Content uploaded by Alvaro Lopez-Samanes
Author content
All content in this area was uploaded by Alvaro Lopez-Samanes on Jan 12, 2017
Content may be subject to copyright.
This article was downloaded by: [HINARI]
On: 13 December 2013, At: 12:39
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Biological Rhythm Research
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/nbrr20
Circadian rhythm effects on
neuromuscular and sprint swimming
performance
Jesús G. Pallarésa, Álvaro López-Samanesa, Jaime Morenoa,
Valentín E. Fernández-Elíasa, Juan Fernando Ortegaa & Ricardo
Mora-Rodrígueza
a Exercise Physiology Laboratory, University of Castilla-La Mancha,
Toledo, Spain.
Accepted author version posted online: 18 Apr 2013.Published
online: 25 Jun 2013.
To cite this article: Jesús G. Pallarés, Álvaro López-Samanes, Jaime Moreno, Valentín E.
Fernández-Elías, Juan Fernando Ortega & Ricardo Mora-Rodríguez (2014) Circadian rhythm effects
on neuromuscular and sprint swimming performance, Biological Rhythm Research, 45:1, 51-60, DOI:
10.1080/09291016.2013.797160
To link to this article: http://dx.doi.org/10.1080/09291016.2013.797160
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &
Circadian rhythm effects on neuromuscular and sprint swimming
performance
Jesús G. Pallarés, Álvaro López-Samanes, Jaime Moreno, Valentín E. Fernández-Elías,
Juan Fernando Ortega and Ricardo Mora-Rodríguez*
Exercise Physiology Laboratory, University of Castilla-La Mancha, Toledo, Spain
(Received 6 March 2013; final version received 3 April 2013)
The aim of this study was to determine the effect of time-of-day on sprint swimming
performance and on upper and lower body, maximum strength, and muscle power.
Twelve well-trained junior swimmers (six male and six female) were tested for
bench press (BP) maximum strength and muscle power, jump height countermove-
ment vertical jump (CMJ), crank-arm peak power (10s Wingate test), and time to
complete 25 m freestyle at 10:00 am and at 18:00 pm in a random order. Perfor-
mance was significantly enhanced in the pm compared to the am in 25 m swimming
time (1.7%; p= 0.01), BP maximum strength (3.6%, p= 0.04, ES = 1.87), BP muscle
power (5.1%, p= 0.00, ES = 2.10), and CMJ height (5.8%; p= 0.02), but not in
crank-arm power (4.1%; p= 0.08). Time-of-day increased swimming performance in
a magnitude of one-third of the effects observed on upper and lower neuromuscular
power, which suggests that factors beyond peak muscle power (i.e. swimming
technique) affect 25 m freestyle performance.
Keywords: time-of-day; chronobiology; bench press; crank-arm Wingate; muscle
power; muscle strength
1. Introduction
During the day, the different aspects of physical performance (i.e. muscle endurance,
muscle power, and cardiorespiratory endurance) oscillate, scoring higher during midday
and early evening, and being depressed during the late night and early morning hours
(Baxter & Reilly 1983; Kline et al. 2007; Souissi et al. 2007; Sedliak et al. 2008;
Souissi et al. 2010; Taylor et al. 2010). Accompanying these diurnal changes of motor
performance, researchers have found changes on basal body temperature and blood
concentration of hormones, which in turn, could affect body fluids, muscle metabolism,
and the cardiovascular response to exercise (e.g. heart rate and blood pressure)
(Atkinson & Reilly 1996; Decostre et al. 2005). Other studies, focusing on the effects
of circadian rhythm on the muscle itself, suggest alterations in the actin–myosin cross-
bridging processes (Starkie et al. 1999), phosphagen metabolism, and muscle buffering
capacity (Atkinson & Reilly 1996). Thus, circadian rhythm may have a profound
impact on motor performance through systemic and local muscle mechanisms that are
still open for clarification.
The changes in motor performance associated with circadian rhythm have been
mostly described for long- and medium-term efforts, which depend mainly on
*Corresponding author. Email: Ricardo.Mora@uclm.es
Biological Rhythm Research, 2014
Vol. 45, No. 1, 51–60, http://dx.doi.org/10.1080/09291016.2013.797160
Ó2013 Taylor & Francis
Downloaded by [HINARI] at 12:39 13 December 2013
cardiorespiratory endurance (Atkinson et al. 2005; Simmonds et al. 2010). However,
circadian rhythm could also affect short-term competition events that rely on peaks of
muscle strength and power output (Souissi et al. 2007; Teo et al. 2011). For instance,
studies conducted with experienced swimmers have found a close association between
swimming performance and muscle power output, mainly when analyzing the official
short-distance events (i.e. 25 m, 50 m, and 100 m) (Zampagni et al. 2008; Bishop et al.
2009; Potdevin et al. 2011; West et al. 2011). The few studies that have actually exam-
ined the effects of circadian rhythm on swimming performance have found a significant
reduction from 1.2 to 3.5% in swimming performance when testing 50-m, 100-m, and
200-m freestyle in the early morning (i.e. 6:00 h–10:00 h) in comparison to the results
of swimming the same distances in the evening (i.e. 17:00 h–22:00 h) (Baxter & Reilly
1983; Deschodt & Arsac 2004; Kline et al. 2007; Martin et al. 2007). However, to our
knowledge, no study has examined the effects of circadian rhythm on the sprint swim-
ming performance (i.e. 25 m).
Based on the published high association between muscle peak power output and
short distance swimming performance (Zampagni et al. 2008; Bishop et al. 2009;
Potdevin et al. 2011; West et al. 2011) and knowing the deleterious effect that perform-
ing in the morning has upon neuromuscular performance (i.e. 3.0–7.5% reduction)
(Mora-Rodriguez et al. 2012), it is our hypothesis that all-out 25 m swimming perfor-
mance will be affected by circadian rhythm. Moreover, knowing the effects that time-
of-day has on 25 m swimming sprint could be useful to develop strategies that allow
coaches to avoid reduced performance during competition or to optimize the adaptations
during regular training. Therefore, the main aim of this study was to examine the circa-
dian rhythm effects on short-distance swimming performance (i.e. 25 m). A second
objective was to assess if muscle strength and power output of the upper and lower
body were affected similarly by time-of-day and its correlation with 25 m swimming
performance. We hypothesize a parallel decline in 25m swimming performance and
neuromuscular power in the morning, compared with the evening performance.
2. Methods
2.1. Subjects
Twelve well-trained junior swimmers (six male and six female in the age range of 17.1
± 2.7 years) volunteered to participate in this study. The physical and anthropometric
characteristics of the subjects are shown in Table 1. All the participants were experi-
enced swimmers with 8.8 ± 2.6 years of training career. However, none of them had
been involved in a resistance training program for more than six consecutive months
Table 1. Subjects’characteristics.
All (n= 12) Male (n= 6) Female (n=6)
Age (years) 17.1 ± 2.7 18.3 ± 3.3 15.9 ± 1.5
Height (m) 1.72 ± 0.10 1.81 ± 0.06 1.64 ± 0.04
BM (kg) 65.6 ± 10.2 73.2 ± 7.6 58.0 ± 5.8
BMI (kg m
2
) 22.0 ± 1.7 22.4 ± 1.2 21.5 ± 2.1
Fat free mass (kg) 30.9 ± 6.8 36.6 ± 4.1 25.1 ± 2.4
Fat mass (%) 16.5 ± 6.8 11.8 ± 4.4 21.1 ± 5.6
Data are presented as mean ± SD.
52 J.G. Pallarés et al.
Downloaded by [HINARI] at 12:39 13 December 2013
per year. Therefore, they were all considered moderately resistance-trained individuals.
The subjects were informed in detail about the experimental procedures and the possible
risks and benefits of the project. The study complied with the Declaration of Helsinki
and was approved by the Bioethics Commission of the University of Murcia. Written
informed consent was obtained from each athlete or from their parents or guardians
prior to participation.
2.2. Experimental design
In a random order, participants underwent the same battery of tests in two separated
days at different times of the day: (i) morning (10:00 h) and (ii) evening (18:00 h).
Trials were separated by 36 h in between. The experimental trials were designed to
evaluate the main effects of the time-of-day (morning vs. evening) on swimming and
neuromuscular performance. We selected those times of day for testing (i.e. 10:00 in
the morning and 18:00 in the evening) because they are common competition schedules
for this group of junior competitive swimmers. Participants underwent three familiariza-
tion sessions with the testing techniques and protocols performed in the actual study to
avoid the bias of progressive learning on test reliability. The last familiarization session,
performed in the morning (10:00 a.m.) of the second day prior to the beginning of each
experiment, included the determination of the following variables for each subject
(described later in detail): (i) the individual load (kg) that elicited a 1.00 m s
1
mean
propulsive velocity (MPV) in the free-weight bench press (BP) exercise and (ii) the
individual load (kg) corresponding to 75% of 1RM in BP exercise (Figure 1).
2.3. Experimental protocol
During the 48 h before testing, subjects refrained from physical activity other than that
required by the experimental trials. The day before the onset of the experiment, height
was measured to the nearest 0.5 cm during a maximal inhalation using a wall-mounted
stadiometer (Seca 202, Seca Ltd., Hamburg, Germany). Upon arrival to the testing facil-
ity, the subjects’body weights were determined and body fat estimated in a fasted state
using a 4-contact electrode body composition bioimpedance analyzer (Tanita TBF-
300A, Tanita Corp., Tokyo, Japan). After a standardized warm-up that consisted of
5 min of pedaling a stationary bicycle at low intensity and 5 min of static stretches and
joint mobilization exercises, the subjects entered the laboratory to start the neuromuscu-
lar test battery assessments under controlled environmental conditions (i.e. 22 ± 1 °C
and 29 ± 3% relative humidity) and a strict-paced schedule (see Figure 1). These tests
consisted of the measurement of a standard countermovement vertical jump (CMJ)
height and the bar displacement velocity, for loads that elicit maximum muscle strength
(75% of 1 RM) and power output (1 m s
1
) adaptations in the BP exercise. The neuro-
muscular test battery ended with the assessment of peak muscle power output in a 10 s
crank-arm Wingate test. Finally, all the participants performed a swimming test, cover-
ing a distance of 25 m in freestyle, for which they were timed. The total time session of
each experimental protocol was 70 min.
2.4. Jumping test (CMJ)
Participants were instructed to complete a standard CMJ in which they squatted down
into a self-selected depth at/or below 100° knee flexion, prior to explosively performing
Biological Rhythm Research 53
Downloaded by [HINARI] at 12:39 13 December 2013
the concentric action. Participants were instructed to keep their hands on their hips at
all times and to maintain the same position at take-off and landing. Flight times were
measured using a vertical jump mat (Optojump, Microgate, Italy). The intraclass
coefficient correlation (ICC) and coefficient of variation (CV) were 0.94 and 3.3%,
respectively. The recorded height for this test was the average of three trials.
2.5. Maximum dynamic strength and maximal muscle power
During the last familiarization session, the individual loads that elicited a bar displace-
ment of 1.00 m s
1
and the load of 75% of 1RM for BP exercise were identified in a
graded loading test using a linear encoder and its associate software (T-Force System,
Ergotech, Murcia, Spain, 0.25% accuracy). Loads that allow bar displacement at a
velocity of 1.00 m s
1
are very close to those that maximize the mechanical power out-
put for isoinertial upper body multijoint resistance exercises (e.g. free-weight BP)
(Izquierdo et al. 2002; Sanchez-Medina & Gonzalez-Badillo 2011). In turn, 75% of 1
RM has been described as the minimal load that allows positive adaptations for maxi-
mum strength development in well resistance-trained athletes (American College of
Figure 1. Experimental protocol.
54 J.G. Pallarés et al.
Downloaded by [HINARI] at 12:39 13 December 2013
Sports 2009, Garcia-Pallares et al. 2010). After those loads were individually deter-
mined, changes in bar displacement velocity during the BP exercise as a consequence
of time-of-day (am vs. pm) were measured. Detailed description of the BP and SQ
execution technique, as well as the validity and reliability data of the dynamic measure-
ment system (ICC = 1.00; CV = 0.57%) have recently been reported (Sanchez-Medina &
Gonzalez-Badillo 2011).
2.6. Wingate test
The crank-arm Wingate test was performed on an adjustable, speed dependent arm
ergometer (Monark Cardio Rehab 891E, Varberg, Sweden) fitted to the individual sub-
ject’s dimensions to align the mid-line of the sternum with the bottom bracket. Subjects
warmed up for 5 min with a frictional load of 2.0% of their individual body mass (BM)
using a self-selected cadence. During the warm-up period, two short sprints of 5-s dura-
tion were administered. Then, subjects were requested to crank at 60 rpm without load
(Reiser et al. 2000) at which point, a 5.0% BM resistance was dropped and a timer was
started. At this point subjects cranked as hard and fast as possible for the next 10 s. We
chose a 10-s test duration to avoid the fatiguing effects of performing a 30 s Wingate
test on the subsequent swimming bout. It has been reported that even 4–5 s Wingate test
is reliable for the measurement of anaerobic power in active university students (Balmer
et al. 2004). After completion of the test, subjects cycled against a light load for as long
as needed for recovery. Subjects were required to remain seated during the entire test.
Crank-arm peak power was identified as the highest cadence (in RPM) times the
frictional resistance in kilopond.
2.7. Swimming test
All participants performed a 25 m swimming test in a 25 m indoor swimming pool.
Swimmers performed a 400-m warm-up swim at 75% of their 400-m competition veloc-
ity, followed by a 5min passive resting period. After the warm-up, the subjects were
instructed to perform one all-out 25 m freestyle swimming test. The swimmers started
in a standardized position in the water, holding the backstroke handle with one hand
and having both feet on the wall. Both trials were held in the lane closest to the wall
(lane 6). Water temperature (27.5 ± 1.0 °C), air temperature (22.4 ± 0.8 °C, relative
humidity (43 ± 3%) and swimming pool lighting were held similar in both trials. All the
starts were on the initiative of the participants. Swim performance was assessed as the
time spent in covering 25 m which was recorded by two independent and experienced
coaches using handheld chronographs able to discriminate up to 1/100 of a second
(Namaste 988, Spain). The average time recording of the two timers was used for
subsequent analyses.
3. Statistical analysis
Data are presented as means and standard deviation (SD). Shapiro–Wilk test was used
to assess normal distribution of data. Neuromuscular differences between trials (am vs.
pm) were analyzed using one-way analysis of variance for repeated measurements. The
Greenhouse-Geisser adjustment for sphericity was calculated. After a significant F test,
pairwise differences were identified using the Bonferroni significance post hoc
procedure. Pearson correlation analysis was used to assess the associations between the
Biological Rhythm Research 55
Downloaded by [HINARI] at 12:39 13 December 2013
circadian rhythm declines on neuromuscular tests and 25-m swimming performance.
The significance level was set at p6.05. Cohen’s formula for effect size (ES) was used
and the results were based on the following criteria: >0.70 large effect; 0.30–0.69
moderate effect; 60.30 small effect (Cohen 1988).
4. Results
4.1. Countermovement jump height and velocity against loads for maximum
dynamic strength and muscle power adaptations
The CMJ height was significantly higher during the evening session (pm) when com-
pared to the morning (am) (4.3%; p= 0.02; ES = 0.65) (Figure 2(C)). Likewise, velocity
for maximal power (i.e. load that allow 1 m·s
1
) and maximum strength loads (i.e. load
of 75% 1RM) in BP exercise were significantly greater in the pm protocol when
compared to the am (5.1%, p= 0.00, ES = 2.10; 3.6%, p= 0.04, ES = 1.87; respectively;
Figure 2(A) and (B)).
4.2. Wingate and swimming test
The crank-arm Wingate peak power recorded in the evening (pm) was 3.2% higher
without reaching significance (p= 0.08, ES = 0.37) when compared to the morning
values (am) (Figure 2(D)). The time spent to cover 25 m freestyle swimming was
Figure 2. Time-of-day effects on velocity for (A) maximal power and (B) maximum strength
loads in BP, jump height (C) and crank-arm Wingate peak power output (D). Data are means
± SD.
⁄
Significant differences compared to the am values. p60.05.
56 J.G. Pallarés et al.
Downloaded by [HINARI] at 12:39 13 December 2013
significantly lower in the pm protocol (13.4 ± 0.3s) compared to the am (13.7 ± 0.3s)
(1.8%, p= 0.01, ES = 0.72). Ten out of the 12 swimmers improved their 25 m swimming
times in the pm trial while two of them did not respond to time-of-day effect (Figure 3).
5. Discussion
This study examines the effects of time-of-day on shortest official swimming distance
(i.e. 25 m freestyle) and neuromuscular performance of young well-trained swimmers at
two times of the day that fit with their habitual training and competition schedules (i.e.
10 am and 18 pm). The novel finding is that the time to complete one all-out 25 m
freestyle swim was significantly longer (1.8%; p= 0.01) in the morning trial (10:00 h)
compared to the evening (18:00 h). Likewise, neuromuscular performance of upper (BP)
and lower body (countermovement jump) musculature showed significant performance
decline in the morning when compared to the evening (3.6–5.1%). This findings
corroborate results in endurance-trained and active subjects, where time-of-day effects
on neuromuscular performance were tested using either dynamic isoinertial contraction
(Mora-Rodriguez et al. 2012) or isometric and isokinetic maximal voluntary contrac-
tions (Gauthier et al. 2001; Racinais et al. 2005). However, to our knowledge we are
first to test in the same group of athletes, the effects of time-of-day in an unspecific
power task that involve a single all-out movement (i.e. BP of counter movement jump)
in a 10-s arm cycling task that is somehow more specific to swimming, and finally in
25 m swimming performance.
Only a few studies have actually examined the time-of-day effects on swimming
performance in well and highly trained athletes (Baxter & Reilly 1983; Deschodt &
Arsac 2004; Kline et al. 2007; Martin et al. 2007). On the distances of 50 m, 100 m,
and 200 m, these authors have reported a maximum time-of-day performance decline of
2.5–3.6% which is slightly higher than the decline presently found for the 25 m free-
style distance (i.e. 1.7%). The differences in the daily fluctuation in motor performance
between studies may be related to the specific time of day chosen to test. We tested
swimmers with 8 h separation between trials (i.e. 10:00 h vs. 18:00 h) while larger
differences in performance have been reported if trials are separated further away.
Baxter and Reilly (1983) used a repeated measures study on well-trained swimmers in
Figure 3. Time-of-day effects on swimming performance. Data are means ± SD.
⁄
Significant
differences compared to the pm values. p60.05.
Biological Rhythm Research 57
Downloaded by [HINARI] at 12:39 13 December 2013
the 100-m distance at 5 different circadian times (i.e. 6:30, 9:00, 13:30, 17:00, and
22:00 h). They detected the largest performance difference (3.5%) between 22:00 h (best
result) and 6:30 h (worst result). Similarly, Kline et al. (2007) in a study designed to
examine the circadian rhythm effects on the 200-m swimming performance addressed 8
different circadian times (i.e. 2:00, 5:00, 8:00, 11:00, 14:00, 17:00, 20:00, and 23:00 h)
and reported the largest performance fluctuation (3.4%) between 23:00 and 5:00 h (i.e.
worst performance). Of note in both studies, the performance differences reported
between 10:00 h am and 18:00 h pm is very similar to ours (i.e. 1.0–2.0%)
To the best of our knowledge we are first to correlate the effects of time-of-day on
neuromuscular power in the upper and lower body musculature with performance in the
shortest-distance swimming event (i.e. 25 m freestyle). It was our hypothesis that upper
and lower neuromuscular force would be intimately related to performance in this very
short swimming distance (i.e. 25 m). We expected associations much higher than with
longer swimming distances where variables dependent on swimming technique (e.g.
stroke rate and stroke length) are more relevant (Martin et al. 2007). However, we have
found that associations between pm and am on neuromuscular tests and 25 m swimming
performance were not high, and only one correlation approached significance without
reach it (swimming vs. BP at a load of 1 m s
1
;r= 0.44; p= 0.08). The magnitude of
the decline in BP maximal movement velocity at 1 m s
1
in the am was around 5.1%
while swimming performance decreased by only 1.7% which is one third of the decline
in BP performance. Thus, it seems that up to two thirds of the decline in upper body
peak power could be compensated during 25 m freestyle where 12–15 complete arm
stroke cycles are executed in around 13 s. The lack of stronger association suggests that
factors like muscle endurance or swimming technique also play an important role in
25 m swimming performance.
The association between the decline in am to pm in swimming time to complete
25 m freestyle and the decline in pm to am in CMJ height (a surrogate of leg power)
was low (i.e. r= 0.12, p= 0.70). Other authors have reported that the CMJ height is
highly correlated with 15-m swimming performance when starting from a block start
(West et al. 2011). In our study, we measure the time-of-day effects in the jumping abil-
ity of swimmers and our results are in line with those reported by Teo et al. (2011) and
Racinais et al. (2004) on college students. However, we found a poor correlation
between the reductions in swimming performance between am and pm and the reduc-
tions in jumping power. This could be due to the fact that our swimmers did not start
from the block but from the water and thus leg extension peak power was probably not
possible to reach due to water resistance. We did not measure time to complete half a
swimming pool lap (12.5 m) and therefore it is possible that a stronger correlation may
have been found with that intermediate time.
Crank-arm peak power also seemed to be under circadian influence as the other
neuromuscular variables, but the effects did not reach statistical differences. The am
and pm differences (3.7%, p= 0.10) are lower than those described for well-trained
swimmers by Deschodt and Arsac (Deschodt and Arsac 2004) using leg cycling
Wingate test. These authors reported a 7.8% enhancement in peak power during pm in
comparison to am. However, other researchers that have evaluated the circadian rhythm
effects on the lower-body Wingate test on experienced athletes, have reported differ-
ences similar to ours between am and pm protocols (i.e. 2.5–5.7%) (Souissi et al. 2010;
Chtourou et al. 2011). We contend that our data on crank- arm peak power is more spe-
cific to swimming than leg cycling peak power and thus more applicable to swimming.
However, we recognize that more studies with a larger number of subjects are needed
58 J.G. Pallarés et al.
Downloaded by [HINARI] at 12:39 13 December 2013
to discard or accept an association between crank-arm cycling and swimming
performance.
In conclusion, time-of-day significantly affects 25 m freestyle swimming perfor-
mance in conjunction with neuromuscular peak performance (i.e. power or maximal
force in the upper and lower body musculature) under climate controlled conditions in
junior competitive swimmers with significant reductions in morning compared to the
evening. Coaches and swimmers should expect an average of 2% reduction in 25 m
freestyle sprint performance in the morning with some swimmers reducing performance
upto 5%, while much fewer having no effect on their performance (18% in our case).
These findings highlight the need to adequate swimming training schedules of sprinting
swimmers to reduce the morning effects on their performance.
References
Atkinson G, Reilly T. 1996. Circadian variation in sports performance. Sports Med. 21:292–312.
Atkinson G, Todd C, Reilly T, Waterhouse J. 2005. Diurnal variation in cycling performance:
influence of warm-up. J Sports Sci. 23:321–329.
Balmer J, Bird SR, Davison RCR, Doherty M, Smith PM. 2004. Mechanically braked Wingate
powers: agreement between SRM, corrected and conventional methods of measurement. J
Sports Sci. 22:661–667.
Baxter C, Reilly T. 1983. Influence of time of day on all-out swimming. Br J Sports Med.
17:122–127.
Bishop DC, Smith RJ, Smith MF, Rigby HE. 2009. Effect of plyometric training on swimming
block start performance in adolescents. J Strength Cond Res. 23:2137–2143.
Chtourou H, Zarrouk N, Chaouachi A, Dogui M, Behm DG, Chamari K, Hug F, Souissi N. 2011.
Diurnal variation in Wingate-test performance and associated electromyographic parameters.
Chronobiol Int. 28:706–713.
Cohen J. 1988. Statistical power analysis for the behavioral sciences. Hillsdale: Lawrence
Erlbaum.
American College of Sports M. 2009. American college of sports medicine position stand.
Progression models in resistance training for healthy adults. Med Sci sports exerc. 41:687–
708.
Decostre V, Bianco P, Lombardi V, Piazzesi G. 2005. Effect of temperature on the working stroke
of muscle myosin. Proc Nat Acad Sci USA. 102:13927–13932.
Deschodt VJ, Arsac LM. 2004. Morning vs. evening maximal cycle power and technical swim-
ming ability. J Strength Cond Res. 18:149–154.
Garcia-Pallares J, Sanchez-Medina L, Esteban Perez C, Izquierdo-Gabarren M, Izquierdo M.
2010. Physiological effects of tapering and detraining in world-class kayakers. Med Sci Sports
Exerc. 42:1209–1214.
Gauthier A, Davenne D, Martin A, Van Hoecke J. 2001. Time of day effects on isometric
and isokinetic torque developed during elbow flexion in humans. Eur J Appl Physiol.
84:249–252.
Izquierdo M, Hakkinen K, Gonzalez-Badillo JJ, Ibanez J, Gonzalez-Badillo JJ, Ibanez J,
Gorostiaga EM. 2002. Effects of long-term training specificity on maximal strength and
power of the upper and lower extremities in athletes from different sports. Eur J Appl
Physiol. 87:264–271.
Kline CE, Durstine JL, Davis JM, Moore TA, Devlin TM, Zielinski MR, Youngstedt SD. 2007.
Circadian variation in swim performance. J Appl Physiol. 102:641–649.
Martin L, Nevill AM, Thompson KG. 2007. Diurnal variation in swim performance remains,
irrespective of training once or twice daily. Int J Sports Physiol Perform. 2:192–200.
Mora-Rodriguez R, Garcia Pallares J, Lopez-Samanes A, Fernando Ortega J, Fernandez-Elias VE.
2012. Caffeine ingestion reverses the circadian rhythm effects on neuromuscular performance
in highly resistance-trained men. PLoS ONE. 7:e33807. Available from: http://www.ncbi.nlm.
nih.gov/pubmed/22496767.
Biological Rhythm Research 59
Downloaded by [HINARI] at 12:39 13 December 2013
Potdevin FJ, Alberty ME, Chevutschi A, Pelayo P, Sidney MC. 2011. Effects of a 6-week
plyometric training program on performances in pubescent swimmers. J Strength Cond Res.
25:80–86.
Racinais S, Hue O, Blonc S. 2004. Time-of-day effects on anaerobic muscular power in a
moderately warm environment. Chronobiol Int. 21:485–495.
Racinais S, Blonc S, Jonville S, Hue O. 2005. Time of day influences the environmental effects
on muscle force and contractility. Med Sci Sports Exerc. 37:256–261.
Reiser RF, Broker JP, Peterson ML. 2000. Inertial effects on mechanically braked Wingate power
calculations. Med Sci Sports Exerc. 32:1660–1664.
Sanchez-Medina L, Gonzalez.-Badillo JJ. 2011. Velocity loss as an indicator of neuromuscular
fatigue during resistance training. Med Sci Sports Exerc. 43:1725–1734.
Sedliak M, Finni T, Peltonen J, Hakkinen K. 2008. Effect of time-of-day-specific strength
training on maximum strength and EMG activity of the leg extensors in men. J Sports
Sci. 26:1005–1014.
Simmonds MJ, Minahan CL, Sabapathy S. 2010. Caffeine improves supramaximal cycling but
not the rate of anaerobic energy release. Eur J Appl Physiol. 109:287–295.
Souissi N, Bessot N, Chamari K, Gauthier A, Sesbouee B, Davenne D. 2007. Effect of time
of day on aerobic contribution to the 30-s wingate test performance. Chronobiol Int.
24:739–748.
Souissi N, Driss T, Chamari K, Vandewalle H, Davenne D, Gam A, Fillard J-R, Jousselin E.
2010. Diurnal variation in wingate test performances: influence of active warm-up. Chronobi-
ol Int. 27:640–652.
Starkie RL, Hargreaves M, Lambert DL, Proietto J, Febbraio MA. 1999. Effect of temperature on
muscle metabolism during submaximal exercise in humans. Exp Physiol. 84:775–784.
Taylor K-L, Cronin J, Gill ND, Chapman DW, Sheppard J. 2010. Sources of variability in
iso-inertial jump assessments. Int J Sports Physiol Perform. 5:546–558.
Teo W, McGuigan R, Newton MJ. 2011. The effects of circadian rhythmicity of salivary cortisol
and testosterone on maximal isometric force, maximal dynamic force, and power output. J
Strength Cond Res. 25:1538–1545.
West DJ, Owen NJ, Cunningham DJ, Cook CJ, Kilduff LP. 2011. Strength and power predictors
of swimming starts in international sprint swimmers. J Strength Cond Res. 25:950–955.
Zampagni ML, Casino D, Benelli P, Visani A, Marcacci M, De Vito G. 2008. Anthropometric
and strength variables to predict freestyle performance times in elite master swimmers. J
Strength Cond Res. 22:1298–1307.
60 J.G. Pallarés et al.
Downloaded by [HINARI] at 12:39 13 December 2013
