Download Plyometric Supraspinatus Strengthening in High School Baseball

INJURY PREVENTION &
PERFORMANCE ENHANCEMENT
Joe J. Piccininni, EdD, CAT(C), Report Editor
Plyometric Supraspinatus Strengthening
in High School Baseball Players
Matthew J. Somma, PT, DPT, CSCS • OA Center for Orthopaedics
and Travis L. Orth, PT, MS, DPT • Therapeutic Associates, Inc.
C
omplex coordination of numerous muscle
contractions is required to effectively throw
a baseball. The complexity of the task is
heightened during a game, during which
the velocity and location of the pitch determine success. The inherent instability of the shoulder makes
baseball players highly susceptible to injury, and adolescent players are especially susceptible.1 Shoulder
injuries in baseball range in severity from general
tenderness to Little Leaguer’s shoulder, which involves
a stress fracture of the proximal humeral epiphysis.2,3
Such injuries are often associated with overuse and
pitching while fatigued.4 Previous research has demonstrated that type of pitch, number of pitches thrown
per game, and number of pitches thrown during
the season can contribute to shoulder pain in youth
baseball pitchers.5 Fleisig et al.6 reported that fundamental pitching mechanics remain constant during
progression through youth, high school, college, and
professional levels of competition, but joint forces
increase as an athlete matures. Thus, players at high
levels of competition possess elevated risk for injury.
Fortunately, increasing strength as the body matures
can help prevent such injuries.
The incidence rate of injuries requiring medical
intervention in adolescent baseball players appears
to be increasing,7 which is believed to be associated
with an increase in both the intensity and frequency
of competition.8 Many overuse shoulder injuries do
not develop until the mid to late teens (i.e., high school
age).9Guidelines for injury prevention in baseball have
been focused on limitation of the total number of
pitches thrown during a game or season and regulation
of the types of pitches thrown.4,5
Research has demonstrated that proper preparation and strengthening of the shoulder musculature can
prevent injuries in throwing athletes.7,10-12 Many of the
training programs developed exclusively for baseball
players have focused on strengthening the rotator cuff
muscles (i.e., subscapularis, supraspinatus, infraspinatus, and teres minor),13,14 which dynamically stabilize
the glenohumeral joint.15 The supraspinatus tendon is
especially vulnerable to injury during performance of
the throwing motion due to its anatomical proximity
to the inferior surface of the acromion. Both overuse
tendinosis and also impingement of the supraspinatus
tendon between the head of the humerus and the acromion are associated with muscular weakness.16 Supraspinatus weakness has been related to the incidence
of shoulder injury in professional baseball players.17
Yanagisawa et al.18 identified increased MRI signal
intensity in the supraspinatus muscle after a pitching
session. Thus, adequate strength of the supraspinatus
muscle appears to be an important factor for prevention of throwing injuries in baseball players.
Plyometric exercises, which involve rapid transitions from eccentric to concentric muscle contractions,
have been advocated for rotator cuff strengthening.19
Rapid transition in contraction mode during the stretchshortening cycle is believed to enhance muscle reactive capabilities that improve dynamic joint stability.20
Plyometric training regimens often use medicine balls
for performance of exercises that replicate the eccentric and concentric forces associated with pitching.
© 2011 Human Kinetics - IJATT 16(6), pp. 21-25
international journal of Athletic Therapy & training
november 2011  21
Despite widespread use of plyometric training, very
little research has been done to assess the effectiveness
of such programs. The “Ballistic Six” is a sport-specific
plyometric training program designed to strengthen the
rotator cuff muscles in the throwing athlete.21 Carter
et al.22 found that this program significantly improved
throwing velocity in college baseball players, but the
strength increase that resulted was not significantly
greater than that observed in players who performed
an alternate off-season strengthening program that
involved elastic resistance and dumbbells, and they did
not specifically assess strength increase in the supraspinatus muscle. We examined the effectiveness of the
“Ballistic Six” for strengthening of the supraspinatus
musculature in high school baseball players.
Discussion
Numerous studies have documented that high school
baseball players are at high risk for the occurrence of
a shoulder injury,2,8,29 which is primarily due to the
ballistic nature of the throwing motion.6,15 The supraspinatus muscle is particularly susceptible to injury.17,18
Procedures and Findings Four high school baseball players were recruited from
two high schools in Portland, Maine: one catcher, one
pitcher, one infielder, and one outfielder (average 16.25
years of age, 174.1 cm height, 71.4 kg weight). Three
of the participants played at the varsity level and one
was on a freshman baseball team. One participant who
was also engaged in a separate off-season program of
exercises and baseball pitching was dismissed after
shoulder fatigue precluded continued participation in
the “Ballistic Six” training program.
Hand-held dynamometry was used to obtain two
pretraining assessments of the supraspinatus strength
that were at least seven days apart (Figure 1). Kelly
et al.23 demonstrated that isolated activation of the
supraspinatus muscle is best achieved in a position
of 90 degrees of scapular elevation and 45 degrees of
glenohumeral external rotation, and hand-held dynamometry is an accepted method for determination
of upper extremity strength.24-28 The two pretraining
strength assessments were averaged to establish baseline strength level, after which participants completed
a 10-week training program (Table 1).The “Ballistic
Six” program consists of six plyometric exercises
that are performed two times per week (Figure 2).21
Each exercise session was supervised by the principal investigators to ensure program completion and
to monitor participant safety. A single post-training
strength assessment was performed within one week
of completion of the 10-week training program. All
three of the athletes demonstrated an increase in
supraspinatus strength (Table 2), which averaged 4.28
kg of increased force output.
22  november 2011
Figure 1 Positioning for hand-dynamometer measurement of supraspinatus strength.
Table 1. Progression of the
Ballistic Six Exercise Program
Phase
Volume
Intensity
Weeks
1-4
3 sets of 10 repetitions, 30 seconds rest
between sets
2.2-lb ball for onehanded throws
6 lb-ball for twohanded throws
Weeks
5-7
3 sets of 15 repetitions, 30 seconds rest
between sets
2.2-lb ball for onehanded throws
8-lb ball for twohanded throws
Weeks
8-10
3 sets of 20 repetitions, 30 seconds rest
between sets
2.2-lb ball for onehanded throws
10-lb ball for twohanded throws
international journal of Athletic Therapy & training
Figure 2 Components of the “Ballistic Six” exercise program: (a) external rotation in adducted position
against elastic resistance, (b) external rotation exercise in abducted position against elastic resistance, (c)
overhead weighted-ball toss, (d) externally rotating weighted-ball toss, (e) deceleration catch of weightedball toss, (f) acceleration toss of weighted-ball.
Table 2. Athletes Demonstrating an Increase in
Supraspinatus Strength
Player
Pretraining
Strength Trial 1
Pretraining
Strength Trial 2
Pretraining
Strength Mean of
Trials 1 & 2
Pre- to
Posttraining
Posttraining Strength
Strength
Change
1
10.85
8.05
9.45
13.40
3.95
S2
6.10
7.10
6.60
12.95
6.35
3
10.55
10.05
10.30
13.15
2.85
international journal of Athletic Therapy & training
november 2011  23
Trakis et al.12 reported that adolescent baseball pitchers
with shoulder pain demonstrated less supraspinatus
strength compared to those without pain and suggested
that it might result from repetitive eccentric loading.
They also suggested that prophylactic strengthening of
the rotator cuff muscles might prevent injury in adolescent baseball players. Weakness of the supraspinatus in
professional baseball players has been associated with
elevated risk for in-season throwing-related shoulder
injuries that require surgical intervention.30
Several studies have assessed the effectiveness of
different exercises for strengthening of the supraspinatus muscle,31-33 but none of them involved multidirectional functional movement patterns that replicate
components of the baseball throwing action. The
“Ballistic Six” program was designed to replicate the
stresses imposed by throwing a baseball through plyometric exercises, which have been shown to be very
effective for realization of strength gains.34 Carter et
al.22 examined the effect of an 8-week “Ballistic Six”
exercise program on pitch velocity, as well as internal
and external rotation strength, in collegiate baseball
players, but the strength measurements did not isolate
the force output of the supraspinatus muscle.
The exercise program we administered closely
followed the progression described by Pretz.21 The
players were encouraged to perform both single-arm
and double-arm throwing exercises with the greatest
amount of force possible, without compromising form.
Each athlete was closely monitored during each training session to ensure compliance with proper exercise
performance technique, with verbal cues provided
when necessary to correct improper form.
An advantage of this program is the minimal
amount of equipment that is required. The entire program can be completed with resistive elastic tubing
material and four weighted balls (2.2-lb, 6-lb, 8-lb,
and 10-lb). The exercises can be performed by pairs
of athletes, with one player throwing the weighted ball
while the second player monitors form and tosses the
weighted ball back to the exercise partner.
Conclusion
The results of this pilot study suggests that supraspinatus muscle strength can be improved through a
10-week, sport-specific, plyometric training program,
which may reduce the risk of shoulder injuries in male
high school baseball players.
24  november 2011
End Note
A detailed Study Methods file for this study can be
found on the IJATT website under Extras. 
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international journal of Athletic Therapy & training
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Matthew Somma is a staff physical therapist with OA Center for
Orthopaedics in Saco, ME.
Travis Orth is a staff physical therapist, Seattle PT, Therapeutic Associates Inc. in Seattle, WA.
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