EXERCISE AND QUALITY OF LIFE
Research article
Volume 3, No. 1, 2011, 31-40
UDC 796.342-053.6:796.015.52
THE EFFECT OF STRENGTH TRAINING ON TENNIS SERVICE
PERFORMANCE OF JUNIOR TENNIS PLAYERS
Paraskevi Malliou (1), Dimitris Papadimitriou (1), Vasiliki Malliou (2), Anastasia Beneka (1),
Georgios Pafis (1), Christos Katsikas (2) Stiliani Roka (1) , and Ioannis Fatouros (1)
(1)Department of physical education and sport science
Democritus University of Thrace, Komotini, Greece
(2) Department of physical education and sports science
National and Kapodistrian University of Athens, Greece
Abstract
The purpose of the present study was to evaluate the effect of a 7-week shoulder specific
strength training program additional to tennis training sessions on the service velocity of junior
tennis players. Initially 60 junior tennis players (29 boys and 31 girls) with at least 2 years of
tennis experience and never followed a routine strength program, volunteered to participate in the
study. All the subjects followed a regular tennis training session (75 min). The subjects were
randomly assigned into three groups: i) group-A, which practiced in addition 15 min service after
the tennis session, ii) group-B which practiced a 7-week strength training program (15 min per
session, 3 times per week) after the tennis session, and iii) a group-C, control group, which did not
follow any extra programs after the tennis session. Two-way repeated measures analysis of
variance was performed to detect differences in each group before and after the experimental
period. The independent variable was the group (two experimental groups with different training
protocol and the control group with only tennis training), and the repeated factor was the ìtestî
(pre and post test, before and after the training period). Statistical significance was accepted at
p<.05. It was measured an overall significant quantitative improvement on service performance
while, the qualitative findings showed significant improvement in service technique only in group
A.
Keywords: tennis, shoulder strength program, service, service velocity
Introduction
Tennis skills are composed by complex movements.One of these skills, service
performance, is a result of the effective transfer of torque production that depends on technique,
muscle strength and flexibility (Cohen, Mont, Campbell, Vogelstein, & Loewy, 1994; Mont,
Corresponding author. Department of Physical Education and Sport Sciences, Democritus University of Thrace,
Campus 69100 Komotini, Greece, E-mail: pmalliou@phyed.duth.gr
© 2010 Faculty of Sport and Physical Education, University of Novi Sad, Serbia
P. Malliou et al.
Coen, Campbell, Gravare, & Mathur, 1994). An important factor for tennis service is the ability
to exert high muscular force and power to the racquet. Therefore, the ball speed in tennis service
is generated by the speed of the racquet immediately before the impact (Gordon, & Dapena,
2006). Gordon and Dapena (2006) measured the contributions of the motion of body segments to
the racquet head speed during the tennis service and suggested that among the main contributors
were the external shoulder rotation, wrist extension and twist rotation of the lower trunk, twist
rotation of the upper trunk relative to the lower trunk, shoulder abduction, and wrist flexion.
Also, Gordon and Dapena (2006) suggested that there was a positive contribution of shoulder
internal rotation shortly before the impact with the ball.
In addition, it has been shown that the internal rotators of the dominants shoulder in
tennis players produce greater torque than those who don't play tennis (Ng, & Kramer, 1991).
The internal rotators of the dominant shoulder are typically stronger of the non-dominant
shoulder in tennis players (Chandler, Kibler, Stracener, Ziegler, & Pace, 1992). Also, tennis
players tend to have muscle strength imbalance of internal versus external rotators (Mont et al.
1994; Chandler et al. 1992; Ellenbecker, Davies, & Rowinski, 1988). Although muscle strength
plays a key role to the overheads sports performance
(Wooden, Greenfield, Johansonm,
Litzelman, Mundrane, & Donatelli, 1992; Bartlett, Storey, & Simons, 1989; Perry, 1983) there
are only a few studies evaluating the effect of strength training on shoulder rotators muscles and
the related functional performance (Treiber, Lott, Duncan, Slavens, & Davis, 1998; Mont et al.
1994). It has been suggested that the upper and lower strength in a tennis player can be
extremely useful not only in the enhancement of athletic performance but also in the prevention
and rehabilitation of injuries (Ellenbecker, & Roetert, 2004). More specific Treiber et al. (1998)
showed that strength training for four weeks with Therabands and light weight drumbells appears
to increase service velocity of college tennis players.
The purpose of the present study was to evaluate whether an additional 7-week shoulder
specific strength training program would significantly increase service velocity of junior tennis
players compared to the group which practice only service in addition to tennis training sessions.
Method
Experimental Approach to Problem
Service in tennis is based on complex motor movement and depends on technique,
muscle strength and flexibility. The purpose of the present study was to evaluate the effect of
shoulder specific strength training program additional to tennis training sessions on the service
velocity of junior tennis players in order to define the need of strength exercise for junior tennis
players.
Subjects
Initially 60 junior tennis players (29 boys and 31 girls) from three different Greek tennis
clubs volunteered to serve as subjects. All subjects practiced tennis with a coach for at least 2
years (two to three times per week), and never followed a routine strength. All the subjects
participated in a regular tennis practice session (75 min). Each session included warm-up, drills
practicing ground strokes and volley, as well as drills practicing tactics of the games for 60 min
and 15min practicing service. The subjects were randomly assigned into three groups: i) group-
A, which practice in addition 15 min service after the tennis session, ii) group-B which practice a
7-week strength training program (15 min per session, 3 times per week) after the tennis session,
and iii) a group-C, control group, which did not follow any extra programs after the tennis
session.
32
Effects of strength training on tennis service
Four of the subjects failed to complete the study: three (two experimental and one control
subject) participated in less than 75% the sessions, and one subject could not complete the study
because of an injury. The data from these four subjects were dropped from the study.
The subjects ranged from 13 to 14 years old (group-A 13.3 ± 1, group-B 14.2 ± 0.8, and
group-C 14.4± 0.7, M±SD respectively), had an average weight for group-A 45.75 ± 7.74 kg,
group-B 38.33 ± 8.14 kg, and group-C 41.83 ± 7.16 kg, M±SD respectively and an average
height for group-A 153.25 ± 7.2 cm, and group-B 144.4 ± 9.6cm, and group-C 145.3 ± 5.8 cm,
M±SD respectively.
All players were right handed-dominant. Subjects were evaluated pre and post training
program for service performance: a) ball speed (quantitative evaluation) and b) technique of the
service (qualitative evaluation). In addition, the range of motion and the strength of the internal
and external rotation of the shoulder were evaluated.
Quantitative service evaluation
The service performance was conducted on an indoor tennis court. Each subject was
instructed to perform service from the baseline (0-40 m to the right of the center mark) with new
Wilson USA Open balls, with maximal velocity and control until a total of five balls landed in
the left service box. No limit was placed on the number of the attempts. If the player did not
succeed after 10 efforts had a rest break for 3-4 min. The average velocity of service was the
mean of the best three. Ball velocity was assessed in (km/h) with a calibrated radar gun (Jug
Company, 2000). The radar gun was positioned 5 meters behind the baseline, opposite to the
subject, at a height 2 meters (Jug Company, 2000). Before the evaluation the subjects played
tennis for 10-12 min and had 10-15 service from the baseline for warm-up.
Qualitative service performance evaluation
The subjects underwent service technique evaluation by three experienced tennis coaches.
Before the beginning of the procedure, the coaches were informed about the procedure and the
goals of the study. A pilot procedure has been followed, where the three coaches watched (2
times in 10 days) a videotape with service skills in similar conditions with the present study. The
correlation coefficients between the coaches (r = .92) and between the trials (r = .91) were high.
No player was found to have faulty technique and thus no player was excluded from the
participation in the study. There were observed six technical elements in service motion: 1) the
basic position, 2) the grip, 3) the body orientation, 4) the back swing 5) the touch with the ball,
6) the follow through (Eason, Smith, & Plaisance, 1989; Magill, 1985). When one of those
elements was missing, the score was 0, while it was 1 when it was appeared (Mcpherson, &
Thomas, 1989). Ten trials were assessed and the sum of the score for each element was recorded.
The score for the technique evaluation was computed by adding the scores for all the technical
elements for 10 trials.
Shoulder rotator strength assessment
The subjects underwent shoulder rotator strength evaluation that is usually used by
exercisers and is also accepted by many authors uses the (Brzycki, 1993; Mayhew, Ware, &
Rinster, 1993) equations. This is an indirect method of assessing maximal strength that is based
on the maximal number of repetitions that the exerciser accomplishes. The testing procedure that
was followed by Giannakopoulos, Beneka, & Malliou
(2004).
is now described. Each
participant is positioned supine holding a dumbbell with stabilization straps secured at the pelvis
and midthoracic levels. The assessed extremity is positioned on a table with stabilization straps
also secured at humeral level. The test is initiated with the arm in 90° of external rotation. To test
the internal rotation movement, the trial is initiated with the arm in 90° of external rotation.
33
P. Malliou et al.
Respectively, when the external rotation is tested, the trial is initiated with the arm in 90° of
internal rotation. The participants try to complete the maximal number of repetitions (e.g., 12
repetitions) with a dumbbell of their choice (e.g., 2.5kg). According to Brzyckiís and Mayhewís
equations, the maximal number of repetitions for a given weight corresponds to a specific
coefficient (e.g., 0.75). Dividing the dumbbellís weight (2.5kg) by that coefficient results in a
number indicating maximal strength (e.g., 2.5/0.25 = 3.33). The result, in this case 3.33, is
considered to be the maximal strength of the muscle group tested. Similarly, the maximal
strength of the other muscle group is assessed (Beneka, Malliou, Giannakopoulos, Kyrialanis, &
Godolias, 2002; Giannakopoulos et al. 2004; Kibler, Chandler, & Livingston, 1996).
Range of motion evaluation of shoulders rotator cuff
The testing position of the participant for the internal rotation was supine with the arm
abducted to
90degrees, the elbow flexed to
90degrees and the forearm pronated and
perpendicular to the table. A towel was placed under the humerus to bring the arm into the
scapula plane. The goniometer was aligned along the ulnar styloid process and perpendicular to
the table.
The testing position of the participant for the external rotation was supine, with the arm abducted
to 90deg, the elbow flexed to 90deg and the forearm pronated and perpendicular to the table. A
towel was placed under the humerus to bring the arm into the scapula plane. The goniometer was
aligned along the ulna to the ulnar styloid process and perpendicular to the table (Andrews,
Harrelson, & W. K., 2004).
Service training program (group-A)
The participants in group-A followed a service training session (15 min per session, 3
times per week) after the tennis practice. The service session included a) toss practice, and b)
serve practice with 2 targets (ìTî and diagonal) from both sides (deuce and advantage).
Shoulder strength intervention programs (group-B)
The subjects from group B participated in a strength training program, 6 exercises for
both shoulders (left and right), 15 min, 3 times per week for 7 weeks. (From 0 to the 3rd week
performed 2 sets of 10-15 repetitions with 0.5-1.0 kg free weights. After the 3rd week the
program progressed to 3 sets with the same repetitions and increase in the free weights by 0.5 kg
(Table 1). There was at least one day rest between practice days.
The subjects were instructed to breathe normally. The subjects from both groups were
given detailed written, verbal and physical instructions by the trainer for the various exercises.
Before the beginning of the intervention period each subject had to demonstrate proper technique
to the trainer.
Post assessments
Within 2 days, after the completion of the 7 ñweek intervention period, the follow up
assessment for all groups was begun (serving velocity and technique).
Statistical Analyses
Means and standard deviations were calculated for all depended variables. Two-way
repeated measures analysis of variance (ANOVA) (2X3, tests by different training protocol) was
performed on depended variables to detect differences in each group before and after the
34
Effects of strength training on tennis service
experimental period. The independent variable was the group (two experimental groups with
different training protocol and the control group with only tennis training), and the repeated
factor was the ìtestî
(pre and post test, before and after the training period). Statistical
significance was accepted at p<.05.
Results
Two-way repeated measures analysis of variance was used to test the differences in all
depended variables before and after training period for each group. The independent variable
was the group (two experimental groups and one control group), and the repeated factor was the
test
(before and after the training period). Tables 1 and 2 illustrate the means and standard
deviations for external and internal rotation range of motion values for all the groups.
Table 1
Means and standard deviations for external rotation range of motion values for all the groups
Range of motion / External Rotation
PreTest
PostTest
F
Groups
M
SD
M
SD
Control
68.92
10.6
71.83
7.71
.706
Service
61.50
15.5
86.75
17.2
52.9***
Strength/Service
73.5
14.5
79.08
13.3
2.58
F
14.17***
*p<.05, **p<.01, ***p<.001
Table 2
Means and standard deviations for internal rotation range of motion values for all the groups
Range of motion / Internal Rotation
PreTest
PostTest
F
Groups
M
SD
M
SD
Control
49.58
16.03
58.25
22.61
3.172
Service
50.75
8.27
82.75
19.25
43.242***
Strength/Service
44.25
8.92
54.83
14.11
4.730*
F
7.086**
*p<.05, **p<.01, ***p<.001
For external rotation range of motion test, the results showed (Table 1) that all the groups
improved their performance between the two tests but this improvement was significant only for
the ìService Groupî F(1,33)=43.24, p<.001
For internal rotation range of motion test, statistical analysis showed that all the groups
improved their performance between pre and post test but in a different way (F (2, 33) =7.086,
p<.05). Sidak Multiple Comparison test was performed to test the differences in performance for
35
P. Malliou et al.
each group. The results showed that there was a significant performance improvement in the
internal rotation range of motion test only for the experimental groups, and not for the control
group (Table 2).
Tables 3 and 4 illustrate the means and standard deviations for external and internal
rotation strength values for all the groups. For strength performance in external rotation
movement statistical analysis showed that all the groups improved their performance between
pre and post test but in a different way F (2, 33) =8.012, p<.05. Sidak Multiple Comparison test
was performed to test the differences in performance for each group. The results showed that
there was a significant performance improvement in the external rotation strength performance
only for the ìService Groupî F (1, 33) = 19.79 the ìStrength Service Groupî F (1, 33) =38.009
and not for the control group.
For strength performance in internal rotation movement (Table 4) statistical analysis
showed that all the groups improved their performance between pre and post test but in a
different way F(2,33)=7.98, p<.05. Sidak Multiple Comparison test was performed to test the
differences in performance for each group. The results showed that there was a significant
performance improvement in the internal rotation strength performance only for the ìStrength
Service Groupî F (1, 33) =15.96 and the ìService Groupî F (1, 33) = 4.25 and not for the others.
Table 3
Means and standard deviations for external rotation strength values for all the groups
Strength / External Rotation
PreTest
PostTest
F
Groups
M
SD
M
SD
Control
4.20
.57
4.45
.57
5.93
Service
4.47
.55
4.85
.69
19.79**
Strength/Service
3.98
.66
4.50
.65
38.009***
F
8.012*
*p<.05, **p<.01, ***p<.001
Table 4
Means and standard deviations for internal rotation strength values for all the groups
Strength / Internal Rotation
PreTest
PostTest
F
Groups
M
SD
M
SD
Control
4.90
.79
5.10
.95
2.33
Service
6.01
1.36
6.27
1.52
4.25
Strength/Service
4.54
.98
5.06
1.09
15.96***
F
7.98*
*p<.05, **p<.01, ***p<.001
36
Effects of strength training on tennis service
Tables
5 and 6 illustrate the means and standard deviations for quantitative
and
qualitative service evaluation test for all the groups.
Table 5
Means and standard deviations for quantitative service evaluation test for all the groups
Quantitative service evaluation test
PreTest
PostTest
F
Groups
M
SD
M
SD
Control
47
12.5
48.17
12.23
.943
Service
53
9.31
60.83
10.89
42.512***
Strength/Service
44.33
14.63
52.08
17.35
41.612***
F
10.137***
*p<.05, **p<.01, ***p<.001
Table 6
Means and standard deviations for qualitative service evaluation test for all the groups
Qualitative service evaluation test
PreTest
PostTest
F
Groups
M
SD
M
SD
Control
41.66
6.14
39.16
5.1
1.40
Service
48.33
4.34
55.00
3.74
10.1*
Strength/Service
45.83
7.4
49.16
5.96
2.50
F
4.848**
*p<.05, **p<.01, ***p<.001
For the Quantitative service evaluation test (Table 5), results showed that all groups
improved their performance between pre and post test but in a different way (F (2, 33) =10.137;
p<.001). Sidak Multiple Comparison test was performed to test the differences in performance
for each group. The results showed that there was a significant performance improvement in the
quantitative service evaluation test for the experimental groups between pre and post tests, but no
significant improvement was found for the control group.
However, difference in service performance was found only for experimental groups for
the qualitative evaluation test F (2, 33) =4.848, p<.05, and this improvement was significant only
for the Service Group (F (1, 33) =10.01, p<01) and not for the Strength Service Group (F (1, 33)
=2.5, p>.05) (Table 6).
37
P. Malliou et al.
Discussion
The present study evaluated the service performance in young tennis players with
quantitative and qualitative evaluations. It was concluded an overall significant quantitative
improvement on service performance while, the qualitative findings showed significant
improvement in service technique only in group A. These findings support the significant impact
of the technique in tennis performance. It is evident that for this age group with at least 2 years
tennis practice, improvement only in the technique can increase significantly the service
performance. As the player developed and the technique reached at a high level then, strength
and flexibility are more important physical abilities to be developed (Elliot, Fleisic, Nicholls, &
Escamilia, 2003).
In the present study both groups (A and B) increased average speed of service. Previous
investigations have been shown that strength training can increase athletic performance in tennis
(ITF). More specific, studies on tennis service showed low correlation between ball speed and
isokinetic strength of the upper body (Cohen et al. 1994; Ellenbecker, & Roetert, 1999). The ball
speed during service maybe a combination of several factors such as technique, coordination,
flexibility and strength. Cohen et al. (1994) found low correlation between shoulder internal
rotation and ball speed. The present study showed that although only group B had significant
increase in strength of internal rotation, both groups (A and B) increase significantly the range of
motion in the internal rotation. Furthermore, group A had greater increase in the range of internal
rotation compared to group B. This evidence suggests that strength training program may be an
important factor in reassuring shoulder stability. Consecutively, a smaller increase in range of
motion in group B may be related to less increase of ball speed compared to group A.
The present study showed that both groups (A and B) increased significantly the strength
of external rotation muscles, but only group A showed significant increase in the range of motion
of external rotation muscles. Thus, it is suggested that for the external rotators muscles, strength
training program restricted the improvement of range of motion, revealing again the important
role of strength training in keeping joint stability. Gordon, & Dapena (2006) measured the
contributions of the motion of body segments to the racquet head speed during the tennis service
and suggested that among the main contributors were the external shoulder rotation.
Both groups (A and B) improved significantly the quantitative performance of the
service. The findings from the strength intervention program in the present study are in
agreement with the study by Treiber et al. (1998), although, this study had different age group
(college tennis players) and different duration of the program (4 weeks). The improvement in the
present study ranged from 44.33±14.63 to 52.08±17.35 km/h in average service velocity. Others
studies (Mont et al. 1994; Ellenbecker et al. 1988) found also increase in service performance.
The average and peak service velocity increased 7.9 % and 6.0 % respectively (Treiber et al.
1998). These increases are less than the finding of Mont et al. (1994) study and Ellenbecker et al.
(1988) study. These discrepancies of the results may due in the different age groups and the
designs of the studies, such as the duration of the intervention program, method of training and
the intensity of the program.
Previous studies (Cohen et al. 1994; Ellenbecker, & Roetert, 1999; Pugh, Kovaleski,
Heitman, & Gilley, 2003) indicate a moderate correlation between upper body strength and ball
speed in the tennis service. This suggests that an absolute level of strength is necessary but not
sufficient for ultimate ball speed.
The present study showed that since service is complex movement and requires optimal
timing, coordination, and strength of many segments of human body, it is crucial to primary
develop the service movement skill for an efficient service performance.
38
Effects of strength training on tennis service
The findings of the present study suggest that for young athletes with at least two years
tennis practice improving technique can significantly increase tennis performance. As the athlete
is growing up and his technique reaches at a higher level, then strength and flexibility are more
important physical abilities to be developed.
The results of the present study also suggest that although only strength training can
increase the internal rotators strength; both strength training and service practice can increase
significantly the range of motion in the internal rotation. Furthermore, service practice in young
tennis players can better increase the internal rotators range of motion compared to strength
training. This evidence suggests that strength training program may be an important factor in
reassuring shoulder stability for young athletes. It is suggested also for the external rotators
muscles, strength training program restricted the improvement of range of motion, revealing
again the important role of strength training in keeping joint stability. Finally, both strength
training and service practice can efficiently improve the service ball speed.
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Submitted 25 January, 2011
Accepted 17 March, 2011
40