Research on baseball hitting has reported that bat velocity (BV) is an important component for successful hitting (3,7,16). Baseball players from all levels traditionally swing weighted devices in the on-deck circle to warm up before stepping into the batter's box to hit. The type of warm-up device used by baseball players varies; however, it is usually a heavier implement such as a 453.6-g (16-oz) donut ring or 680.4-g (24-oz) Pow'r Wrap added onto their game bat, or a 2,721.5-g (96-oz) Schutt Dirx (warm-up device that has an adjustable weight). The premise is that using a heavier warm-up device than one's game bat in the on-deck circle will increase the BV when attempting to make bat-ball contact during a game with the player's standard (normal) game bat. If one can produce a greater BV, the pitched ball will be hit with a greater batted-ball exit velocity, farther, or both (1,16). This could potentially improve a player's offensive performance (batting average, home runs, and slugging percentage).
Southard and Groomer (19) stated that “perceptual distortion of movement as a result of experience with a previous object is the crux of experimental designs in which bat weight was manipulated to determine the effect on bat speed. Such perceptual distortion is referred to as kinesthetic aftereffect.” Although the number of studies involving kinesthetic aftereffect with baseball have been increasing, BV research involving female softball players is sparse. Why this is the case is unknown. One possible explanation is the speculation that softball coaches assume that the results of baseball BV research would apply to softball BV because one of the important components of hitting, whether baseball or softball, is BV. Another possible explanation is that, in the past, softball has not received as much national research attention as baseball has. We are not supporting this comment, only stating speculation. Finally, it is speculated that there has not been many researchers interested in softball research even though it is a popular women's sport. The only women's softball warm-up study to date has been by Dabbs et al. (4). They investigated the effects of whole-body vibration (MedVibe NitroFit Deluxe vibration machine) on BV with 11 Division I softball players and 11 recreationally trained female softball players. There were no differences between maximal BV after any of the 3 warm-up conditions for either group. The results indicated that whole-body vibration alone provided no effect compared with swinging a standard 84-cm, 717.5-g (33-in, 25-oz) softball bat or whole-body vibration plus standard bat swings in the on-deck circle.
However, previous baseball research by DeRenne et al. has shown that warm up with implements weighing between 765.4 and 963.9 g (27 and 34 oz) produced the greatest BV for high school (7) and college, excollege, and professional (5,6) baseball players when swinging a standard 83.8-cm, 850.5-g (33-in, 30-oz) baseball bat. Furthermore, this baseball research has indicated that very heavy (>1,190.7 g or 42 oz), very light (<765.4 g or 27 oz), and implements added on (donut ring, Power Sleeve, Power Swing) to the standard bat have had the most adverse effect on BV (5-7). This baseball research, conducted between 1982 and 1992, suggested that there is a specific percentage of the standard implement weight (±12%) that produced the most positive effects on BV. Furthermore, there has also been additional baseball research that has demonstrated that implements heavier than a standard bat do not produce the greatest BV but do provide "kinesthetic illusion" or feeling of greater velocity (11,12,15). Baseball research by Kim and Hinrichs (11) indicated that warm up with weighted bats of 113.4 g (4 oz), 907.2 g (32 oz), or 1,474.1 g (52 oz) did not provide any significant difference in BV, but they did report significantly different "kinesthetic feelings" of BV after swinging the heavy bat regardless of nondifference on BV. In 2008, Kim and Hinrichs (12) reported that there was no significant difference on BV between using a standard baseball game bat (909 g or 31 oz), a standard baseball game bat plus the commercial donut ring (1,452 g or 51 oz), or a standard game bat while wearing an overweighted arm device on both upper arms (2,327 g or 82 oz). Southard and Groomer (19) reported that swinging a standard 83.8-cm, 963.9-g (33-in, 34-oz) baseball bat or an 83.8-cm, 340.2-g (33-in, 12-oz) light baseball bat in the on-deck circle resulted in a faster BV than that for an 83.8-cm, 1,587.5-g (33-in, 56-oz) heavy baseball bat. Recently, Montoya et al. (14) reported results similar to those of previous research (7,19), indicating that recreational baseball players should swing either a light (272.2-g or 9.6-oz) bat or normal (893-g or 31.5-oz) baseball bat in the on-deck circle as a warm-up device because they both produced greater BV than a heavy (83.8-cm, 1,564.9-g or 33-in, 55.2-oz) baseball bat with the donut ring added.
Reyes and Dolny (17) investigated the immediate effects of various weighted bat warm-up protocols on BV of Division III baseball players. Nine weighted bat warm-up protocols, using 3 weighted bats (light, standard, heavy) were swung in 3 sets of 6 repetitions in different orders. The investigators reported that there was no significant effect on standard bat (850.5 g or 30 oz) BV using any of the 9 protocols. However, they recommended that baseball players use the order of standard (850.5-g or 30-oz), light (793.8-g or 28-oz), and heavy (1,530.8-g or 54-oz) bats in the on-deck circle because this order produced the highest increase (6.0%) in BV compared with only swinging the standard bat. Most recently, Szymanski et al. (20) indicated that there was no difference in mean BV using 10 different warm-up devices on standard bat (83.8 cm, 850.5 g or 33 in, 30 oz) BV of intercollegiate baseball players.
Because one cannot assume that the results of men's baseball BV warm-up studies produce similar positive or negative effects on female softball players' BV because there being only 1 softball warm-up study completed to date, it is not generally accepted as to which device(s) produce(s) the greatest BV. Furthermore, because the absolute strength of women is less than that of men, including known differences in stature, body mass, lean body mass, percent body fat, relative strength, and power (8), we cannot assume that the results of men's baseball BV research apply to female softball players. To partially support this statement, female softball players swing bats of the same length that are lighter than baseball bats. The range of bat mass used by female high school/college softball players is less than the range of bat mass of baseball bats used by male high school and college baseball players. For example, Louisville Slugger (Louisville, KY, USA) makes female high school/college fast pitch softball bats that are 83.8 cm (33 in) in length but range in mass from 595.3–708.7 g (21–25 oz). On the other hand, Louisville Slugger only makes 1 length and mass high school/college baseball bat that is 83.8 cm (33 in.) and 850.5 g (30 oz). They also make other bats for baseball players, for example 81.3 cm (32 in.) and 822.1 g (29 oz), but they do not make different weighted bats for a given bat length. So, the question remains, “What kind of warm-up device should a female softball player use in the on-deck circle to produce the greatest BV in a game situation?” “Should it be any different than what is suggested for male baseball players?” In addition to warm-up implements or devices placed on the bat, there are commercial companies that make devices that can be worn by players that claim that their product also increases BV without any research data to support their statements. Therefore, the primary purpose of this study was to examine the effects of various warm-up devices on BV of intercollegiate female softball players and compare the results with those of male baseball players. A secondary purpose was to evaluate 2 new commercially available resistance devices as warm-up aids. Based on the results of this study, softball coaches and players may be able to select a warm-up device that provides the greatest BV.
Experimental Approach to the Problem
This research project was designed to evaluate the effect of various resistance devices swung in the on-deck circle on softball player's BV and to see if the results were similar to those of male baseball players. Furthermore, 2 of the devices, the weighted weighted gloves and the resistance band device worn on the back arm and leg of the batter while they swing their bat, have not been used in previous softball research. Nineteen intercollegiate female softball players participated in 8 separate testing sessions where they randomly swung a different warm-up device that ranged from 510.3 to 2,721.5 g (18–96 oz) each session. This investigation was conducted at the same time of the year as a recently published collegiate baseball study (20) at the same university during the off season and used many of the same devices, but the results from that study cannot be assumed to occur for female softball players because of anthropometric and physiological differences between genders. A single-factor (BV) within-subject design with 8 levels was implemented to see if any of the resistance devices positively or negatively affected BV. To accomplish this, the BV was measured and recorded to determine the acute effect of the warm-up device.
Nineteen Division I female intercollegiate softball players (age = 19.8 ± 1.2 years, height = 167.0 ± 4.7 cm, body mass = 69.2 ± 8.6 kg, lean body mass = 49.6 ± 3.6 kg, % body fat = 27.9 ± 5.9) from Ruston, LA, USA, volunteered to participate in this study. Only position players (excluding the pitcher) were involved in the study. An Institution Review Board approved the study for human subjects, and written informed consent was obtained from each subject before any testing.
Instantaneous BV was measured by a Setpro SPRT5A chronograph (Setpro, Westbrook, CT, USA) and recorded in meters per second (Figure 1). This device provided instant feedback concerning BV (18) and has been used in previous research (2,10,20,22-25). The chronograph is no larger than a small alarm clock. There are 2 sensors (A and B) placed 10.16 cm (4 in.) apart. The sensors pick up reflective tape placed on the end cap of the test bat. The sensor is 1.27 cm (0.5 in.) in diameter. The optical system was designed to extract a midpoint from the entire duration of time the reflective tape appeared in the sensor. For example, sensor A would take start the timer based on the midpoint in time from which it could “see” the reflective tape. Then, the timer was stopped based upon the value from which sensor B calculated as the midpoint of “seeing” the reflective tape.
For optimal use, the unit was placed (55.9 cm or 22 in.) from where the bat would be coming through the zone of the 2 sensors. Best efforts were made to align the unit properly, but varying types of swings (slice angle) can affect the chronograph's reliability. For example, if a player's swing comes in at a steep slice angle, one of the sensors may not be able to “read” the reflective tape on the bat end for the full duration that it is able to read a swing that goes cleanly through the sensors (7). So, every effort was made to measure accurate BV. A qualitative judgment was made by the principal investigator so as to include only level swings in the analysis. Therefore, it is reasonable to assume that slice angle had a negligible effect on the results of this study (7). According to the manufacturer, the unit was calibrated with a crystal source and radar to ensure accuracy.
All players were medically cleared by the university athletic training staff before being involved in this study. This was provided by the university before athletes could participate in National Collegiate Athletic Association athletics. During the initial session participants answered a modified Physical Activity Readiness Questionnaire (PAR-Q) to assess their health. If they progressed through the athletic training and PAR-Q screenings, they were considered healthy to participate in this study. Participants also completed a Descriptive Data Questionnaire, designed by the principal investigator, which described their playing and exercising experiences. The procedure for testing BV and the various warm-up devices used in this study were verbally explained to the participants by the prinicipal investigator. To control for outside influences, all participants were instructed to consume a normal diet and fluids and to abstain from additional resistance training and taking ergogenic aids during the study. Furthermore, athletes were asked to maintain normal sleep habits (6–8 hours per night).
After the initial session, the subjects were randomly placed into 1 of 8 groups to swing the 8 different warm-up devices. Groups 1–5 had 2 subjects in each, whereas groups 6–8 had 3 subjects in each. Each group participated in 1 session per day over 8 days during the off season when no intercollegiate games were played. Order of experimental session (warm-up device used) was counterbalanced across groups. This means that each day, at the same time of the day, each group swung a different warm-up device until all devices were tested. All devices were used by 1 group in each testing session. The testing took place over 8 days because no testing was performed on the weekend. Each day, the athletes used a different warm-up device until all devices were tested. Proper bat swings were demonstrated and verbally explained by the principal investigator who was a former intercollegiate baseball player and coach.
The 8 different warm-up devices (Figure 2) used in this study were a standard Louisville Slugger TPS 83.8 cm, 652 g (33 in., 23 oz) aluminum softball bat, 6 overweighted implements that included 2 new products on the market, and 1 lighter bat. The new, novel devices were the Pitcher's Nightmare Swing Trainer (Launch Pad 39A, Macon, GA, USA) (10.5 lb force/ft resistance tubing device worn between the back leg and back arm while swinging a standard bat) and 567-g (20-oz) Draz (Draz Athletics, Decorah, IA, USA) weighted gloves (totaling = 1,134 g or 40 oz) while swinging a standard bat. The other 4 overweighted devices were the 2,721.5-g (96-oz) Schutt Dirx (Schutt Sports, Litchfield, IL, USA), 453.6-g (16-oz) donut ring (added to standard bat; total weight = 1,105.6 g or 39 oz), 396.9-g (14-oz) Power Fins (Markwort Sporting Goods Company, St. Louis, MO, USA) (air resisted device added to standard bat; total weight = 1,048.9 g or 37-oz), and Louisville Slugger TPS 83.8-cm, 737.1-g (33-in., 26-oz) aluminum softball bat. The underweighted device was a 78.7-cm, 510.3-g (31-in., 18-oz) Louisville Slugger TPS aluminum softball bat. The reason for using such a wide variety of warm-up devices was to include implements commonly used by baseball players and in previous research (5-7,10-13,15,17,19,20). The reason why a commercially available very light warm-up device (10-oz plastic bat) was not used in this study was because it was significantly shorter in length (63.5 cm, 25 in.) compared with the 78.7-cm (31-in.) and 83.8-cm (33-in.) warm-up bats used in this study.
Warm-Up and Testing Protocols
A standardized warm-up procedure, reported in previous research (5,7,20), was followed by all subjects for each experimental trial. These procedures included overhead and behind-the-back dynamic stretching exercises with the warm-up device for 1 minute as commonly done by players in the on-deck circle during an actual game. The subjects were then instructed to swing the warm-up device 3 consecutive times as fast as possible in their respective batting motion. Immediately after the warm-up swings, players walked 3 m (10 ft) to the simulated batter's box. Once in the batter's box, players swung the standard 83.8-cm, 652-g (33-in., 23-oz) softball bat 2 times in a way that was “comfortable for them” before the experimental trial. The players had to complete the walk and the 2 “comfortable” swings within 20 seconds. For the experimental trial, the subjects were positioned perpendicular to the Setpro SPRT5A in their normal batting stance. The subjects were instructed to swing 3 consecutive times, attempting to generate maximum velocity while hitting a softball off a batting tee that was aligned with their pubic arch (a location that represented a pitch in the middle of the strike zone). To simulate a normal game batting situation, a 20-second rest period was given between each swing. However, the subjects were not allowed to practice swinging between trials. The testing order of different devices was assigned randomly to each group. Each subject was tested on 8 days, using 1 device per day.
SPSS (version 11.5; SPSS, Inc., Chicago, IL, USA) was used for the statistical analysis. A 1 (group) × 3 (BV) repeated measures analysis of variance (ANOVA) was conducted on each of the 3 maximal swings taken in the batter's box with the standard game bat after warming up with each on-deck circle device separately to see if there were statistical differences between the BV of each swing. In addition, a 1 (group) × 8 (BV) repeated measures ANOVA was conducted on the standard bat mean BV after swinging the 8 warm-up devices to see if there were statistical differences between them. The overall alpha level was set at p ≤ 0.05 for all analyses.
The 1 × 3 repeated measures ANOVAs indicated that there were no significant differences in BV between the 3 swings (trials) with the standard game bat in the batter's box after using the same warm-up device. Therefore, the mean BV of the 3 trials with the standard game bat was used to represent each condition (Table 1). The test-retest reliability (intraclass correlation coefficient) between swing trials for all players averaged 0.91. Power computations revealed a 0.62 score, with an effect size of 0.111. The 1 × 8 repeated measures ANOVA indicated no overall significant difference between the mean BV after swinging any of the 8 warm-up devices, F(7, 126) = 2.237, p = 0.077. Therefore, pairwise comparisons were not conducted.
There were no statistically significant differences in mean BV after using any of the 8 warm-up devices. For Division I female intercollegiate softball players, these results suggest that warm-up implements varying from 510.3 to 2,721.5 g (18–96 oz) did not significantly change mean BV of a standard 83.8 cm, 652 g (33 in., 23 oz) softball bat. These results are very similar to those of the study by Szymanski et al. (20), which performed the same warm-up and swing sequence for baseball players used by DeRenne et al. (7) at the same time of the year (off season), at the same university. These data suggest that the BV results for female softball players after swinging various warm-up devices are very similar to the BV results for male baseball players regardless of anthropometric and physiological differences. Although not reported in either study, data were collected on these athletes for the medicine ball side toss, grip strength, vertical jump, estimated peak power, and absolute and relative strength for the parallel squat, bench press, and 1-arm dumbbell row because the lead author was also responsible for sports performance testing of the baseball and softball teams. For all these data, there were significant differences between the female softball and male baseball players. Besides the anthropometric and physiological differences between the subjects, there were differences of some of the warm-up devices used and the weight of the standard bat. In this study, 8 warm-up devices were used by female intercollegiate softball players before swinging an 83.8-cm, 652-g (33-in., 23-oz) softball bat, whereas in the baseball study (20), 10 warm-up devices were used by male intercollegiate players before swinging an 83.8-cm, 850.5-g (33-in., 30-oz) baseball bat. However, most of the warm-up devices were the same. The reason why the Pow'r Wrap and 623.7-g (22-oz) fungo bat were not used in this study was that the Pow'r Wrap did not fit on a standard softball bat, and the fungo bat was only 28.3 g (1 oz) lighter than the standard 652-g (23-oz) softball bat used by the female softball players. Results of the baseball study (20) indicated that there were no statistically significant differences in BV after using 10 different warm-up devices. The current research findings are very similar to those of the baseball study in that the weighted gloves and the donut ring resulted in the slowest BV. These results of this study and of Szymanski et al. (20) are similar to those of previous baseball studies (7,15,19) that found that the donut ring produced the slowest BV.
When trying to make comparisons between the results of this study and the only other female softball BV warm-up study (4), it is challenging because this study used various weighted devices and Dabbs et al. (4) used whole-body vibration as a warm-up. However, similar to this study, Dabbs et al. (4) did not find a significant difference between any of the 3 conditions investigated. This specifically relates to the 2 warm-up conditions that used the 745.5-g, 84-cm (25.31-oz, 33-in.) standardized test softball bat. The softball players in this study used a 23-oz, 33-in standard test bat, and there were no significant differences between that bat and any of the other resisted devices used as a warm-up implement. It is interesting to note that there are some other differences between the 2 studies that should be discussed. One difference was the device used to measure BV. In the current study, a Setpro SPRT5A chronograph, with its 2 horizontal sensors separated by 10.16 cm (4 in.), was used, whereas Dabbs et al. (4) used an apparatus which consisted of 2 vertical photoelectric sensors (Model E3Z, Omron Electronics, Schaumburg, IL, USA) separated by 45 cm (the depth of the home plate). However, pilot work mean test-retest reliability of the Setpro SPRT5A chronograph was r > 0.97 (p ≤ 0.05), whereas the mean test-retest reliability over 8 days for the principal investigator was r > 0.93 (p ≤ 0.05). The test-retest reliability between swing trials for all players averaged 0.91. Another difference was the BV values. Dabbs et al. (4) reported maximal BV ranging between 16.9 and 18.9 m·s−1 (37.98–42.39 mph) for college softball players, similar to that reported by Giardina et al. (9), whereas this study reported mean BV ranging between 28.5 and 29.9 m·s−1 (63.81–66.83 mph) for intercollegiate softball players. The velocities of this study are similar to those that others reported by previous softball BV research using the Setpro SPRT5A chronograph (2,13,25) or 3D motion capture system (21). A third difference between Dabbs et al. (4) and this study pertained to the subjects. Dabbs et al. (4) had 11 Division I softball players and 11 recreationally trained softball players that were in 2 separate groups. This study had 19 Division I intercollegiate softball players.
When comparing the results of this softball study with those of other baseball warm-up studies, these results statistically differ from those of previous baseball research where weighted bats ±12% of the standard game bat weight demonstrated the greatest BV (5-7) and others where light and normal bats (14), underweighted and standard bats (19), or an ordinary bat (15) produced faster BVs than heavier bats did. However, the warm-up protocol and swing sequence in this study were very similar to the one used by DeRenne et al. (7) with a similar range of weighted warm-up devices. Three notable differences between this study and that of DeRenne et al. (7) were the gender (female vs. male), level of play of the subjects (college vs. high school), and the equipment (Setpro SPRT5 chronograph vs. photosensing computerized timing unit) used to measure BV.
The results of this study are statistically similar to those of Reyes and Dolny (17), who used Division III intercollegiate baseball players who swung 9 different combinations of light (794-g or 28-oz), standard (850-g or 30-oz), and heavy (1,531-g or 54-oz) bats over 9 days and did not find 1 weighted bat warm-up protocol that significantly increased standard bat BV. Research by Kim and Hinrichs also indicated that there was no significant difference in BV of a standard bat after swinging a wiffle bat (113-g or 4-oz), standard bat (909 g or 32 oz), and standard bat with a donut ring (1,477 g or 52 oz) for 8 male and 5 female subjects between the ages of 22 and 28 years (11), or for 20 competitive high school and intercollegiate baseball players who swung a standard bat (885 g or 31 oz), overweighted arm warm-up (2,327 g or 82 oz), and standard bat with a donut ring (1,452 g or 51 oz) (12).
Finally, the only other study to use the 2 new, novel resistance devices (weighted gloves and resistance bands worn on the back arm and leg while swinging a bat) was that of Szymanski et al. (20). In both studies, these devices did not produce any BV results better than any other device for intercollegiate male baseball or female softball players.
Intercollegiate female softball players interested in having the highest BV during a game at-bat can use any of the 8 warm-up devices tested because BVs were not significantly different from one another like the findings reported on collegiate baseball players (20). Thus, from these data, it appears that BV results are similar for both genders of collegiate players. However, previous baseball research has demonstrated that implements either similar in mass to the standard game bat or lighter produce significant differences in BV compared with that produced by heavy bats (5-7,14,19). Additionally, Southard and Groomer (19) stated that using a bat with a larger moment of inertia not only slows down a player's swing, but it also changes the batter's swing pattern. If this occurs, then the chances of the batter successfully hitting the ball accurately may be decreased. This could ultimately lead to poor offensive statistics (i.e., batting average, slugging percentage, on-base percentage). On the other hand, Otsuju et al. (15) stated that although swinging weighted bats as a warm-up did not provide any greater BV for a standard baseball bat, it did provide a psychological advantage because player's felt that the standard baseball bat was lighter. Therefore, personal preference as to which warm-up device to use in the on-deck circle is advised. The 2 new devices studied in this study, the Draz weighted gloves and the Pitcher's Nightmare, did not provide any BV greater than that of any other device. So, any claims of increased BV by the manufacturers of these devices as a warm-up device to use in the on-deck circle is, at this time, not supported by this study. Finally, it must be stated that the most common warm-up device used in amateur and professional baseball, the donut ring, produced the slowest BV similar to in previous baseball research (7,14,19,20). For this reason, it is not recommended to swing a donut ring as a warm-up device for softball or baseball players regardless of how the player feels.
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