Advances in Physical Education
2013. Vol.3, No.2, 71-75
Published Online May 2013 in SciRes (http://www.scirp.org/journal/ape) http://dx.doi.org/10.4236/ape.2013.32011
Time of Day Effect on Soccer—Specific Field Tests in
Tunisian Boy Players
Adnene Gharbi1,2, Liwa Masmoudi1, Sleheddine Ghorbel1, Noureddine Ben Saïd3,
Riadh Maalej1, Zouhair Tabka2, Monia Zaouali2
1High Institute of Sport and Physical Education, Sfax University, Sfax, Tunisia
2Laboratory of Cardio-Circulatory, Respiratory, Metabolic and Hormonal Adaptations to
the Muscular Exercise, Faculty of Medicine Ibn El Jazzar, Sousse, Tunisia
3College of Sport Sciences & Physical Activity, King Saud University, Riyadh, Saudi Arabia
Received March 7th, 2013; revised April 10th, 2013; accepted April 25th, 2013
Copyright © 2013 Adnene Gharbi et al. This is an open access article distributed under the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the
original work is properly cited.
The purpose of this study was to investigate the diurnal variation in some specific skills performance dur-
ing field testing in boy’s footballer. In a balanced and randomized study design, 15 boys (mean ± SD; age
12.7 ± 1.1 years; height 1.54 ± 9.1 m; body mass 45.1 ± 3.2 kg) participated in the study. Subjects per-
formed some specific soccer skills (kicking accuracy, ball control with the body, ball control with the
head, coordination test, zigzag running (i.e., agility), zigzag with the Ball (i.e., dribbling) and the skill in-
dex (i.e., the ratio of the zigzag running without and with the ball) at two different times of day: 07:00 and
17:00 h. Moreover, intra-aural temperature was measured at both time-of-days. Intra-aural temperature
was higher in the evening than the morning (P < 0.01). Likewise, a significant time-of-day effect was
found for dribbling (P < 0.05) and agility (P < 0.001) with higher performances observed at 17:00 h.
However, no significant differences were noticed between 07:00 and 17:00 h for the skill index, kicking
accuracy, ball control with the body, ball control with the head and coordination tests. The intra-aural
temperature was found to be significantly correlated with the speed of dribbling and agility (P < 0.001). In
conclusion, a diurnal variation in intra-aural temperature, agility and dribbling were shown to be present.
No time-of-day effect was observed for the coordination, skill index, kicking accuracy and juggling per-
formance.
Keywords: Circadian Rhythm; Intra-Aural Temperature; Boy Players; Field Tests; Soccer Skills
Introduction
Football games may take place at various times throughout
the day whilst training may be held in the morning or afternoon.
Despite its popularity as a sport, few scientific studies have
focused on the circadian variation in soccer players’ perform-
ance. For instance, some investigators, who are interested in
soccer performance, reported that aerobic (Chtourou et al.,
2012b), anaerobic performances (Chtourou et al., 2012a, 2012b;
Hamouda et al., 2012) and repeated sprint ability (Chtourou et
al., 2012b) fluctuate with time of day. Indeed, peak and mean
power during maximal cycling test (Chtourou et al., 2012b;
Hamouda et al., 2012; Aloui et al., 2012), maximal voluntary
contraction (Aloui et al., 2012), Flexibility (Reilly et al., 2007),
hand-grip strength (Reilly et al., 2007), total work during the
repeated sprint ability test (Chtourou et al., 2012b), total dis-
tance and maximal aerobic velocity during the Yo-Yo test
(Chtourou et al., 2012b) were significantly higher in the eve-
ning than in the morning. Most of studies showed that peak
soccer performances have been found to occur in the early eve-
ning corresponding to the peak of the body temperature rhythm.
Furthermore, worst performance has been found in the morning
(Aloui et al., 2012; Reilly et al., 2007; Bernard et al., 1998;
Melhim et al., 1993). Circadian rhythm in exercise performance
for soccer players with morning lows and evening peaks are
common findings in many laboratory tests performed on cycle
ergometer (Chtourou et al., 2010a, 2012b; Hamouda et al., 2012;
Aloui et al., 2012). However, each test is measured in athletes,
it is important that the test include the activity pattern of the
specific sport. Therefore, testing soccer should be performed on
field and including some soccer skills, as opposed to a cycle er-
gometer to improve the specificity in the activity patterns in the
football. Sport science support workers can, therefore, use field
tests to evaluate specific aspects of soccer performance, which
may provide a better indication of the ability to perform in a
soccer match than laboratory-based evaluations. There are a
wide range of skills which form the foundation of soccer per-
formance. Other skills are important in the game but have re-
ceived much less attention. The actual motor tasks of passing,
controlling, dribbling, starting, stopping, changing direction
and shooting the ball are all important skills in soccer but have
received little detailed analysis. To date, a little attention has
been paid to circadian and diurnal rhythms in skill measures,
particularly those specifically related to a particular soccer
game.
Previous research indicated that many aspects of soccer per-

A. GHARBI ET AL.
formance vary according to a circadian rhythm (Reilly et al.,
2004a, 2004b, 2007). Football-specific skills of juggling per-
formance showed significant diurnal variation (peak at 16:00 h),
whereas performance on the wall-volley test tended to peak at
20:00 h (Reilly et al., 2004a, 2007). Nevertheless, no time-of-
day effect was described in the dribbling test (Reilly et al.,
2004a, 2007). Diurnal variation was also described in some
football-specific tests, including dribbling time and chip test
performance, being more accurate in the evening (Reilly et al.,
2004b). Reilly et al. (2007) indicated that adult football players
perform at an optimum between 16:00 and 20:00 h not only for
football-specific skills but also for some physical performances.
Reilly et al. (2004a, 2004b, 2007) investigated the diurnal
variation of skill measures only in adult subjects. In this context,
various chronobiological studies suggest that the temporal order
of children differs from that of adults (Huguet et al., 1995).
To our knowledge, there is no study available in soccer has
been paid to diurnal variation in skill measures, particularly
those specifically related to a particular game in boys. Conse-
quently, the aim of the present study was to assess the effects of
time-of-day in some specific skills performance during field
testing in boy’s footballer.
Protocol Experimental
Subjects
15 boys belonging to an academy of soccer (Maracana) and
having 4.2 ± 1.1 years of playing experience were recruited to
participate in our study. Subjects and their parents were in-
formed about the experimental procedure. The study was con-
ducted according to the declaration of Helsinki and the protocol
was approved by the local Ethics Committee. Moreover, all the
subjects were classified as “neither type” from their responses
to the self-assessment questionnaire of Horne and Ostberg
(1976), which determines morningness-eveningness. The mean
age, height and body mass of the subjects were 12.7 ± 1.1 years,
1.54 ± 9.1 m and 45.1 ± 3.2 kg, respectively.
Experimental Design
Participants arrived 1 h before the start of the test and lay
down and relaxed. Then the subject’s intra-aural temperature
was measured by an infrared ear thermometer (ThermoScan
IRT 4520, Braun GmbH, Kronberg, Germany). After a stan-
dardized warm-up of 10 - 15 min, subjects performed some
specific soccer skills in this order: kicking accuracy, ball con-
trol with the body, ball control with the head, coordination tests,
Zigzag Test (i.e., agility), Zigzag with the Ball (i.e., dribbling)
and the skill index (i.e., the ratio of the zigzag running without
and with the ball). Subjects performed two trials of each test
(except accuracy test), with a 3 minute interval, and the best
performances in each test were used for analysis. There was a 5
minute rest session between the two tests. The measurements
were taken at two different times of the day: 07:00 and 17:00 hr
in a randomized order over two days with a minimum recovery
period of 36 hr. Tests were conducted outdoors on a playing
field of artificial grass where the mean ambient temperature and
relative humidity were 24.5˚C ± 0.2˚C, 53.1% ± 0.2% and
23.9˚C ± 0.2˚C, 52.7% ± 1% for the morning and the evening,
respectively. These conditions indicated that the weather was
slightly modified throughout the study. The subjects were asked
to avoid all vigorous activity before each test, to sleep normally,
to wear the same sportswear and shoes for all tests. All the
subjects had been familiarized with the tests before participat-
ing in the study.
Tests Description
 Kicking accuracy: every subject used dominant foot to per-
form 10 kicks. We constructed a plywood target measuring
system with 243.5 cm wide × 122 cm high. Carbon paper
was applied to the surface of the target. The distance be-
tween target and ball position is 610 cm. The distance be-
tween bull’s-eye and ground is 120 cm (Finnoff et al., 2002).
To determine the accuracy of the kick, we analyzed video
recordings of each trial. The distance between ball mark
and bulls-eye after each kick was measured. The mean error
of the 10 kicks was retained for analysis, so that the smaller
the score, the better the KA (Finnoff et al., 2002).
 Ball control with the body: Within a 9 × 9 m square, the
player had to keep the ball in the air without using the arms
or hands. The score recorded was the number of the ball
before it fell to the floor. Counting stopped when the ball
hit the floor, the participant moved out of the square or he
touched the ball with the arms or hands. One trial was ad-
ministered, although the participant could start the trial
again if he failed to contact the ball three times in the initial
attempt (Malina et al., 2005).
 Ball control with the head: Within a 9 × 9 m square, the
player had to keep the ball in the air using only the head.
The score recorded was the number of hits of the ball before
it fell to the floor. Counting stopped when the ball hit the
floor, the participant moved out of the square or he touched
the ball with any part of the body except the head. One trial
was administered, although the participant was allowed to
start the trial again if he failed to contact the ball three times
in the initial attempt (Malina et al., 2005).
 Coordination test: This test enables to evaluate the football
coordination of various parts of the body. The researcher
throws the ball to the player from a distance of 5 m. The
player starts to play with ball in the order of chest-foot-head,
head-left foot-right foot and foot-chest-head. The researcher
measures them and every successful play brings 1 point
(Rosch et al., 2000).
 Zigzag Test. This test assessed running agility from changes
in direction. A zigzag course consisted of 5 m sections set
out at 100 angles. The selection of this test was based on
rapid acceleration, deceleration, and balance control re-
quired for short running time, which represented the result
of the test (Little et al., 2005).
 Zigzag with the Ball. The ability to control the ball while
changing direction was assessed. Subjects were instructed
to run with the ball as fast as possible along the same zigzag
path used in the previous test (Mirkov et al., 2008). The
time in Zigzag Test and Zigzag with the Ball (all running
tests) measurement is made with a stopwatch in units of 0.1
seconds (Rosch et al., 2000).
 Skill Index. The ratio of the results obtained from the zig-
zag test without and with the ball was calculated. A higher
index (i.e., a smaller relative increase in the zigzag running
time when the ball had to be controlled) was interpreted as a
higher skill of controlling the ball (Mirkov et al., 2008).
72

A. GHARBI ET AL.
Statistical Analysis
All results are expressed as mean (±SD). After checking the
normality of the distribution with the Komolgorov-Smirnov test,
we used a paired Student’s t-test to investigate differences be-
tween morning and evening for all measurement. Pearson cor-
relations were used to assess the relationships between vari-
ables. Statistical significance was set at P < 0.05.
Results
A significant diurnal variation was observed for temperature
when measured at 7:00 h and 17:00 h. (P < 0.01). The in-
tra-aural temperature was 0.68˚C higher in the evening (Figure
1) than the morning. Results showed a significant main effect
of time of day for Zigzag Test (i.e., agility) (P < 0.001), and
Zigzag with the Ball (i.e., dribbling) (P < 0.05): the perform-
ances were better in the evening than in the morning. The diur-
nal gains were 6.7% ± 5.5% and 4.6% ± 5.9% for Zigzag Test
and Zigzag with the Ball respectively. However, there was no
significant time of day effect for other skills including juggling
performance (Ball control with the body and with the head),
coordination tests, skill index and kicking accuracy (Table 1).
Interestingly, as reported in Figure 2, the speed for agility
and dribbling were positively and significantly correlated with
intra-aural temperature (r = 0.67and r = 0.76, respectively, P <
0.001).
Discussion
The aim of the current study was to investigate diurnal varia-
tion in some specific skills performance in boy’s footballers.
The main finding was the increase of agility and dribbling in
the evening. The measures showed that the best performance
was at 17:00 h and the intra-aural temperature fluctuates con-
comitantly. However, the diurnal variation in the juggling per-
formance (Ball control with the body and ball control with the
head) just failed to reach significance. The coordination tests,
skill index and kicking accuracy did not show a significant
time-of-day effect.
Our results showed a significant diurnal variation in in-
tra-aural temperature as it was described in previous studies
(Reilly et al., 2004a, 2004b, 2007) (Figure 1). Body tempera-
ture as a marker of circadian rhythms, shows a diurnal variation
with higher values recorded at 17:00 h (Figure 1). Moreover,
Morning Evenin g
36.6
36.4
36.2
36
35.8
35.6
35.4
35.2
35
Temperature (˚C)
Figure 1.
Time of day effect in intra-aural temperature. **P < 0.01. Sig-
nificantly different from morning.
Table 1.
Mean (±SD) values for Zigzag test (s), kicking accuracy (cm), Ball
control with the body, Ball control with the head (number of hits) and
coordination measured in the morning and in the afternoon.
Test 07:00 hr 17:00 hr
Zigzag with the ball (s) 7.69 ± 0.32 7.36 ± 0.31*
Zigzag test (s) 5.92 ± 0.32 5.55 ± 0.21**
kicking accuracy (cm) 46.7 ± 12.2 43.1 ± 13.1
Ball control with the body
(number of hits) 32.53 ± 19.93 36.07 ± 30.11
Ball control with the head
(number of hits) 6.33 ± 3.09 7.27 ± 3.39
Skill index 0.77 ± 0.02 0.75 ± 0.02
Coordination
chest-foot-head (points) 2.33 ± 1.11 2.07 ± 1.22
head- foot- foot (points) 1.53 ± 0.83 1.40 ± 0.83
foot-chest-head (points) 0.80 ± 0.56 0.73 ± 0.70
Note: *,**significant difference in comparison with 07:00 h at the levels of P <
0.05 and P < 0.01.
34 35 36 37 38
4.0
3.5
3.0
2.5
2.0
Speed: agility and dribbling (m·s–1)
Temperature (˚C)
y = 0.227x – 4.687
R2 = 0.570
y = 0.127x – 1.919
R2 = 0.445
Figure 2.
Correlation between intra-aural temperature and speed for dribbling
(closed circles) and agility (open circles).
the gains observed in our experimental population (around
0.68˚C) are in accordance with the amplitude (peak-to-trough
variation) demonstrated on boys which showed an amplitude
ranging from 0.5˚C to 1˚C (Melhim et al., 1993; Souissi et al.,
2010; Zarrouk et al., 2012).
The results of the present investigation, focused on the diur-
nal fluctuations of boy’s footballers, showed that agility and
dribbling fluctuate with time-of-day, with morning nadirs, eve-
ning highest values and an amplitude equal to 8% ± 6.7% and
4.5% ± 5.9%, respectively. The worst performance of dribbling
and agility observed in the morning can be explained by the
significant low body-temperature (P < 0.01) which can modify
muscular electric activity, causing a change in muscular coor-
dination and, consequently, a performance decrease (Oksa et al.,
1996). Moreover, the effect of time of day on muscle contrac-
tile properties could be attributed, in part, to an intracellular

A. GHARBI ET AL.
variation in the muscle (e.g., a circadian variation in inorganic
phosphate concentration) and/or, in part, to the circadian
rhythm in the central temperature, which could influence cal-
cium release by the sarcoplasmic reticulum (Guette et al.,
2005).
The findings of this study were in agreement with previous
studies who reported that physical (Chtourou et al., 2012a,
2012b; Hamouda et al., 2012; Aloui et al., 2012; Reilly et al.,
2007, Bernard et al., 1998; Melhim et al., 1993) and some spe-
cific skill soccer (Reilly et al., 2004a, 2004b, 2007) perform-
ances were significantly higher in the evening than the morning
(Chtourou et al., 2012a, 2012b; Hamouda et al., 2012; Aloui et
al., 2012; Reilly et al., 2007, Bernard et al., 1998; Melhim et al.,
1993). Nevertheless, it was reported that time of day have no
effect on dribbling time (Reilly et al., 2004a, 2007). The dis-
agreement with our study is probably due to differences in the
study protocol, as the distance dribble (40 m) is higher than the
present one (20 m).
A major finding of the present study was that the high intra
aural temperature was associated with a significant increase in
agility and dribble performance. It would seem, therefore, that
changes in some skills soccer performance are justified by
changes in body temperature during the course of the day time.
Similar findings were reported in swimming (Zarrouk et al.,
2012), running (Chtourou et al., 2012b), tennis (Drust et al.,
2005), football (Reilly et al., 2004a, 2004b, 2007), badminton
(Edwards et al., 2005). It can, thus, be concluded that there is a
circadian rhythm in some specific skills performance in boy’s
footballer. Indeed, the association between the diurnal tem-
perature variation and the different aspects of physical (Souissi
et al., 2010; Winget et al., 1985), mental (Reilly et al., 2007),
perceptual, sensory motor, psychomotor (Weipeng et al., 2011)
and cognitive performances (Winget et al., 1985) were found
on many studies in adults (Reilly et al., 2007; Winget et al.,
1985) and in children ((Souissi et al., 2010) performances.
Usually, peak performances were found to occur in the early
evening and correspond to the maximum body (Aloui et al.,
2012; Reilly et al., 2007, Bernard et al., 1998; Melhim et al.,
1993; Souissi et al., 2010). Although the exact mechanisms
explaining this relationship remain unclear, it has been sug-
gested that the increase in body temperature allows an increase
in energy metabolism, improved muscle compliance, facilitate
actin-myosin crossbridging (Weipeng et al., 2011), enhance
metabolic reactions, increase the extensibility of connective
tissue, reduce muscle viscosity and increase conduction veloc-
ity of action potentials (Sedliak et al., 2007). Even though it is
still largely accepted that temperature is the primary circadian
indicator of physical performance, recent evidence has chal-
lenged the traditional views about the relationship between
body temperature and exercise performance. Recent studies
investigating the neuromuscular performance at different time-
of-day revealed a distinct circadian rhythm in physiological
variables independent of temperature changes (Guette et al.,
2005). This can explain the fact that circadian rhythm in sport-
ing performance is affected by multi-factorial mechanisms,
such as time since waking, level of fatigue, alertness (Atkinson
et al., 1998; Edwards et al., 2007) and mood state (Drust et al.,
2005). Therefore, the elucidation of these mechanisms is ex-
tremely complicated to be attributed to one variable. Future
studies should investigate the complexity of these variables.
Nevertheless, there was no significant time of day effect on
juggling (i.e., Ball control with the body, ball control with the
head), coordination tests, skill index and kicking accuracy (Ta-
ble 1). This might reflect in some way the level of skill and the
modest experience (4.2 years) of the players recruited for this
study. In addition, This finding can be related to the fact, as
mentioned in the methods sections, that the measurements of
the specific tests used were taken only at two times of day:
07:00 and 17:00 h and, therefore, we could not determine the
exact time of peak specific technical skills performance (i.e.,
coordination, control with body and with head and kicking
accuracy). Measuring performance continuously is not easy to
implement and these time points (07:00 and 17:00 h) were
chosen as they are generally reported in the literature (Chtourou
et al. 2012a, 2012b; Hamouda et al., 2012; Aloui et al., 2012).
Our results differ from those of previous studies which showed
that the accuracy and consistency of badminton (Edwards et al.,
2005), tennis serves (Atkinson et al., 1998), shooting accuracy
(Reilly et al., 2004b) and juggling (Reilly et al., 2007) seems to
be time of day dependent with higher accuracy observed in the
evening (Reilly et al., 2004b) and in the middle of the day
(Drust et al., 2005; Edwards et al., 2005). Circadian rhythms
are also observed for other soccer-specific performance tests
such as chipping, dribbling, and juggling. The discrepancy
between our results and those of many workers (Reilly et al.,
2004b; Drust et al., 2005; Edwards et al., 2005), could be in
part accounted for the differences in the task performed and
muscle groups solicited (upper vs. lower extremities), the ways
of the accuracy measurements (radial error, distance from the
target, number of points, scores per trial vs. mean error), the
type of projectile (arrow and tennis ball vs. soccer ball), the
distance between target and service line or ball position (2.37 m,
3.56 m. vs. 6.1 m), the age (adults vs. boys), and the specificity
of sport (racquet sport vs. football).
Although the precise mechanisms of this response require
further investigation, coaches and sport scientists should con-
sider these findings when attempting to develop the specific
skills performance for soccer players. In other respects, from
the results of the present study, it is understood that the ability
of some skills at different times of the day varies, due to the
circadian rhythmicity.
Conclusion
An increase of intra-aural temperature, agility and dribbling
were shown in the evening compared to morning values. The
measures showed the best performance at 17:00 h and the in-
tra-aural temperature fluctuates concomitantly. No time-of-day
effect was observed for the ball control with the body, ball con-
trol with the head, coordination tests, skill Index and kicking
accuracy performance.
REFERENCES
Aloui, A., Chaouachi, A., Chtourou, H., Wong, D., Haddad, M.,
Chamari, K., & Souissin, N. (2012). Effects of Ramadan on the di-
urnal variations of repeated sprints performances. International
Journal of Sports Physiology and Performance (in press).
Atkinson, G., & Spiers, L. (1998). Dirunal variations in tennis serve.
Perceptual and Motor Skills, 86, 1335-1338.
doi:10.2466/pms.1998.86.3c.1335
Bernard, T., Giacomoni, M., Gavarry, O., Seymat, M., & Falgairette, G.
(1998). Time-of-day effects in maximal anaerobic leg exercise.
European Journal of Applied Physiology and Occupational Physiol-
ogy, 77, 133-138. doi:10.1007/s004210050311
74

A. GHARBI ET AL.
Chtourou, H., Hammouda, O., Chaouachi, A., Chamari, K., & Souissi,
N. (2012a). The effect of time-of-day and Ramadan fasting on an-
aerobic performances. International Journal of Sports Medicine, 33,
142-147. doi:10.1055/s-0031-1286251
Chtourou, H., Hammouda, O., Souissi, H., Chamari, K., Chaouachi, A.,
& Souissi, N. (2012b). Diurnal variations in physical performances
related to football in adolescent soccer players. Asian Journal of
Sports Medicine, 3, 139-144.
Drust, B., Waterhouse, J., Atkinson, G., Edwards, B., & Reilly, T.
(2005). Circadian rhythms in sports performance-an update. Chrono-
biology International, 22, 21-44. doi:10.1081/CBI-200041039
Edwards, B., Lindsay, L., & Waterhouse, J. (2005). Effect of time of
day on the accuracy and consistency of the badminton serve. Ergo-
nomics, 48, 1488-1498. doi:10.1080/00140130500100975
Edwards, B., Waterhouse, J., & Reilly, T. (2007). The effects of cir-
cadian rhyhmicity and time-awake on a simple motor task. Chrono-
biology Internation al, 24, 1109-1124.
doi:10.1080/07420520701795316
Finnoff, J. T., Newcomer, K., & Laskowski, E. R. (2002). A valid and
reliable method for measuring the kicking accuracy of soccer players.
Journal of Science and Medicine in Sport, 5, 348-353.
doi:10.1016/S1440-2440(02)80023-8
Guette, M., Gondin, J., & Martin, A. (2005). Time-of-day effect on the
torque and neuromuscular properties of dominant and nondominant
quadriceps femoris. Chronobiology Interna tional, 22, 541-558.
doi:10.1081/CBI-200062407
Hamouda, O., Chtourou, H., Farjallah, M. A., Damien, D., & Souissi, N.
(2012). The effect of Ramadan fasting on the diurnal variations in
aerobic and anaerobic performances in Tunisian youth soccer players.
Biological Rhythm Research, 43, 177-190.
doi:10.1080/09291016.2011.560050
Horne, J. A., & Ostberg, O. (1976). A self-assessment questionnaire to
determine morningness-eveningness in human circadian rhythms.
International Journa l o f C hr onobiology, 4 , 97-110.
doi:10.3109/07420529709001458
Huguet G., Touitou Y., Reinberg A. (1995). Diurnal Changes in Sport
Performance of 9 - 11-Year-Old School Children. Chronobiology
International, 14, 371–384.
Little, T., & Williams, A. G. (2005). Specificity of acceleration, maxi-
mum speed, and agility in professional soccer players. Journal of
Strength and Conditioning, 19, 76-78.
Malina, R. M., Cumming, S. P., Kontos, A. P., Eisenmenn, J. C.,
Ribeiro, B., & Aroso, J. (2005). Maturity-associated variation in
sport-specific skills of youth soccer players aged 13 - 15 years.
Journal of Sports Sciences, 23, 515-522.
doi:10.1080/02640410410001729928
Melhim, A. F. (1993). Investigation of circadian rhythms in peak power
and mean power of female physical education students. International
Journal of Sports Medicine, 14, 303-306.
doi:10.1055/s-2007-1021182
Mirkov, D. M., Nedeljkovic, A., Kukolj, M., Ugarkovic, D., & Jaric, S.
(2008). Evaluation of reliability of soccer-specific field tests. Journal
of Strength and Conditioning, 22, 1046-1050.
doi:10.1519/JSC.0b013e31816eb4af
Oksa, J., Rintamaki, H., Makinen, T., Martikkala, V., & Rusko, H.
(1996). EMG activity and muscular performance of lower leg during
stretch-shortening cycle after cooling. Acta Physiologica Scandina-
vica, 157, 71-78. doi:10.1046/j.1365-201X.1996.452172000.x
Reilly, T., Atkinson, G., Edwards, B., Waterhouse, J., Farrelly, K., &
Fairhurst, E. (2007). Diurnal variation in temperature, mental and
physical performance, and tasks specifically related to football (soc-
cer). Chronobiology International, 224, 507-519.
doi:10.1080/07420520701420709
Reilly, T., Fairhurst, E., Edwards, B., & Waterhouse, J. (2004a). Time
of day and performance tests in male football players. In T. Reilly, J.
Cabri, & D. Araujo (Eds.), Science and Football V. London:
Routledge, 275-279.
Reilly, T., Farrelly, K., Edwards, B., & Waterhouse, J. (2004b). Effects
of time of day on the performance of soccer-specific motor skills. In
T. Reilly, J. Cabri, & D. Araujo (Eds.), Science and Football V.
London: Routledge, 272-274.
Rosch, D., Hodgson, R., Peterson, T. L., Graf-Baumann, T., Junge, A.,
Chomiak, J., & Dvorak, J. (2000). Assessment and evaluation of
football performance. American Journal of Sports Medicine, 28,
29-39.
Sedliak, M., Finni, T., Cheng, S., Kraemer, W. J., & Häkkinen, K.
(2007). Effect of time-of-day-specific strength training on serum
hormone concentrations and isometric strength in men. Chronobiol-
ogy International, 224, 1159-1177.
doi:10.1080/07420520701800686
Souissi, H., Chaouachi, A., Chamari, K., Dogui, M., Amri, M., &
Souissi, N. (2010). Time-of-day effects on short-term exercise per-
formances in 10 - 11-years-old Boys. Pediatric Exercise Science, 22,
613-623.
Weipeng, T., Michael, J., & Michael, R. (2011). Circadian rhythms in
exercise performance: Implications for hormonal and muscular ad-
aptation. Journal of Sports Science and Medic i n e , 10, 600-606.
Winget, C. M., DeRoshia, C. W., & Holley, C. (1985). Circadian
rhythms and athletic performance. Medicine and Science in Sports
and Exercise, 17, 498-516. doi:10.1249/00005768-198510000-00002
Zarrouk, N., Chtourou, H., Rebai, H., Hammouda, O., Souissi, N.,
Dogui, M., & Hug, F. (2012). Time of day effects on repeated sprint
ability. International Journal of Spor ts Medicine, 33, 975-980.
doi:10.1055/s-0032-1312626