Mohamed Dogui

Effect of Time of Day and Partial Sleep Deprivation on Short‐Term, High‐Power Output

The purpose of this study was to determine whether delaying bedtime or advancing rising time by 4 h affects anaerobic performance of individuals the following day in the morning and afternoon. Eleven subjects participated in the study, during which we measured the maximal, peak, and mean powers (i.e., Pmax [force‐velocity test], Ppeak, and Pmean [Wingate test], respectively). Measurements were performed twice daily, at 07∶00 and 18∶00 h, following a reference normal sleep night (RN), a partial sleep deprivation timed at the beginning of the night (SDB), and a partial sleep deprivation timed at the end of the night (SDE), and oral temperature was measured every 4 h. Each of the three experimental conditions was separated by a one‐week period. Our results showed a circadian rhythm in oral temperature, and analysis of variance revealed a significant sleep×test‐time effect on peak power (Ppeak), mean power (Pmean), and maximal power (Pmax). These variables improved significantly from the morning to the afternoon for all three experimental conditions. Whereas the morning‐afternoon improvement in the measures was similar after the RN and SDB conditions, it was smaller following the SDE condition. There was no significant difference in the effect of the two sleep‐deprivation conditions on anaerobic performances at 07∶00 and at 18∶00 h under the SDB condition in comparison with the post‐reference night. However, the performance variables were significantly lower at 18∶00 h after the SDE condition. In conclusion, a 4 h partial sleep deprivation at the end of the night appears to be more disturbing than partial sleep deprivation at the beginning of the night.

THE EFFECT OF TRAINING AT THE SAME TIME OF DAY AND TAPERING PERIOD ON THE DIURNAL VARIATION OF SHORT EXERCISE PERFORMANCES

Chtourou, H, Chaouachi, A, Driss, T, Dogui, M, Behm, DG, Chamari, K, and Souissi, N. The effect of training at the same time of day and tapering period on the diurnal variation of short exercise performances. J Strength Cond Res 26(3): 697–708, 2012—The purpose of this investigation was to assess the effects of training and tapering at the same time of the day on the diurnal variations of short exercise performances. Thirty-one physically active men underwent 12 weeks of lower-extremity resistance training and 2 weeks of tapering. These subjects were matched and randomly assigned to a morning training group (MTG, training times 0700–0800 hours, n = 10), an evening training group (ETG, training times 1700–1800 hours, n = 11), and a control group (CG, completed all tests but did not train, n = 10). Muscular strength and power testing was conducted before (T0) and after 12 weeks of training (T1) and after 2 weeks of tapering (T2) in the morning (0700–0800 hours) and in the evening (1700–1800 hours). All morning and evening tests were performed in separate sessions (minimum interval = 36 hours) in a randomized design. In T0, the oral temperature and performances during the Wingate, vertical jump (squat jump and countermovement jump), and maximal voluntary contraction tests were higher in the evening than in the morning for all the groups. In T1, these diurnal variations were blunted in the MTG and persisted in the ETG and CG. In T2, the 2 weeks of tapering resulted in further time of day–specific adaptations and increases in short-term maximal performances. However, there was no significant difference in the relative increase between the MTG and the ETG after both training and tapering. From a practical point of view, if the time of competition is known, training and tapering sessions before a major competition must be conducted at the same time of the day at which ones critical performance is programmed. Moreover, if the time of the competition is not known, a tapering phase after resistance training program could be performed at any time of the day with the same benefit.

Diurnal Variation in Wingate-Test Performance and Associated Electromyographic Parameters

The present study was designed to evaluate time-of-day effects on electromyographic (EMG) activity changes during a short-term intense cycling exercise. In a randomized order, 22 male subjects were asked to perform a 30-s Wingate test against a constant braking load of 0.087 kg·kg−1 body mass during two experimental sessions, which were set up either at 07:00 or 17:00 h. During the test, peak power (Ppeak), mean power (Pmean), fatigue index (FI; % of decrease in power output throughout the 30 s), and evolution of power output (5-s span) throughout the exercise were analyzed. Surface EMG activity was recorded in both the vastus lateralis and vastus medialis muscles throughout the test and analyzed over a 5-s span. The root mean square (RMS) and mean power frequency (MPF) of EMG were calculated. Neuromuscular efficiency (NME) was estimated from the ratio of power to RMS. Resting core temperature, Ppeak, Pmean, and FI were significantly higher (p < .05) in the evening than morning test (e.g., Ppeak: 11.6 ± 0.8 vs. 11.9 ± 1 W·kg−1). The results showed that power output decreased following two phases. During the first phase (first 20s), power output decreased rapidly and values were higher (p < .05) in the evening than in the morning. During the second phase (last 10s), power decreased slightly and appeared independent of the time of day of testing. This power output decrease was paralleled by evolution of the MPF and NME. During the first phase, NME and MPF were higher (p < .05) in the evening. During the second phase, NME and MPF were independent of time of day. In addition, no significant differences were noticed between 7:00 and 17:00 h for EMG RMS during the whole 30 s. Taken together, these results suggest that peripheral mechanisms (i.e., muscle power and fatigue) are more likely the cause of the diurnal variation of the Wingate-test performance rather than central mechanisms. (Author correspondence: n_souissi@yahoo.fr)

Effect of Ramadan on the Diurnal Variation in Short‐Term High Power Output

This study examined the effects of Ramadan fasting on anaerobic performances and their diurnal fluctuations. In a balanced and randomized study design, 12 subjects were measured for maximal power (Pmax; force‐velocity test), peak power (Ppeak), and mean power (Pmean) with the Wingate test at 07:00, 17:00, and 21:00 h on four different occasions: one week before Ramadan (BR), the second week of Ramadan (SWR), the fourth week of Ramadan (ER), and two weeks after Ramadan (AR). There was an interval of 28 h between any two successive tests. Oral temperature was measured before each test. Under each condition, the results showed a time‐of‐day effect on oral temperature. Analysis of variance revealed a significant (Ramadan×time‐of‐day of test) interaction effect on Pmax. This variable improved significantly from morning to evening before Ramadan (1.1±0.2 W · kg−1), during the second week of Ramadan (0.6±0.2 W · kg−1), and two weeks after the end of Ramadan (0.9±0.2 W · kg−1). However, daily fluctuations disappeared during the fourth week of Ramadan. For Ppeak and Pmean, there was no significant Ramadan×test‐time interaction. These variables improved significantly from morning to evening before Ramadan ([1±0.3 W · kg−1] for Ppeak and [1.7±1.6 W · kg−1] for Pmean) and in the second week of Ramadan ([0.9±0.6 W · kg−1] for Ppeak and [1.7±1.5 W · kg−1] for Pmean). However, they were not affected by time‐of‐day in the fourth week of Ramadan. Considering the effect of Ramadan on anaerobic performances, in comparison with before Ramadan, no significant difference was observed during Ramadan at 07:00 h. The variables were significantly lower in the second week of Ramadan and in the fourth week of Ramadan at 17:00 h and 21:00 h. Pmean was not affected during the second week of Ramadan. In conclusion, the time‐of‐day effect on anaerobic power variables tends to disappear during Ramadan. In comparison with the period before Ramadan, anaerobic performances were unaffected in the morning but impaired in the evening during Ramadan.

Effects of Time-of-day and Partial Sleep Deprivation on Short-term Maximal Performances of Judo Competitors

Abstract Souissi, N, Chtourou, H, Aloui, A, Hammouda, O, Dogui, M, Chaouachi, A, and Chamari, K. Effects of time-of-day and partial sleep deprivation on short-term maximal performances of judo competitors. J Strength Cond Res 27(9): 2473–2480, 2013—This study assessed the effects of partial sleep deprivation on short-term maximal performances of judokas in the morning and afternoon of the following day. In a randomized design, 12 judokas completed the maximal voluntary contraction, the handgrip, and the Wingate tests before and after a judo combat. Measurements were performed at 09:00 and 16:00 hours after a reference-normal sleep night and 2 conditions of 4-hour partial sleep deprivation timed at the beginning (SDB) or at the end of the night (SDE). The results showed that muscle power and strength were significantly higher at 16:00 than 09:00 hours (p < 0.05). These diurnal variations disappeared after SDB and SDE and after the combat. In addition, SDE resulted in significant decreases of short-term maximal performance in the afternoon (p < 0.01). In conclusion, SDE decreased muscle strength and power at 16:00 hours and, therefore, might have blunted the diurnal variations of short-term maximal exercise. Thus, early rising is more detrimental than late bedtime to muscle strength and power for judo athletes when competitions are scheduled in the afternoon hours.

Effects of Partial Sleep Deprivation on Proinflammatory Cytokines, Growth Hormone, and Steroid Hormone Concentrations During Repeated Brief Sprint Interval Exercise

The purpose of this study was to evaluate the effects of partial sleep deprivation (PSD) on circulating concentrations of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in relation to the secretory profiles of growth hormone (GH), cortisol, and testosterone during a repeated brief sprint interval exercise. Thirty healthy football players (mean age: 21.1 [range: 18–24] years; body mass index [BMI]: 22.6 [range: 18.47–24.46] Kg/m2) completed two test sessions at 08:00 h, one scheduled after a baseline night (bedtime: from 22:30 to 07:00 h) and the other after a PSD night caused by an early awakening (bedtime: from 22:30 to 03:00 h). During each session, participants performed 4 × 250-m run on a treadmill at a constant intensity of 80% of the personal maximal speed with a 3-min recovery in between. Tests session were performed at 08:00 h. Blood samples were collected before, immediately after the first and the fourth 250-m run, and 60 min after the exercise. The results showed that cortisol concentrations were not affected by the PSD. However, GH and testosterone concentrations were higher (p < .05) 60 min after the exercise during PSD in comparison with baseline. Likewise, plasma concentrations of IL-6 and TNF-α were higher (p < .05) after PSD during the exercise (i.e., the first and the fourth run) and remained elevated during the recovery period (i.e., 60 min after the exercise). In conclusion, these results showed that sleep restriction increases the proinflammatory cytokine, GH, and testosterone concentrations after physical exercise but did not affect the cortisol responses. (Author correspondence: n_souissi@yahoo.fr)

Effect of time-of-day of aerobic maximal exercise on the sleep quality of trained subjects

This study was designed to assess the effects of time-of-day of maximal aerobic exercise on the subsequent sleep of trained subjects. Twelve subjects (22.6 ± 2.1 years, 178 ± 4.4 cm and 72.2 ± 6.3 kg) completed the Yo-Yo intermittent-recovery-test level 1 (YYIRT) at 14:00 and 20:00 h. Then, sleep polysomnography was recorded from 22:00 to 07:00 h. Oral temperature was measured before and after the YYIRT and the sleep period. Performance during the YYIRT was not statistically different between afternoon and evening. However, core temperature was significantly higher in the evening than afternoon before (p < 0.05) and after (p < 0.01) the YYIRT. Moreover, sleep-onset-latency, number-of-awakenings, slow-wave-sleep and rapid-eye-movement-sleep-latency were significantly higher after the evening test session (p < 0.05). However, time-in-bed, total-sleep-time, rapid-eye-movement-sleep and sleep-efficiency were higher after the afternoon test session (p < 0.05, p < 0.001, p < 0.01 and p < 0.01 respectively). In conclusion, maximal aerobic exercise performed later in the evening is “worse” than training in the afternoon and might result in a markedly poor subsequent sleep quality (disturbing and fragmenting sleep).

Time of Day Effects on Repeated Sprint Ability

The present study aimed at investigating the effects of time-of-day on muscle power and associated electromyographic (EMG) activity level of 4 thigh muscles during a repeated pedalling sprint exercise. After a familiarization session, 12 male subjects were asked to perform the repeated sprint ability test during 2 experimental sessions (randomized order), which were set up either at 06:00 or 18:00 h. For each sprint, peak power output, percentage of peak power decrement and total work were calculated. EMG activity of vastus lateralis, rectus femoris, vastus medialis and biceps femoris muscles was recorded throughout the test and analyzed for each sprint. Total work and percentage of peak power decrement were higher in the evening than in the morning (p<0.01 and p<0.05, respectively). Likewise, peak power was significantly higher at 18:00 than 06:00 h during the first 3 sprints (p<0.01 for sprint 1 and p<0.05 for sprint 2 and 3). There was no time-of-day effect for EMG activity level. The neuromuscular efficiency decreased significantly over the repeated sprint ability test at the 2 times of testing (p<0.01). Despite diurnal fluctuation in muscular power and neuromuscular fatigue during the repeated sprint ability test, EMG activity of major thigh muscles was not time-of-day dependent.

Changes in EEG activity before and after exhaustive exercise in sedentary women in neutral and hot environments

This study examined the effect of hyperthermia on brain electrical activity measured with encephalography during prolonged exhaustive exercise in a group of sedentary women (VO(2)max = 35 +/- 4 mL kg min(-1)). Two strenuous cycling exercises were performed either in neutral (N-Ex) or in heat (H-Ex) conditions. Tympanic temperature (Tty), heart rate (HR), body mass loss (BML), plasma volume decrease, and brain electrical activity [EEG: alpha (8-13 Hz) and beta(13-30 Hz)-band and alpha/beta index of fatigue: the ratio between EEG activity in the alpha band and beta-band] were recorded throughout the cycling sessions. The Tty increase 1.0 degrees C in the N-Ex and 1.8 degrees C in H-Ex. HR increased in both sessions but with significantly higher values during the H-Ex session when compared with the N-Ex session (p < 0.001) (from 85 +/- 4 beats min(-1) to 164 +/- 6 beats min(-1) and from 83 +/- 6 beats min(-1) to 181 +/- 8 beats min(-1), respectively in N-Ex and in H-Ex). This was associated with a significantly higher BML (p < 0.05) and a higher plasma volume decrease in the H-Ex session (p < 0.01). The alpha/beta index increased significantly during both trials particularly during the H-Ex session (p < 0.05). This was associated with a significant decrease of time to exhaustion (-34%). We suggest that exhausting work in the heat induced a change in gross brain activity (alpha/beta ratio) compared to a longer, less thermally demanding exposure. Fatigue in the heat could be attributed to central factors as well as thermal, cardiac and hydro-electrolytic impairment.

Effects of three types of chronobiotics on anaerobic performances and their diurnal variations

The aim of this study was to evaluate the effects of three types of chronobiotics on anaerobic performances and their diurnal fluctuations. Twelve physical education students have performed the vertical jump (i.e. squat jump (SJ) and counter movement jump (CMJ)) and the Wingate tests during three consecutive days. They have taken one of three types of sleeping pills (i.e. promethazine (PRO), diazepam (DZP), or phenobarbital (PHE)) or a placebo (PLA) for three successive nights. For each medication, subjects performed four test sessions as follows: at 08:00 h following the first two nights and at 08:00 h and at 17:00 h after the last night. Anaerobic performances during the SJ, CMJ, and the Wingate test were significantly lower after the PRO, DZP, and PHE protocols than PLA at 08:00 h test sessions. However, negative effect of these hypnotics was significantly lower during the PRO test sessions. In addition, the results showed that the three medications have no effect on the diurnal rhythm of short-term maximal performances. In conclusion, PRO may be the appropriate solution for athletes in facing a sleep deprivation induced by anxiety or stress during competition or transmeridian flights by amending the sleep–wake cycle disorders.