2 km/h (16.9 mph) higher than the softball association’s goal of 137.2 km/h (85.2 mph), which translates into an available pitcher reaction time of 0.420 seconds. However, very little research has been done with respect to quantifying how much time a pitcher, or any player for that matter, needs to safely defend themselves from a batted ball. To date, there have been three published studies in the sport of baseball using ball exit speeds and APRT.
A recent study [Nicholls, et al., 2003] investigated player safety concerning ball exit speed for the sport of baseball and concluded that the maximum safe initial batted-ball velocity that a pitcher can react to is approximately 148 km/h (92 mph), which translates into an APRT of 0.425 seconds. They also concluded that a “certified” metal bat swung by an experienced hitter may produce ball exit velocities exceeding that demonstrated by a robotic hitting machine, which is currently used for establishing safe batted-ball velocities. A second study [Owings, et al., 2003] was conducted investigating the available pitcher reaction time as a consideration in design constraints for baseballs and baseball bats for various age groups. They found that for the 16-year age group, a minimum reaction time of 0.409sec. is necessary to reduce the potential for serious or catastrophic injury. A third study conducted by the NCAA tested a variety of bats on a specially designed batting machine located at the University of Massachusetts in Lowell, [Mississippi State University, 2002]. The recommendation from this study was to drop the exit speed to no more than 149.7 km/h (93 mph) in collegiate baseball, which translates into an APRT of 0.420 seconds.
Two recent studies [Hultsch, et al., 2002] and [Luchies, et al., 2002] address the differences in reaction time between younger and older adults and conclude that reaction time is considerably reduced or varied as a person gets older. Using this research on reaction time and the results of Nicholls and Owings, it can be theorized that when composite bats are in use and a ball is hit directly back at the pitcher or infielder, this can pose a significant risk for injury to older adults which comprise the majority of the millions of recreational softball players.
The results from the composite bat data show that none of the average pitcher response times are slower than the published results for the sport of baseball. In fact the worst case, composite/high-compression ball/BT3, has an APRT of 0.357 sec., which is over 18% lower than the suggested value of 0.425 sec.
For the wooden bat, for all the balls, the APRTs are very close to or better than those suggested by published baseball studies. The lowest APRT is 0.421 sec. and the highest is 0.457 sec. When compared to the wooden softball bats, the composite bats outperform them by as much as 30% which should at least lead to a meaningful discussion on the safety of the sport.
The implications of this study are that the use of composite softball bats is creating an unnecessary safety risk for players and that many players, coaches, league directors and parents are probably not aware of the risk associated with the use of composite softball bats.
A controlled field-test study analyzing the performance of composite and wooden softball bats along with using low-, mid- and high-compression softballs was conducted in order to analyze the various bat/ball combinations. Batted-ball velocity was measured and available pitcher response time calculated and compared to recommended safety limits imposed on the sport as well as published baseball safety studies. The results from this study concluded that using composite softball bats, batted-ball velocities exceeded the recommended safety limits by as much as 27.2 km/h (16.9 mph) or 0.070 seconds. It can be concluded that regardless of the ball used, composite bats may pose an increased safety risk to defensive players, especially the pitcher, in the path of a batted-ball hit.
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- ASTM F 1888-02 (2002). Standard Test Method for Compression-Displacement of baseballs and Softballs. ASTM International.
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- United States Specialty Sports Association (2003). Bat Performance Factor Test. URL: http://www.usssa.com