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Journal of Exercise Physiologyonline
October 2014
Volume 17 Number 5
Editor-in-Chief
Official Research
Tommy
Journal
Boone,
of thePhD,
American
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of Exercise
Todd Astorino,
Physiologists
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Julien Baker, PhD
Steve Brock,
ISSN 1097-9751
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Lance Dalleck, PhD
Eric Goulet, PhD
Robert Gotshall, PhD
Alexander Hutchison, PhD
M. Knight-Maloney, PhD
Len Kravitz, PhD
James Laskin, PhD
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Ben Zhou, PhD
Official Research Journal
of the American Society of
Exercise Physiologists
ISSN 1097-9751
JEPonline
The Effect of On-Court vs. Off-Court Interval Training
on Skilled Tennis Performance and Tolerance to
Fatigue in Young Male Tennis Players
Kanang Srihirun1, Wanchai Boonrod1, Timothy D. Mickleborough2,
Daroonwan Suksom1
1Faculty
of Sports Science, Chulalongkorn University, Bangkok,
Thailand, 2Department of Kinesiology, Indiana University,
Bloomington, Indiana, USA
ABSTRACT
Srihirun K, Boonrod W, Mickleborough TD, Suksom D. The
Effect of On-Court vs. Off-Court Interval Training on Skill Tennis
Performance and Fatigue in Tennis Training. JEPonline 2014;17(5):
11-20. The aim of this study was to investigate the effect of on-court
vs. off-court interval-training on skilled tennis performance and
tolerance to fatigue in young tennis players. Twenty male tennis
players (aged 16.6 ± 0.6 yrs) were randomly assigned to two groups:
(a) an on-court interval-training (On-INT; N = 10) group; and (b) an
off-court interval-training (Off-INT; N = 10) group. The On-INT group
(tennis skill specific interval training in the field) was subjected to 4
sets of 6 repetitions of 10 sec of high-intensity exercise, alternating
with 10 sec o f active recovery (footwork). The Off-INT ( running
interval training on treadmill) group was subjected to 4 sets of 6
repetitions of 10 sec of high-intensity exercise performed by running
at 90-100% of peak treadmill speed (PTS), alternating with 10 sec of
running at 30-40% of PTS. Both the On-INT and the Off-INT groups
trained for 3 days·wk-1 for 8 wks. After interval training, both On-INT
and Off-INT groups had significantly (P<0.05) increased their VO2
max (10.68% and 6.66%, respectively. However, the percentage of
groundstroke accuracy score and mean time to fatigue were
significantly increased (P<0.05) only in the On-INT group. This study
has shown that while both On-INT and Off-INT are effective in the
improvement of aerobic capacity, only the On-INT was effective in
improving skilled tennis performance and tolerance to fatigue.
Key Words: The Loughborough Intermittent Tennis Test (LITT),
Aerobic Capacity, Groundstroke Accuracy, Time to Volitional Fatigue
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INTRODUCTION
Tennis is a sport that has been characterized as having a mixture of short bouts of high-intensity
intermittent exercise and longer periods of lower intensity activity (27). Typically, match time in
tennis is comprised of repetitive ballistic actions. If played in hot and humid conditions, it can disturb
the body’s homeostatic control mechanisms that lead to fatigue and a subsequent decrease in
performance (17).
Interval training e n co m p a ss e s high-intensity exercise that is equal or superior to maximal lactate
steady-state velocity. When interspersed with recovery periods of light exercise or rest, interval
training can be used to improve aerobic performance and overall fitness in endurance sports (3).
Previous studies have shown that interval training improves VO 2 max (1), peak-power output (27),
the lactate threshold ( 6) , and time-trial performance (31) in a variety of sports. Additionally, it has
been shown that mean power output and fatigability after a cycle ergometer intermittent exercise
test can be improved by interval training (30). Within the sport of tennis, coaches are increasingly
utilizing an integrated approach to conditioning and skill training, such as game-specific on-court
exercises that include both technical and tactical drills that form a part of their sport-specific
conditioning program (4-5,27). In fact, it has been reported that on-court tennis-specific interval
training improves aerobic fitness to a similar extent as off-court interval training performed on a
treadmill (10).
To our knowledge, no studies to date have compared the effect of on-court and off-court interval
training on skilled tennis performance and tolerance to fatigue. Therefore, the aim of the present
study was to determine the effects of on-court versus off-court interval training on skilled tennis
performance and tolerance to fatigue in young tennis players. We hypothesized that on-court
interval training would significantly improve physical fitness, skilled tennis performance, and
tolerance to fatigue compared with off-court interval training.
METHODS
Subjects
Twenty high school male tennis players (mean ± SD: age = 16.6 ± 0.6 yrs; height = 171.4 ± 6.99 cm;
body mass = 63 ± 10.9 kg; body fat = 13.9 ± 6.2%; mean tennis training practice = 6.55 ± 1.23 yrs)
gave their written informed consent to participate in this study, which was approved by the Ethical
Review Committee for Research Involving Human Research Subjects, Health Science Group,
Chulalongkorn University, Bangkok, Thailand. The inclusion criteria included male tennis players in
national youth level, who had played tennis for at least 5 yrs and had not performed any interval
training in the past 6 months. Exclusion criteria included a history of any chronic disease (such as
hypertension, diabetes, coronary heart disease, and asthma).
Procedures
Before training, all subjects were required to attend a laboratory “familiarization visit” to introduce the
testing and training procedures used for the baseline measures. The players completed baseline
tests for body composition, VO2 max (maximal oxygen consumption), and skilled tennis performance.
Then, they were randomly divided into 2 training groups: (a) an on-court interval-training (On-INT; N
= 10) group; and (b) an off-court interval-training (Off-INT; N = 10) group. The On-INT group (tennis
skill specific interval training in the field) was subjected to 4 sets of 6 repetitions of 10 sec of highintensity exercise, alternating with 10 sec of active recovery (footwork). The Off-INT (running interval
training on treadmill) group was subjected to 4 sets of 6 repetitions of 10 sec of high-intensity
13
exercise performed by running at 90-100% of peak treadmill speed (PTS), alternating with 10 sec of
running at 30-40% of PTS. Both the On-INT and the Off-INT groups trained for 3 days·wk-1 for 8 wks.
After the training period, post-training tests were conducted using the same protocol as the pretraining test.
Experimental Protocol
Physiological Fitness
Maximal oxygen consumption ( VO2 max) was performed using a cardiopulmonary gas exchange
system (Metamax 3B, Cortex, Leipzig, Germany). T h e su b je cts were asked to run on a treadmill
(Landice, USA) while the grade and intensity were increased every 3 min until exhaustion. Criteria
for determination of VO2 max included a plateau in VO2 despite an increase in workload during the
last 1 min, a respiratory exchange ratio >1.1, and an exercise heart rate (HR) >90% of predicted HR
max (15).
The Skill Tennis Performance after The Loughborough Intermittent Tennis Test
The Loughborough Intermittent Tennis Test (LITT) was used to assess the subjects’ skill level. The
LITT consisted of bouts of maximal hitting of tennis balls of 4 min duration with 40 sec seated
recovery between bouts until volitional fatigue. The players were required to hit returns at maximum
effort, within the singles court but further than the service line, towards either target A or B (Figure
1). A 1.5 x 1.5 m target was placed in the rear corner of both singles court areas. The tennis ball
serving machine fed balls in a random fashion at a frequency of 30 balls·min-1. The on-site scoring
and a video recorder were used to record the players’ ability to return the tennis ball landing into the
target areas. Tennis performance (ground stroke accuracy, consistency, and errors-scores) on the
LITT were recorded throughout the test. Scores for each player were converted into percentages,
whereby ‘ground stroke consistency’ + ‘ground stroke accuracy’ + ‘ground stroke error’ = 100%. The
mean percentage scores were calculated for each parameter (7).
1
A
2
B
= Accuracy score
= Consistency score
Net
= Out score
= Tennis ball machine
= Direction of ball feed
to forehand (1) and
backhand (2)
A
B
Figure 1. The Loughborough Intermittent Tennis Test (7).
14
Time to Volitional Fatigue during the LITT
During the LITT, the subjects were required to hit returns at maximum effort until volitional
exhaustion. Fatigue was considered to have occurred when the required hitting frequency was not
maintained for two consecutive feeds from the tennis ball serving machine or when the players
stopped voluntarily (7).
Time to Volitional Fatigue on the Treadmill Test
The test started at a running speed of 8 km·h-1 with a stepwise 0.5 km·h-1 speed increment every 30
sec until the subject stopped due to volitional exhaustion (25). If the last stage was not fully
completed, the peak treadmill speed (PTS) was calculated using the formula developed by Kuipers
et al. (1985) (18): PTS = Sf + (t/30 x 0.5), where Sf was the last completed speed in km·hr-1 and t
was the time in seconds of the uncompleted stage.
On-Court Interval Training Protocol
The subjects were required to perform forehand and backhand strokes in different positions on the
tennis court. Ball location followed a fixed order, which was previously explained to the subjects. An
experienced professional coach hand-fed new tennis balls to the player at a frequency of
approximately one ball every 2 sec ± 100 cm over the net. The subjects performed movement and
stroke patterns A (Figure 2A) that included 2 sets of 6 repetitions of 10 sec of high-intensity exercise
using forehand and backhand strokes while moving forward as fast as possible and hitting the ball
with maximal effort and maintaining stroke accuracy, which was alternated with 10 sec o f active
recovery (footwork) and 3 min of rest between the sets. Then, the subjects performed movement
and stroke patterns B ( Figure 2B) that included 2 sets of 6 repetitions of 10 sec of high-intensity
exercise using forehand and backhand strokes while moving backward as fast as possible and
hitting the ball with maximal effort and maintaining stroke accuracy, which was alternated with 10
sec of active recovery (footwork) and 3 min of rest between the sets.
Off-Court Interval Training Protocol
During the off-court sessions, subjects were required to perform interval running on a treadmill. The
subjects performed 4 sets of 6 repeated 10-sec sprints at 90-100% of peak treadmill speed (PTS)
alternating 10-sec active recovery.
A: Movement and Stroke Patterns A
B: Movement and Stroke Patterns B
Coach
Coach
4
2
3
1
2
1
4
3
Figure 2. A: Moving Forward Interval Training, B: Moving Backward Interval Training. 1,3 =
Forehand moving forward, 2,4 = Backhand moving forward. Both on-court interval-training (On-INT)
and off-court interval-training ( Off-INT) were equal in training intensity, given that there were no
statistically significant differences in the subjects’ %HR max, blood lactate concentration, and rating
of perceived exertion (RPE) in each set of training.
15
Statistical Analyses
The data were analyzed using SPSS version 17 for Windows statistical software package (SPSS
Inc., Chicago, USA). For each shot of ground stroke the subjects’ raw scores were converted into
‘consistency’, ‘accuracy’, and ‘out’ percentages as a means of generating the dependent variables.
The assessment of VO2 max, skill tennis performance, and time to volitional fatigue, and the
difference in the mean values between the pre-training and post-training, were analyzed using
paired t tests. The independent t tests were used to determine the significance between groups. A
P-value of ≤0.05 was considered to be statistically significant.
RESULTS
Physiological Characteristics
Physical characteristics of the subjects are summarized in Table 1. After 8 wks of training there were
no significant differences (P>0.05) in body weight, body fat, resting heart rate and blood pressure
between the On-INT and Off-INT groups. However, it was found that VO2 max was significantly
increased (P<0.05) in the On-INT and Off-INT groups.
Table 1. Pre-Training and Post-Training Subject Characteristics.
On-INT group (N = 10)
Off-INT group (N = 10)
Parameters
Pre-Training
Age (yr)
Height (cm)
Post-Training
Pre-Training
Post-Training
16.6 ± 0.5
-
16.6 ± 0.7
-
172.4 ± 7.9
-
170.4 ± 6.1
-
6.5 ± 1.3
-
7.1 ± 0.9
-
Body Weight (kg)
62.0 ± 12.6
62.6 ± 12.8
64.0 ± 9.5
63.9 ± 8.3
Body Fat (%)
15.2 ± 8.1
15.0 ± 7.2
12.4 ± 3.2
13.1 ± 3.1
Resting Heart Rate (beats·min-1)
76.8 ± 7.2
75.5 ± 7.8
77.9 ± 6.3
76.5 ± 8.5
116.6 ± 10.7
117.6 ± 10.6
123.2 ± 8.3
120.2 ± 13.6
70.2 ± 9.1
74.7 ± 5.6
73.4 ± 4.8
73.1 ± 5.3
38.4 ± 7.3
42.30 ± 7.56*
41.5 ± 7.2
44.00 ± 6.40*
Tennis Practice (yr)
Systolic BP (mmHg)
Diastolic BP (mmHg)
-1
-1
VO2 Max (mL·kg ·min )
Data are mean ± SD. *Statistical difference from pre-training at P<0.05, On-INT = On-court interval training,
Off-INT = Off-court interval training
Tennis Performance on the Loughborough Intermittent Tennis Test
The amount of total tennis ball hitting significantly increased (P<0.05) in the On-INT and Off-INT
groups. However, the percentage of groundstroke accuracy was significantly increased (P<0.05)
and the percentage of groundstroke stroke error was significantly reduced (P<0.05) only in the OnINT group. There was no significant difference (P>0.05) in the percentage of groundstroke
consistency score between pre-training and post-training in both groups (Table 2).
16
Table 2. The Skilled Tennis Performance after the Loughborough Intermittent Tennis Test.
On-INT group (N = 10)
Off-INT group (N = 10)
Parameter
Total Tennis Ball Hitting (ball)
Pre-Training
Post-Training
Pre-Training
Post-Training
466.8 ± 143.6
596.1 ± 163.6*
399.0 ± 105.8
471.6 ± 117.4*
Percentage Scores of
Groundstroke Accuracy (%)
16.0 ± 7.5
20.0 ± 6.1*
14.6 ± 4.8
16.7 ± 2.9
Percentage Scores of
Groundstroke Consistency (%)
52.1 ± 0.5
52.0 ± 0.1
51.9 ± 0.1
51.9 ± 0.1
Percentage Scores of
Groundstroke Error (%)
31.6 ± 8.8
26.3 ± 6.7*
31.7 ± 7.2
25.8 ± 4.0
Data are mean ± SD. *Statistical difference from pre-training at P<0.05, On-INT = On-court interval training,
Off-INT = Off-court interval training
Time to Volitional Fatigue Data
Only the On-INT group significantly increased (P<0.05) time to volitional fatigue during the LITT and
on treadmill test after 8 wks of training. There were no significant differences (P>0.05) in time to
volitional fatigue on the LITT and treadmill test in the Off-INT training after 8 wks of training (Figure 3).
Time to Volitional Fatigue on LITT Test
*
Time to Volitional Fatigue on Treadmill test
Pre-training
Pre-training
Post-training
Post-training
*
Figure 3. The Mean Time to Volitional Fatigue after The Loughborough Intermittent Tennis
Test (LITT) and Treadmill Test. Data are mean ± SD. *Statistical difference from pre-training at P<0.05,
On-INT = On-court interval training, Off-INT group = Off-court interval training, LITT test = The Loughborough
Intermittent Tennis Test
17
DISCUSSION
The present study has shown that both On-INT and Off-INT training are effective in improving
aerobic fitness in young tennis players. However, the percentage of groundstroke accuracy and time
to volitional fatigue increased only in the On-INT group. Therefore, these findings suggest that Oncourt interval training has more beneficial effects in terms of improving skilled tennis performance
and tolerance to fatigue in young tennis players.
Interval training is a time efficient strategy to stimulate a number of skeletal muscle adaptations that
are comparable to traditional endurance training (14). It has been demonstrated that interval-training
is more effective than continuous training in improving VO2 max (8,16,23). The data from the present
study indicate that both interval training groups significantly increased VO2 max post-training ( OnINT group = 10.6% and Off-INT group = 6.6%) compared to baseline. Based on the VO2 max data, it
makes sense that interval training should be recommended for tennis players to improve their
aerobic capacity. These findings are consistent with previous investigations that studied the effects
of interval training on aerobic fitness in cross-country skiers (3.5%) (28), football players (5.8%) (12),
and in well-trained cyclists (5.4%) (21).
While cardiovascular changes in elite tennis players are less pronounced than in endurance trained
athletes (24) in response to training, VO2 max has been shown to be markedly increased in world
class tennis players compared with untrained individuals or recreational tennis players (24). High
aerobic capacity is an important requirement in order to meet the high demands of athletes on the
professional tennis circuit (18). The improvements in aerobic capacity following interval training may
occur through increases in both oxygen delivery ( i.e., increase in stroke volume) and/or oxygen
utilization by active muscles (i.e., increases in capillarization and mitochondrial density) (2). Interval
training has also been shown to increase the capacity of muscle to produce energy via oxidative
metabolism (14).
The Loughborough Intermittent Tennis Test ( LITT) has been shown to be effective in producing
fatigue after tennis-specific maximal hitting (6,22,32). It has been shown that tennis performance
deteriorates near or at volitional exhaustion (7). The findings from the present study demonstrate
that tennis performance during the LITT test was improved in both On-INT and Off-INT groups.
However, groundstroke accuracy performance was significantly improved in the On-INT group only,
which is important since previous investigations have shown correlations between stroke quality and
success in match play (13). Moreover, it has been reported that the number of errors made by a
player during a tennis match is a good predictor of tennis performance (29). The improvements in
groundstroke accuracy in the On-INT group, compared to the Off-INT group, may be due to the
increase in time to volitional fatigue (on both the LITT test and treadmill test).
A possible reason as to why there was a reduction in the time to fatigue in the On-INT group only
may be due to a higher energy expenditure (i.e., higher muscle activation during sliding movements
and higher ground reaction forces with a higher rate of acceleration movement in On court interval
training) (9). Another possible explanation may be attributed to neural adaptations and learning
effects induced by the On-court interval training program (19). The On-INT group used a number of
muscle groups during the acceleration and deceleration movements (e.g., biceps femoris, rectus
femoris, hip adductors, iliopsoas) during training, which may have led to an enhanced coordination
and agility for the tennis-specific maximal hitting during the LITT test (4-5,11). Therefore, our data
suggest that the On-court interval training protocol, that included both technical and tactical tasks as
part of a specific conditioning program, is appropriate to optimize cardiorespiratory fitness, skilled
tennis performance, and tolerance to fatigue in competitive young tennis players.
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CONCLUSIONS
While both the On-INT and Off-INT groups experienced beneficial effects on aerobic capacity,
skilled tennis performance (groundstroke accuracy score and time to fatigue during the LITT test)
was improved only in the On-INT group. Based on the data from the present study, we propose that
On-INT is an effective training regimen for tennis players as shown by an improvement in aerobic
fitness and skilled tennis performance. Therefore, tennis players should use On-court interval
training as an additional conditioning program to achieve a high level of tennis performance during
match play.
ACKNOWLEDGMENTS
The authors would like to thank the subjects in this study, The 90th Anniversary of Chulalongkorn
University fund ( Ratchadaphiseksomphot endowment fund) and Faculty of Sports Science,
Chulalongkorn University fund.
Address for correspondence: Daroonwan Suksom, PhD, Faculty of Sports Science,
Chulalongkorn University, Rama 1 Rd, Patumwan, Bangkok 10330, Thailand. Tel: +66 81 341 5736,
Fax: +66 2 218 1035. Email: daroonwanc@hotmail.com
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