RESEARCH ARTICLE
The effects of short term detraining and
retraining on physical fitness in elite soccer
players
Chang Hwa Joo*
Department of Football Science, Honam University, Gwangsan-gu, Gwangju, South Korea
* footballer@honam.ac.kr
Abstract
Purpose
The aim of this study was to examine the effects of aerobic high-intensity training with
reduced volume and training cessation on body composition and physical fitness after the
end of season and the time required to recapture physical fitness with intensified retraining
following two weeks of detraining in elite soccer players.
Method
Twenty male semi-professional soccer players participated in this study. The soccer players
were assigned to either a group that completed high-intensity aerobic training (HAT, n = 10)
or to a detraining and retraining group (DHAT, n = 10) for a 5-week period immediately after
the end of the season. The first 2 weeks of the period, members of the HAT group performed
high-intensity aerobic exercise (80–90% of HRmax, 12 min × 3, three times per week),
whereas members of the DHAT group abstained from any physical activity. During the sub-
sequent 3 weeks, members of both the HAT and DHAT groups completed high-intensity
aerobic exercise. Exercise performance testing and body composition analysis were per-
formed before; after 2 weeks of detraining; and at 1, 2 and 3 weeks of retraining.
Results
Intensified high-intensity training for 5 weeks maintained the performance in the Yo-Yo Inter-
mittent Recovery level 2 test (Yo-Yo IR2) and repeated sprints at any time point (P > 0.05).
However 2 weeks of detraining resulted in significant decreases in the performance on the
Yo-Yo IR2 (P < 0.01) and repeated sprints test (P < 0.05). Performance on the Yo-Yo IR2
enhanced after 2 weeks of retraining and was maintained up to 3 weeks after retraining, with
no significant differences between conditions (P > 0.05). In addition, repeated sprint perfor-
mance markedly decreased after the detraining period (P < 0.05) and was continuously
lower compared to the baseline at 2 weeks after retraining (P < 0.05). Furthermore, this
value reached baseline level at the end of the experimental period (P > 0.05). There were no
significant differences between conditions in body composition, performance of agility, or
sprint ability throughout the 5-week experimental period (P > 0.05).
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OPEN ACCESS
Citation: Joo CH (2018) The effects of short term
detraining and retraining on physical fitness in elite
soccer players. PLoS ONE 13(5): e0196212.
https://doi.org/10.1371/journal.pone.0196212
Editor: Alessandro Zagatto, Sao Paulo State
University - UNESP, BRAZIL
Received: August 23, 2017
Accepted: March 7, 2018
Published: May 10, 2018
Copyright: © 2018 Chang Hwa Joo. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the paper, its Supporting Information file,
and Dryad Digital Repository (doi:10.5061/dryad.
mc60n0c).
Funding: The author has no support or funding to
report.
Competing interests: The author has declared that
no competing interests exist.
Conclusions
The present data suggest that short-term detraining after the competitive season can
markedly decrease performances in the Yo-Yo IR2 test and repeated sprints. To return to a
previous level of ability on the Yo-Yo IR2 and/or sprint test with retraining through high-inten-
sity aerobic training after a period of detraining, a similar or longer period of retraining is
required. However, the high-intensity training with reduced amount of training after competi-
tive season can prevent reductions in physical fitness.
Introduction
Soccer is a high intensity intermittent exercise that requires a high level of physical fitness for
players to successfully perform in the game. Elite soccer players perform 587±133 m of high-
speed running (19.8–25.2 km/h) and 184 ± 87 m of sprinting (>25.2 km/h) during a typical
game [1]. The total distance of high-intensity running depends on the position of the player
and team success in a league [2]. The amount of high-intensity running performed during a
game also depends on the competitive standards between leagues: top-class professional soccer
player perform more high-intensity running compared with moderate professional soccer
players [3]. Thus, high level of physical performance is an important factor in determining
team success in soccer.
Due to the high intensity performance required in soccer, players should perform system-
atic and scientific physical fitness training. Several studies have shown that high-intensity
training improves soccer players’ fitness levels and skills, such as sprint, strength, and speed
endurance [4, 5]. The organization of fitness training for soccer players varies according to the
time frame of the periodization along with changes in training volume and intensity. These
changes seek to the optimize player’s physical condition and minimize injury [6]. For example,
training is conducted to improve physical fitness during the preseason in preparation for the
impending competitive season [7, 8].
Elite soccer players normally cease training or perform training with reduced volume and
lower intensity for more than two weeks after the end of the competitive season for physical
and mental recovery. A prolonged period of rest after the competitive season causes the partial
or complete loss of training-induced physiological and performance adaptations, which is
defined as detraining [9]. The magnitude of changes during training-induced adaptations after
detraining is different depending on the fitness level and the duration of training cessation or
insufficient training [9]. Three to six weeks of detraining did not result in changes in aerobic
capacity and muscle strength in recreational players and untrained individuals [10–12]. How-
ever, decreases in physical fitness are inevitable after such a period of detraining in well-trained
elite players who have a relatively higher level of fitness compared to recreational players [9,
13]. Unlike reduced physical fitness after a prolonged period of detraining in elite players, the
effects of short-term detraining (~2 weeks) on fitness are controversial. Buchheit et al. [14]
observed that short-term detraining after a competitive season improved levels of strength and
cardiorespiratory fitness in Australian football players [14]. In contrast, several studies
reported that physical fitness was reduced after a short-term detraining period in elite soccer
players [5, 15]. The reasons for these contrasting results are not apparent, but may be due to
differences in sports and testing methods.
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During the preseason, the aim of training is mainly to improve physical fitness, while dur-
ing the in-season period, it is performed to develop playing strategies and to enhance perfor-
mance, while maintaining physical fitness. High-intensity training is a more efficient method
of inducing skeletal muscle adaptation in comparison to moderate-intensity training [16].
High-intensity aerobic training has been widely used by athletes to improve physical fitness
during the preseason. Indeed, high-intensity aerobic training consisting of 4 bouts of 4 min at
90–95% of the maximum heart rate during the preseason significantly improved aerobic fit-
ness and match performance in soccer players [17]. Those results indicated that high-intensity
aerobic training might be effective at improving the physical fitness of soccer players and
inducing rapid training adaptation in skeletal muscle during the preseason.
In order to start the season without injury, athletes must gradually improve their post-sea-
son, resting period-induced reduction in physical fitness with an appropriate exercise intensity
and volume. However, there is limited information available regarding the effects of retraining
during pre-season training in well-trained elite soccer players. Therefore, the aim of the study
was to investigate 1) the effects of aerobic high-intensity training with reduced volume and
training cessation on body composition and physical fitness after the end of season and 2) the
time required to return to the previous level of physical fitness with intensified retraining fol-
lowing two weeks of detraining in semi-professional soccer players.
Materials and methods
Participants
Twenty semi-professional male Korea soccer players (age: 22.1±1.8 years, height: 175.5±4.7
cm). The Korean professional soccer league is divided into K League Classic (first division)
and K League Challenge (second division). The semi-professional league consists of the
National League and K3 Leagues (K3 League Advanced [12 teams] and K3 League Basic [8
teams]). The soccer players participating in this study were members of K3-league teams. All
participants had experience of elite soccer players for at least more than 7 years. All partici-
pants were non-smokers, no history of neurological disease or musculoskeletal abnormality
and none were under any pharmacological treatment during the course of the study.
Ethics statement
Before testing, all participants gave written informed consent to participate after details and
procedures of the study had been fully explained. All of the fitness testing and exercise were
performed in the research institute for sport and exercise science at Honam Unviersity. All of
the experimental protocols and related procedures were approved by the ethical committee of
Honam University.
Intervention period and training
All players participating in the study trained for more than 2 hours per day for 4–5 times per
week (excluding matches) during the previous season. An independent research assistant
selected the 20 participants from among 35 players who were between 20 and 23 years of age
by drawing a sealed envelope containing a player’s name followed by drawing another sealed
envelope containing the name of the group to which they were assigned (i.e., high-intensity
aerobic training (HAT) or detraining and high-intensity aerobic training (DHAT) group). The
two-week detraining period started immediately after the last match of the season. The fitness
tests were conducted two days and one day before the last match as a pre-test; after two weeks
of detraining; and at one, two, and three weeks of retraining.
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During the detraining experimental period, high-intensity aerobic training was performed
three times per week for two weeks in the HAT group. After approximately a 20-min warm-up
period, the players performed a soccer drill (Fig 1) on an artificial grass surface and three repe-
titions of 12 min of exercise at 80–90% of the maximum heart rate (HRmax) measured during
Yo-Yo IR2 test. These repetitions were interspersed by 3 min active recovery. The players con-
trolled exercise intensity by watching their HR monitor that recorded at 5 s intervals (Polar
Team System, Polar, Electro Oy, Kempele, Finland). These data were downloaded to a per-
sonal laptop for further analysis. The mean HR during the 12 min exercise sessions was
87.3±1.5% of HRmax. The DHAT group did not perform any exercise sessions during the two
weeks of detraining and conducted normal daily activities.
Fig 1. Diagram of high-intensity training.
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During the retraining period, the HAT and DHAT groups performed high-intensity aero-
bic training (12 min × 3) four times per week for three weeks. The mean HR during the 12
min exercise sessions was 86.5±1.4% of HRmax in the HAT group. The DHAT group com-
pleted moderate intensity aerobic training (HRmax 70–80%; 76.5±3.2%) for two days before
completing the high-intensity training (HRmax 80–90%; 87.7±1.3%).
Experimental protocol
A schematic illustration of the experimental design is shown in Fig 2. The subjects completed
the 30 m sprint test, Yo-Yo intermittent recovery level 2 (Yo-Yo IR2) test, arrowhead agility
test, repeated sprint test, and isokinetic strength test. The tests were conducted for two days.
The participants refrained from alcohol and caffeine in the 24 h prior to the test. The partici-
pants arrived at the laboratory having completed the appropriate diet regime to monitor the
diet level. The participants were instructed to ingest water 5 mL of water for every kilogram of
their body mass 2 h before arriving at the laboratory. Upon the arrival at the laboratory, body
composition (Inbody 520, Biospace, Seoul, Korea) and height (BSM, Seoul, Korea) were mea-
sured. Following the completion of the baseline assessments, the participants commenced the
tests on an artificial grass surface. A 30-m sprint test, arrowhead agility test, and repeated
sprints test were performed in the morning. The Yo-Yo IR2 test was conducted in the evening
with 5 hours of recovery after lunch. Isokinetic strength tests were performed in the laboratory
the next day. Body composition and exercise tests were completed immediately before the end
of the season; after two weeks of detraining; and at one, two, and three weeks of retraining
intervention.
30m sprint test
The sprint tests which consisted of 2 maximal sprints of 30 m with 2-minute rest between each
sprint were conducted. The sprint times at 5, 10, 20 and 30 m were recorded using the photo-
cell gates (Microgate, Bolzano, Itaia). The participants started to run 50 cm before the photo-
cell gate recordings. The fastest times at the distances were recorded for data analysis.
Fig 2. A schematic illustration of the experimental design.
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Repeated sprint test
The repeated sprint test consisted of seven maximal 34.2 m sprints, interspersed by 25 s of
active recovery (40 m jogging distance) [18]. Recovery was timed so that the subjects returned
to the start line between the 23rd and 24th second. Additionally, verbal feedback was given at 5,
10, 15 and 20 s of the recovery. Performance was measured as the total sprint time in seconds.
Yo-Yo intermittent recovery test (level 2)
The Yo-Yo IR2 test was performed on an artificial turf. The Yo-Yo IR2 test consists of 2 × 20
m shuttle runs at increasing speeds, controlled by audio signals from a compact disk. Between
each bout of running, the subjects completed 10 s of active recovery, consisting of 2 × 5 m jog-
ging [19]. The test was terminated when the subjects failed twice to reach the start line on time
and the distance (meters) covered at the end point was recorded [5].
Arrowhead agility test
The arrowhead agility tests consisted of 4 sprints (2 right, 2 left), with 2-minutes rest between
each sprint [20]. Each subject started 50 cm behind the start line and sprinted 10 m forward to
a cone. From the cone, the subjects turned at a right angle to a cone being apart from 5m
before turning to a cone 15 m straight from the start line. They turned again from the cone to
accelerate in a straight line for 15 m over the initial start line to complete the run. The fastest
times were recorded for data analysis. Timing gates were used to accurately assess the time to
completion.
Isokinetic strength
The subjects performed the Isokinetic dynamometry (Cybex MET-300, New York, USA) to
evaluate the unilateral strength of the concentric contraction of the flexors and extensors of the
knee [21]. The angular speed parameters of 60˚ × s-1, 180˚ × s-1, and 240˚ × s-1 were used for
the measurements. The results of the measurements were expressed in absolute peak torque
(Nm) for the purposes of the off-seasonal variation comparisons.
Statistical analysis
All data are presented as means ± SD. Two-way analysis of variance (ANOVA) with repeated
measure was conducted to determine any treatment differences between the HAT and DHAT
conditions. The assumption of sphericity (homogeneity of covariance) was assessed and cor-
rected for using the Huynh-Feldt epsilon. Because there were only 2 levels in the main effect of
condition, follow-up multiple comparisons were not necessary. A significant effect of time was
followed up with planned multiple contrasts in line with the a priori hypotheses. Therefore,
data at the specific time points were compared with the baseline (first) time point using New-
man-Keuls multiple contrasts. Where a significant interaction between condition and time
was observed, differences between conditions were examined at each time point using New-
man-Keuls multiple contrasts. Baseline values were compared using an independent samples t
test. The alpha level for evaluation of statistical significance was set at P < 0.05. Effect sizes
were assessed by partial eta squared (Z2
P), which were defined as trivial (<0.1), small (0.1–0.3),
moderate (0.3–0.5) and large (>0.5) [22].
Results
Body weight and body fat were similar between the HAT and DHAT groups throughout the
experimental period (P > 0.05; Tables 1 and 2). There was no significant effect of condition
Detraining and retraining affect physical fitness
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nor was there an interaction of condition and time (P > 0.05) in the performance of players
on sprint and agility tests (Tables 3 and 4). However, a significant effect of time was observed
for sprint test at 5 m, 10 m, and 30 m as well as in the left direction of arrowhead agility
(P < 0.05). Isokinetic strength at all angular speeds remained similar to baseline under both
conditions throughout the experimental period, with no significant effects of time, condition,
or an interaction between the two (P > 0.05; Tables 5 and 6). There was a significant interac-
tion in the Yo-Yo IR2 test (F = 3.273; P < 0.05; Z2
P ¼ 0:267), while the measurement time
(F = 1.517; P > 0.05; Z2
P ¼ 0:144) and condition were not significant (F = 1.938; P > 0.05;
Z2
P ¼ 0:177). Compared to the pre-detraining performance, the Yo-Yo IR2 test performance
decreased significantly after the two-week detraining period (P < 0.01) and the values reach
before detraining level after two weeks of retraining in the DHAT group (P > 0.05). No differ-
ences were detected at three weeks post-retraining between conditions (P > 0.05), whilst val-
ues in the HAT group remained stable throughout the experimental period (P > 0.05; Fig 3).
A main effect of time was found (F = 3.539; P < 0.05; Z2
P ¼ 0:282), along with a significant
interaction between condition and time for repeated sprint performance (F = 3.127; P < 0.05;
Z2
P ¼ 0:258). No changes in repeated sprint performance were observed at any time point
under HAT conditions (P > 0.05), whereas repeated sprint performance declined after two
weeks of detraining (P < 0.05) and remained lower than at baseline by two weeks post-
Table 1. Body composition of the subjects before, after two weeks of detraining and at one, two and three weeks of retraining (mean ± SD).
Pre
2W DT
1W RT
2W RT
3W RT
Body weight (kg)
HAT
68.1±7.1
68.5±7.1
68.6±7.2
68.6±7.3
68.4±7.3
DHAT
67.5±7.3
67.8±7.3
67.9±7.3
68.2±7.2
67.9±7.3
Body mass index (kg/m2)
HAT
22.7±0.4
22.7±0.5
22.7±0.5
22.5±0.6
22.9±0.4
DHAT
22.1±0.8
22.4±0.9
22.4±0.6
22.5±0.9
22.3±0.8
Skeletal muscle mass (kg)
HAT
32.6±3.5
32.5±3.3
32.3±3.2
32.6±3.6
32.4±3.3
DHAT
33.0±3.5
33.2±2.3
33.1±3.2
33.4±3.3
33.3±3.3
Percent body fat (%)
HAT
9.6±0.7
9.7±0.7
9.8±1.3
9.5±0.9
9.9±1.3
DHAT
9.3±1.2
9.8±1.3
9.8±1.1
9.7±1.2
9.5±1.4
Values are means ± standard deviation
https://doi.org/10.1371/journal.pone.0196212.t001
Table 2. Differences in the body composition of the subjects between conditions in each test (n = 20).
F
P
Z2
P
Body weight
Condition
0.048
0.831
0.005
Time
12.372
0.001
0.579
Condition x Time
0.628
0.646
0.065
Body mass index
Condition
2.524
0.147
0.219
Time
0.716
0.587
0.074
Condition x Time
1.776
0.155
0.165
Skeletal muscle mass
Condition
0.228
0.644
0.025
Time
0.178
0.948
0.019
Condition x Time
0.117
0.976
0.013
Percent body fat
Condition
0.046
0.834
0.005
Time
2.201
0.088
0.197
Condition x Time
0.653
0.629
0.068
F; testing criteria level, P; level of statistical significance, Z2
P; partial eta squared
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retraining under DHAT conditions (P < 0.05). It reached baseline level at the end of the exper-
imental period (P > 0.05; Fig 4).
Discussion
The major findings in the present study were that two weeks of detraining after competitive
season decreased performance in the Yo-Yo IR2 test and repeated sprints. The detraining-
induced reductions in the Yo-Yo IR2 test performance improved compared to baseline levels
after two weeks of high-intensity aerobic training. Meanwhile, three weeks were required to
Table 3. Sprint and agility before, after two weeks of detraining and at one, two and three weeks of retraining (mean ± SD).
Pre
2W DT
1W RT
2W RT
3W RT
5 m
HAT
1.04±0.04
1.05±0.03
1.06±0.04
1.02±0.05
1.02±0.05
DHAT
1.05±0.04
1.04±0.03
1.05±0.03
1.01±0.04
1.01±0.04
10 m
HAT
1.75±0.06
1.74±0.10
1.73±0.05
1.71±0.04
1.72±0.06
DHAT
1.78±0.05
1.73±0.05
1.73±0.05
1.71±0.06
1.72±0.07
20 m
HAT
3.00±0.09
3.01±0.13
3.02±0.08
2.99±0.06
2.99±0.09
DHAT
3.05±0.05
3.07±0.08
3.03±0.06
2.99±0.09
2.99±0.09
30 m
HAT
4.13±0.11
4.22±0.17
4.25±0.12
4.21±0.11
4.23±0.13
DHAT
4.23±0.07
4.30±0.12
4.29±0.09
4.23±0.12
4.25±0.10
Agility (R)
HAT
8.04±0.19
8.09±0.22
8.13±0.17
7.99±0.21
8.03±0.22
DHAT
8.06±0.16
8.09±0.22
8.09±0.19
8.04±0.25
8.05±0.25
Agility (L)
HAT
7.99±0.17
8.12±0.20
8.10±0.20
7.98±0.23
8.00±0.18
DHAT
8.04±0.18
8.14±0.24
8.14±0.18
8.08±0.15
8.08±0.20
Values are means ± standard deviation. R; right, L; left
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Table 4. Differences in sprint and agility between conditions in each test (n = 20).
F
P
Z2
P
5 m
Condition
0.095
0.765
0.010
Time
7.657
0.001
0.460
Condition x Time
1.586
0.199
0.150
10 m
Condition
0.305
0.594
0.033
Time
4.672
0.004
0.342
Condition x Time
1.010
0.415
0.101
20 m
Condition
0.480
0.506
0.051
Time
2.500
0.060
0.217
Condition x Time
1.167
0.342
0.115
30 m
Condition
0.879
0.373
0.089
Time
5.357
0.002
0.373
Condition x Time
1.619
0.191
0.152
Agility (R)
Condition
0.013
0.912
0.001
Time
2.516
0.058
0.218
Condition x Time
0.357
0.838
0.038
Agility (L)
Condition
0.499
0.498
0.053
Time
3.542
0.015
0.282
Condition x Time
0.382
0.820
0.041
R; right, L; left, F; testing criteria level, P; level of statistical significance, Z2
P; partial eta squared
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return to the initial level of repeated sprint performance with retraining using high-intensity
training. Ultimately, a reduced amount of high-intensity training after the competitive season
facilitated the maintenance of physical fitness.
The HAT group that continued to perform high-intensity aerobic exercise after the compet-
itive season maintained their performance level in the Yo-Yo IR2 test over the five week treat-
ment period. These results are supported by previous studies, which indicate that, after the last
match of the season, 10 training sessions, consisting of high-intensity training for two weeks,
do not change performance in the Yo-Yo IR2 test in elite soccer players [15]. However, Naka-
mura et al. [23] observed that running and plyometric training for two days per week for three
weeks after the completion of a competitive season did not prevent the decrease in perfor-
mance in The Yo-Yo IR2 test in elite soccer players. The reason of these differences in results
is unclear but it probably related to exercise intensity. Indeed, there was no significant decrease
in performance in the Yo-Yo IR2 test during off-season in the present study and Christensen
et al. [15]’s study applying high-intensity exercise despite reduced exercise time compared to
that in-season. Furthermore, the exercise intensity was higher than that in the previous study
conducted by Nakamura et al. [23], which modulated endurance training (70–80% of
HRmax).
In the present study, we found that two weeks of detraining after the competitive season
markedly decreased performance in the Yo-Yo IR2 test in elite soccer players. Accordingly,
Table 5. Peak torques (Nm) during concentric knee flexion and extension before, after two weeks of detraining and at one, two and three weeks of retraining
(mean ± SD).
Pre
2W DT
1W RT
2W RT
3W RT
DL-PT-E-60
HAT
208.2±12.3
208.2±12.3
209.6±27.3
210.0±25.2
205.2±19.8
DHAT
211.5±13.9
212.7±15.9
214.2±15.9
216.7±17.5
208.3±12.4
DL-PT-F-60
HAT
135.8±32.3
135.8±30.6
135.8±37.7
139.2±29.5
135.2±28.2
DHAT
121.2±21.6
137.2±26.9
140.3±29.1
137.2±27.7
136.5±19.1
NL-PT-E-60
HAT
189.9±33.1
194.6±39.0
197.0±35.2
200.9±38.1
191.0±31.0
DHAT
198.1±28.0
189.1±24.2
183.9±26.8
193.0±24.6
187.0±16.4
NL-PT-F-60
HAT
129.1±30.5
127.9±26.4
125.1±34.8
128.1±26.1
127.1±31.5
DHAT
132.6±23.1
127.1±20.2
125.7±23.1
131.9±24.6
135.3±26.2
DL-PT-E-180
HAT
138.8±18.9
146.6±21.4
146.6±23.9
145.3±23.3
140.4±18.8
DHAT
145.2±23.6
146.1±15.1
152.0±20.1
150.3±15.4
152.6±18.8
DL-PT-F-180
HAT
105.4±17.3
105.2±14.8
108.5±13.8
107.3±10.9
107.7±13.4
DHAT
108.5±9.8
107.2±14.2
110.6±15.7
110.5±17.3
106.1±15.3
NL-PT-E-180
HAT
136.9±18.9
137.0±25.4
139.5±21.1
141.1±18.0
137.7±19.5
DHAT
138.1±16.5
139.6±16.6
137.9±21.9
142.7±21.4
138.5±20.8
NL-PT-F-180
HAT
97.4±18.7
93.7±18.4
99.7±24.4
96.4±18.9
95.7±21.6
DHAT
102.6±16.7
100.5±15.3
100.7±19.2
101.7±17.5
102.6±19.9
DL-PT-E-240
HAT
114.9±19.0
115.9±15.9
116.9±17.6
115.2±15.6
113.4±17.1
DHAT
116.2±16.2
118.6±12.4
117.5±13.6
119.5±12.7
115.8±11.7
DL-PT-F-240
HAT
84.6±15.1
83.8±16.8
84.8±14.1
87.3±12.2
86.2±13.8
DHAT
89.1±9.3
87.8±13.4
92.6±17.4
92.9±16.0
89.3±12.7
NL-PT-E-240
HAT
113.3±16.7
112.7±15.4
112.6±13.7
114.4±11.2
110.3±14.6
DHAT
115.2±10.8
110.3±13.1
116.1±14.6
114.2±16.8
115.4±13.2
NL-PT-F-240
HAT
83.3±15.2
83.4±18.6
81.0±19.2
85.1±16.2
86.3±12.8
DHAT
88.4±14.6
81.7±14.5
86.3±18.4
89.2±18.6
87.2±18.6
Values are means ± standard deviation. DL; dominant leg, NL; non-dominant leg, PT; peak torque, E; extensors, F; flexors, 60, 180, 240; angular velocities (˚s-1)
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Thomassen et al. [5] and Christensen et al. [15] observed that the Yo-Yo IR2 test performance
after detraining for two weeks decreased from 845 m to 654 m in elite soccer players. In addi-
tion, a study from another laboratory reported that a prolonged detraining period can induce
an 8% decline in maximal oxygen consumption [24], which is strongly associated with distance
on the Yo-Yo IR2 test [25]. The degree of deterioration of physical fitness over the course of
the detraining period after the competitive season is closely related to the fitness level of
Table 6. Differences in sprint and agility peak torques (Nm) during concentric knee flexion and extension
between conditions in each test (n = 20).
F
P
Z2
P
DL-PT-E-60
Condition
1.674
0.228
0.157
Time
1.665
0.180
0.156
Condition x Time
0.100
0.982
0.011
DL-PT-F-60
Condition
0.032
0.862
0.004
Time
1.249
0.308
0.122
Condition x Time
1.156
0.346
0.114
NL-PT-E-60
Condition
0.113
0.744
0.012
Time
0.721
0.583
0.074
Condition x Time
1.050
0.395
0.104
NL-PT-F-60
Condition
0.059
0.814
0.007
Time
1.287
0.293
0.125
Condition x Time
0.469
0.758
0.050
DL-PT-E-180
Condition
0.355
0.566
0.038
Time
1.283
0.295
0.125
Condition x Time
0.695
0.600
0.072
DL-PT-F-180
Condition
0.143
0.714
0.016
Time
0.419
0.794
0.045
Condition x Time
0.268
0.896
0.029
NL-PT-E-180
Condition
0.007
0.935
0.001
Time
0.485
0.747
0.051
Condition x Time
0.177
0.949
0.019
NL-PT-F-180
Condition
0.373
0.556
0.040
Time
0.481
0.749
0.051
Condition x Time
0.520
0.721
0.055
DL-PT-E-240
Condition
0.097
0.762
0.011
Time
0.549
0.701
0.057
Condition x Time
0.153
0.960
0.017
DL-PT-F-240
Condition
0.872
0.375
0.088
Time
0.834
0.512
0.085
Condition x Time
0.297
0.878
0.032
NL-PT-E-240
Condition
0.047
0.833
0.005
Time
0.651
0.630
0.067
Condition x Time
0.971
0.435
0.097
NL-PT-F-240
Condition
0.147
0.711
0.016
Time
1.786
0.153
0.166
Condition x Time
0.696
0.600
0.072
DL; dominant leg, NL; non-dominant leg, PT; peak torque, E; extensors, F; flexors, 60, 180, 240; angular velocities
(˚s-1), F; testing criteria level, P; level of statistical significance, Z2
P; partial eta squared
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athletes [23]. Therefore, these results can support the notion that performance in the Yo-Yo
IR2 test can be reduced despite only a few days of detraining in elite soccer players with a high
level of physical fitness. These decreases in performance in the Yo-Yo IR2 test can be explained
at the muscle level. Several weeks of detraining lead to a return in muscle capillarization to
Fig 3. Yo-Yo IR2 performan for the high-intensity training (HAT; n = 10) and detraining + retraining (DHAT;
n = 10) before, after two weeks detraining and at one, two and three weeks of retraining (n = 11, mean ± SD).
P < 0.01; significantly different from pre. P < 0.05; significantly different from pre. ##P < 0.01; significantly
between conditions. #P < 0.05; significantly between conditions.
https://doi.org/10.1371/journal.pone.0196212.g003
Fig 4. Repeated sprint test for the high-intensity training (HAT; n = 10) and detraining + retraining (DHAT;
n = 10) before, after two weeks detraining and at one, two and three weeks of retraining (n = 11, mean ± SD).
P < 0.05; significantly different from pre. #P < 0.05; significantly between conditions.
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baseline before detraining in athletes and a 25%-45% decline in oxidative enzyme activities,
which result in reduced mitochondrial ATP production in skeletal muscle [9].
Several previous studies have reported that high intensity training improves the perfor-
mance in the Yo-Yo IR2 test of elite soccer players [25, 26]. In line with these results, high-
intensity aerobic training after two weeks of detraining was found to improve performance in
the Yo-Yo IR2 test in the present study. Two weeks of retraining with high-intensity exercise is
required to return close to the baseline level of performance. This result is inconsistent with a
previous study that suggested that athletes with a high fitness level must perform exercise
training for a period that is at least twice as long as the resting time period in order to improve
their physical fitness to a level of before detraining [24]. The discrepancy in time periods
required to return to the physical fitness level at baseline can be due to variations in the length
of the detraining period (four weeks versus eight weeks) and the fitness level of the athletes
(compared to end of season versus before the Olympic game). Indeed, the performance in the
Yo-Yo IR2 test decreased by 11% at the end of the season compared to the start of the season
and a 42% increase was observed during the eight weeks of pre-season training [25]. This phe-
nomenon is likely due to accumulated fatigue experienced during the competitive season. This
assumption is supported by the finding from the present study that the performance in the Yo-
Yo IR2 test was higher at three weeks of post retraining compared to baseline. Furthermore,
Noon et al. [20] and Oliver et al. [27] observed that perceptual well-being (e.g., motivation,
sleep quality, recovery, appetite, fatigue, stress, muscle soreness, stiffness) deteriorated with
an increase in training exposure and accumulated fatigue as the season progressed in elite
athletes.
Repeated sprint performance did not change over five weeks of high-intensity training after
competitive season in the present study. In contrast to the present study, previous studies
reported that two weeks of high-intensity training immediately after the end of season
enhanced repeated sprint performance in elite soccer players [5, 15]. These different results
may be associated with the high-intensity training method used during the retraining period.
Aguiar et al. [28] observed that intermittent training for 12 weeks consisting of 20 minutes per
training session resulted in greater improvements in repeated sprint performance than did
continuous training. Indeed, the training sessions in the present study largely comprised of
high-intensity endurance exercise, whereas the training sessions used in previous studies con-
sisted of five high-intensity aerobic training, including small-sided (4 vs. 4 and 3 vs. 3) soccer
drills (8 × 2 min) and five speed endurance training (10–12 × 25–30 s sprints) over the course
of two weeks. In other respects, since well-trained athletes are more sensitive to changes in
physical fitness with inadequate training intensity and do not easily experience improvements
following further training due to the ceiling effect [25], the capacity of repeated sprint perfor-
mance of the players in the present study might be optimal by the end of the competitive sea-
son. This is supported by the observation that repeated sprint performance in players from the
present study was similar to previous study conducted with professional soccer players during
the competitive season [18].
It is well known that anaerobic exercise performance decreases in highly trained elite soccer
players, despite a short period of detraining after the competitive season [9]. There was also a
significant decrease in repeated sprint performance over two weeks of detraining after the end
of a match in the present study. The detraining-induced decrease in performance gradually
increased during the three weeks retraining period. The aerobic high-intensity training-
induced increase in repeated sprint performance in the present study is likely to be the result
of training-induced biochemical adaptation in skeletal muscles. Thomassen et al. [5] and
Christensesn et al. [15] observed that two weeks of high-intensity exercise immediately after
the last match of the season enhanced Na+-K+ pump α2-isoform expression by 15%, increased
Detraining and retraining affect physical fitness
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May 10, 2018
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the FXYD1ser68-to-FXYD1 ratio by 27%, increased the level of pyruvate dehydrogenase by
17%, and improved repeated sprint performance. In comparison, cessation of training for two
weeks did not affect the expression of Na+-K+ pump isoform expression and resulted in a
reduction of the AB_FXYD1ser68 signal by 18%; decreased pyruvate dehydrogenase level by
17%; a drop in citrate synthase and 3-hydroxyacyl-CoA activity to 12% and 18% of maximal,
respectively; and a reduction in performance. However, repeated sprint performance at 3
weeks post-retraining was still lower than the performance recorded at baseline. As men-
tioned, aerobic high-intensity training is not optimal for improving repeated sprint perfor-
mance, which represents the capacity for anaerobic exercise performance. On the contrary,
improvements in repeated sprint performance through aerobic high-intensity training might
be associated with the training period during the preseason. Recently, Teixeira et al. [29]
reported that high-intensity aerobic training involving shuttle-run intervals (4 × 4 min) for
five weeks during the preseason enhanced repeated sprint ability with increased aerobic per-
formance in elite athletes. When considered, these findings suggest that more than three weeks
of high-intensity aerobic training is required to develop repeated sprint performance during
preseason in elite players.
The observed lack of changes in body composition and sprint performances (10 m, 20 m,
30 m) for five weeks during the study period in both groups disagrees with previous studies
that engaged in more than two weeks of detraining [13, 30]. For example, Koundourakis et al.
[13] examined the effect of detraining on exercise performance and body composition in
professional soccer players. They observed that prolonged detraining period (six weeks) signif-
icantly increased body weight and body fat percentage and reduced maximal oxygen con-
sumption and performances in squat-jump, countermovement-jump, and sprints (10 m, 20
m). These results suggest that a short period of detraining (approximately two weeks) may not
lead to changes in body composition and explosive exercise performance in well-trained soccer
players. This is supported by findings that there were changes in neither isokinetic strength at
any angular speeds in the present study nor squat, vertical jump, or isometric and isokinetic
knee force following two weeks detraining in high fitness athletes [31]. A possible explanation
for the absence of changes in explosive exercise performance after a short period of detraining
is the lack of changes in muscle fiber characteristics. Mujika and Padilla. [9] reported that two
weeks of detraining did not alter muscle fiber distribution in well-trained athletes. However,
three weeks of detraining after the first half of a competitive season in elite soccer players
resulted in changes in skeletal muscle morphology, including a reduction in mean fast twitch
(FT) fiber cross-sectional area and reduction in mitochondrial enzyme activities and exercise
performance [32]. Taken together, these data suggest that more than two weeks of detraining
in elite soccer players could have resulted in a decrease in explosive exercise performance by
reduced ATP production in skeletal muscle.
Conclusions
In conclusion, the findings demonstrate that two weeks of detraining after the competitive sea-
son resulted in a marked decrease in performance in the Yo-Yo IR2 test and repeated sprints.
To return to a previous level of physical fitness with retraining through high-intensity aerobic
training after a period of detraining required a similar period of retraining for performance in
Yo-Yo IR2 and/or more periods for repeated sprint performance. The off-season rest period
did not result in changes in explosive exercise performances and body composition. Aerobic
high-intensity training with reduced training volume after a competitive season can prevent
reductions in performances in the Yo-Yo IR2 test and repeated sprints. On the contrary, the
decrease in aerobic and anaerobic performance induced by two weeks of detraining was
Detraining and retraining affect physical fitness
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May 10, 2018
13 / 15
recovered within a few weeks of adequate training during the preseason. Therefore, these find-
ings suggest that elite soccer players can be allowed to take short periods of rest (~2 weeks)
without training during the off-season for the release of mental and physical stress that is accu-
mulated throughout the competitive season.
Supporting information
S1 File. Raw data of Figs 3 and 4 and Tables 1, 2, 3, 4, 5 and 6.
(XLSX)
Author Contributions
Writing – original draft: Chang Hwa Joo.
References
1.
Carling C, Bradley P, McCall A, Dupont G. Match-to-match variability in high-speed running activity in a
professional soccer team. J Sports Sci. 2016; 34(24):2215–23. Epub 2016/05/05. https://doi.org/10.
1080/02640414.2016.1176228 PMID: 27144879.
2.
Di Salvo V, Gregson W, Atkinson G, Tordoff P, Drust B. Analysis of high intensity activity in Premier
League soccer. Int J Sports Med. 2009; 30(3):205–12. Epub 2009/02/14. https://doi.org/10.1055/s-
0028-1105950 PMID: 19214939.
3.
Mohr M, Krustrup P, Bangsbo J. Match performance of high-standard soccer players with special refer-
ence to development of fatigue. J Sports Sci. 2003; 21(7):519–28. Epub 2003/07/10. https://doi.org/10.
1080/0264041031000071182 PMID: 12848386.
4.
Kotzamanidis C, Chatzopoulos D, Michailidis C, Papaiakovou G, Patikas D. The effect of a combined
high-intensity strength and speed training program on the running and jumping ability of soccer players.
J Strength Cond Res. 2005; 19(2):369–75. Epub 2005/05/21.
5.
Thomassen M, Christensen PM, Gunnarsson TP, Nybo L, Bangsbo J. Effect of 2-wk intensified training
and inactivity on muscle Na+-K+ pump expression, phospholemman (FXYD1) phosphorylation, and
performance in soccer players. J Appl Physiol (1985). 2010; 108(4):898–905. Epub 2010/02/06. https://
doi.org/10.1152/japplphysiol.01015.2009 PMID: 20133439.
6.
Mara JK, Thompson KG, Pumpa KL, Ball NB. Periodization and physical performance in elite female
soccer players. Int J Sports Physiol Perform. 2015; 10(5):664–9. Epub 2015/01/23. https://doi.org/10.
1123/ijspp.2014-0345 PMID: 25611789.
7.
Jeong TS, Reilly T, Morton J, Bae SW, Drust B. Quantification of the physiological loading of one week
of "pre-season" and one week of "in-season" training in professional soccer players. J Sports Sci. 2011;
29(11):1161–6. Epub 2011/07/23. https://doi.org/10.1080/02640414.2011.583671 PMID: 21777053.
8.
Buchheit M, Racinais S, Bilsborough JC, Bourdon PC, Voss SC, Hocking J, et al. Monitoring fitness,
fatigue and running performance during a pre-season training camp in elite football players. J Sci Med
Sport. 2013; 16(6):550–5. Epub 2013/01/22. https://doi.org/10.1016/j.jsams.2012.12.003 PMID:
23332540.
9.
Mujika I, Padilla S. Detraining: loss of training-induced physiological and performance adaptations. Part
I: short term insufficient training stimulus. Sports Med. 2000; 30(2):79–87. Epub 2000/08/31. PMID:
10966148.
10.
Moore RL, Thacker EM, Kelley GA, Musch TI, Sinoway LI, Foster VL, et al. Effect of training/detraining
on submaximal exercise responses in humans. J Appl Physiol (1985). 1987; 63(5):1719–24. Epub
1987/11/01. https://doi.org/10.1152/jappl.1987.63.5.1719 PMID: 3693207.
11.
Izquierdo M, Ibanez J, Gonzalez-Badillo JJ, Ratamess NA, Kraemer WJ, Hakkinen K, et al. Detraining
and tapering effects on hormonal responses and strength performance. J Strength Cond Res. 2007;
21(3):768–75. Epub 2007/08/10.
12.
Mujika I, Padilla S. Detraining: loss of training-induced physiological and performance adaptations. Part
II: Long term insufficient training stimulus. Sports Med. 2000; 30(3):145–54. Epub 2000/09/22. PMID:
10999420.
13.
Koundourakis NE, Androulakis NE, Malliaraki N, Tsatsanis C, Venihaki M, Margioris AN. Discrepancy
between exercise performance, body composition, and sex steroid response after a six-week detraining
period in professional soccer players. PLoS One. 2014; 9(2):e87803. Epub 2014/03/04. https://doi.org/
10.1371/journal.pone.0087803 PMID: 24586293.
Detraining and retraining affect physical fitness
PLOS ONE | https://doi.org/10.1371/journal.pone.0196212
May 10, 2018
14 / 15
14.
Buchheit M, Morgan W, Wallace J, Bode M, Poulos N. Physiological, psychometric, and performance
effects of the Christmas break in Australian football. Int J Sports Physiol Perform. 2015; 10(1):120–3.
Epub 2014/05/09. https://doi.org/10.1123/ijspp.2014-0082 PMID: 24806508.
15.
Christensen PM, Krustrup P, Gunnarsson TP, Kiilerich K, Nybo L, Bangsbo J. VO2 kinetics and perfor-
mance in soccer players after intense training and inactivity. Med Sci Sports Exerc. 2011; 43(9):1716–
24. Epub 2011/02/12. https://doi.org/10.1249/MSS.0b013e318211c01a PMID: 21311360.
16.
Bartlett JD, Close GL, MacLaren DP, Gregson W, Drust B, Morton JP. High-intensity interval running is
perceived to be more enjoyable than moderate-intensity continuous exercise: implications for exercise
adherence. J Sports Sci. 2011; 29(6):547–53. Epub 2011/03/02. https://doi.org/10.1080/02640414.
2010.545427 PMID: 21360405.
17.
Impellizzeri FM, Marcora SM, Castagna C, Reilly T, Sassi A, Iaia FM, et al. Physiological and perfor-
mance effects of generic versus specific aerobic training in soccer players. Int J Sports Med. 2006;
27(6):483–92. Epub 2006/06/13. https://doi.org/10.1055/s-2005-865839 PMID: 16767613.
18.
Abrantes C, Macas V, Sampaio J. Variation in football players’ sprint test performance across different
ages and levels of competition. J Sports Sci Med. 2004; 3(YISI 1):44–9. Epub 2004/11/01. PMID:
24778553.
19.
Bangsbo J, Iaia FM, Krustrup P. The Yo-Yo intermittent recovery test: a useful tool for evaluation of
physical performance in intermittent sports. Sports Med. 2008; 38(1):37–51. Epub 2007/12/18. PMID:
18081366.
20.
Noon MR, James RS, Clarke ND, Akubat I, Thake CD. Perceptions of well-being and physical perfor-
mance in English elite youth footballers across a season. J Sports Sci. 2015; 33(20):2106–15. Epub
2015/09/19. https://doi.org/10.1080/02640414.2015.1081393 PMID: 26383605.
21.
Kilinc BE, Kara A, Camur S, Oc Y, Celik H. Isokinetic dynamometer evaluation of the effects of early
thigh diameter difference on thigh muscle strength in patients undergoing anterior cruciate ligament
reconstruction with hamstring tendon graft. J Exerc Rehabil. 2015; 11(2):95–100. Epub 2015/05/12.
https://doi.org/10.12965/jer.150100 PMID: 25960982.
22.
Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine
and exercise science. Med Sci Sports Exerc. 2009; 41(1):3–13. Epub 2008/12/19. https://doi.org/10.
1249/MSS.0b013e31818cb278 PMID: 19092709.
23.
Nakamura D, Suzuki T, Yasumatsu M, Akimoto T. Moderate running and plyometric training during off-
season did not show a significant difference on soccer-related high-intensity performances compared
with no-training controls. J Strength Cond Res. 2012; 26(12):3392–7. Epub 2011/12/31. https://doi.org/
10.1519/JSC.0b013e3182474356 PMID: 22207263.
24.
Godfrey RJ, Ingham SA, Pedlar CR, Whyte GP. The detraining and retraining of an elite rower: a case
study. J Sci Med Sport. 2005; 8(3):314–20. Epub 2005/10/27. PMID: 16248472.
25.
Krustrup P, Mohr M, Nybo L, Jensen JM, Nielsen JJ, Bangsbo J. The Yo-Yo IR2 test: physiological
response, reliability, and application to elite soccer. Med Sci Sports Exerc. 2006; 38(9):1666–73. Epub
2006/09/09. https://doi.org/10.1249/01.mss.0000227538.20799.08 PMID: 16960529.
26.
Mohr M, Krustrup P. Comparison between two types of anaerobic speed endurance training in competi-
tive soccer players. J Hum Kinet. 2016; 51:183–92. Epub 2017/02/06. https://doi.org/10.1515/hukin-
2015-0181 PMID: 28149381.
27.
Oliver JL, Lloyd RS, Whitney A. Monitoring of in-season neuromuscular and perceptual fatigue in youth
rugby players. Eur J Sport Sci. 2015; 15(6):514–22. Epub 2015/09/15. https://doi.org/10.1080/
17461391.2015.1063700 PMID: 26366619.
28.
Aguiar M, Abrantes C, Mac¸ãs V, Leite N, Sampaio J, Iba´ñez S. Effects of intermittent or continuous
training on speed, jump and repeated-sprint ability in semi-professional soccer players. The Open
Sports Sciences Journal. 2008; 1:15–9.
29.
Teixeira AS, Arins FB, De Lucas RD, Carminatti LJ, Dittrich N, Nakamura FY, et al. Comparative effects
of two interval shuttle-run training modes on physiological and performance adaptations in female pro-
fessional futsal players. J Strength Cond Res. 2017. Epub 2017/09/14. https://doi.org/10.1519/JSC.
0000000000002186 PMID: 28902113.
30.
Ostojic SM. Seasonal alterations in body composition and sprint performance of elite soccer players.
Journal of Exercise physiology online. 2003; 6(3).
31.
Hortobagyi T, Houmard JA, Stevenson JR, Fraser DD, Johns RA, Israel RG. The effects of detraining
on power athletes. Med Sci Sports Exerc. 1993; 25(8):929–35. Epub 1993/08/01. PMID: 8371654.
32.
Bangsbo J, Mizuno M. Morphological and metabolic alterations in soccer players with detraining and
retraining and their relation to performance1988.
Detraining and retraining affect physical fitness
PLOS ONE | https://doi.org/10.1371/journal.pone.0196212
May 10, 2018
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The effects of short term detraining and retraining on physical fitness in elite soccer players.
Joo, Chang Hwa