Early Sports Specialization
Is Associated With Upper Extremity
Injuries in Throwers and Fewer Games
Played in Major League Baseball
Jamie Confino,* MD, James N. Irvine,* MD, Michaela O’Connor,* BA,
Christopher S. Ahmad,* MD, and T. Sean Lynch,*
Investigation performed at Columbia University Irving Medical Center, New York, New York, USA
Background: Single-sport athletes who specialize in baseball at a young age may have a greater predisposition to overuse injury,
burnout, and decreased career longevity when compared with multiple-sport athletes. The effect of sport specialization has not
been studied in professional baseball players.
Hypothesis: Major League Baseball (MLB) players who played multiple sports in high school would experience fewer injuries,
spend less time on the disabled list, play more games, and have a longer career than athletes who played only baseball in high
Study Design: Descriptive epidemiology study.
Methods: First- and second-round MLB draft picks from 2008 to 2016 who played in at least 1 professional game were included in
this study. Athletes who participated in 1 or more sports in addition to baseball during high school were considered multisport
athletes, and athletes who participated in only baseball were considered single-sport athletes. For each athlete, participation in
high school sports, injuries sustained in MLB and Minor League Baseball, number of days on the disabled list for each injury,
number of games played in both leagues, and whether the athlete was still active were collected from publicly available records.
Results: A total of 746 athletes were included in this study: 240 (32%) multisport and 506 (68%) single sport. Multisport athletes
played in significantly more mean total games (362.8 vs 300.8; P<.01) as well as more mean MLB games (95.9 vs 71.6; P¼.04)
than single-sport athletes. There was no difference in the mean number of seasons played in the major leagues (1.8 vs 1.6; P¼.15)
or minor league (5.25 vs 5.20; P¼.23) between multisport and single-sport athletes. Single-sport athletes had a significantly higher
prevalence of upper extremity injuries compared with multisport athletes (136 [63%] vs 55 [50%]; P¼.009). Single-sport pitchers
also had a higher prevalence of shoulder and elbow injuries (86 vs 27; P¼.008) and were more likely to have recurrent elbow
injuries (33% vs 17% recurrence; P¼.002) compared with multisport pitchers.
Conclusion: Professional baseball players who participated in multiple sports in high school played in more major league games
and experienced lower rates of upper and lower extremity injuries than players who played only baseball in high school.
Keywords: professional baseball; pitchers; MLB; sports specialization; throwers
Participation in youth sports has grown rapidly in recent
years, with an increase from 45 million athletes in 1997 to
60 million in 2008.
As this number has grown, we have
also observed a high percentage of youth athletes special-
izing in sports, with 27%of this 2008 cohort focusing on just
Sport specialization is defined as year-round
training in a single sport to the exclusion of other sports.
At the high school level, there are 7.8 million adolescents
playing organized high school sports annually, many of
which have specialized in 1 sport before high school.
In 2016, the American Academy of Pediatrics released its
third policy statement regarding the potential sequelae of
early sport specialization and high-intensity training at a
young age, including burnout, overuse injuries, and psycho-
The American Medical Society for Sports
Medicine also released a 2014 position statement advising
athletes to avoid sport specialization before adolescence.
is believed that sport specialization leads to young athletes
not having the opportunity to develop the proper neuro-
muscular skills and general fitness that can protect against
McGuine et al
prospectively evaluated 1544
The Orthopaedic Journal of Sports Medicine, 7(7), 2325967119861101
ªThe Author(s) 2019
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high school athletes and reported an association between
sport specialization and lower extremity injuries. Mean-
while, Bell et al
showed that single-sport high school ath-
letes were more likely to experience a history of overuse
knee and hip injuries.
Baseball requires repetitive technical skills, especially
during the act of pitching. In recent years, there has been
a dramatic increase in the number of high school and col-
legiate pitchers undergoing surgery for throwing-related
injuries. One study found a 4-fold increase in the number
of elbow surgical procedures performed on collegiate base-
ball pitchers and a 6-fold increase for high school pitchers
over a 10-year period.
Hodgins et al
found a 193%
increase in ulnar collateral ligament (UCL) reconstructions
from 2002 to 2011 in the state of New York, with a signif-
icant increase in the frequency of UCL reconstructions for
individuals 17 to 20 years of age.
These findings coincide
with a 2017 study reporting a higher percentage of high
school athletes specializing in baseball (60%vs 45%)ata
significantly earlier age (12.3 vs 15.4 years) than they were
10 years ago.
Fleisig and Andrews
found that pitching volume is a
risk factor for elbow injuries, as an increased number of
pitches per game, innings pitched per season, months
pitched per year, and pitching for multiple teams were all
significantly associated with an increased risk for these
injuries. Throwers who pitched more than 8 months per
year had a 500%increased risk for undergoing shoulder
or elbow surgery.
It is speculated that sport specialization
in baseball leads to more games played, a longer season,
and playing for multiple teams. All of these factors combine
to increase the risk for overuse injuries and the potential
need for surgery.
The purpose of this study was to (1) compare the incidence
in professional baseball players of single-sport specialization
versus multisport participation during high school, (2) iden-
tify differences in length of Major League Baseball (MLB)
career and total number of MLB games played between ath-
letes with a history of single-sport specialization versus mul-
tisport athletes, and (3) distinguish differences in injury
patterns and their incidence in those with single-sport ver-
sus multisport backgrounds. We hypothesized that MLB
players who played multiple sports in high school would
experience fewer injuries, spend less time on the disabled
list (DL), play more games, and have a longer career than
athletes who played only baseball in high school.
First- and second-round draft picks for all MLB teams from
2008 to 2016 were identified on www.MLB.com. First- and
second-round draft picks represented a higher-level baseball
player and were likely to have more public information avail-
able as well as a greater likelihood of playing professionally.
Athletes who played in at least 1 minor league game were
included in this study. A total of 751 athletes were isolated, 5
of whom never played a minor or major league game, result-
ing in 746 players being included in this study.
For each player, we collected high school sport participa-
tion, number of minor and major league games played, num-
ber of injuries sustained during minor and major league
games, number of days on the DL for each injury, and dura-
tion of career. Baseline characteristics were collected, such
as age, height, weight, and body mass index at the time of
draft, as wellas position played. Player data were obtained by
searching websites such as www.MiLB.com, www.MLB.com,
www.ESPN.com, www.FoxSports.com, www.MaxPreps.
com, and www.DraftExpress.com, as well as undergraduate
athletic websites through June 15, 2018. News articles were
used when internet data were limited.
Players were considered multisport athletes if they had
played a varsity, junior varsity, or competitive club sport in
addition to baseball during high school. Sports played before
high school or recreationally did not qualify as multisport.
We considered as injuries those that occurred during Minor
League Baseball (MiLB) and MLB games that resulted in
the athlete being on the DL for at least 7 days. Injuries
attributed to trauma, including fractures, concussions, con-
tusions, and lacerations, as well as illnesses, were excluded
from this study. Injuries were characterized by type, loca-
tion, and duration of time spent on the DL. The injury had to
occur while the athlete was employed by an MiLB or MLB
team to be included. MiLB injuries were excluded from sub-
analysis of type of injury, as there was a lack of reliable
public data for injury details. As a result, type and location
of injury were analyzed only for those sustained in MLB
Based on www.MiLB.com and www.MLB.com, the total
number of games played in professional baseball were com-
piled. The percentage of possiblegames played was calculated
by dividing the number of games played by the number of
games for which the athlete was listed as available.
status was characterized as active on the basis of whether the
player remained under contract with the MLB or MiLB.
Athletes were stratified by position into pitchers or posi-
tion players (nonpitchers). Analysis of injury prevalence
and number of total and possible games played was con-
ducted for pitchers only, position players only (nonpitch-
ers), and all athletes (pitchers and position players).
The unpaired ttest, 2-tailed chi-square test, and 2-tailed
Fisher exact test were all utilized. The specific use of each
Address correspondence to T. Sean Lynch, MD, 622 West 168th Street, PH-11, New York, NY 10032, USA (email: firstname.lastname@example.org).
*Department of Orthopedic Surgery, Columbia University Medical Center, New York, New York, USA.
One or more of the authors has declared the following potential conflict of interest or source of funding: C.S.A. has received consulting fees from Arthrex,
royalties from Arthrex, and hospitality payments from DePuy. T.S.L. has received educational support from Smith & Nephew and Arthrex and nonconsulting
payments from Smith & Nephew. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an inde-
pendent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Ethical approval was not sought for the present study.
2Confino et al The Orthopaedic Journal of Sports Medicine
test is listed in Table 1. Statistical significance in this study
was defined as a Pvalue <.05, and all statistical analyses
were performed with SPSS (v 24; IBM).
A total of 746 athletes were identified as first- or second-
round draft picks who played in the MLB or MiLB. Of these
athletes, 240 (32%) were multisport and 506 (68%)
were single sport. Besides baseball, the multisport
athletes played football (n ¼142), basketball (n ¼98),
soccer (n ¼15), hockey (n ¼12), track (n ¼7), golf (n ¼6),
and wrestling (n ¼2) in high school. There were no signifi-
cant differences between the multisport and single-sport
cohorts with respect to age, height, weight, or body mass
index at the time of the draft (Table 2). When player position
was compared between the cohorts, there was a significantly
higher percentage of pitchers in the single-sport cohort
(51.68%) than in the multisport cohort (41.42%,P¼.01)
Of the 746 athletes drafted, 326 (43.7%) played in at least
1 major league game from 2008 to 2018. The percentage of
multisport athletes who made it to the MLB was 46%as
compared with 43%for single-sport athletes. The multi-
sport athletes played in significantly more total games on
average (363 vs 301, P¼.004) and more MLB games on
average (96 vs 72, P¼.04) than the single-sport cohort
(Table 4). However, there was no significant difference in
percentage of possible games played between multisport
and single-sport athletes (84.0%vs 82.4%,P¼.157). There
was also no significant difference in in average career
length (P¼.157), mean number of seasons played in the
major and minor leagues (P¼.15, P¼.23 respectively), or
percentage of total games spent on the DL (P¼.229).
For athletes drafted in the first 2 rounds from 2008 to
2016, the most common MLB injuries were shoulder
impingement, elbow sprain, UCL tear requiring recon-
structive surgery, lumbar strain, and oblique strain
(Table 5). In MLB, single-sport athletes had a significantly
higher number of upper extremity injuries (shoulder,
elbow, forearm, wrist, and hand) compared with multisport
athletes (136 [63%] vs 55 [50%], P¼.009) (Table 6). Single-
sport athletes also had a higher number of knee and ankle
injuries than multisport athletes (30 [14%]vs10[9%], P
.001). Within multisport athletes, there was no difference
in the type of sport played outside of baseball or the ath-
letes’ risk of subsequent injury.
When only MLB pitchers were examined, single-sport
athletes had significantly more elbow and shoulder injuries
compared with multisport athletes (86 [75.44%]vs27
[56.25%], P¼.008) (Table 7). Additionally, among pitchers
Statistical Tests Used to Determine the Differences
Between the Multisport and Single-Sport Athlete Cohorts
Statistical Test Value Assessed
Unpaired ttest Baseline characteristics
Number of MLB games played and percentage
of total games played
Number of major injuries sustained, injury
type, and current MLB status
MLB, Major League Baseball.
Mean Baseline Characteristics at Time of Draft
(n ¼240) P
Age, y 19.80 20.01 .06
Height, in 74.45 74.13 .29
Weight, lb 198.50 198.59 .95
Body mass index 25.27 25.44 .35
Bold indicates P<.05.
Percentage Pitchers vs Position Players
(n ¼240) P
Pitchers, %51.68 41.42 .01
Position players, %48.32 58.58 .01
Bold indicates P<.05.
Mean Number of Games Played per Player
(n ¼240) P
Total games played, n 300.79 362.80 <.01
Major league games played, n 71.60 95.87 .04
Percentage of possible games
82.4 84.0 .157
Bold indicates P<.05.
Games for which the athlete was listed as available.
Most Common Injuries by Type (Major League Baseball)
(n ¼110) P
39 14 .046
Elbow sprain 23 7
UCL tear requiring Tommy
Lumbar strain 20 11
Oblique strain 17 12
Hamstring strain 14 12
Data are shown as No. of injuries. Bold indicates P<.05. UCL,
ulnar collateral ligament.
The Orthopaedic Journal of Sports Medicine Sport Specialization in Major League Baseball 3
who had at least 1 elbow injury, single-sport pitchers had a
higher rate of reinjury than the multisport players (33%vs
17%,P¼.002). Furthermore, a higher percentage of mul-
tisport pitchers made it to the major leagues as compared
with single-sport pitchers; however, this result was not sig-
nificant (48.0%vs 43.7%,P¼.181). No difference was found
in the number of All-Star Game appearances between the
groups (16 [14.6%]inmultisportvs29[13.4%]insingle
When only position players (nonpitchers) were exam-
ined, single-sport athletes continued to have significantly
more total injuries than multisport athletes (78.4%vs
61.3%,P¼.013). However, there was no difference in the
number of shoulder and elbow injuries between the position
player groups (49%vs 45%,P¼.153).
Limited information has been published on the effects of
early sports specialization asitpertainstoprofessional
baseball athletes. Our study is the first to report on the
incidence of specific baseball injuries, career longevity, and
the impact that early specialization has on MLB and MiLB
players. Unique to our study was the finding that single-
sport pitchers were at an increased risk of upper extremity
injury with a decreased number of games played when com-
pared with multisport pitchers. We also found that single-
sport athletes experienced significantly higher rates of both
upper and lower extremity injuries, suggesting that early
sports specialization may be placing young athletes at a
higher risk of injury as they progress throughout their
careers. In addition to these higher injury rates, these early
specializers played in significantly fewer total games in
their careers, including games played at the MLB level.
However, there was no difference between the cohorts with
respect to possible games played. Therefore, young athletes
interested in a baseball career at the highest professional
level can minimize their risk of overuse injuries and have the
potential for greater future longevity by participating in
multiple sports during high school. These findings should
be reiterated to parents and coaches who might influence
young athletes to train and participate in a single sport.
About one-third of the players included in our cohort
were multisport athletes, while a 1980s study on profes-
sional baseball players found that well over half of the
included athletes in its cohort had played basketball
(68.7%) or football (59.3%) while in high school.
shift toward specialization has occurred because of the mis-
conception that early sport specialization provides a perfor-
mance advantage that could lead to an earlier and higher
MLB draft opportunity or highly coveted collegiate scholar-
ships. A recent study of collegiate athletes found that the
primary drivers of specialization included personal inter-
est, skill level, time constraints, and the prospect of poten-
tial scholarship opportunities.
leads parents and coaches to encourage young athletes to
play on multiple teams and dedicate more hours to devel-
oping their game. However, the athletes themselves seem
to believe otherwise. In a study published by Wilhelm
only 27%of players believed that early specializa-
tion is helpful, while nearly two-thirds (63.4%)feltthat
early specialization is not advantageous.
In an attempt to ameliorate the misconception of the
benefits of early sports specialization, the American Ortho-
paedic Society for Sports Medicine released a consensus
statement emphasizing that early specialization places
young athletes at risk for overuse injuries and burnout.
Our results concur, as MLB and MiLB players with early
specialization had significantly higher rates of upper
extremity injuries (shoulder, elbow, forearm, wrist and
hand) as well as lower extremity injuries (knee and ankle).
Our findings may be due to increased training and throw-
ing volume for single-sport athletes, with many single-sport
athletes playing baseball for more months per year than
their multisport counterparts. In addition, it is possible
that multisport athletes benefit from neuromuscular train-
ing through sports other than baseball, causing a protective
effect against future injury. This was further reflected in
recent data showing an increasing frequency of early sport
specialization as well as UCL reconstruction in New York
State, particularly in the adolescent thrower between the
ages of 17 and 20 years.
This highlights the importance for
parents and coaches to recognize the connection between
early sports specialization and the risk of overuse throwing
This study has several limitations given our methodol-
ogy, which has been previously applied.
was the use of internet data to determine if an athlete
played multiple sports in high school; however, several pub-
lished baseball studies have used internet data in their
Injuries by Body Part
(n ¼110) P
Elbow 42 (19) 17 (15)
Shoulder 53 (25) 20 (18)
Forearm 12 (6) 6 (5)
Wrist 7 (3) 2 (2)
Bicep 8 (4) 2 (2)
Hand 14 (7) 8 (7)
Knee 21 (10) 8 (7)
Ankle 9 (4) 2 (2)
Total shoulder and elbow 95 (44) 37 (34) <.01
Total upper extremity 136 (63) 55 (50) <.01
Total 166 (77) 65 (59) <.01
Data are shown as n (%). Bold indicates P<.05.
Injuries by Body Part in Pitchers
(n ¼48) P
Elbow 40 (35) 14 (29)
Shoulder 46 (40) 13 (27)
Total shoulder and elbow 86 (75) 27 (56) .008
Data are shown as n (%). Bold indicates P<.05.
4Confino et al The Orthopaedic Journal of Sports Medicine
study design. The inability to accurately determine high
school sport participation from public sources is a signifi-
cant limitation. It is possible that athletes were categorized
as single sport when they actually participated in multiple
sports during high school. Another limitation is the use of
online sources for injury data, which can be inaccurate or
incomplete as compared with the MLB Health and Injury
Additionally, we did not investigate
injuries that occurred prior to the draft. There may have
been single-sport athletes who experienced a greater num-
ber of injuries in high school and college and were less likely
to make it to the first and second draft rounds for the MLB.
This is a potential area for injury risk assessment research.
Another limitation was the exclusion of minor league injury
specifics to include type and location, as these data were not
reliably available. Last, we looked at only the first 2 rounds
of the MLB draft, which provided us with an athlete cohort
with a skill set capable of playing at the professional level;
however, this cohort may not be representative of profes-
sional baseball as a whole.
Our findings suggest that professional baseball players
who participated in multiple sports during high school sus-
tain fewer upper extremity injuries (shoulder, elbow, fore-
arm, and hand) and lower extremity injuries (knee and
ankle) while also playing in more MLB games during their
career. In addition, pitchers who specialized early in life
had significantly higher rates of shoulder and elbow inju-
ries as well as higher reinjury rates. It is important for
parents, coaches, and players to understand that the
long-term impact of early specialization can have a delete-
rious downstream effect at the professional level.
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The Orthopaedic Journal of Sports Medicine Sport Specialization in Major League Baseball 5