data-based interval throwing programs for … axe, windley, and snyder-mackler interval throwing...

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Data-Based Interval Throwing Programsfor Baseball Position PlayersFrom Age 13 to College Level

Michael J. Axe, Thomas C. Windley, and Lynn Snyder-MacklerObjective: To design interval throwing programs for baseball players other than pitch-ers from 13 years of age to the college level. Design: The authors recorded throws to base, distance of throws, and perceived effort of throws at 4 levels of play. For catchers they also recorded number of throws to the pitcher, number of sprints to first or third base, and time in the squat stance. From these data they designed throwing programs specific to outfielders, infielders, and catchers. Results: No significant difference was found between the number of throws and distance of throws for infielders and catch-ers across all age groups. The mean distance of throws differed significantly between 13-year-olds and all other levels of play. Conclusion: The authors devised 1 program for infielders and catchers of all age groups, 1 program for 13-year-old outfielders, and 1 for all other levels. Key Words: rehabilitation, return to play, training

Axe MJ, Windley TC, Snyder-Mackler L. Data-based interval throwing programs for baseball position play-ers from age 13 to college level. J Sport Rehabil. 2001;10:267-286. © 2001 Human Kinetics Publishers, Inc.

Approximately 16 million children play organized baseball in the United States each year. Little League Baseball includes 190,000 teams in 80 coun-tries and is recognized as the largest sport organization in the world.1 Participation rates decrease as children age and enter higher levels of competition. At the college level there are approximately 25,000 athletes playing baseball, and in the professional ranks the number of participants is even lower.2 Throughout these ranges of ages, many injuries occur. Many of them result in time lost from sport. The National Collegiate Athletic Association’s injury-surveillance system (ISS) reports injury demograph-ics from 15 college sports each year. During the 1998–99 college baseball season, the ISS reported that the shoulder was the most often injured body part, and McFarland et al reported that 58% of college baseball injuries were to the upper extremity. Both studies reported strains and sprains to be the most frequent types of injury. In addition, 27% to 32% of college baseball injuries have been found to result in 7 or more days of time lost

Axe and Snyder-Mackler are with the Dept of Physical Therapy at the University of Dela-ware, Newark, DE 19716. Windley, who was a master’s student in the department at the time of the research, is now with Schweizer’s Therapy and Rehabilitation in Middletown, DE.

268 Axe, Windley, and Snyder-Mackler Interval Throwing Programs for Baseball Position Players 269

from baseball, and 75% of time-lost injuries are to the upper extremity. Injury rates have been reported to be between 2.2 and 6.1 injuries per 1000 athletic exposures. Most often the practice injury rate is at the low end of the spectrum, whereas the game injury rate is higher. An athletic exposure is defined as 1 athlete participating in 1 practice or game in which he or she is at risk for an athletic injury.3,4 In a study of Little League Baseball players age 7 to 18, Pasternack et al found an injury rate of 0.057 per 100 player hours.5 Powell et al studied sex-related injury patterns in various high school sports. They found that 44.3% of injuries to high school baseball players were to the upper extremity.6

To this date there has been very little research on the differences in injuries between pitchers and positional players. There are few to no reports on injury demographics in baseball players other than pitchers at any level of play. McFarland and Wasik4 recognized this fact and attempted to outline injury incidence and distribution for pitchers and positional players at the college level. They found that infielders sought treatment for shoulder problems more often than any other position did. Following the infielders (42% of all shoulder problems) were pitchers (31%), outfielders (21%), and catchers (6%).4 The low percentage of catcher injuries might be a result of the fact that there is usually only 1 catcher participating per game, whereas there are usually 4 infielders, 3 outfielders, and several pitchers. The most common injury to the shoulder for pitchers, infielders, and outfielders was rotator-cuff tendinitis, and catchers most often sustained muscle strains. Infielders with shoulder injuries required surgery as often as did pitchers. McFarland et al recognized the fact that infielders must throw from a variety of angles, often from an off-balance position. This can lead to biomechanical changes during throwing, which can cause increased stresses to the upper extremity.4

Bigliani et al7 studied 148 professional baseball players with no history of shoulder problems in order to compare glenohumeral range of motion and laxity in pitchers and positional players. They found increased external rota-tion and decreased internal rotation in the dominant shoulders of all play-ers. In addition, they discovered that 61% of pitchers and 47% of positional players had positive sulcus signs.7 Although these data reflect uninjured athletes, they verify that the altered range of motion in pitchers’ shoulders also exists in positional players’ shoulders. Although these athletes had no injury history, the findings suggest a propensity for injury secondary to the repetitive microtrauma that had allowed these biomechanical changes to occur. In addition to the lack of injury data, there are no documented kinetic or kinematic studies on the dynamics of the upper extremity during throwing in positional players other than the pitcher.

Rehabilitation exercises commonly used for the shoulder concentrate on building strength and endurance in the glenohumeral and scapular stabi-lizers in order to decrease the forces placed on the passive restraints of the glenohumeral joint. Rehabilitation exercises commonly applied for injuries


to the elbow focus on strengthening and endurance training of the muscles that cross the elbow joint in order to decrease the stresses on the joint struc-tures.8,9 There are common techniques used in rehabilitation for both joints. Programs designed to rehabilitate the injured shoulder and elbow include stretching the glenohumeral-joint capsule; range-of-motion and flexibility exercises; strengthening the rotator cuff, scapular stabilizers, and muscles crossing the elbow joint; open- and closed-chain strengthening exercises; functional plyometric exercises; proprioceptive neuromuscular feedback; multidirectional and unidirectional dynamic stabilization techniques; and concentric and eccentric exercises.10-23 These therapies are necessary for suc-cessful return to throwing; however, the forces and torques experienced by the upper extremity can only be reproduced by throwing a baseball.8

In order to maximize the effectiveness of a rehabilitation program for a baseball player, we believe that an interval throwing program (ITP) should be included as a functional progression toward return to play. The intention of an ITP is to slowly increase the stresses and loads placed on the upper extremity through a stepwise progression of throwing. The proper use of an ITP provides for the most efficient and safe return to sport. The throwing programs are designed to avoid placing too much stress on healing tissues. If an athlete were to increase throwing too quickly, healing time might be slowed, and a safe and efficient return to sport would be compromised.8 Most of the throwing programs available in the literature are based on the clinical experience of the authors about how quickly an athlete should return to play.24-27 Only a few are based on data and take into account the types of injury sustained by the athletes.8,9,28 ITPs take into account the stresses placed on the baseball player during competition. They are designed for 9- to 12-year-old Little League Baseball pitchers,28 baseball pitchers at all levels from 13 years old to professional,8 and college-level softball players of all positions including pitcher.9 The ITPs we suggest are designed for baseball players, other than pitchers, at all levels of play from the age of 13 to college level. There are no published data-based throwing programs for baseball positional players other than the pitcher at any level.

In addition to an ITP, we suggest that a simulated game be used as a return-to-play criterion. A simulated game is based on the maximum pos-sible game situation for a given position at a particular level of play. A true simulated game is derived from data that detail the situations a given athlete might experience during a game.9 Coleman et al29 suggested a simulated game for pitchers at the professional level, based on data collected during 3 seasons of professional baseball. The goal of their work was to determine a pitcher’s readiness for return to pitching after an injury. The program they suggested was based on number of pitches per inning, innings pitched per game, time between innings, and preinjury pitch mix for a particular ath-lete.29 Their simulated game is a good tool for establishing game readiness, but it does not include a functional progression toward return to play.8 We believe that a safer and more efficient return to play will be achieved if the


effectiveness of an ITP is combined with that of a simulated game.The purpose of this study was to devise a data-based ITP followed by

a simulated game for nonpitching baseball players at all levels of play. An ITP is not intended to replace commonly used rehabilitation programs but rather is intended to increase the efficiency of return to play through a step-by-step functional progression. The goal is to safely and efficiently progress the athlete to return to play while minimizing the amount of stress applied to the healing tissues.8,9 The program does take into account the type of injury sustained by the baseball player, but we also suggest using this program for off-season and preseason conditioning. We have developed an ITP followed by a simulated game for catchers, infielders, and outfielders in baseball at all levels of play from 13 years of age to college. Our goal is to promote safe and efficient return to play for injured players and off-season and preseason conditioning programs.

MethodsData Acquisition

We collected data for all age groups of organized baseball between the age of 13 and college level for every position other than pitcher. The age groups we observed were 13-year-olds, 14- and 15-year-olds, 16- to 18-year-olds, and college athletes. We collected the data on 13-year-olds over 307 innings of play, the data on 14- and 15-year-olds over 51 innings of play, the data on 16- to 18-year-olds over 67 innings of play, and the data on col-lege-level players over 349 innings of play. We used NCAA Baseball Rules30 to help construct all throwing programs, because all of the age groups we observed play on the same-size field. The depth of the outfield fences is the only dimension that varies. As for the number of innings played, the college players play 9-inning games, and all other age groups that we ob-served play only 7-inning games. All game data are based on the number of innings per game at each level.

For catchers, we recorded the number of throws back to the pitcher (60 ft, 6 in),30 number of sprints to back up plays at first or third base (90 ft),30 time in the squat stance, number of throws other than throws back to the pitcher, distance of these throws, and percent effort of these throws. We then calculated the means per inning and per game for all data, as well as the ranges of distances and efforts. We used these data and NCAA Baseball Rules30 to construct the catcher throwing programs.

The infielder and outfielder data that we recorded included number of throws, distance of those throws, and percent effort of those throws. We then calculated the means of these data per inning and per game. In ad-dition, we noted the ranges of distance and percent effort. We constructed the throwing programs for the infielders and outfielders from these data and NCAA Baseball Rules.30


Data Management

We used the mean throws per game and mean distance of throws to compare the data on the catchers, infielders, and outfielders. We used the data for the shortstop to represent the infielders because they had the most plays, and, similarly, we used the data for the center fielders to represent the out-fielders. We then used an independent t test to compare the means across the age groups. We believed that a significant (P < .001) difference in the data between age groups would constitute the need for separate throwing programs for the levels of play that differed.

In constructing the ITPs for all players, we considered the competitive level at which they participate, the dimensions of the field on which they play, their position of play, the data collected, the types of injuries that baseball players commonly sustain, and a comprehensive understanding of tissue-healing properties. Separate programs were developed for catch-ers, infielders, and outfielders because the imposed demands of the game are different at each position. The throwing programs we designed are representative of the range of activities a player will encounter at a specific level of play and a particular position. The simulated game is based on the maximums of all data collected, because in any given game an athlete might have to perform at the maximum level of play.9

Results

Catchers

The catchers averaged from 4.39 (14- to 15- and 16- to 18-year-olds) to 6.51 (13-year-olds) throws to base per game at an average effort from 90.23% (college) to 96.53% (13-year-olds). The distance of their throws ranged from 50 to 150 ft. We found no significant (P < .001) differences between the number of throws to base per game or mean distance of throws to base for the catchers at different levels of play. We did, however, find that 16- to 18-year-old catchers only throw the ball back to the pitcher an average of 74.81 times per game. The other age levels ranged from 88.83 (college) to 95.25 (14- to 15-year-olds). We attribute this discrepancy to the small sample size of data for the 16- to 18-year-olds. We only collected data on them over 67 half-innings of play, compared with 307 for 13-year-olds and 349 for college level. We devised only 1 throwing program for catchers at all levels of play because of the lack of significant differences between age groups. Figure 1 details the throwing data for the catchers.

Infielders

We found no significant differences (P < .001) in the data between infielders at different levels of play. The most representative positions of our data were


the shortstops and third basemen. The mean distance of throws for the third basemen and shortstops of all ages were within 7 ft of one another, and the maximum distances ranged from 130 to 190 ft. The longest distances thrown were between 125 and 190 ft for all positions, and the minimum distances thrown were between 5 and 35 ft. All players had mean percent efforts in the low to mid 80s. The similarity of the data for all ages led us to design 1 ITP for infielders at all levels of play. The infielder distance of throws and maximum distances are shown in Figure 2.

Outfielders

The results of the data for the outfielders differed from that of the infielders and catchers. Although we could have written 1 throwing program for all age groups at the infielder and outfielder positions, we were not inclined to do so for the outfielders because we found a significant difference be-tween the mean distance of throws for the 13-year-old players and that of all other levels of play. The 13-year-old outfielders had mean distances of throws between 87.01 (left fielders) and 91.39 ft (right fielders) and longest distances of throws from 200 to 230 ft. The outfielders playing at higher levels of baseball had mean distances between 130.42 (14- to 15-year-old left fielders) and 171.13 ft (college right fielders) and high ends of the range of distance between 250 and 320 ft. Figure 3 shows the differences in mean distance of throws among the age groups we observed.

Throwing Program Design

Our data lead us to write 4 ITPs. Only 1 catcher and 1 infielder throwing

Figure 1 Catcher throwing data.


program were necessary for athletes at all levels of play. The outfielder pro-grams, however, were written separately for 13-year-old baseball players. The programs are designed to take an injured athlete from no throwing to a simulated game in which the player performs at the maximum possible level. All programs include short-toss and long-toss components. The long-toss component of the throwing program is designed to increase endurance in the muscles that are active during throwing.8 All long tosses should be thrown beginning with a “crow-hop.” The crow-hop is a hop and skip to gain momentum before throwing the ball. It allows the player to use the trunk and lower extremities to help the upper extremity deliver the ball to the target. The crow-hop is believed to minimize the risk of poor mechanics during long throws.27 Between each 2 steps of the throwing program, the throwing volume is increased by increasing the number of throws, number of sets, or the intensity of the throws.8 The instructions and soreness rules

Figure 2 Shortstop throwing data.

Figure 3 Center fielder throwing data.


guide the player through the progression and are necessary for the effec-tiveness of the programs to be maximized.

The catchers’ program is designed for all baseball catchers from the ages of 13 to college level. The catchers’ ITP consists of 2 phases and a total of 13 steps. The first phase is 5 steps long and readies the player for returning the ball to the pitcher. Throws begin at only 30 ft and progress to a mound distance of 60 ft, 6 in.30 In addition, long tosses between the distances of 60 and 90 ft are included at the end of each step in order to build endurance in the throwing arm.8 All throws in this phase are made at 50% effort. In phase II the catcher begins each step by completing the final step of phase I. The athlete then begins to return to live ball throws. The distances are tailored to the size of the field and the most common distances thrown by a catcher in a game situation.30 The intensities of the throws are progressed throughout the phase. Sprints are included in the program, and we believe that the catchers will normalize the amount of time in the squat stance to their preinjury preference. Active rest days are included on off days. Active-rest workouts include a warm-up to 60 ft, catching 5 pitches in the squat stance without returning the ball to the pitcher by throwing, 25 easy long tosses from distances of 60 to 90 ft, and 90-ft sprints after each long toss. The frequency of active-rest workouts increases throughout the program. Step 13 is a simulated game in which the catcher’s ability to participate in a game situation is tested. The catchers’ throwing program is detailed in Figure 4, and the instructions are listed in Figure 5.

Similar to the catchers’ program, the infielders’ ITP is designed for all infielders in all the age groups we observed. The throwing program for the infielders begins with throws up to 60 ft at only 50% effort. The player is then progressed over 6 steps to a simulated game in which all throws are made at 100% effort. Distances correlate with most common distances thrown by an infielder during a game situation and reach a maximum of 180 ft. An active-rest program is instituted after step 4 is completed without any soreness. The active-rest-day workouts consist of throws up to 50% ef-fort and up to 120 ft. The infielders’ program and instructions are located in Figures 6 and 7, respectively.

The data led us to develop 2 throwing programs for outfielders. One program is designed for 13-year-old outfielders, and the other, for all other outfielders. The 13-year-old program includes 7 steps, the last of which is a simulated game. The program begins with light tosses up to 60 ft and progresses toward a simulated game. In the simulated game, the player throws all throws at maximum effort up to distances of 210 ft. The adult outfielder ITP is also 7 steps long, but the distances thrown by the player are increased. The culmination of the program has the players throwing up to distances of 300 ft, as they sometimes do in a game situation. The active-rest program for the outfielders consists of throwing the warm-up and long-toss distances of the previous day’s workout. The throwing in-structions are designed to allow users of both programs to follow the same


Figure 4 Catcher throwing program.


Figure 5 Catcher instructions.

set of instructions. The throwing program for 13-year-old outfielders is detailed in Figure 8, and the adult outfielder program is found in Figure 9. The throwing instructions for both programs are in Figure 10.

Program Progression


The progression of an injured athlete through a throwing program is dictated by soreness rules and the type of injury the player sustained. Program pro-gression for a healthy athlete during the off-season or preseason is dictated by the soreness rules only.

Soreness Rules. Soreness rules were developed by Axe et al in order to dictate progression of throwing programs for baseball pitchers at all levels of play and for college softball players at all positions of play. The rules help dictate the rate of progression through the program by monitoring symptoms. It is important to note that athletes heal at different rates and therefore need to progress at different rates. Using the soreness rules so that the healing tissues are not overstressed controls for this variable. The soreness rules determine when a baseball player can progress to the next step, remain at that step, or drop down 1 step. In addition, they, along with the type of injury, dictate the amount of rest time between steps.8,9,28 The

Figure 6 Infielder throwing program.


Figure 7 Infielder instructions.

soreness rules are located in each set of instructions and in Figure 11.Injuries. We have classified the types of injuries that commonly occur

in baseball into 4 categories. These categories are non-throwing-arm injury; throwing-arm bruise; mild throwing-arm tendon or ligament injury; and moderate, severe, or post-op throwing-arm tendon or ligament injury. These categories determine how soon an athlete can return to throwing


and how quickly he or she can progress through the throwing program, including the number of rest days necessary between throwing days. The first day of throwing must be determined by the treating physician and the rehabilitation specialist working with the athlete. The decision will include the athlete’s progress with traditional therapies, tissue-healing times, and whether the parties involved believe that the athlete can withstand the stresses of throwing. The throwing instructions and soreness rules dictate the progression once the athlete has resumed throwing.8,9

CommentsThe purpose of our research was to develop ITPs for baseball players at all positions of play, except for the pitcher. In addition, our goal was to de-termine any age-related differences, that would suggest the use of different rehabilitation programs. Our goal was to provide appropriate programs for players from the age of 13 through college. A program for pitchers at these levels of play already exists8 and therefore did not need to be con-

Figure 8 13-year-old outfielder throwing program.


structed. The programs we are suggesting are to be used in conjunction with traditional therapeutic techniques.8,9 They are in the form of a functional progression toward return to play, and the simulated game is intended to determine readiness for play at a particular position and a particular level of play.29 For the effectiveness of these programs to be maximized, the instruc-tions and soreness rules must be followed. The purpose of the throwing programs is twofold. They can be used to return an injured athlete to play or as a training regimen for off-season or preseason workouts. We believe that, if followed as instructed, the ITPs we are suggesting will allow for the safest and most efficient return to play.9

Earlier we referred to the differences between pitchers and positional

Figure 9 Adult outfielder throwing program.


Figure 10 Outfielder instructions.

Figure 11 Soreness rules.


players and the paucity of research documenting these discrepancies. The well-documented pitcher studies are designed for a position of play that might only require an individual to participate at that position 1–2 times per week. The other positional players participate in every game and therefore must be conditioned differently. The programs we have designed account for this by adding active-rest workouts on the off days of the program. At most levels of play preceding college and professional, pitchers participate at several positions of play. The pitcher is usually the best thrower but is not able to pitch every day. The programs we have designed could allow an injured pitcher to return to another position before he or she is ready to pitch. The simulated game can be used to determine the game readiness we describe. The other important flexibility of our programs is the ability to rehabilitate a player to participate at several positions. Baseball players often participate at several positions of play. This is especially true at lower levels of play, when the players have not yet specialized at a particular position. The throwing programs we have designed allow, for example, infielders to follow a functional progression that will prepare them to play any position in the infield. The same is true for outfielders. The catcher, however, is a specialized position requiring an individualized program, which we have provided.

As indicated, few injury data are available on positional players other than the pitcher at any level of play. All published material outlines com-mon injuries to the upper extremity in pitchers. Common shoulder injuries in the overhead-throwing athlete are rotator-cuff impingement,11,12,17,21,31-39 rotator-cuff tears,12,17,21,32,37-40 rotator-cuff tendinitis,4,37,38 bicipital tendonitis,4,38 glenoid-labral tears,12,17,21,33,34,37-41 and glenohumeral instability.4,11,12,17,21,37,38,40 Common elbow injuries in the thrower are ulnar-collateral-ligament tearing or laxity,4,17,21,26,42,43 medial epicondylitis or flexor/pronator injury,4,43 tricipital tendinitis,43,44 osteochondral defects of the capitellum,17,21,43,44 osteophytic changes and loose bodies,17,21,26,43,44 and ulnar neuritis.17,21,26,43 Although these injuries are not specific to infielders, outfielders, or catchers, they do occur in overhead throwers, of which group these players are a part.

The listed injuries, however, do not encompass those of all ages. The programs we have designed cover a wide age range across several levels of play. The dynamics of throwing produces a different set of injuries on the adolescent arm. It is possible for the injuries that occur in adults to also occur in adolescents, but the epiphysis and changes occurring at the growth plate make the young athlete vulnerable to injuries not found in adults. Because the ligaments in adolescents are stronger than the epiphyseal sites are, an injury that might normally occur to the ligament in an adult often results in a fracture through the growth plate in a child.1,45-47 These dynamics lead to the prevalence of “little leaguer’s elbow” and “little leaguer’s shoul-der.” These terms encompass the multitude of injuries to young throwing athletes caused by the lack of a fused epiphyseal plate.1,47-50 Unfortunately, no data have been published showing the effects of throwing on young baseball players at positions other than pitcher. As previously described,


however, young players participate at several positions and therefore can-not be considered strictly pitchers. It is our belief that most of the injuries documented are a result of the combination of pitching and participating at other field positions.

The results of our study suggest that the younger outfielder is not re-quired to throw the long distance required in older age groups. This find-ing substantiates the need for 2 separate programs for baseball outfielders. Ignoring this fact and allowing a 13-year-old athlete to throw the distances required in older age groups could lead to the adolescent injuries described above. The infielders and catchers did not differ significantly in mean dis-tance or number of throws per game. All players age 13 and older play on the same size infield and therefore throw similar distances. In this case a need for separate throwing programs was not indicated.

We suggest that these data-based ITPs for baseball players age 13 through college be used as functional progressions within traditional rehabilitation programs after clearance by all medical professionals involved. This decision is based on an athlete’s ability to withstand the forces placed on the upper extremity during throwing at the low intensities required by the first step of his or her particular throwing program.8,9 In addition, we believe these ITPs to be useful as off-season or preseason conditioning programs. The programs are designed to be practical in order for self-implementation to be maximized. The need for supervision by an athletic trainer, physical thera-pist, or other qualified rehabilitation specialist might only be necessary to ensure that the athlete understands all instructions. The current standards in health care necessitate programs that patients are capable of administering on their own. We believe that we are suggesting a set of ITPs for baseball players of various levels and positions of play that, if used correctly, will provide for the safest and most efficient return to sport possible.

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AcknowledgmentsWe would like to thank Chris Kuchta; Tom Beddow, ATC; and Robbin Wickham,

MSPT, for their help in this research.

data-based interval throwing programs for … axe, windley, and snyder-mackler interval throwing...

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