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.
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.
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.
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.
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.
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.
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.
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.
1. Axe, MJ, Snyder-Mackler, L, Konin, JG, and Strube, MJ. Development of a distance-based interval throwing program for Little League
-aged athletes. Am J Sports Med
24: 594-602, 1996.
2. Carter, AB, Kaminski, TW, Douex, AT Jr, Knight, CA, and Richards, JG. Effects of high volume upper extremity plyometric training on throwing velocity and functional strength ratios of the shoulder rotators in collegiate baseball players. J Strength Cond Res
21: 208-215, 2007.
3. Conte, S, Requa, RK, and Garrick, JG. Disability days in major league baseball. Am J Sports Med
29: 431-436, 2001.
4. Faigenbaum, AD, Kraemer, WJ, Blimkie, CJ, Jeffreys, I, Micheli, LJ, Nitka, M, and Rowland, TW. Youth resistance training
: updated position statement paper from the national strength and conditioning association. J Strength Cond Res
23: S60-S79, 2009.
5. Fleisig, GS, Barrentine, SW, Zheng, N, Escamilla, RF, and Andrews, JR. Kinematic and kinetic comparison of baseball pitching among various levels of development. J Biomech
32: 1371-1375, 1999.
6. Grezios, AK, Gissis, IT, Sotiropoulos, AA, Nikolaidis, DV, and Souglis, AG. Muscle-contraction properties in overarm throwing movements. J Strength Cond Res
20: 117-123, 2006.
7. Nissen, CW, Westwell, M, Ounpuu, S, Patel, M, Tate, JP, Pierz, K, Burns, JP, and Bicos, J. Adolescent baseball pitching technique: A detailed three-dimensional biomechanical analysis. Med Sci Sports Exerc
39: 1347-1357, 2007.
8. Sabick, MB, Kim, YK, Torry, MR, Keirns, MA, and Hawkins, RJ. Biomechanics of the shoulder in youth baseball pitchers: implications for the development of proximal humeral epiphysiolysis and humeral retrotorsion. Am J Sports Med
33: 1716-1722, 2005.
9. Stone, MH, O'Bryant, HS, Garhammer, J, McMillan, J, and Rozenek, R. A theoretical model of strength training. NSCA J
4: 36-40, 1982.
10. Szymanski, DJ, McIntyre, JS, Szymanski, JM, Bradford, TJ, Schade, RL, Madsen, NH, and Pascoe, DD. Effect of torso rotational strength on angular hip, angular shoulder, and linear bat velocities of high school baseball players. J Strength Cond Res
21: 1117-1125, 2007.
11. Szymanski, DJ, McIntyre, JS, Szymanski, JM, Molloy, JM, Madsen, NH, and Pascoe, DD. Effect of wrist and forearm training on linear bat-end, center of percussion, and hand velocities and on time to ball contact of high school baseball players. J Strength Cond Res
20: 231-240, 2006.
12. Szymanski, DJ, Szymanski, JM, Bradford, TJ, Schade, RL, and Pascoe, DD. Effect of twelve weeks of medicine ball training on high school baseball players. J Strength Cond Res
21: 894-901, 2007.
13. Szymanski, DJ, Szymanski, JM, Molloy, JM, and Pascoe, DD. Effect of 12 weeks of wrist and forearm training on high school baseball players. J Strength Cond Res
18: 432-440, 2004.
14. Treiber, FA, Lott, J, Duncan, J, Slavens, G, and Davis, H. Effects of Theraband and lightweight dumbbell training on shoulder rotation torque and serve performance in college tennis players. Am J Sports Med
26: 510-515, 1998.
15. Wooden, MJ, Greenfield, B, Johanson, M, Litzelman, L, Mundrane, M, and Donatelli, RA. Effects of strength training on throwing velocity and shoulder muscle performance in teenage baseball players. J Orthop Sports Phys Ther
15: 223-228, 1992.
Keywords:© 2010 National Strength and Conditioning Association
resistance training; little league; ball velocity