- A study of over 700 minor league baseball players found that 52% did not specialize in baseball until at least age 17, with non-white American players less likely to specialize early. Climate was also a factor, with players from warmer climates specializing earlier. - Hamstring injuries are common in baseball, with a rate of 0.7 injuries per 1000 athletic exposures. The Nordic hamstring exercise was found to reduce hamstring injury rates by 25% in MLB. - Concussions made up 0.42% of injuries in MLB regular season play. Catchers accounted for 40% of MLB concussions despite being only 7.4% of non-concussive injuries. Pitchers

1. Update from Baseball Academia:
What’s New in Baseball Medical
Research
Aaron Gray, M.D. (@MizzouSportsDoc)
Assistant Professor, Departments of Family
Medicine & Orthopaedics
University of Missouri

2. Overview
• Youth Baseball Specialization
• Hamstring Injuries
• Concussions
• Tommy John (Ulnar Collateral Ligament) Injuries
• Inverted W

3. Patterns of Specialization in
Professional Baseball Players
• Ginsburg et al. Journal of Clinical Sport Psychology
2014.
– Surveyed 708 minor league baseball players
• 20% Spanish speaking not from North America
• Mean age of sports specialization 15.52 years
– 52% didn’t specialize until at least age 17

4. Age of Specialization by Ethnicity
Survey
Respondents
Age began
playing
baseball
Age
specialized
in baseball
% who
specialized
after age 16
Total Sample n=708 6.2 15.5 64%
White
American
438 (63%) 5.3 16.5 75%
African
American
34 (5%) 10.5 17.2 79%
Asian 10 (1%) 8.9 10.9 0%
Hispanic non-
American
140 (20%) 6.1 12.7 39%
Hispanic
American
44 (6%) 6.1 14.1 43%
Other 27 (4%) 6.6 14.5 42%

5. Climate Effects on Specialization in
Professional Baseball Players
• 59% of North American players came from “warm
climate” conducive to year-round practice
– Warm climate specialized earlier (15.8)
– Cool climate (17.6)
• Analysis was done that determined “ethnicity and climate
were both related to specialization age, irrespective to
the other”

6. Major League Baseball Injury
Surveillance System
• 2010 - MLB, players union, and minor league affiliates
reached agreement on creating a electronic medical
records system and injury tracking system
– Ability to track traded players
• 2011 - first year of 100% involvement of all MLB and
MiLB teams
– MiLB ~245 clubs and ~7500 players
– MLB 30 clubs and ~1200 players

7. Major League Baseball Injury
Surveillance System
• MLB Health and Injury Tracking System (HITS)
– Centralized database with de-identified medical data from MLB
Electronic Medical Record (EMR)

8. Hamstring Injuries
• Studies in multiple sports show re-injury risk of 12-31%
• 2011 – Players with hamstring injuries collected $30
million while disabled

9. Major and Minor League Baseball
Hamstring Injuries
• Christopher Ahmad et al. AJSM, 2014.
• Epidemiological Findings from the Major League
Baseball Injury Surveillance System
• Only recorded time loss hamstring injuries occurring in a
game (spring training, regular season or post season)

10. Athlete Exposure
• 1 athlete involved in a practice or game = 1 athlete
exposure
– Basically, every player in the box score
• Example of National League game
• 9 players start game + 2 relief pitchers + 2 pinch hitters =
13 athlete exposures
• Limitations

11. 2011 Major and Minor League Baseball
Time Loss Injuries
Major League Minor League Total
Avg # of players
per game
14 13 13
# of athlete
exposures (AE)
69,076 302,744 366,886
# of players
injured
541 2558 3099
Total game
injuries
871 3697 4568
Injury rate (per
1000 AE
12.5 12.0 12.1

12. Time Loss Injuries by Body Part and
Injury Type
Injury Diagnosis Major
League
Number
Major
League
Percentage
Minor
League
Number
Minor
League
Percentage
Hamstring Strain 50 5.7 218 5.9
Adductor Strain 36 4.1 85 2.3
Oblique Muscle Strain 36 4.1 88 2.4
Hand Contusion 32 3.7 203 5.5
Leg Contusion 26 3.0 124 3.4
Concussion 18 2.1 101 2.7

13. Hamstring Injuries
• In 2011 - MLB & MiLB: Hamstring injury rate 0.7 per
1000 AE
• ~1 hamstring injury per 100 games per team

14. Hamstring Strains by Activity
MLB # MLB % MiLB # MiLB %
Base running 31 62 154 70.6
Fielding 10 20 29 13.3
Unknown 4 8 8 3.7
Pitching 2 4 14 6.4
Other 1 2 2 0.9
Catching 1 2 3 1.4
Hitting 1 2 6 2.8
Majority of base running injuries were running to first and majority of those were
right handed.

15. Time-Loss to Hamstring Injuries
12
22
30
10
26
5
21
27
25
23
0
5
10
15
20
25
30
35
1-3 days 4-7 days 8-15 days 16-30 days >30 days
PercentageofHamstringInjuries
MLB % MiLB %
Average time-loss
MLB - 24 days
MiLB - 27 days

16. Recurrent Hamstring Injuries
• Only reported if player had an injury in 2010 and 2011
• 20% of major league injuries were recurrent
• 8% of minor league injuries recurrent
• Much greater recurrence rates than oblique or adductor
groin strains

17. Recurrent Hamstring, Oblique and
Groin Injuries
Major League Minor League
Total in 2010 Recurrent in
2011
Total in 2010 Recurrent in
2011
Hamstring 50 10 375 18
Oblique 44 0 148 4
Groin 34 2 100 1

18. Hamstring Injury Seasonal Timing
0
20
40
60
80
100
120
140
160
April May June July August September
TEMPDEGREESORNUMBEROFGAMES
Injury Rate (1 Hamstring Injury Every n Games)
MLB MiLB Avg Temp

19. Hamstring Injury Prevention

20. Hamstring Injury Prevention
• Soccer Hamstring Injury Rates
– Recurrence rate of 22% within first 2 months
– 25% recur the following season
• Petersen et al. AJSM 2011
– ~1000 professional & amateur soccer teams randomized to 10
week eccentric training program followed by weekly seasonal
program

21. Nordic Hamstring Exercise

22. Nordic Hamstring Exercise Protocol

23. Results
3.8 3.1
7.1
13.1
8.1
45.8
Overall Initial Recurrent
Hamstring Injuries per 100 Player Seasons
Intervention Control

24. MLB Hamstring Prevention Pilot
Program
• Some Minor and Major League teams started using the
Nordic Hamstring Curl preventative exercises
– 25% reduction in hamstring injuries in MLB
– Decreased days lost to 14.25 days from 24 days previously

25. Concussions
• Gary Green et al. AJSM 2015.
• Mild Traumatic Brain Injury in Major and Minor League
Baseball Players

26. Concussions
• 2010 Pilot Data was collected
– 50% of concussions got better in 7 days or less
• This data led to the 7 day concussion disabled list
• Data for this study from 2011-2012

27. Concussions
• Injury rates were only calculated for regular season and are
per 1000 Athlete Exposures
Total MLB MiLB
Concussions 307 266 41
Regular Season 277 241 36
Used to calculate
time loss
207 170 31
Injury Rate 0.42 0.46 0.26

28. Excluded from Time Loss Calculation
• Injuries occurred less than 30 days from end of season
and they did not return
• Injured toward end of spring training with more than a
week until regular season game
• If they participated in short season
• Season ending injury

29. Time Loss Results from Concussion
• Majors
– TL HITS: Mean 11, median 8 (range 0-51)
– TL Medical Director: Mean 11, median 9 (range 1-44)
– TL Box Score: Mean 13, median 9 (range 0-60)

30. Activity During Concussion
53.4
27.4
9 10.1
51.2
19.5
14.6 14.6
0
10
20
30
40
50
60
Fielding Batting Running Other
Minors Majors

31. Fielding Concussions by Position
14.8
40.8
26.1
18.3
9.5
47.6
28.6
14.3
Pitcher Catcher Infield Outfield
Percentage of Concussions by Position
Minors Majors

32. Catchers
• 7.4% of all non-concussive injuries but 40% of MLB
concussions!
Major League Minor Leagues
Player Collision 4 (40%) 24 (41%)
Contact w/ batted
ball
6 (60%) 18 (31%)
Contact w/ non-
pitched ball
0 5 (9%)
Contact w/
pitched ball
0 0
Contact w/ bat 0 9 (3%)

33. Pitchers
• 23 concussions by pitchers
– 15 hit with batted ball and 2 in MLB
• ~750,000 pitches per year in MLB and on avg 1-2
pitchers hit in head each year
Bryan Mitchell

34. Tommy John Injuries
• Prevalence of Ulnar Collateral Ligament Surgery in
Professional Baseball Players
• Conte et al. AJSM, 2015.
• Online survey administered by certified athletic trainers
for each MLB team to all MLB and MiLB players

35. Tommy John Injuries
• 5088 players responded
– Pitchers 53% of respondents
• 10% of players reported previous Tommy John surgery
– 16% of pitchers
– 3% of non-pitchers

36. Tommy John Injuries
• Major League Pitchers
– 25% had a history of Tommy John surgery
– 86% had TJ surgery as a professional
• Minor League Pitchers
– 15% had history of Tommy John surgery
– 61% had TJ surgery during high school or college
• No difference in prevalence in pitchers born in United
States vs Latin America

37. The Inverted W: Good or Bad?

38. Early Cocking Phase Mechanics and Upper
Extremity Surgery Risk in Starting Professional
Baseball Pitchers
• Douoguih et al. Orthopedic Journal of Sports Medicine,
2015.
• 250 starters during 2010 season included in study
• Video for each pitcher was reviewed for Inverted W and
early trunk rotation
• Identified shoulder or elbow surgery from beginning of
career to end of 2010

39. • Inverted W – defined as elevated of 1 or both elbows
above the shoulder in early cocking phase of throwing
motion

40. Early Trunk Rotation – trunk rotation before stride foot hits the ground
and occurrence of non vertical trunk rotation at initiation of trunk
rotation

41. Results
• 2 investigators achieved consensus on inverted-W in
88% of players and early trunk rotation in 86% of players
Rate of Surgery, n/Total (%)
Position With Position Without Position
Inverted-W 28/93 (30%) 42/155 (27%)
Early trunk rotation 37/111 (33%) 30/132 (23%)

42. Future Directions
Return from injury studies using pitch tracking, batted ball
tracking, and defensive player tracking

43. Questions or Comments?
Email: grayad@missouri.edu
Twitter: @MizzouSportsDoc