Introduction
Of the roughly 2.5 million baseball players in the USA, approximately 80% participate in the 14 and under youth leagues, and another 15-20% participate at the high school youth level (3). Less than 1% of all baseball players are at the collegiate or professional levels (3). With approximately 99% of baseball players participating in youth and high school leagues, it is important for strength and conditioning specialists to be knowledgeable in performance enhancement and training in youth (under 18 years of age) baseball players.
There are limited studies that have investigated the effects of resistance training programs in youth baseball players on baseball performance variables. Szymanski et al. (11,13) investigated the effects of a 12-week periodized training program, largely comprising wrist and forearm training, on bat velocity in high school baseball players. Szymanski et al. (10,12) investigated a 12-week medicine ball, torso rotation training, and a stepwise periodized resistance training program with bat swings on bat velocity and torso rotational and sequential hip-torso-arm rotational strength. Wooden et al. (15) investigated the effects of a 5-week resistance training program in teenage baseball players consisting of isolated shoulder internal and external rotation exercises on shoulder internal and external rotation shoulder torque and throwing velocity. However, there are no known studies that have investigated the effects of a baseball-specific conditioning program on throwing velocity in youth baseball players.
One component of performance enhancement in baseball is throwing velocity. For example, a pitcher with a good fastball sets up other pitches that help fool the hitter, such as the changeup and curveball. Throwing the fastball pitch with greater throwing velocity allows less time for the batter to identify the pitch and decide whether or not to swing. Therefore, a fastball pitch thrown with greater velocity is often more difficult to hit compared to a fastball pitch thrown with less velocity, assuming similar ball movement and location over the plate.
Throwing velocity is also important to position players. For example, a ground ball softly hit to the short stop or third baseman requires a hard throw with high velocity and accuracy to throw out the runner. Similarly, an outfielder trying to throw out a base runner at home plate requires high throwing velocity and accuracy. Throwing velocity may increase by improving throwing mechanics or by employing an effective baseball conditioning program, which can enhance muscular strength and power. Although several studies have analyzed the throwing mechanics in youth pitchers (5,7,8), it is unclear how improving throwing mechanics affects throwing velocity.
Although other studies have examined the effects of resistance training on bat velocity (10,11), to our knowledge, this is the first study that has examined the effects of a baseball conditioning program on throwing velocity in youth baseball players. The purpose of this study was to determine the effects of a 4-week youth baseball conditioning program (comprising throwing, stretching, and resistance tubing exercises) on maximum throwing velocity. It was hypothesized that after a 4-week baseball conditioning program, the training group would exhibit a significant increase in throwing velocity. It was also hypothesized that there would not be a significant difference between all pretest and posttest throwing velocity measurements in the control group.
Methods
Experimental Approach to the Problem
Because throwing velocity is important for all positions in baseball (as described above), this study examined whether a short-term 4-week baseball conditioning program was effective in increasing throwing velocity. Because youth athletes increase musculature strength through maturation, which can affect throwing velocity, we used an age-matched control group to compare to the experimental (training) group.
Subjects
Thirty-four youth baseball players between 11 and 15 years of age volunteered as subjects and were randomly and equally divided into control and training groups. Both control and training groups participated in their normal school activities (e.g., physical education class) and extracurricular activities, such as running and playing school sports other than baseball, because baseball was not in season at the time of this study. Both the control and training groups were asked to list any activities or sports they performed during the 4-week period of the study, and both groups listed similar activities and sports, such as running, playing basketball, soccer, or tennis, playing catch with a baseball, and performing push-ups and sit-ups in physical education class. The primary difference between the control and training groups is that the training group participated in a 4-week baseball-specific conditioning program, whereas the control group did not.
The subjects mean (SD) age, mass, and height were 12.5 (1.5) years, 52.4 (17.7) kg, and 159.7 (12.8) cm, respectively, in the control group, and 12.9 (1.7) years, 53.9 (20.7) kg, and 163.8 (14.0) cm, respectively, in the training group. Inclusion criteria for all subjects required each participant to be a healthy baseball player, no history of upper extremity surgery, no shoulder pain for the past 12 months, no rehabilitation for the past 12 months, no participation in a formal resistance training program the 4 weeks before the study (all subjects in both control and training groups were untrained individuals and did not have a regular resistance training routine), no participation in a formal resistance training program during the 4-week period of the study, such as a weight training class in school (not including push-ups, sit-ups, or related calesthenic exercises that may be a daily part of physical education class), and no participation in a school or league baseball program during the 4-week period of the study. All subjects and their parents provided written informed consent, and the protocol used for this study was approved by the Institutional Review Board at California State University, Sacramento.
Procedures
Description of Baseball Conditioning Program
The baseball conditioning program for the training group was approximately 75 minutes in duration thrice a week for 4 weeks. Two experienced trainers trained all 17 subjects in the training group throughout the 4-week duration. The initial 10 minutes of the program comprised general warm-up and range of motion exercises, including arm circles in multiple directions, side stretch to the right and left, forearm supination and pronation range of motion exercises, and wrist flexion and extension range of motion exercises, each performed for 2 sets of 25 repetitions.
The subsequent 30 minutes of the program consisted of using elastic tubing (“MVP Band,” A Change of Pace, Inc, Davis, CA, USA) for 17 upper extremity resistance exercises for muscular strength, power, and endurance. The MVP Band is different from most elastic tubing devices, because it was attached around the wrist instead of a handle that was held in the hands. The 17 resistance exercises were performed for 1 set of 20-25 repetitions and included the following: (a) elbow extension (Figures 1A, B); (b) arm extension (Figures 2A, B); (c) chest fly (Figures 3A, B); (d) reverse chest fly (performed the opposite of chest fly); (e) rowing (Figures 4A, B); (f) internal rotation with shoulder flexed 90° (Figures 5A, B); (g) external rotation with shoulder flexed 90° (Figures 6A, B); (h) internal rotation with shoulder abducted 0° (Figures 7A, B); (i) external rotation with shoulder abducted 0° (performed the opposite of internal rotation with shoulder abducted 0°); (j) internal rotation with shoulder abducted 90° (Figures 8A, B); (k) external rotation with shoulder abducted 90° (performed the opposite of internal rotation with shoulder abducted 90°); (l) shoulder abduction to 90° (Figures 9A, B); (m) shoulder abduction to 180° (Figures 10A, B); (n) D2 diagonal pattern flexion (Figures 11A, B); (0) reverse throw (Figures 12A, B); (p) D2 diagonal pattern extension (reverse of D2 Diagonal pattern flexion, starting with shoulder flexed and externally rotated and elbow bent and ending with shoulder extended and internally rotated and elbow straight with hand at opposite hip); (q) standard forward throw (Figures 13A, B).
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Figure 1: A, B) Elbow extension.
Figure 2: A, B) Arm extension.
Figure 3: A, B) Chest fly (horizontal adduction).
Figure 4: A, B) Rowing.
Figure 5: A, B) Internal rotation with shoulder flexed 90°.
Figure 6: A, B) External rotation with shoulder flexed 90°.
Figure 7: A, B) Internal rotation with shoulder abducted 0°.
Figure 8: A, B) Internal rotation with shoulder abducted 90°.
Figure 9: A, B) Shoulder abduction to 90°.
Figure 10: A, B) Biceps curl.
Figure 11: A, B) D2 diagonal pattern flexion.
Figure 12: A, B) Reverse throw.
Figure 13: A, B) Standard forward throw.
Each resistance exercise was performed in a 3-second repetition (1 second for the concentric phase and 2 seconds for the eccentric phase). Each subject was instructed on how to perform each exercise with proper form and technique and use enough resistance for each exercise that allowed them to perform 20-25 repetitions but no more. The subjects adjusted the tension in the MVP Band tubing to accommodate their improvements in muscular strength throughout the 4-week duration.
The next 30 minutes consisted of a distance-based interval throwing long toss program, which has been shown to be effective in enhancing throwing performance in youth baseball players (1). After a 5-minute warm-up throwing at a 50-ft distance, each subject performed pivot throws with an arc (no step allowed) for 15 minutes (60-ft throws for 5 minutes, 75-ft throws for 5 minutes, and 100-ft throws for 5 minutes). Subsequently, each subject performed long toss throws with an arc (1 step allowed) for 10 minutes (100-ft throws for 5 minutes and 125-ft throws and beyond for 5 minutes). Subjects 13-15 years of age ended their throwing by performing 5 hard throws at 150 ft, 5 hard throws at 125 ft, and 5 hard throws at 100 ft. Subjects 11-12 years of age ended their throwing by performing 5 hard throws at 100 ft, 5 hard throws at 75 ft, and 5 hard throws at 50 ft. The final 5 minutes of the program consisted of shoulder external rotation stretches, which consisted of 15 repetitions for each arm for external rotation at 0° shoulder abduction, external rotation at 90° shoulder abduction, and external rotation at 0° shoulder flexion.
Throwing Velocity Assessment
Assessment of throwing velocity was performed for all subjects at Results Physical Therapy and Training Center (Sacramento, CA, USA) 2 days before the start of the baseball conditioning program (pretest) and 2 days after the completion of the baseball conditioning program (posttest). All subjects were tested at approximately the same time in the afternoon or evening during both the pretest and posttest. All subjects were instructed to be well rested and hydrated before testing, and not have eaten any food at least 2 hours before testing. After approximately 5 minutes of a general warm-up consisting of walking, lunging, step-up drills to a box, and stretching, and approximately 5 minutes of light to moderate effort throwing, the throwing velocity of each subject was then assessed. Each subject threw overhand from flat ground at maximal effort to a target positioned at approximately chest level and 13.7 m away. Subjects started with both feet on a line and were then allowed to take one stride toward the target as they threw the ball. Throwing velocity was recorded from a calibrated Jugs Tribar Sport radar gun (Jugs Pitching Machine Company, Tualatin, OR, USA) as the ball left the pitcher's hand and was accurate within 0.22 m·s−1. Five maximum effort-throwing trials were performed and recorded. Approximately 30 seconds of rest was provided between all throwing trials to prevent muscular fatigue from occurring.
Questionnaire
During the posttest, subjects in the training group completed a questionnaire asking their satisfaction with the conditioning program, and their perception of how the conditioning program affected their throwing velocity. The questionnaire given to the training group asked them if they felt the conditioning program did not help, may have helped, probably helped, or definitely helped increase throwing velocity. Subjects in the control group and training group also completed a posttest questionnaire answering questions regarding what activities and sports they participated in during the 4-week period between the pretest and posttest.
Statistical Analyses
Dependent t-tests were used assess significant differences in throwing velocity between pretest and posttest throwing velocity measurements in the control group and in the training group. Independent t-tests were also used to assess significant differences in age, mass, and height between control and training groups. The level of significance used was p ≤ 0.05.
Results
There were no significant differences in age, mass, and height comparisons between control and training groups. Mean (±SD) throwing velocity comparisons between pretest and posttest measurements for the control and training groups are shown in Table 1. In the training group, throwing velocity was significantly greater after the conditioning program (posttest measurements) compared to before the conditioning program (pretest measurements), whereas in the control group, there were no significant differences between pre and posttest throwing velocity measurements.
Table 1: Mean ± SD data are shown between pretest and posttest throwing velocity for the training (n = 17) and control (n = 17) groups.
All subjects in the training group did not miss any training sessions, except 2 subjects, who missed 1 session, demonstrating excellent compliance with the training program. Moreover, all subjects in the training group were satisfied with the conditioning program. Approximately 80% of the training group subjects responded to the questionnaire by saying they felt the conditioning program definitely helped increase their throwing velocity, whereas the remaining 20% of the subjects said the conditioning program may have helped or probably helped increase their throwing velocity.
Discussion
As hypothesized, throwing velocity increased in the training group after the 4-week baseball conditioning program. These results demonstrate that even a short-term conditioning program can result in increased throwing velocity in youth baseball players. Because youth are often involved in multiple sports and activities, and often have a shorter attention span compared to older athletes, a short-term baseball conditioning program may be an attractive alternative compared to a longer duration program (e.g., 10-12 weeks), especially because the results of this study demonstrate that baseball performance variables can be enhanced in a short-term program.
The improvement in ball velocity may have been affected by both the training intensity and training volume, and more research is needed in this area. The resistance training program in this study involved employing moderate intensity rather than high intensity, the latter being more conducive in maximizing strength gain (9). However, it was important that the young subjects in this study be able to perform each resistance exercise with proper form and technique, and in a controlled manner, and higher intensity training may compromise proper form and technique in youth (4). Moreover, it is common when using elastic tubing for resistance training to use lower to moderate intensities with higher number of repetitions, typically between 10 and 25 repetitions (14), and high resistance training with lower repetitions is typically reserved for free weight or machine resistance training (9). Although the 1 set of 20-25 repetitions in this study was more conducive for maximizing muscular endurance improvement and to a lesser extent improving muscular strength (4,9), both muscular strength and endurance are important components to achieve for baseball players. Another reason high intensity was not employed in this study is that performing high-intensity resistance training with low repetitions in prepubescent youth is not recommended (4), because this type of training may increase injury risk in youth.
Because throwing velocity improvement in youth may simply occur from normal aging and maturation, it was important to use a control group in the current. Certain school activities, such as performing push-up and sit-ups in physical education class, and extracurricular activities, such as participating in overhead throwing type sports, may affect throwing velocity gains in youth, and these activities were not controlled in either the control or training groups. Given the random assignment of the subjects within the 2 groups, and given that the baseball conditioning program the only variable that differed between the groups, it can be concluded that the conditioning program was the primary reason for the improvement in throwing velocity in the training group, especially given that the control group did not improve in throwing velocity.
Improvements in throwing velocity from resistance training programs have been previously reported. Carter et al. (2) investigated the effects of 8 weeks of upper extremity plyometric training on isokinetic strength and throwing velocity in collegiate baseball players. Compared to a control group that participated in off-season nonplyometric strength and conditioning activities, a plyometric training group exhibited significantly greater throwing velocity at the end of the 8-week plyometric program (83.2 mph in pretraining vs. 85.2 mph in posttraining). These authors concluded that although both resistance training and plyometric training resulted in strength gains, only the plyometric training group improved their throwing velocity. These results are supported by data from Grezios et al. (6), who reported that the stretch-shortening cycle, which is the foundation of plyometric training, is the type of muscle contraction that primarily occurs in overhead throwing, such as in throwing a baseball.
Wooden et al. (15) reported that youth who performed a 5-week resistance training program consisting of isolated shoulder internal and external rotation exercises increased throwing velocity by 2.06 mph. The 2- and 2.06-mph increases in throwing velocity reported by Carter et al. (2) and Wooden et al. (15), respectively, are similar to the 2.2-mph increase in throwing velocity reported in this study. Although this study demonstrated a throwing velocity increase in the training group, it is unknown which components of the baseball conditioning program (resistance training program or throwing program) was most influential in producing the increased throwing velocity. Because the baseball conditioning program in the current combined warm-up, stretching, resistance training, and throwing, further research is needed in this area to determine the relative contribution of each of these training components with respect to increasing throwing velocity.
Future research should focus on comparing the effects of shorter duration (e.g., 4-6 weeks) vs. longer duration (e.g., 10-12 weeks) conditioning programs to assess if longer duration conditioning programs result in greater increases in throwing velocity compared to shorter duration conditioning programs. It should also be investigated whether youths are as compliant with a long-term conditioning program compared to a shorter duration program, especially because youths are often very active in both school and extracurricular activities. Future research is also needed in older postpubescent youth, such as those in high school, as the mean subject age of 12.5 (1.5) years in this study primarily involved prepubescent youth in junior high school.
Practical Applications
The results of this study demonstrate that a short-term baseball conditioning program is effective in enhancing throwing velocity in youth baseball players. In only 4 weeks, throwing velocity increased approximately 4% in the group that participated in the baseball conditioning program but changed <1% in the group that did not participate in the baseball conditioning program. Increased throwing velocity may be helpful for a pitcher, because the batter will have less time to make a decision as to whether or not to swing at the pitch, and may help position players, such as a catcher, infielder, or outfielder trying to throw out a runner attempting to advance to the next base.
Acknowledgments
The authors would like to thank Adel Aitali, Adam Beckenger, Jeff Blankenship, Rama Bowen, Wes Haven, and Fallon Hookailo for their assistance during data collection.
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