Rhythmicity is a fundamental feature of life, and circadian rhythms have been observed in many human physiological variables (29). The sleep-wake cycle is of fundamental importance to human circadian rhythms, and its disruption can have negative effects on athlete’s mental and physical performance in various settings (19). Indeed, successful sports performance requires optimal functioning and coordination of its physical, psychomotor, and cognitive elements (27,34).
To date, there is conflict in the literature with regard to the impact of sleep deprivation on short-term high-intensity exercise. Although some studies show no significant effect of sleep deprivation on short-term maximal performances (5,39), other studies showed that partial or total sleep deprivation reduce anaerobic performances (7,36,37). The reasons for these discrepancies may be that various exercise modes, frequencies, intensities, and durations have been employed and different evaluation procedures, durations of sleep deprivation, and subjects' ages are also the reasons (38). Moreover, Souissi et al. (36,37) demonstrated that the effects of sleep loss on muscular performances are time-of-day dependent. Indeed, Souissi et al. (36) showed that 1 night of sleep deprivation impaired anaerobic performance in the evening but not in the morning of the following day. More recently, Souissi et al. (37) showed that 4 hours of partial sleep deprivation at the end of the night seems to be more disturbing than partial sleep deprivation at the beginning of the night in the following evening, although the morning performance were unchanged. These 2 latter studies used recreationally active individuals. More recently, in recreationally trained subjects, Abedelmalek et al. (1) showed that 4 hours of partial sleep deprivation at the end of the night may reduce the afternoon performances during the Wingate test and, therefore, inverse the diurnal variations of short-term maximal performances. At present, however, no study has investigated the effects of partial sleep deprivation on physical performance of highly trained athletes undertaking arduous training regimens (i.e. judokas).
Although sleep loss can be either total or partial, as the majority of sports entail competition (e.g. judo) within a single day, the study of partially reduced sleep in the day or days before sports contests has more relevance than the study of total sleep deprivation or chronic sleep loss (30). Such partial sleep deprivation occurs as a result of rapid travel across multiple meridians, Muslims Ramadan fasting, early start of a competitive event, and competition-related anxiety (3,12,13,30). These conditions are frequently observed in judo competition (20).
In a high-level competition, judokas perform 5–7 combats by the fact that each judoka can be involved in morning (i.e. eliminations) and afternoon (i.e. finals) combats to classify among the best 5 competitors (19–21). In this context, it has been well documented that performances of short duration present the common characteristic to be better in the afternoon (e.g. between 16:00 and 20:00 hours) than in the morning (e.g. between 06:00 and 10:00 hours) (9–11,14,17). This diurnal increment has been observed for various exercises such as the vertical jump height (9,11,32) and power output during the Wingate test (9–11,14,17,31).
Therefore, an additional difficulty (i.e. in addition to sleep deprivation) that of “muscle fatigue” arises with the judo match. In this context, to the best of our knowledge, the effects of a partial sleep deprivation on short-term maximal performances of judokas before and after a judo match the subsequent morning and evening have not been investigated. The fact that a partial sleep deprivation might negate any influence on the diurnal variation of short exercise performances in trained subjects is perhaps of greatest interest to applied sports scientists.
In view of the above considerations, the aim of the present study was to determine whether partial sleep deprivation in the beginning vs. end of the night impacted short-term maximal performances of trained judokas (i.e. before and after a judo match) and whether the eventual impact is time-of-day dependent.
Experimental Approach to the Problem
To date, data of the literature concerning the effect of partial sleep deprivation on short-term maximal performances are inconclusive. In addition to the authors’ knowledge, there seems to be only 1 study that has investigated the effect of partial sleep deprivation on the diurnal variations of short-term maximal performances in untrained subject (37). Because Atkinson et al. (4) showed that the amplitude of the diurnal rhythm was higher in physically active than inactive subjects (i.e. therefore the diurnal variations could be different between untrained and well-trained subjects), by comparing physical performances of judokas at 2 different time-of-day and during 3 sleep conditions, we sought to investigate the effect of partial sleep deprivation on muscle power, strength, and fatigue and their diurnal variations. To achieve this, judokas performed the handgrip (HG), the maximal voluntary contraction (MVC), and the Wingate tests before and immediately after a judo match. The HG, rating of perceived exertion (RPE), MVC, and the Wingate test performances (peak power [PP] and mean power [MP]) were the dependent variables and the sleep, combat, and time-of-day are the independent variables of the present study.
Twelve male judokas (age: 18.6 ± 2.4 years; height: 177.75 ± 5.79 cm; body-mass: 77.09 ± 10.74 kg; mean ± SD) volunteered to participate in this study after having signed an informed written consent. They were informed in detail about the experimental procedures and the possible risks and benefits of the project, and written informed consent was obtained from each athlete or from their parents prior to participation. Parental consent was obtained for all subjects under the age of 18. The study was conducted according to the Declaration of Helsinki, and the protocol was fully approved by the Clinical Research Ethics Committee of the National Centre of Medicine and Science of Sports, Tunis before the commencement of the assessments. To have a group without “extreme type,” subjects were selected as “neither type” on the basis of their answers to the Horne and Ösberg self-assessment questionnaire, which assesses morningness-eveningness (25). Moreover, they were selected according to their weight categories (≤81 kg). All the judokas participated in official judo competitions during that year, were trained 4–5 times a week, and were first kyu (brown belt) or first dan (black belt). They all have had more than 10 years of experience in national championships. The weekly training program of all the subjects was the same as follows: 4–5 days (90 minutes per session), which focused on technical-tactical training and on conditioning improvement.
One week before the start of the experimental period, subjects were familiarized with the experimental testing procedures to minimize the learning effect during the course of the experiment. Anthropometrical measurements were also determined for each subject at this time. Digital scales were used to determine body mass (Tanita, Tokyo, Japan; precision: 100 g).
The experimental protocol comprised 3 parts as follows: during the first part, termed the normal reference night (RN) sleep condition, each judoka slept at the laboratory between 22:30 and 06:00 hours; during the second and third parts, judokas were partially deprived for 4 hours of sleep either in the beginning (SDB) or at the end of the night (SDE), respectively. In SDB, they were asked to come to the laboratory at 22:00 hours and were not allowed to sleep before 03:00 hours; they were then allowed to sleep from 03:00 to 06:00 hours. In SDE, judokas were asked to come to the laboratory at 22:00 hours; they went to bed at 23:00 hours and were woken at 02:00 hours. They were not allowed to sleep thereafter. To keep the judokas awake during the SDB and SDE protocols, they watched television, read books, listened to music, or used computers. Moreover, they were not allowed to napping during each testing day. The subjects were invited to sleep in our laboratory and were strictly supervised by 2 experimenters during each night. The 3 protocols were carried out at least 1 week apart and in random order.
Judokas were tested on 6 different occasions (i.e. 6 test sessions) in a randomized order using identical protocols (HG, MVC, and Wingate test) as follows: after RN, SDB, and SDE in the morning (09:00–10:00 hours) and in the afternoon (16:00–17:00 hours) (Figure 1). Before testing, a standardized warm-up consisting of both a general and a specific phase was performed. The general phase involved performing 5 minutes of low-intensity jogging and stretching. The specific warm-up consisted of 5 minutes of repeated attacks (executing techniques) without (Uchi-Komi: Kuzushi and Tai-Sabaki only) and with (Nage-Komi) throwing. After this, judokas were tested before (T0) and after (T1) a judo match. A recovery period of 15 minutes was allowed between the Wingate test and the combat.
Each combat was performed in accordance with the international rules (i.e. 5 minutes duration). Even if thrown, the judokas continued until the end of the 5-minute period. Each judoka’s opponent was the same in all conditions. To create a demanding competitive environment, both opponents were of the same weight category and technical level. Moreover, an official judo judge conducted all combats. Rating of perceived exertion was determined at the end of the combat using the Borg scale (6). The test sessions were conducted on January 2011 in Tunisia.
To minimize confounding factors, instructions related to sleep and diet were given to the subjects before the commencement of the experiment. During the week preceding each test session, subjects were asked to keep their usual sleeping habits (≥7 hours). During the period of investigation, they were prohibited from consuming any known stimuli (e.g. caffeine) or depressants (e.g. alcohol) that could possibly enhance or compromise wakefulness. Subjects were requested to maintain their habitual physical activity and to avoid strenuous activity in the day before each test session. Before the morning test session, only 1 glass (150–200 mL) of water was allowed to avoid the postprandial thermogenesis effects. After the morning session, unrestricted food intake was allowed. Before the afternoon session, they had the same standard isocaloric meal at 12:00 hours, which was consumed at the most 5 hours before the test. The overall daily energy intake goal was set at 10.5 MJ (2,500 kcal) per capita per day. After that meal, only water was allowed ad libitum.
Rating of Perceived Exertion Scale
The RPE scale allows judokas to give a subjective exertion rating for the physical task. The scale presents a 15-point scale ranging from 6 (very very light) to 20 (very very hard). The higher the RPE score, the higher the RPE. The RPE scale is a reliable indicator of physical discomfort, has sound psychometric properties, and is strongly correlated with several other physiological measures of exertion (6).
The maximal handgrip strength of the dominant hand was measured with a calibrated hand dynamometer (T.K.K. 5401; Takei, Tokyo, Japan). The judokas were standing comfortably with the shoulder adducted. The dynamometer was held freely without support; it was not touching the judoka’s trunk. The position of the hand remained constant with a downward direction. The palm did not flex on the wrist joint. The judokas were required to exert maximal strength on the dynamometer. They performed 3 trials with 2 minutes in between, and the best performance was used for further analysis.
Maximal Voluntary Contraction
Judokas performed 3 5 seconds MVC of the elbow flexor muscles of the dominant arm at 90° angle. They were strongly encouraged although visual feedback was provided to reach maximal level. Subjects were seated in an apparatus that held the shoulder abducted at 90° and 45° angles anterior to the frontal plane, the elbow flexed at 90° angle, and the forearm in a neutral position between supination and pronation. The elbow was supported on a padded shelf with the lateral epicondyle aligned directly below the axis of a multiaxial force transducer (Globus Italia, Codogne, Italy). The forearm was stabilized in a padded wrist cuff attached to a metal arm extending from the transducer. Elbow flexion efforts were performed by pulling against the wrist cuff. The shoulders and waist were also stabilized using a shoulder harness and waist belt to prevent unwanted contributions of other body segments to elbow flexion torque readings. The force generated during muscle contraction was measured by a strain gauge (9). The signal from the strain gauge was sampled at 100 Hz and stored on a computer for later analysis with commercially available software (TCS-SUITE 400; Globus, Italia). The MVC was determined as the highest torque over the 5-second duration. Three trials were performed, separated by 2 minutes rest, and the highest value retained for subsequent analysis.
As previously described by Chtourou et al. (15), the Wingate test was conducted on a friction-loaded cycle ergometer (Monark 894E; Stockholm, Sweden) interfaced with a microcomputer. This test consisted of an all-out cycling for 30 seconds against a constant braking resistance dependent on the subjects’ body mass (0.087 kg·kg−1 body mass) (26). The test began from a rolling start, at 60 rpm against minimal resistance (weight basket supported). When a constant pedal rate of 60 rpm was achieved, a countdown was given by the experimenter. At the start signal, judokas were instructed to pedal as fast as possible throughout 30 seconds. During the test, they had to remain seated and were strongly encouraged by the same investigator to reach the maximal pedaling rate as quickly as possible. The PP was calculated as the highest value achieved during the 30 seconds. The MP corresponded to the average mechanical power obtained across the 30 seconds of the test. The PP and MP values have been normalized to body mass.
All statistical tests were processed using STATISTICA Software (StatSoft, Paris, France). Within the text and tables, data are reported as mean ± SD. The Shapiro-Wilk W-test of normality revealed that the data were normally distributed. Once the assumption of normality was confirmed, parametric tests were performed. Data of MVC, HG, and Wingate test performances were analyzed using a 3-way analysis of variance (3 [sleep] × 2 [pre/post combat] × 2 [time-of-day]) with repeated measures on all factors. For RPE, a 2-way (3 [sleep] × 2 [time-of-day]) analysis of variance with repeated measures was used. When appropriate, significant differences between means were assessed using the least significant different Fisher's post hoc tests. Effect sizes were calculated as partial eta squared
to assess the practical significance of the findings. Test-retest reliability was assessed by intraclass correlation coefficients (ICCs) and SEM. Statistical significance was set at p ≤ 0.05.
Rating of Perceived Exertion
The mean values of RPE scores are presented in Figure 2. There were significant main effects for time-of-day (F(1.11) = 8.90, p < 0.05) and sleep (F(2.22) = 4.66, p < 0.05). However, the sleep × time-of-day interaction (F(2.22) = 0.67, p < 0.05) was not significant.
The post hoc test revealed that RPE scores were significantly higher in the afternoon than in the morning during SDE condition (p < 0.01). In addition, RPE scores were significantly higher during SDE than RN (p < 0.001) and SDB (p < 0.01).
Muscle Strength (HG and MVC)
The mean values of HG and MVC recorded at 09:00 and 16:00 hours during RN, SDB, and SDE are presented in Figures 3 and 4, respectively.
Intraclass correlation coefficient and SEM for HG and MVC showed high reliability (ICC higher than 0.84 and 0.92 and absolute SEM lower than 2.3 kg and 27.1 N, respectively).
The main sleep effect (F(2.22) = 5.46, p < 0.05,
= 0.44 and F(2.22) = 20.00, p < 0.001,
= 0.88 for HG and MVC, respectively) and pre/post combat (F(1.11) = 101.72, p < 0.001,
= 0.91 and F(1.11) = 100.85, p < 0.001,
= 0.89 for HG and MVC, respectively) were significant. However, the time-of-day effect (F(1.11) = 0.07, p > 0.05,
= 0.09 and F(1.11) = 0.63, p > 0.05,
= 0.13 for HG and MVC, respectively) and the sleep × pre/post combat × time-of-day interaction (F(2.22) = 0.51, p > 0.05,
= 0.08 and F(2.22) = 0.15, p > 0.05,
= 0.05 for HG and MVC, respectively) were not significant.
The post hoc analysis revealed that HG and MVC values were significantly higher in the afternoon than the morning during RN (p < 0.05 and p < 0.01 respectively) (Amplitude: 3.5 ± 3.9 and 11.8 ± 7.4%, respectively). However, these diurnal variations disappeared both after the judo combat and after the 2 partial sleep deprivation conditions.
Concerning the partial sleep deprivation effect, HG and MVC decreased significantly (≈3.1–8.4 and 15–24%, respectively) only during SDE in the afternoon before and after the judo combat (p < 0.001).
Considering the effect of combat, HG and MVC decreased significantly from before to after the judo combat at the 2 times of testing and during the 3 experimental conditions (p < 0.05 and p < 0.001, respectively). The relative decrease ranged between 3.1 and 10.8% for HG and between 17.5 and 29.7% for MVC.
Wingate Test Muscle Power (PP and MP)
Figures 5 and 6 shows, respectively, the mean values of PP and MP recorded at 09:00 and 16:00 hours before and after the combat during the 3 experimental conditions.
ICC and SEM for PP and MP showed very high reliability (ICC higher than 0.99 and 0.92 and absolute SEM lower than 0.1 W·kg−1 and 0.2 W·kg−1 respectively).
There was a significant main sleep effect (F(2.22) = 15.48, p < 0.001,
= 0.84 and F(2.22) = 11.76, p < 0.001,
= 0.83 for PP and MP, respectively) and pre/post combat (F(1.11) = 26.20, p < 0.001,
= 0.86 and F(1.11) = 86.00, p < 0.001,
= 0.82 for PP and MP, respectively). However, the time-of-day effect (F(1.11) = 0.29, p > 0.05,
= 0.08 and F(1.11) = 4.19, p > 0.05,
= 0.14 for PP and MP, respectively) and the sleep × pre/post combat × time-of-day interaction (F(2.22) = 2.6, p > 0.05, ηp2 = 0.14 and F(2.22) = 0.65, p > 0.05,
= 0.11 for PP and MP, respectively) were not significant.
Post hoc analysis revealed that PP and MP were significantly higher at 16:00 than 09:00 h during RN (p < 0.05) (Amplitude: 2.4 ± 2.3 and 2.7 ± 3.9%, respectively). However, these diurnal variations disappeared after the combat and after SDB and SDE.
Concerning the partial sleep deprivation effect, PP and MP decreased significantly (≈3.9–9.0% and 2.6–6.6%, respectively) only during SDE in the afternoon before (p < 0.01) and after (p < 0.001) the combat.
Considering the effect of combat, PP and MP decreased significantly from before to after the judo combat at the 2 times of testing and during the 3 experimental conditions (p < 0.05). The relative decrease ranged between 2.2 and 9.3% for PP and between 2.8 and 7.3% for MP.
The present study is the first to examine the effect of 2 types of partial sleep deprivations on muscle strength and power of judokas the following day and their diurnal variations before and after a judo combat. The results showed that muscle power and strength decreased (a) after the judo combat independently of time of day and (b) after SDE in the afternoon. Moreover, the results showed that a judo combat in addition to 4 hours of partial sleep deprivation in the beginning or at the end of the night blunted the diurnal variations of muscle strength and power due to a decrease in performances at 16:00 hours.
In the present study, the lower limb power output and the upper limb isometric strength were higher in the afternoon than in the morning during RN condition. These results are consistent with previous reports (2,16,23,24,40,41). These time-of-day effects may be due to higher core temperature and better aerobic participation in energy production during this exercise in the afternoon (35). Moreover, some authors suggested that these diurnal fluctuations are linked to variations in contractile properties of muscle tissue (i.e. peripheral mechanisms) rather than alternation in central nervous command (17,31). However, other authors suggested that both central (neural input to the muscles) and peripheral (contractile state of the muscle) mechanisms might be altered across the day (22).
Muscle strength and power decreased significantly from before to after the combat both in the morning and afternoon. These findings are in line with those of the previous findings (19,21) that reported significant decrease of performance during the upper-body Wingate test and the special judo fitness test after a judo combat. During a judo combat, the anaerobic system provides the short, quick, all-out bursts of maximal power and strength, and its solicitation seems to be very important (19–21). This anaerobic nature of judo combat is confirmed by higher postbout blood lactate concentrations (10 ± 2.1 mmol·L−1) and the typical time structure of the combat (21). Moreover, we showed that the judo combat could affect the diurnal variations of short-term maximal performances. These results might be due to a higher fatigue in the afternoon as previously shown by Chtourou et al. (17). In agreement, our results showed that the decrease in performances from before to after the judo match was higher in the afternoon.
A major finding of this study was that a partial sleep deprivation caused by advancing the rise time by 4 hours might reduce short-term performance in the afternoon but not in the morning. However, a partial sleep deprivation caused by delaying bedtime by 4 hours did not alter anaerobic power in the morning and slightly alter (i.e. not significant reduction) the evening’ performances the following day.
The findings of the present study are in agreement with previous reports (1,5,36,37) that showed that partial sleep deprivation either in the beginning or at the end of the night did not have any adverse effect on muscle strength or power in the morning the following day. Moreover, the present results confirm those of Bambaeichi et al. (5), Mougin et al. (28), and Souissi et al. (37) who showed that the afternoon’ muscle strength and power were not affected following SDB. However, the present study shows that the SDE condition resulted in a decrement of muscle strength and power at 16:00 hours. These results agree with a previous study (37) showing a significant impairment of muscle power during the Wingate and the force-velocity tests in the evening after SDE. Moreover, Souissi et al. (36) showed that total sleep deprivation resulted in decrement of short-term performances only in the afternoon of the following day.
At present, the mechanisms responsible for such an effect are difficult to understand. However, the disruption of melatonin rhythms could affect the sleep quality (e.g. sleep efficiency and slow wave sleep) and, then, may explain the reduced performances (18). In this context, previous studies showed a mood disturbance toward increased anxiety, depression, confusion, and fatigue and decreased vigor after sleep loss (29). In this context, Reilly and Deykin (29) showed that 1 night's sleep of only 2.5 hours had a negative effect on psychomotor function, whereas HG strength remained unchanged. The mood disturbance may explain the greater performances reduction after SDE. In this context, the results of the present study demonstrated a higher fatigue in the evening after SDE than RN. In support of this hypothesis, the present results showed that RPE values were higher in the afternoon after SDE than RN.
The present study also showed that 4 hours of partial sleep deprivation could affect the typical diurnal variations of short-term maximal performance by a higher decrease in muscle strength and power at 16:00 hours. These findings agree, in part, with those of Souissi et al. (37) who showed that the diurnal variations of muscle power during the Wingate and the force-velocity tests were blunted after SDE. Contrarily to our findings, these authors showed that anaerobic performance improved significantly from morning to afternoon after SDB. Likewise, Callard et al. (8) reported that total sleep deprivation did not affect the circadian rhythm of the isometric maximal. The discrepancies in the findings between our results and previous studies might be due to the subject's fitness level (30). Indeed, performances of untrained subjects are more affected by time-of-day than those of trained subjects (4). Another possible explanation is that the judokas of the present study were routinely undertaking morning and evening training sessions, which might have reduced the time-of-day effect on muscle strength and power (9,11,32). In addition, these discrepancies could also be explained by the higher muscle fatigue observed in the afternoon during a normal day (17). This higher level of fatigue observed in the afternoon might be increased subsequent to the longer time of being awake (18,33).
The present study showed that partial sleep deprivation (a) at the beginning of the night slightly affect (i.e. not statistically significant) the performances of judokas and (b) at the end of the night resulted in a significant reduction on muscle strength and power only in the afternoon hours (i.e. at 16:00 hours) and, therefore, might have blunted the diurnal variations of short-term maximal performances. Based on these results, early rising seems to be more difficult to support than late bedtime when judokas participated in afternoon competitions. However, morning performances were not affected by both partial sleep deprivations at the beginning or at the end of the night. Therefore, coaches and judokas need to prevent anxiety (e.g. mental preparation, etc.) and to be aware of the techniques for coping with jet lag (e.g. melatonin supplementation, napping, etc.) during the competitive events, especially those scheduled in the evening hours, to avoid the negative impact of partial sleep deprivation on performances. Moreover, it is also important to keep a regular sleep schedule not only during the competition period but also during the normal training phase. In addition, sports scientists should be aware, during chronobiological investigations, of factors such as partial sleep deprivation that could reduce the amplitude of the diurnal rhythm of short-term maximal performances.
The authors thank all subjects for their voluntary participation in this study. The authors have no conflicts of interest that are directly relevant to the contents of this article. This study was financially supported by the Ministry of Higher Teaching and Scientific Research, Tunis, Tunisia.
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Keywords:Copyright © 2013 by the National Strength & Conditioning Association.
diurnal variation; partial sleep deprivation; muscle power; muscle strength; judo