Shoulder Dysfunction in High School Tennis Players - an exploratory study

Abstract

Previous studies have investigated sports activity related shoulder dysfunction, such as scapular dyskinesis and glenohumeral internal rotation deficit (GIRD), mainly in high-level tennis players. The prevalence of these dysfunctions in comparatively low to moderate level tennis players, such as those at the high school level is poorly understood. The purpose of this study was to explore the prevalence of scapular dyskinesis and GIRD at the high school level and identify some of the factors that makes a high school tennis player more susceptible to developing shoulder dysfunction. A survey related to sports-related shoulder dysfunction was developed in collaboration with physical therapists and was completed by twenty-seven high school level tennis players. The results show that players who have more years of experience, played tennis more often on a weekly basis, and were on the varsity team are more likely to develop shoulder pain and dysfunction. The average number of symptoms increased with years of playing experience and a higher frequency of playing tennis every week, with more than 40% of players on the varsity team reporting a decrease in the velocity, control, and arm motion during their serve. While male players reported more symptoms related to pain, decreased performance and strength, female players reported almost three times more occurrence of lower shoulders compared to male players. Players who consistently did workouts for shoulder and back muscles were less likely to develop shoulder pain and dysfunction, regardless of their level of experience and gender.

Full text

Shoulder Dysfunction in High School Tennis
Players - An Exploratory Study
Sandheep Ranganathan1 and Jothsna Kethar#
1Gifted Gabber, USA
#Advisor
ABSTRACT
Previous studies have investigated sports activity related shoulder dysfunction, such as scapular dyskinesis and
glenohumeral internal rotation deficit (GIRD), mainly in high-level tennis players. The prevalence of these
dysfunctions in comparatively low to moderate level tennis players, such as those at the high school level is
poorly understood. The purpose of this study was to explore the prevalence of scapular dyskinesis and GIRD
at the high school level and identify some of the factors that makes a high school tennis player more susceptible
to developing shoulder dysfunction. A survey related to sports-related shoulder dysfunction was developed in
collaboration with physical therapists and was completed by twenty-seven high school level tennis players. The
results show that players who have more years of experience, played tennis more often on a weekly basis, and
were on the varsity team are more likely to develop shoulder pain and dysfunction. The average number of
symptoms increased with years of playing experience and a higher frequency of playing tennis every week,
with more than 40% of players on the varsity team reporting a decrease in the velocity, control, and arm motion
during their serve. While male players reported more symptoms related to pain, decreased performance and
strength, female players reported almost three times more occurrence of lower shoulders compared to male
players. Players who consistently did workouts for shoulder and back muscles were less likely to develop shoul-
der pain and dysfunction, regardless of their level of experience and gender.
Introduction
Players involved in sports that require extensive overhead action, such as tennis and handball, are said to be at
higher risk for developing shoulder dysfunction such as scapular dyskinesis and glenohumeral internal rotation
deficit (GIRD). Lehman (1988) reported that high-level tennis players had a 24% prevalence of shoulder pain,
with prevalence increasing to 50% in middle aged participants. Similarly, Abrams et al. (2012) and Hutchinson
et al. (1995) found that shoulder injuries were present in 4% to 17% of tennis players at all levels. Recently,
Hickey et al. (2018) observed that athletes with scapular dyskinesis were at 43% greater risk for developing
shoulder pain even if the athletes were asymptomatic.
Scapular dyskinesis is the altered control of the shoulder blade muscles (Ruotolo, 2014). The overhead
action in throwing sports, specifically the serve motion in tennis, has been described as “unnatural and highly
dynamic, often exceeding the physiological limits of the joint” (van der Hoeven and Kibler, 2006). There are 5
stages during a tennis serve (Figure 1): wind up, early cocking, late cocking, acceleration, and follow-through.
During the cocking stages, the shoulder blade must retract as the racquet is brought back. The muscles that
retract the shoulder blade must also control it as the racquet is swung through the acceleration stage to the
follow-through stage within a fraction of a second. This motion causes the shoulder blade to be pulled forward,
which then needs to be pulled back again for the following serve or shot. As it is repeatedly put under stress,
the shoulder blade could sit in a protracted position and usually lower than the other shoulder, also known as
the “SICK scapula” shoulder pathology. This positioning of the scapula leads to an abnormal movement of the
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scapula during the overhead motion of a serve and a loss of muscular control (Ruotolo, 2014; van der Hoeven
and Kibler, 2006).
Fi g ure 1 . Five stages of a tennis serve (Ruddock, 2022)
GIRD is the tightening of the posterior capsule, or the tissue on the back of the glenohumeral (shoulder)
joint. As stress is repetitively put on the back of the shoulder capsule from serving, the capsule will thicken,
causing tennis players to lose internal rotation of their shoulder. The thickening of the capsule can affect how
the shoulder rotates and can result in superior labrum tears or tears in the cartilage where the biceps tendon
attaches to the top of the shoulder socket. A superior labral tear will cause a tennis player to drop significantly
in performance level if they are even able to play at all (Ruotolo, 2014).
Studies have mainly investigated scapular dyskinesis, GIRD, and other shoulder injuries in high-level
tennis players, but not much is known about their prevalence in comparatively lower-level tennis players, such
as those playing at the high school level. Since overhead sports have a lower rate of return to sport than others
due to the unnatural motion of an overhead action, such as a serve, it is crucial to take preventative measures as
early as possible. The purpose of this study was to explore the prevalence of scapular dyskinesis and GIRD
among students playing in high-school tennis teams and identify factors that make players more susceptible to
developing shoulder dysfunction. A better understanding of the risk factors will allow high school tennis players
to take preventive measures and possibly reduce the risk of developing shoulder dysfunctions such as scapular
dyskinesis and GIRD.
Methods
A sample size of convenience was used for this exploratory study. Players from the tennis team of a high school
located in greater Cleveland, Ohio were invited to participate in this study. Twenty-seven players agreed to
participate. A survey to collect information related to sports activity related shoulder dysfunction was developed
in collaboration with physical therapists associated with a local health system. The survey (Table 1) consisted
of 16 questions that were based on studies done by Kekelekis et al. (2020), Geier (2018), Roche et al. (2015),
Ruotolo (2017), and van der Hoeven and Kibler (2006). The survey collected information regarding partici-
pants' demographics, experience with tennis and/or other sports involving an overhead throwing motion, and
shoulder/ back workouts. A series of questions were used to identify (self-reported) whether or not the partici-
pants demonstrated symptoms indicative of scapular dyskinesis, “SICK scapula”, and/or GIRD.
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Table 1 . Survey questions and responses.
S urv e y Que stions
Possible Responses
Age (years)
Gender
Male
Female
Other
Prefer not to answer
How long have you been playing tennis? (years)
Do you play any other sport that requires an overhead
throwing motion?
Yes
No
Do you work out/exercise your back and shoulders on a
regular basis?
Yes
No
How often do you play tennis (times a week)?
1
2
3
4
5
6
7
Which team are you on?
Varsity
Junior Varsity
Which arm do you serve with?
Right
Left
Have you been diagnosed with any type of shoulder in-
jury/condition at some point in time? If yes, please name
the injury/condition. If no, type "No".
Free text
Do you have any pain around your shoulder blade on
your serving side?
Yes
No
Have you noticed any muscle fatigue in your shoulder
blade area on the side of your serving arm?
Yes
No
Have you noticed any decreased velocity, control, or
motion on your serves?
Yes
No
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Have you noticed any decrease in strength on your serv-
ing side?
Yes
No
Have you noticed a limited range of motion on your
serving side?
Yes
No
Have you noticed any level of protrusion of your shoul-
der blade?
Yes
No
Have you noticed that your serving shoulder sits lower
than the non-serving shoulder?
Yes
No
The survey responses were collected and transferred into a spreadsheet for analysis. Each subject was
assigned a pseudo identification and only the de-identified data was used. Mean and percentages were calculated
for the individual survey questions. Any relationship between player demographics, years/frequency of playing
tennis, team placement, specific workouts and symptoms related to shoulder pain, scapular dyskinesis, and
GIRD were explored.
Results
Of the 27 players who completed the survey, 37% were 16 years of age and 59% were male (Table 2). 48% of
the players had at least 4 years of experience playing tennis and 52% played at least 3 times a week. About 44%
of the responses came from varsity level players and 56% came from junior varsity level players.
Table 2 . Demographics and experience level for the survey respondents (n=27).
Play e r Demographics
Years of tennis experience (mean ± SD, range)
3.3 ± 2.1, 0 - 8
Playing frequency, times a week (mean ± SD, range)
3.0 ± 2.0, 0 - 7
Age in years (mean ± SD, range)
15.9 ± 1.3, 14 - 18
Gender
Male (n = 16, 59%)
Female (n = 11, 41%)
Participate in workout
Yes (n = 12, 44%)
No (n = 15, 56%)
Play other sports Yes (n = 11, 41%)
No (n = 16, 59%)
School tennis team
Varsity (n = 12, 44%)
Junior Varsity (n = 15, 56%)
Tennis serving arm
Right (n = 26, 96%)
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Left (n = 1, 4%)
Of the 27 players, 5 players reported having shoulder pain, 5 players reported a decrease in strength
on their serving side and 7 players reported a decrease in the velocity, control, or motion during their serves.
Almost half of the players reported at least one symptom of scapular dyskinesis or GIRD. The average number
of symptoms increased with years of playing experience (Figure 2). The most common symptom overall was
muscle fatigue (11 out of 27 players) with more than half of varsity level players reporting this symptom (Figure
3). More than 40% of varsity level players also reported a decrease in velocity, control or motion while playing.
Overall, players reported 1.33 symptoms on average. Players who played tennis 4-7 times a week reported 2.56
symptoms on average while those who played 1-3 times a week reported 0.72 symptoms on average. Players
on the varsity team reported 2.08 symptoms on average while players on the junior varsity team reported 0.73
symptoms on average. Male players reported 1.5 symptoms on average while female players reported 1.09
symptoms on average. Table 3 provides a breakdown of the number of players from various groups reporting
symptoms related to shoulder dysfunction.
Fi g ure 2 . Average number of shoulder dysfunction symptoms reported increases with years of experience.
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Fi g ure 3 . More than half of varsity level players reported muscle fatigue.
Table 3 . Breakdown of players (n, % of players) reporting various symptoms for shoulder dysfunction.
Gro u p
Pain
Decrease in
velocity,
control or
motion
Decrease in
strength
Limi ted
range o f mo-
tion
Sho ulder
Bl ade protru-
sion
Low er shoul-
der
Entire Group
(n = 27)
5 (18.5%)
7 (25.9%)
5 (18.5%)
2 (7.4%)
1 (3.7%)
4 (14.8%)
Male
(n = 16)
4 (25.0%)
4 (25.0%)
5 (31.3%)
2 (12.5%)
1 (6.3%)
1 (6.3%)
Female
(n = 11)
1 (9.1%)
3 (27.3%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
3 (27.3%)
Varsity
(n = 12)
3 (25.0%)
5 (41.7%)
3 (25.0%)
2 (16.7%)
1 (8.3%)
3 (25.0%)
Junior Varsity
(n = 15)
2 (13.3%)
2 (13.3%)
2 (13.3%)
0 (0.0%)
0 (0.0%)
1 (6.7%)
Do workouts
(n = 12)
0 (0.0%)
1 (8.3%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
3 (25.0%)
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No workouts
(n = 15)
5 (33.3%)
6 (40.0%)
5 (33.3%)
2 (13.3%)
1 (6.7%)
1 (6.7%)
Play another
sport
(n = 11)
2 (18.2%)
3 (27.3%)
2 (18.2%)
1 (9.1%)
0 (0.0%)
3 (27.3%)
No other sport
(n = 16)
3 (18.8%)
4 (25.0%)
3 (18.8%)
1 (6.3%)
1 (6.3%)
1 (6.3%)
Shoulder Dysfunction in Players Who Did Not Do Workouts or Play Other Sports
Out of the 27 players, 12 did not do shoulder and back muscle workouts on a consistent basis and did not play
another sport that involved an overhead throwing motion. Nearly 40% of these players reported a decrease in
their tennis performance, possibly related to shoulder dysfunction. In this group, players (n = 2) with 8 years of
experience reported at least 3 symptoms of scapular dyskinesis, with one player reporting 5 symptoms of scap-
ular dyskinesis and 1 symptom of GIRD. 80% of players (n = 5) with only a year of experience reported 0 signs
of scapular dyskinesis or GIRD. The maximum number of symptoms exhibited by a male player in this group
was 6 (n = 2), while the maximum number of symptoms exhibited by a female player was 3 (n = 1). Players
that played tennis only once a week (n = 8) reported 0 symptoms of shoulder dysfunction, whereas 56% of those
that played tennis 4 times a week or more (n = 9) reported at least 2 symptoms of shoulder dysfunction. Also,
100% of varsity level players reported at least 2 symptoms of scapular dyskinesis while only 25% of junior
varsity players reported any symptoms for scapular dyskinesis and GIRD.
Shoulder Dysfunction in Players Who Did Workouts
Only 12 out of the 27 players did workout for their shoulder and back muscles on a regular basis. The players
in this subset had 3.67 years of experience on average and played 2.83 times a week on average. The average
number of reported symptoms in this subset was 0.75 per player, which was 0.58 symptoms lower than the
entire group average and 1.05 symptoms lower than the players who do not workout regularly. 50% of players
who regularly work out their shoulder and back muscles reported 0 symptoms of scapular dyskinesis or GIRD
and the maximum number of symptoms reported by this group was 3 (n = 1).
Shoulder Dysfunction in Players Who Played Other Sports Involving Overhead Action
Of the 27 tennis players, 11 played another sport that involved an overhead throwing motion. The players in
this subset had on average 3.18 years of tennis experience and played 3.91 times a week. The average number
of symptoms reported in this subset was 1.45 per player, which was 0.12 symptoms higher than the entire group
and 0.20 symptoms higher than the average of players who do not play another sport involving an overhead
throwing motion. 64% of players who played another overhead sport reported at least 1 symptom, with the
maximum number of symptoms in this group being 6 (n = 1).
Discussion
The purpose of this study was to explore the prevalence of scapular dyskinesis and GIRD in high school
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tennis players and identify any relationship between various factors (years played, team level, practice fre-
quency, workouts, playing other overhead sports) and shoulder dysfunction/pain in high school tennis players.
The results indicate that those who have played tennis for a longer period of time, played more often on a
weekly basis, and/or played on the varsity team are more likely to develop shoulder pain than those with less
experience or played at a lower skill level. The results also show that males are more prone to developing
shoulder problems compared to females. Players who regularly work out their shoulder and back muscles are
less likely to exhibit symptoms of scapular dyskinesis and GIRD than those who do not, regardless of experience
level.
Major symptoms of both scapular dyskinesis and GIRD are shoulder pain and muscle fatigue. A higher
level of experience or exposure to tennis has been shown to increase the probability of a high school tennis
player developing shoulder pain. 48% of players reported having at least one symptom of scapular dyskinesis
or GIRD. 41% of all players and 42% of players who did not work out and did not play other sports requiring
overhead motion reported having muscle fatigue in their scapular region. As stated by van der Hoeven and
Kibler, the tennis serve is an overhead throwing motion that exceeds the physiological limits of the shoulder
joint, which increases the probability of high school tennis players developing shoulder pain. 75% of all varsity
players and 100% of varsity players in the no workout or other sport group reported at least 1 symptom of
scapular dyskinesis or GIRD, whereas only 33% of all junior varsity players and 25% of junior varsity players
in the no workout or other sport group reported at least 1 symptom. With almost half of all players reporting at
least 1 symptom of either pathology, it is not surprising that varsity level players, with longer and more frequent
exposure to tennis, are at higher risk of developing shoulder pain and other shoulder dysfunctions. The results
of this study are similar to those reported by Kekelekis et al. (2020).
In the study by van der Hoeven and Kibler (2006) it was noted that GIRD can lead to shoulder pain
and dysfunction in tennis players. 30% of the tennis players who responded to the survey reported GIRD symp-
toms with 75% of them reporting shoulder pain as well. Geier (2018) and Roche et al. (2015) observed de-
creased control and velocity during throwing and changes in shoulder function such as decreased strength and
arm motion as a result of scapular dyskinesis in tennis players. In the current study, around 30% of players
reported decreased control and velocity during their serves or decreased shoulder motion and strength in general
with 63% of these players also reporting shoulder pain as well.
A high school singles tennis player is expected to serve at least 24 times throughout a three-set match,
assuming that they win every single point. The minimum number of serves drops down to 16 for doubles play-
ers. However, the chances of any tennis player winning every point is extremely low, be it at the high school,
college, or professional level. A study conducted by Myers et al. (2016) noted that tennis players typically serve
40 times per set on average regardless of age and gender. Thus, the average number of serves per match for
high school tennis players would be about 80-120 within a very short period. In addition to matches, the number
of serve repetitions during practices will be even higher, in the order of hundreds of serves each week. When a
tennis player repeats a serve motion in such high volumes, the scapula does not fully retract back to its original
position. This can result in weakness of the muscles that stabilize the scapula (serratus anterior, rhomboids,
levator scapulae, trapezius) as they do not contract to adduct the scapula as often after the follow-through stage
of a tennis serve. In this study, since varsity level players tend to play more matches and have more experience
than junior varsity level players, the varsity players were more susceptible to scapular dyskinesis and GIRD.
Also, while male players reported more symptoms related to pain, decreased performance and
strength, female players reported almost three times more occurrence of lower shoulders compared to male
players.
An interesting observation in this study was the potential protective effect of doing shoulder and back
workouts on shoulder pain and dysfunction. The players who consistently performed shoulder and back
workouts reported less symptoms on average than those who do not. Scapular dyskinesis results from certain
muscles being too weak to stabilize the scapula. Routinely performing shoulder and back exercises to strengthen
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these muscle groups could be a possible scapular dyskinesis prevention technique. In fact, Saini et al (2020)
observed that “The mainstay of treatment for scapular dyskinesis remains an extensive course of physical ther-
apy involving scapular proprioceptive retraining, strengthening, and sport-specific exercises”. Professional ten-
nis players play, practice, and serve much more than players at the high school level but do not suffer from
shoulder dysfunction as often as would be expected, possibly due to the customized workouts and game tech-
niques followed by their personal coaches/therapists.
Tennis players who played another sport that involved an overhead throwing motion reported more
symptoms on average than those who did not. Overhead sports require players to transfer large amounts of
kinetic energy through their shoulders at high speeds with high precision and large ranges of motion. “These
demands may explain the high prevalence of shoulder pain in these populations, with reports of 12% in amateur
golf, 16% in volleyball, 22% to 36% in elite handball” (Hickey et al., 2018). The combination of multiple
overhead sports with the cumulative stress put on the shoulder could lead to a higher probability of developing
shoulder dysfunction.
Seventy five percent of varsity players self-reported at least one symptom of scapular dyskinesis or
GIRD, yet none of them reported being diagnosed with shoulder dysfunction. If the shoulder dysfunction aware-
ness level increases among high school tennis players, proper training regimens and prevention techniques
could be integrated into their respective programs and reduce the risk of developing injuries. Further studies are
needed to investigate the awareness among players and coaches regarding shoulder conditions and appropriate
preventive measures that can be taken.
Limitations
The sample size for this study was based on convenience. The survey was only sent to tennis players who
attended a certain school, and the results cannot be generalized to the entire high school tennis player population
or to players from other age groups or with various levels of tennis experience. Statistical tests were not con-
ducted as the sample size used in the study was too small and included a number of confounding variables. The
study findings are based on self-reported symptoms by high school students who are not familiar with assessing
or diagnosing shoulder conditions unlike medical professionals (sports medicine physicians and physical ther-
apists). Further research is needed to understand the protective effect of specific workouts on shoulder dysfunc-
tion at the high school levels of tennis.
Conclusion
The purpose of this study was to explore the prevalence of scapular dyskinesis and GIRD and identify some of
the factors that make a high school tennis player more prone to developing shoulder dysfunction. The results
show that players who have more years of experience, play more often, and are on the varsity team are more
likely to develop shoulder pain and dysfunction. Males are also more likely to develop shoulder pain and dys-
function compared to females. Players who regularly workout their shoulder and back muscles are less likely
to develop shoulder pain and dysfunction, regardless of their level of experience and gender. High school tennis
programs should start implementing shoulder and back workouts into their practice schedules as a precaution
to help prevent future shoulder dysfunction and injuries. Future research should expand the sample de-
mographics by including a larger group of players from multiple schools with various sports backgrounds, skill
levels as well as physically examining and diagnosing the players by trained clinicians instead of self-reports
of symptoms.
Acknowledgments
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I would like to express my appreciation to Dr. Edward J. Aubé, PT, DPT and Maria M. Nolan, PT, Physical
therapists at Southwest General Hospitals, Broadview Heights, for their time and assistance in the development
of the survey.
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