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A Proposed Study: The Effects of a Rotator Cuff Strength
Training Program on the Flat and Kick Serves in Tennis
Evan K. Liu & Andrew Alstot, Ph.D.
Department of Exercise Science
Pacific University, Forest Grove, OR
Background
The world of strength and conditioning has been renowned for improving
multiple aspects of life and performance. Through many years of
evolution, strength and conditioning can contribute to one’s overall well
being.
An important aspect of strength and conditioning is the process of
training itself. Based off of the sliding filament theory, eccentric
contractions (active lengthening) produces more force than the two other
types of contractions: concentric and isometric. Eccentric actions are the
main decelerators of our actions.7 Some activities that constantly
produce eccentric actions are overhead activities such as the tennis and
volleyball serve or the baseball throw. The rotator cuff group of the
shoulder are a component of the force producing and decelerating
aspects of these activities for protection and performance. 2,3,4 Currently,
a common practice of these activities emphasizes strengthening of the
rotator cuff for increased performance and for possible injury
prevention.1,3,5,6
Tennis is an activity that readily implements a shoulder strengthening
program, specifically for the rotator cuff. Studies have shown that
strengthening the rotator cuff increases the serve velocity. 3,6 Although
the velocity has been shown to increase, the effects of a strength
program on different serves have not been studied. In another type of
serve, the “kick” or “topspin” serve, the athlete applies topspin on the
ball which allows the ball to “bite” or accelerate after the ball contacts
the ground. Thus, the purpose of this experiment is to observe the effects
of a rotator cuff strength program on the kick serve in tennis.
Method
Participants & Setting:
Collegiate male tennis players from a small university located in the
Pacific Northwest of the United States will be used in this study. Each
participant will need to be at least a 4.5 level based off of the National
Tennis Rating Program (NTRP); a United States Professional Tennis
Association (USPTA) certified professional will be used to assess that the
ranking is valid.
Materials:
A Stalker ATS II Pro Radar Gun will be used to measure the velocity and
acceleration of the serves. A new can of ProPenn tennis balls will be used
for every session in order to keep consistent. Golden Set Tennis String, or
the choice of the participants’ string will be kept consistent throughout
the duration of the study. The strength training sessions will be
conducted using kettle balls.
Procedure:
Pre/Post Tests: A pre and post test of rotator cuff strength and range of
motion will be tested to track changes of rotator cuff strength and range
of motion. For the pre- and post-tests of their serves, there will be a box
(2 x 2 feet) at the “t” of the service box for flat serves. Velocity will be
measured by taking the mean of the first 10 serves that go into the
service box. Kick serves will be served out wide (ad-side for right handers
and deuce-side for left handers) and will follow the same procedures as
the flat serves; the only difference being that acceleration will be
measured instead of velocity.
Experimental Design: Participants will all eventually be divided into three
groups. A multiple baseline across participants design will be used to
assess whether there is a functional relationship between rotator cuff
strength and serve accelerations. After participants have performed at a
stable level (consistent serve velocity and acceleration), the intervention
of the strength program will be implemented; if there is an increase in
serve velocity and acceleration once the intervention has been applied,
then a functional relationship can be established (through a visual
analysis of a the data).
Intervention: Upon implementation of the intervention, the rotator cuff
strength training program will be executed twice a week for six weeks
and will be done in the plane of the scapula. Based off of Greenfield,
Donatelli, Wooden, and Wilkes’ experiment5, rotator cuff strengthening
should be performed in the plane of the scapula; this is defined as 90°
abduction and 30-45° anterior flexion about the glenohumeral joint.
Greenfield et al.5 found a statistical difference when training the rotator
cuff in the frontal plane and in the scapular plane; with greater strength
resulting from training in the scapula plane. Other studies have also
implemented their shoulder training using the plane of the scapula5,6,8
The exercise that will be used will be executed eccentrically. Using a
kettle ball or a medicine ball, the administrator will toss the ball over the
participant’s shoulder. The participant will then have to catch the ball
before letting it drop, while maintaining the shoulder in the plane of the
scapula. This exercise simulates the actions of the serve, thus making it
more applicable.
Data Collection: All participants will have their serves tested twice a
week, once in the middle of the week and once at the end. Participants
will have no knowledge of their velocities or accelerations. Participants
will also have their strength and ROM tested weekly to track
improvements to also show that the increase in strength once the
intervention has been implemented, with a possible connection between
strength and velocity and acceleration.
References
1. Anderson, MB (1979). Comparison of muscle patterning in the overarm throw and
tennis serve. Research Quarterly, 50(4), 541-553.
2. Donatelli, R; Ellenbecker, TS; Ekedahl, SR; Wilkes, JS; Kocher, K; & Adam, J (2000).
Assessment of shoulder strength in professional baseball pitchers. Journal of
Orthopaedic & Sports
Physical Therapy, 30(9), 544-551.
3. Ellenbecker, TS; Davies, GJ; & Rowinski, MJ (1988). Concentric versus eccentric
isokinetic
strengthening of the rotator cuff. The American Journal of Sports
Medicine, 16(1), 64- 69.
4. Ellenbecker, TS & Rotert, EP (2002). Effects of a 4-month season on glenohumeral
joint rotational strength and range of motion in female collegiate tennis players.
Journal of
Strength and Conditioning Research, 16(1), 92-96.
5. Greenfield, BH; Donatelli, R; Wooden, MJ: & Wilkes, J (1990). Isokinetic evaluation of
shoulder rotational strength between the plane of scapula and the frontal plane.
The American Journal of Sports Medicine, 18(2), 124-128.
6. Mont, MA; Cohen, DB; Campbell, KR; Gravare, K; & Mathur, SK (1994). Isokinetic
concentric versus eccentric training of shoulder rotators with functional evaluation of
performance enhancement in elite tennis players. The American Journal of Sports
Medicine, 22(4),
513-517.
7. Roig, M; O’Brien, K; Kirk, G; Murray, R; McKinnon, P; Shadgan, B; & et al (2009). The
effects
of eccentric versus concentric resistance training on muscle strength and
mass in
healthy adults: a systematic review with meta-analysis. British Journal of
Sports
Medicine, 43, 556-568.
8. Wooden, MJ; Greenfield, B; Johanson, M; Litzelman, L; Mundrane, M; & Donatelli, RA
(1992).
Effects of strength training on throwing velocity and shoulder muscle
performance in
teenage baseball players. Journal of Orthopaedic and Sports
Physical Therapy, 15(5), 223228.