Search

A sample of NaCr(P2O7) was synthesized using the solid-state reaction method. X-ray diffraction and Rietveld refinement confirmed the formation of a monoclinic structure with the P21/a space group. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis identified the morphology and homogeneity of the chemical composition. The optical absorption spectrum revealed a direct optical band gap of 2.9 eV and an Urbach energy of 0.44 eV. Notably, the absorption spectrum showed an interference dip on the lowest energy band 4T2g(4F), attributed to spin--orbit coupling between states ²Eg(²G) and 4T2g(4F). This phenomenon was analyzed using the Neuhauser model based on coupled potential energy surfaces. From this analysis, the electronic structure of Cr3+ (3d3) ions in the NaCr(P2O7) sample was determined, enabling a reliable calculation of Racah and crystal-field parameters. The results showed good agreement between experimental and theoretical energy levels. The study demonstrates the impact of spin--orbit interactions using the coupled potential energy surface model. [ABSTRACT FROM AUTHOR]

The spinels ZnAl1.99−xHoxCr0.01O4 (with x = 0 and 0.001) were synthesized using a solid-state method, and various techniques were employed for their characterization. X-ray diffraction (XRD) analysis confirmed a cubic spinel structure with the Fd3¯m space group for both spinels. The morphology and homogeneity of the chemical composition were determined using scanning electron microscopy (SEM) and energy dispersive X-ray analysis. Raman and infrared vibrational spectroscopy techniques were also employed for analysis. The optical band gap (Eg) was determined from UV/vis absorption spectra, and the direct transition behavior was confirmed by Tauc's law. The observed large disorder and defect concentration are attributed to the presence of Cr3+ and Ho3+ ions, explaining this behavior. The electron paramagnetic resonance (EPR) measurement presented different types of traps. Room temperature absorption spectra exhibited multiple peaks corresponding to the 3d–3d and 4f–4f transitions of Cr3+ and Ho3+ ions. The results obtained validate the significance of our compounds in optoelectronic device applications. [ABSTRACT FROM AUTHOR]

ZnO nanowires are grown by metal organic chemical vapor deposition using two different zinc precursors, i.e., dimethylzinc-triethylamine which contains nitrogen, and diethylzinc which does not. The growth conditions are varied using different oxygen/zinc pressure ratios (RO/Zn). Temperature dependent Raman spectroscopy shows that the additional Raman modes are related to B1 modes which are activated because of translational symmetry breaking resulting from the nitrogen substitution on oxygen sites and/or Zn-O bond breaking caused by complex defects. Simultaneously, the antiparallel atomic displacements which are at the origin of B1 phonon vibrations are no more compensated, allowing B1 modes to acquire a polar character. The resulting polar phonons, and especially B1² located at 580 cm-1 (i.e., 72meV), are therefore believed to strongly couple to photogenerated electrons through a Fröhlich mechanism and could lead or contribute to the phonon-assisted replicas observed in the photoluminescence (PL) spectrum. Finally, we also discuss the possible defects involved in the Raman and PL responses including native donor and acceptor defects and their interaction with the N-dopant, depending on the growth conditions. [ABSTRACT FROM AUTHOR]

We have studied the photoluminescence emission line at 3.31 eV in ZnO nanowires. In undoped ZnO, this band strongly depends on high oxygen concentration and could originate from recombination of bound-exciton complex related to structural defects. Conversely, in doped ones, the photoluminescence emission appears notably at a low VI/II ratio and with the emergence of donoracceptor pair emission due to the presence of a-No nitrogen complex, which acts as a shallow acceptor in ZnO. We found that this band corresponds to 3LO, the third phonon replica of resonant Raman scattering. Furthermore, a remarkable variation is detected in a number of resonant Raman scattering multiphonons. [ABSTRACT FROM AUTHOR]

Wurtzite ZnO thin films were prepared on sapphire substrate by metal organic chemical vapor deposition (MOCVD). Raman scattering studies on different crystallographic textures were performed in the backscattering geometry, and polarization effect is investigated in different configurations [ABSTRACT FROM AUTHOR]

A sample of NaCr(P 2 O 7 ) was synthesized using the solid-state reaction method. X-ray diffraction and Rietveld refinement confirmed the formation of a monoclinic structure with the P 2 1 / a space group. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis identified the morphology and homogeneity of the chemical composition. The optical absorption spectrum revealed a direct optical band gap of 2.9 eV and an Urbach energy of 0.44 eV. Notably, the absorption spectrum showed an interference dip on the lowest energy band 4 T 2g ( 4 F), attributed to spin-orbit coupling between states 2 E g ( 2 G) and 4 T 2g ( 4 F). This phenomenon was analyzed using the Neuhauser model based on coupled potential energy surfaces. From this analysis, the electronic structure of Cr 3+ (3d 3 ) ions in the NaCr(P 2 O 7 ) sample was determined, enabling a reliable calculation of Racah and crystal-field parameters. The results showed good agreement between experimental and theoretical energy levels. The study demonstrates the impact of spin-orbit interactions using the coupled potential energy surface model.

The Lithium-chromium phosphate Li 3 Cr 2 (PO 3 ) 4 sample was synthesized via the solid-state reaction method. The morphological integrity and chemical homogeneity were verified by energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). Infrared and Raman patterns were also analyzed. Optical absorption spectrum analysis, conducted within the range of 10000 cm -1 to 30000 cm -1  at room temperature, yielded some optical parameters (Eg, E u , δ , k, n). The Neuhauser model is used to interpret the interference dip which was on the absorption spectrum of Li 3 Cr 2 (PO 3 ) 4 . The Fourier transform of the autocorrelation function leads to the Zero Phonon Lines of the observed absorption energies. The electronic structure of Cr 3+ (3d (Huang et al., 2009) 33) ions in Li3Cr2(PO3)4 was calculated using Racah method, which allowed for precise calculations of Racah and crystal-field parameters. The results showed good agreement between the theoretical and experimental energy levels., Competing Interests: This work includes an experimental study Lithium-chromium phosphate Li3Cr2(PO3)4 using the solid-state reaction method. The morphological integrity and chemical homogeneity were verified by energy dispersive X-ray analysis (EDX) and scanning electron microscopy (SEM). Infrared and Raman patterns were also analyzed. The optical properties have been study using the absorption characterization. An interference dip was found on the 4T2g(4F) band in the absorption spectrum of Li3Cr2(PO3)4, which was explained by spin-orbit coupling between the 2Eg(2G) and 4T2g(4F) states. The electronic structure of Cr3+ (3d [3]) ions in Li3Cr2(PO3)4 was calculated using the Neuhauser model. The theoretical part is also carried out using software that we have developed ourselves in our laboratory and it is rarely that we find this type of calculation because this software is based on Racah method (the most powerful method that describe the electronic structure of transition ions) and it is not easy and requires specialists. The programming lasted about 6 years and each time we add more precision. This software uses Maple 20 as software is as well tested and gives the same result as another software using the Fortran software and we can prove that. We have published several articles and in well-indexed newspapers., (© 2024 The Authors. Published by Elsevier Ltd.)

The spinels ZnAl 1.99- x Ho x Cr 0.01 O 4 (with x = 0 and 0.001) were synthesized using a solid-state method, and various techniques were employed for their characterization. X-ray diffraction (XRD) analysis confirmed a cubic spinel structure with the Fd 3̄ m space group for both spinels. The morphology and homogeneity of the chemical composition were determined using scanning electron microscopy (SEM) and energy dispersive X-ray analysis. Raman and infrared vibrational spectroscopy techniques were also employed for analysis. The optical band gap ( E g ) was determined from UV/vis absorption spectra, and the direct transition behavior was confirmed by Tauc's law. The observed large disorder and defect concentration are attributed to the presence of Cr 3+ and Ho 3+ ions, explaining this behavior. The electron paramagnetic resonance (EPR) measurement presented different types of traps. Room temperature absorption spectra exhibited multiple peaks corresponding to the 3d-3d and 4f-4f transitions of Cr 3+ and Ho 3+ ions. The results obtained validate the significance of our compounds in optoelectronic device applications.

Abstract: Souissi, MA, Elghoul, Y, Souissi, H, Masmoudi, L, Ammar, A, Hamdi Chtourou, and Souissi, N. The effects of three corrections strategies of errors on the snatch technique in 10-12-year-old children: A randomized controlled trial. J Strength Cond Res 37(6): 1218-1224, 2023-Sports movement correction is one of the major problems for motor control and learning. Therefore, the purpose of the present study was to determine which of the 3 strategies, i.e., the self-observation method with direct instructions (SO-DI), self-observation alone (SO), or the direct instruction (DI), would be useful for correcting errors during the snatch technique. Forty-eight children with 2 months of experience were randomly assigned to one of 4 training conditions: SO-DI, SO, DI, or control. In this study, the experience lasted 15 sessions. Subjects completed the test sessions before (T 0 ) and after (T 1 ) 12 training sessions and a retention test session after 2 weeks (T 2 ). The Kinovea version 0.8.15 software was used to measure the kinematic parameters of weightlifting performance. After the training intervention, the data showed that the SO-DI group registered a greater improvement in all kinematic parameters compared with the SO, DI, and control groups, and this benefit was present 2 weeks later in the retention test (e.g., the horizontal displacement of the bar in the first pull with respect to the starting position [T1 vs. T0: +32.57 ± 6.69%, d = 1.87, p < 0.001; T2 vs. T0: 25.07 ± 11.55%, d = 1.32, p < 0.001] and the horizontal displacement of the bar between the receiving position and the reference line [T1 vs. T0: 24.34 ± 29%, d = 1.17, p < 0.01; T2 vs. T0: 25.53 ± 30.4%, d = 0.99, p < 0.01]). The results of the present study could have practical implications for physical education teachers because, even if practice is required to improve the technique, the effectiveness of the learning process is essential to enhance learner self-efficacy and motivation., (Copyright © 2020 National Strength and Conditioning Association.)

Solid-state and sol-gel procedures were used to prepare ZnAl 1.95 Cr 0.05 O 4 nanocrystal spinels. From the results obtained by X-ray diffraction (XRD) and transmission electron microscopy (TEM), it can be concluded that the samples prepared by sol-gel synthesis are better crystallized than the ones resulting from the solid-state method. Studies by spectroscopy of impedance were done in function of frequency (40-10 7 Hz) and temperature (540-680 K) in the sample prepared by sol-gel synthesis. The electrical conductivity spectra obey Jonscher's law and two models were observed studying the variation of the exponent 's' as a function of temperature, Correlated Barrier Hopping (CBH) and Non-overlapping Small Polaron Tunnelling (NSPT). The predominant conduction mechanism is bipolaron hopping. The scaling behavior of conductivity spectra was checked by Summerfield scaling laws. The time-temperature superposition principle (TTSP) points to a common transport mechanism working for the low and middle frequency ranges. The scaling mechanism fails in the high-frequency ranges suggesting that conduction dynamics, and the usual hopping distance of mobile species, have changed. The values obtained for the activation energy from the hopping frequency, conductivity σ dc , bulk resistance R gb , and relaxation ( f max ), in the temperature range of 540-680 K, are very close. A higher and negative temperature coefficient of resistivity (TCR coefficient) equal to -2.7% K -1 is found at 560 K. This result shows that our compound is suitable for uncooled infrared bolometric applications and infrared detectors., Competing Interests: There is no conflict of interest., (This journal is © The Royal Society of Chemistry.)

This work is devoted to the synthesis and study of the different properties of ZnO nanoparticles (NPs) doped with the Ni element. We have used a simple co-precipitation technique for the synthesis of our samples and various structural, morphological and optical techniques for their analysis. Energy-Dispersive X-ray spectroscopy (EDX) confirms the stoichiometry of the samples. The X-Ray Diffraction (XRD) patterns reveal the hexagonal wurtzite phase of polycrystalline ZnO with a P 63 mc space group. Debye Scherrer and Williamson-Hall methods show that the average size of crystallites is around 40 nm. Transmission electron microscopy (TEM) images confirm the XRD results. The optical spectrum of Zn 0.95 Ni 0.5 O shows the presence of near-band-edge (NBE) ultraviolet emission. The absorption defect bands appearing near the blue-green region and near infrared emission are attributed to the Ni 2+ intra-3d luminescence. The electronic structure of the Ni 2+ doped ZnO NPs confirms the T d site symmetry of Ni 2+ in the ZnO host crystal and leads to a perfect correlation between calculated and experimental energy levels., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

Maintaining postural balance is a key factor in human motor skills, based in part on emotional stimuli. Our objective in this study was to measure the effect of emotion on postural control as influenced by the direction of forthcoming movement. Eighteen right-handed women initiated a step forward or backward or remained in a static position after visualizing an emotional stimulus (positive, negative, or neutral). Center of pressure (COP) parameters (2D velocity, Medio-lateral (ML), and antero-posterior (AP) amplitude) were recorded for 3-second windows for movement direction and emotional stimulus. We observed a motion * direction effect on 2D velocity, characterized by a decrease in the emotional stimulus and static direction windows. The participants' ML amplitude was influenced by direction, and their reduced amplitude was evident in the presence of emotions. AP amplitude was high in the direction versus emotion window. In the static position, the AP amplitude was high in the direction window and low in the emotion window. The participants' movement planning and programming phase (direction window) was characterized by less oscillation for forward or backward movements and more oscillation before movement, suggesting anticipatory postural adjustments in the emotion window. Static direction was characterized by low oscillation, compared to forward and backward movement and in negative versus positive emotional context, proving the interactive impact of direction and emotion on COP amplitudes. Thus, postural control was influenced by both movement (direction) and emotional content (valence). This study provided insight regarding the interactive effect of emotion and direction on planning and programming forthcoming movement.

Our aim in this study was to examine, via technical performance analysis and speed of execution, whether information processing and technical knowledge help explain learning benefits of self-controlled video feedback in children's weightlifting performance. We randomized 24 children (aged 10 to 12 years) into self-controlled (SC) and yoked (YK) feedback groups. Learners underwent test sessions one week before (pre-test) and one day after (post-test) six weightlifting training sessions. During each test session, we recorded kinematic parameters of snatch performance using Kinovea version 0.8.15 software. After the learning sessions, the SC group improved on most kinematic parameters (e.g., the horizontal displacement of the bar between the first and the second pulls [ M DXV  = 25.42%, SD  = 18.96, p  = 0.003) and the maximum height reached by the bar ( M HMV  = 5.51%, SD  = 7.71, p  < 0.05)], while the YK group improved only on the DxV ( M DXV  = 19.08%, SD  = 24.68, p  < 0.05). In addition, the SC group showed a more advanced phase of cognitive processing compared to the YK group, and the SC group showed a superior improvement in their technical knowledge level ( p  < 0.001) compared to the YK group ( p  < 0.05). Thus, key elements to correcting motor errors in children's weightlifting through self-controlled feedback were improvements in information processing and technical knowledge.

In the framework of the Born-Oppenheimer (BO) method, we illustrate our ab-initio spectroscopic study of the of silver hydride molecule. The calculation of 48 electrons for this system is very difficult, so we have been employed a pseudo-potential (P.P) to reduce the big number of electrons to two electrons of valence, which is proposed by Barthelat and Durant. This allowed us to make a configuration interaction (CI). The potential energy curves (PECs) and the spectroscopic constants of AgH have been investigated for Σ + , Π and Δ symmetries. We have been determined the permanent and transition dipole moments (PDM and TDM), the vibrational energies levels and their spacing. We compared our results with the available experimental and theoretical results in the literature. We found a good accordance with the experimental and theoretical data that builds a validation of the choice of our approach.

The purpose of the present study was to investigate which of two strategies, Video Feedback with Pedagogical Activity (VF-PA) or Video Feedback (VF), would be more beneficial for the remote error correction of the snatch weightlifting technique during the confinement period. Thirty-five school aged children with at least three months of weightlifting experience were randomized to one of three training conditions: VF-PA, VF or the Control group (CONT). Subjects underwent test sessions one week before (T0) and one day after (T1) a six-session training period and a retention test session a week later (T2). During each test session, the Kinovea version 0.8.15 software measured the kinematic parameters of the snatch performance. Following distance learning sessions (T1), the VF-PA improved various kinematic parameters (i.e., barbell horizontal displacements, maximum height, looping and symmetry) compared with T0 ( p < 0.5; Cohen's d = 0.58-1.1). Most of these improvements were maintained during the retention test (T2) ( p <0.01, Cohen's d = 1.2-1.3) when compared withT0. However, the VF group improved only twoparameters (i.e., barbell symmetry and horizontal displacement) at T1 ( p < 0.05; Cohen's d = 0.9), which were not maintained at T2. Better horizontal displacement and looping values were registered during the retention test in the VF-PA group compared with theCONT group ( p < 0.05, Cohen's d = 1.49-1.52). The present findings suggest combining video feedback with pedagogical activity during the pandemic induced online coaching or physical education to improve movement learning in school aged children.

Ultraviolet microdisk lasers are integrated monolithically into photonic circuits using a III-nitride-on-silicon platform with gallium nitride (GaN) as the main waveguide layer. The photonic circuits consist of a microdisk and a pulley waveguide, terminated by out-coupling gratings. In this Letter, we measure quality factors up to 3500 under continuous-wave excitation. Lasing is observed from 374 to 399 nm under pulsed excitation, achieving low-threshold energies of 0.14 m J / c m 2 per pulse (threshold peak powers of 35 k W / c m 2 ). A large peak-to-background dynamic of around 200 is observed at the out-coupling grating for small gaps of 50 nm between the disk and the waveguide. These devices operate at the limit of what can be achieved with GaN in terms of operation wavelength.

Background and Objective: Individuals who survive a stroke often display considerable gait impairments that occur in part due to inadequate muscle force production. This study aimed to investigate lower limb muscle forces in poststroke patients during walking., Methods: Kinematics, kinetics, and electromyographic (EMG) measurements were performed on nine poststroke and healthy individuals walking at natural speed in a cross-sectional study. Recorded parameters were used in an EMG-driven model to estimate the forces exerted by the muscles around the knee and ankle joints during the stance (braking and propulsion) and swing phases., Results: For hemiparetic patients, in comparison to healthy controls, the paretic side exhibited (i) lower forces generated by plantar-flexors and quadriceps respectively during the braking and propulsion phases, but (ii) higher knee-flexors forces during the propulsion phase. Regarding the non-paretic side, it displayed (i) higher forces generated by knee-flexors and quadriceps (only for the propulsion phase) forces during the stance phase, and (iii) higher plantar-flexors forces during the swing phase, in comparison to controls., Conclusion: Reduced forces exerted by the plantar-flexors and the knee-extensors along with increased force generated by the knee-flexors on the paretic side give possible explanation for hemiparetic gait abnormalities. Increased muscle forces exerted by the non-paretic side might be a compensatory strategy to better support body weight and properly adjust the center of mass forward.

Background: Impairments resulting from hemiparetic stroke lead to persistent difficulties with walking. Abnormal co-contraction patterns of lower limb muscles might be a compensatory mechanism to deal with its resulting gait impairments., Aim: The aim of this study was to assess muscle co-contraction obtained from muscle moments in chronic hemiparetic patients presenting a stiff-knee gait (SKG) during walking., Design: Cross-sectional study., Setting: Clinical movement analysis laboratory in a health center and a community hospital., Population: Twelve hemiparetic patients 6 months' post-stroke (mean±SD age 49.3±12.5) walking with a SKG and twelve healthy adults (mean±SD age 23.5±7.7)., Methods: Hemiparetic patients walked at their natural gait speed while healthy adults walked at their natural and slow gait speed. Spatiotemporal, kinetic and kinematic gait parameters were determined for both lower limbs. Co-Contraction Index at the knee and the ankle was calculated from muscle moments estimated using an EMG-driven model during the first (DS1) and second (DS2) double support and the single support (SS) phases and the swing phase (SW)., Results: The results revealed that chronic stroke patients have reduced ankle co-contraction and increased knee co-contraction during DS1 phase, increased ankle co-contraction during DS2 phase and increased knee co-contraction during SW phase on the paretic side. On the non-paretic side, muscle co-contraction was higher at the knee during SS phase., Conclusions: Increased co-contraction during walking in both the paretic and the non-paretic side, in patients with hemiparesis exhibiting a SKG, might be an adaptive strategy to increase walking stability, as it may be related to spasticity, but also could result in a high metabolic cost., Clinical Rehabilitation Impact: The information obtained in this study may be used to support rehabilitation programs focusing on the selectivity of movement control such as strength or power training.

Purpose: Chemical and mechanical irritation of the tracheal mucosa influences the incidence of cough at emergence from general anesthesia, potentially leading to significant postoperative complications. This study evaluates the benefits of endotracheal tube (ETT) intracuff alkalinized lidocaine during N2O-free general anesthesia by 1) assessing the in vitro effect of alkalinization on lidocaine diffusion kinetics across the cuff's membrane and 2) evaluating, in a randomized controlled clinical trial, the impact of 160 mg of intracuff alkalinized lidocaine on cough upon emergence from anesthesia for surgery lasting > 120 min., Methods: In the in vitro study, diffusion kinetics of various intracuff alkalinized lidocaine amounts (40, 80, and 160 mg) were compared to their non-alkalinized lidocaine controls. In the clinical trial, 80 adult patients (American Society of Anesthesiologists physical status I-III) undergoing urological or gynecological surgery expected to last > 120 min and scheduled for N2O-free general anesthesia were enrolled. The ETT cuffs (high-volume, low-pressure) were filled with either 160 mg of alkalinized lidocaine or a comparable volume of 0.9% saline. The primary outcome was the incidence of cough upon emergence from anesthesia. Sore throat, hoarseness, and postoperative nausea and vomiting were evaluated as secondary outcomes., Results: Our in vitro study confirmed that alkalinization increases lidocaine diffusion across the membrane of ETT cuffs and suggested that the lidocaine diffusion rate is associated with the initial intracuff lidocaine quantity. Our clinical trial demonstrated that, compared with the saline group, 160 mg of intracuff alkalinized lidocaine reduced the incidence of cough upon emergence from N2O-free general anesthesia (76% vs 34%, respectively; difference 42%; 95% confidence interval, 21% to 62%; P < 0.001) while having no clinical impact on secondary outcomes., Conclusions: The use of 160 mg of intracuff alkalinized lidocaine is associated with a decreased incidence of cough upon emergence from N2O-free general anesthesia > 120 min. This trial was registered at www.clinicaltrials.gov (NCT01774292).

In boys, muscle power and strength fluctuate with time-of-day with morning nadirs and afternoon maximum values. However, the exact underlying mechanisms of this daily variation are not studied yet. Thus, the purpose of this study was to examine the time-of-day effects on electromyographic (EMG) parameters changes during a Wingate test in boys. Twenty-two boys performed a 30-s Wingate test (measurement of muscle power and fatigue) at 07:00 and 17:00-h on separate days. Surface EMG activity was recorded in the Vastus lateralis, rectus femoris and vastus medialis muscles throughout the test and analyzed over a 5-s span. The root-mean-square (RMS) and mean-power-frequency (MPF) were calculated. Neuromuscular efficiency (NME) was estimated from the ratio of power to RMS. Muscle power (8.22 ± 0.92 vs. 8.75 ± 0.99 W·kg(-1) for peak power and 6.96 ± 0. 72 vs. 7.31 ± 0.77 W·kg(-1) for mean power, p < 0.001) and fatigue (30.27 ± 7.98 vs. 34.5 ± 10. 15 %, p < 0.05) during the Wingate test increased significantly from morning to evening. Likewise, MPF (102.14 ± 18.15 vs. 92.38 ± 12.39 Hz during the first 5-s, p < 0.001) and NME (4.78 ± 1.7 vs. 3.88 ± 0.79 W·mV(-1) during the first 5-s, p < 0.001) were higher in the evening than the morning; but no significant time-of-day effect was noticed for RMS. Taken together, these results suggest that peripheral mechanisms are more likely the cause of the child's diurnal variations of muscle power and fatigue during the Wingate test. Key pointsIn boys, performances during the Wingate test fluctuate with the time-of-day.MPF and NME are higher in the evening during the Wingate cycling test.RMS is unaffected by the time-of-day.The evening improvement in muscle power and fatigue is due to an enhancement of the muscle contractile properties.

Purpose: This study investigated the effects of time-of-day on aerobic and anaerobic performances during the Yo-Yo, repeated sprint ability (RSA) and the Wingate tests in young soccer players., Methods: In a counterbalanced and a random order, twenty junior male soccer players completed the Yo-Yo, the RSA, and the Wingate tests at two different times-of-day: 07:00 and 17:00 h. During the Yo-Yo test, the total distance (TD) covered and the estimated maximal aerobic velocity (MAV) were determined. The peak power (PP) during each sprint, the percentage of decrement of PP (PD) and total work (Wtotal) during the RSA test were, also, measured. In addition, during the Wingate test, the peak (P(peak)) and mean (P(mean)) powers were recorded., Results: During the Wingate test, P(peak) and P(mean) were significantly higher at 17:00 than 07:00 h (P<0.05) with diurnal gains of 3.1±3.6 and 2.9±3.5% respectively. During the RSA test, PP during the first two sprints, Pdec and Wtotal were, also, higher in the evening (P<0.05) with amplitudes of 4.8±4.6, 3.1±3.0, 13.1±32.1, and 4.1±2.5% respectively. Likewise, TD and MAV during the Yo-Yo test were higher at 17:00 than 07:00 h with diurnal gains of 13.1±10.7 and 4.2±3.3 respectively., Conclusions: The present study confirms the daily variations of both aerobic and anaerobic performances during the Yo-Yo, the RSA, and the Wingate tests in trained young Tunisian soccer players.

The aim of this study was to assess the effect of time-of-day-specific training on the diurnal variations of short-term performances in boys. Twenty-four boys were randomized into a morning-training-group (07:00-08:00h; MTG), an evening-training-group (17:00-18:00h; ETG) and a control-group (CG). They performed four tests of strength and power (unilateral isometric maximal voluntary contraction of the knee extensor muscles, Squat-Jump, Counter-Movement-Jump and Wingate tests) at 07:00 and 17:00h just before (T0) and after 6 weeks of resistance training (T1). In T0, the results revealed that short-term performances improved and oral temperature increased significantly from morning to afternoon (amplitudes between 2.36 and 17.5% for both oral temperature and performances) for all subjects. In T1, the diurnal variations of performances were blunted in the MTG and persisted in the ETG and CG. Moreover, the training program increase muscle strength and power especially after training in the morning hours and the magnitude of gains was greater at the time-of-day-specific training than at other times. In conclusion, these results suggest that time-of-day-specific training increases the child's anaerobic performances specifically at this time-of-day. Moreover, the improvement of these performances was greater after morning than evening training.

Purpose: This study was designed to assess the effects of Ramadan fasting on the profile of mood state and perceived exertion in young soccer players and aerobic and anaerobic performances during the Yo-Yo, repeated sprint ability (RSA) and the Wingate tests., Methods: Twenty junior male soccer players completed the Yo-Yo, the RSA, and the Wingate tests on three different occasions: one-week before Ramadan (BR), the second week (SWR) and the fourth week (ER) of Ramadan. The total distance (TD) covered and the estimated maximal aerobic velocity (MAV) during the Yo-Yo test were recorded. During the RSA test, peak power (PP) during each sprint, the percentage of decrement of PP (PD) and total work (Wtotal) were calculated. During the Wingate test, peak (P(peak)) and mean (P(mean)) powers and fatigue index (FI) were recorded., Results: TD and MAV (P=0.01) during the Yo-Yo test and PP (P=0.01, P=0.004, P=0.001, P=0.01, P=0.03 for sprints 1, 2, 3, 4, and 5, respectively) and Wtotal (P=0.02) during the RSA test were significantly higher during BR than ER. Furthermore, muscle fatigue during the RSA test increased significantly from BR to ER (P=0.01). P(peak) and P(mean) during the Wingate test decreased significantly from BR to SWR and ER (P<0.0005). FI was higher during SWR (P=0.001) and ER (P<0.0005) than BR. In addition, rating of perceived exertion scores and fatigue estimated by the profile of mood state questionnaire were higher during Ramadan in comparison with BR., Conclusions: The present study suggests that both aerobic and anaerobic performances during the Yo-Yo, the RSA and the Wingate tests were affected by Ramadan fasting in young soccer players.

The purpose of this study was to examine the time-of-day effects on short-term performances in boys. In a balanced and randomized study design, 20 boys performed four anaerobic tests of strength and power (grip strength, Squat-Jump, Five-jump and cycle Wingate tests) at 08:00, 14:00 and 18:00 hr on separate days. The results showed a time-of-day effect on oral temperature. Analysis of variance revealed a significant time-of-day effect for short-term performances for strength, cycle, and jump tests. The post hoc analysis revealed that performances improved significantly from morning to afternoon but no significant differences were noticed between 14:00 and 18:00 hr. The differences between the morning and the afternoon (the highest value measured either at 14:00 or at 18:00 hr) reached 5.9% for grip strength, 3.5% for the squat jump test, 5% for the five jump test, and 5.5% for P(peak) and 6% for P(mean) during the Wingate test. A significant positive correlation was found between temperature and short-term performances. In conclusion, a time-of-day effect in the child's maximal short-term exercise performances exists in relation with core temperature. Such variations would have pronounced effects when expressed in training programs and competitions.