Tarak Driss - Academia.edu (original) (raw)

Papers by Tarak Driss

European Journal of Applied Physiology, 2001

The present investigation has been designed to confirm the effect of instruction (hard-and-fast i... more The present investigation has been designed to confirm the effect of instruction (hard-and-fast instruction compared to fast instruction) upon maximal voluntary isometric force (MVF) and maximal rate of force development (MRFD) in muscle groups which differ with regards to muscle mass and usage. In addition, we took advantage of the force data collected during unilateral and bilateral leg extension, to compare the instruction effects on the indices of the bilateral deficits (BI, the differences between the data collected during bilateral extensions and the sum of the data collected during unilateral left and right extensions) with regard to MVF (BIMVF) and MRFD (BIMRFD). Force-time curves were recorded during maximal isometric contractions of the elbow flexors, the leg extensors of the take-off and lead legs and during bilateral leg extension in 26 healthy young male volunteers from the track-and-field national team of Tunisia. In the first protocol, the subjects were instructed to produce MFV as hard-and-fast as possible (instruction I). In the second protocol (instruction II) the subjects were instructed to provide MFRD, that is the most explosive force, by concentrating on the fastest contraction without concern for achieving maximal force. The present study confirmed the importance of an appropriate instruction for the measurement of MRDF. The MRFD (F=40.8, PF=52.1; PANOVA, F=0.562; P=0.454). Moreover, the results of the present study suggested that the effect of instruction was significantly larger for BIMRFD than forBIMVF.

The Journal of sports medicine and physical fitness, Jan 11, 2016

To evaluate the effect of two types of partial sleep deprivation (PSD) on biomarkers of muscle an... more To evaluate the effect of two types of partial sleep deprivation (PSD) on biomarkers of muscle and cardiac injuries in response to acute intermittent exercise in professional athletes. In a counterbalanced order, Ten healthy male Taekwondo athletes were asked to perform the Yo-Yo Intermittent Recovery Test (YYIRT) in three conditions, allowing a 36 h recovery period in between: i) following a full night of habitual sleep known as a reference sleep night (RN); ii) following PSD in the beginning of the night (PSDBN), and iii) following PSD in the end of the night (PSDEN). Heart rate (HR) and arterial oxygen saturation (SaO2) were measured during exercise. Blood samples were taken just before and 3 min after the YYIRT to measure biomarkers related to muscle and cardiac injuries. No significant effect of PSD was observed for physiological parameters (i.e., HR and SaO2). However, a significant alteration of resting ultra-sensitive C-reactive protein (P < 0.05) and myoglobin (MYO) (P &...

Journal of Exercise Rehabilitation, 2016

Athletes and coaches believe that adequate sleep is essential for peak performance. There is ampl... more Athletes and coaches believe that adequate sleep is essential for peak performance. There is ample scientific evidence which support the conclusion that sleep loss seems to stress many physiological functions in humans. The aim of this study was to determine the effect of one night&amp;amp;amp;amp;#39;s sleep deprivation on intermittent exercise performance in the evening of the following day. Ten male Taekwondo players performed the Yo-Yo intermittent recovery test (YYIRT) in three sleep conditions (reference sleep night [RN], partial sleep deprivation at the beginning of night [PSDBN], partial sleep deprivation at the end of night [PSDEN]) in a counterbalanced order, allowing a recovery period ≥36 hr in between them. Heart rate peak (HRpeak), plasma lactate concentrations (Lac) and rating of perceived exertion (RPE) were measured during the test. A significant effect of sleep restriction was observed on the total distance covered in YYIRT (P&amp;amp;amp;amp;lt;0.0005) and Lac (P&amp;amp;amp;amp;lt;0.01) in comparison with the RN. In addition, performance more decreased after PSDEN (P&amp;amp;amp;amp;lt;0.0005) than PSDBN (P&amp;amp;amp;amp;lt;0.05). Also, Lac decreased significantly only after PS-DEN (P&amp;amp;amp;amp;lt;0.05) compared with RN. However, there were no significant changes in HRpeak and RPE after the two types of partial sleep deprivation compared to RN. The present study indicates that short-term sleep restriction affect the intermittent performance, as well as the Lac levels of the Taekwondo players in the evening of the following day, without alteration of HRpeak and RPE.

Http Dx Doi Org 10 1080 23311916 2015 1029237, Apr 13, 2015

The first friction-cycle ergometers of the end of the nineteenth century and the beginning of the... more The first friction-cycle ergometers of the end of the nineteenth century and the beginning of the 20th century are presented before the description of more recent ergometers such as Fleisch ergometer (1954), Ergoméca TM (1985), sinusbalance ergometer, and weight-basket loaded ergometer. The limits of each ergometer are debated. The interest of friction-loaded ergometers was renewed with the proposal of different protocols enabling the assessment of maximal power during short all-out sprints on a cycle ergometer. These protocols are succinctly presented: corrected peak power protocol, force-speed test during repeated all-out sprints against different loads, torque-velocity relationship during a single all-out sprint. The different calibration procedures (static, dynamic, and physiological calibrations) of friction-loaded ergometers are described before the presentation of their results in the literature. Some improvements for the future friction-loaded ergometers are presented at the end of the paper.

Proceedings of the 3rd International Congress on Sport Sciences Research and Technology Support, 2015

Qatar Foundation Annual Research Conference, Nov 13, 2014

Http Dx Doi Org 10 1080 02640414 2013 865253, Jan 30, 2014

This study investigated the interaction between emotion-eliciting pictures and power output durin... more This study investigated the interaction between emotion-eliciting pictures and power output during a repetitive supra-maximal task on a cycle ergometre. Twelve male participants (mean (±SD) age, height and weight: 28.58 ± 3.23 years, 1.78 ± 0.05 m and 82.41 ± 13.29 kg) performed 5 repeated sprint tests on a cycle ergometre in front of neutral, pleasant or unpleasant pictures. For each sprint, mechanical (peak power and work), physiological (heart rate) and perceptual (affective load) indices were analysed. Affective load was calculated from the ratings of perceived exertion, which reflected the amount of pleasant and unpleasant responses experienced during exercise. The results showed that peak power, work and heart rate values were significantly lower (P &amp;amp;amp;amp;lt; 0.05) for unpleasant pictures (9.18 ± 0.20 W ∙ kg(-1); 47.69 ± 1.08 J ∙ kg(-1); 152 ± 4 bpm) when compared with pleasant ones (9.50 ± 0.20 W ∙ kg(-1); 50.11 ± 0.11 J ∙ kg(-1); 156 ± 3 bpm). Furthermore, the affective load was found to be similar for the pleasant and unpleasant sessions. All together, these results suggested that the ability to produce maximal power output depended on whether the emotional context was pleasant or unpleasant. The fact that the power output was lower in the unpleasant versus pleasant session could reflect a regulatory process aimed at maintaining a similar level of affective load for both sessions.

European Journal of Applied Physiology, Aug 1, 2001

The present investigation has been designed to con®rm the eect of instruction (hard-and-fast inst... more The present investigation has been designed to con®rm the eect of instruction (hard-and-fast instruction compared to fast instruction) upon maximal voluntary isometric force (MVF) and maximal rate of force development (MRFD) in muscle groups which dier with regards to muscle mass and usage. In addition, we took advantage of the force data collected during unilateral and bilateral leg extension, to compare the instruction eects on the indices of the bilateral de®cits (BI, the dierences between the data collected during bilateral extensions and the sum of the data collected during unilateral left and right extensions) with regard to MVF (BI MVF ) and MRFD (BI MRFD ). Force-time curves were recorded during maximal isometric contractions of the elbow¯exors, the leg extensors of the take-o and lead legs and during bilateral leg extension in 26 healthy young male volunteers from the track-and-®eld national team of Tunisia. In the ®rst protocol, the subjects were instructed to produce MFV as hard-and-fast as possible (instruction I). In the second protocol (instruction II) the subjects were instructed to provide MFRD, that is the most explosive force, by concentrating on the fastest contraction without concern for achieving maximal force. The present study con®rmed the importance of an appropriate instruction for the measurement of MRDF.

Http Dx Doi Org 10 1080 02640414 2013 805238, Jan 2, 2014

The present investigation verified that strength is improved by a training programme consisting o... more The present investigation verified that strength is improved by a training programme consisting of repetitions of maximal isometric voluntary co-contractions without increasing co-activations during contractions against external resistances. Ten participants performed 12 training sessions (four sets of 6 × 4 second maximal isometric co-contraction of the elbow flexor and extensors, 3 days a week for 4 weeks). Surface electromyograms of triceps and biceps brachii were collected during maximal voluntary isometric elbow flexion and extension against a force transducer. Maximal voluntary isometric force increased significantly after training, by 13.8 ± 6.0% (extension) and 9.6 ± 9.5% (flexion), but the observed increases in EMG of agonist muscles during maximal voluntary contraction were not significant. No significant changes in the levels of co-activation of the elbow flexors and extensors were observed. No significant change was observed for all the parameters in a control group of ten participants. These results indicated that the strength improvements after co-contraction training occur without increases in co-activation level.

BioMed Research International, 2015

The present study examined the reliability of the force-velocity relationship during cycling and ... more The present study examined the reliability of the force-velocity relationship during cycling and arm cranking exercises in active males and females. Twenty male and seventeen female physical education students performed three-session tests with legs and three-session tests with arms on a friction-loaded ergometer on six different sessions in a randomized order. The reliability of maximal power ( max ), maximal pedal rate ( 0 ), and maximal force ( 0 ) were studied using the coefficient of variation (CV), the intraclass correlation coefficient (ICC) and the test-retest correlation coefficient ( ). Reliability indices were better for men (1.74 ≤ CV ≤ 4.36, 0.82 ≤ ICC ≤ 0.97, and 0.81 ≤ r ≤ 0.97) compared with women (2.34 ≤ CV ≤ 7.04, 0.44 ≤ ICC ≤ 0.98, and 0.44 ≤ r ≤ 0.98) and in cycling exercise (1.74 ≤ CV ≤ 3.85, 0.88 ≤ ICC ≤ 0.98, and 0.90 ≤ r ≤ 0.98) compared with arm exercise (2.37 ≤ CV ≤ 7.04, 0.44 ≤ ICC ≤ 0.95, and 0.44 ≤ r ≤ 0.95). Furthermore, the reliability indices were high for max and 0 whatever the expression of the results (raw data or data related to body dimensions). max and 0 could be used in longitudinal physical fitness investigations. However, further studies are needed to judge 0 reliability.

PLOS ONE, 2015

The aim of this study was to examine the impact of emotional eliciting pictures on neuromuscular ... more The aim of this study was to examine the impact of emotional eliciting pictures on neuromuscular performance during repetitive supramaximal cycling exercises (RSE). In a randomized order, twelve male participants were asked to perform five 6-s cycle sprints (interspaced by 24 s of recovery) on a cycle ergometer in front of neutral, pleasant or unpleasant pictures. During each RSE, mean power output (MPO) and electromyographic activity [root mean square (RMS) and median frequency (MF)] of the vastus lateralis and vastus medialis muscles were analyzed. Neuromuscular efficiency (NME) was calculated as the ratio of MPO to RMS. Higher RMS (232.17 ± 1.17 vs. 201.90 ± 0.47 µV) and MF (68.56 ± 1.78 vs. 64.18 ± 2.17 Hz) were obtained in pleasant compared to unpleasant conditions (p < 0.05). This emotional effect persisted from the first to the last sprint. Higher MPO was obtained in pleasant than in unpleasant conditions (690.65 ± 38.23 vs. 656.73 ± 35.95 W, p < 0.05). However, this emotional effect on MPO was observed only for the two first sprints.

Several studies have shown the importance of the instruction on maximal voluntary force (MVF) and... more Several studies have shown the importance of the instruction on maximal voluntary force (MVF) and maximal rate of force development (MRFD) (Bemben et al., 1990; Christ et al., 1993; Sahaly et al., 2001, 2003). MRFD is slower when the subjects are instructed to produce their “maximal peak force as fast as possible” than when they are instructed “to focus on MRFD” (Sahaly et al., 2001). The reliability of isometric strength indices is high (Viitasalo et al., 1980; Bemben et al., 1990; Sleivert et al., 1994; Mirkov et al., 2004). However, the effect of instruction on the reliability of explosive force indices has not been studied. We compared the reliability of MRFD and MVF measured with Hard-and-Fast instruction (INST 1) vs. Fast instruction (INST2) in 11 men and 12 women. MVF and MRFD were measured in 3 sessions at one week intervals at the same hour with both protocols. The force time curve was recorded during unilateral maximal isometric knee extensions. After familiarization, the ...

Journal of Strength and Conditioning Research, 2015

Zbidi, S, Zinoubi, B, Vandewalle, H, and Driss, T. Diurnal rhythm of muscular strength depends on... more Zbidi, S, Zinoubi, B, Vandewalle, H, and Driss, T. Diurnal rhythm of muscular strength depends on temporal specificity of self-resistance training. J Strength Cond Res 30(3): 717-724, 2016-The study investigated the effect of the time-of-day at which maximal isometric voluntary co-contraction (MIVCC) training is conducted on the adaptation and diurnal variation of maximal and explosive force production. Twenty active men underwent a 6-week (3 times per week) MIVCC training of the right elbow joint. The participants were randomly assigned to a morning training group (MTG, 07:00-08:00 hours) and evening training group (ETG, 17:00-18:00 hours). The maximal voluntary force (MVF) and maximal rate of force development (MRFD) during isometric elbow flexion (MVFF and MRFDF) and extension (MVFE and MRFDE) were recorded before (T0) and after (T1) training in the morning and evening. At T0, MVF and MRFD were higher in the evening compared with those in the morning for the MTG and ETG (p ≤ 0.05). At T1, MVFF and MVFE increased in the morning and evening for both groups (p &amp;amp;lt; 0.001). The MRFDF and MRFDE increased only if training and test session were scheduled at the same time. The relative increase of MVF was greater at the specific time of training for the MTG (12 and 17.6% in MVFF and MVFE, respectively) and ETG (9.8 and 13.4% in MVFF and MVFE, respectively). The diurnal variations in MVF and MRFD during flexion and extension disappeared in the MTG and persisted in the ETG. Maximal isometric voluntary co-contraction training enhanced muscle strength whatever the time-of-day at which the training was scheduled without alteration of explosive force. In contrast, to optimize the muscle strength, our results suggested that morning training may be accompanied by the greatest muscle strength gain and blunted muscle strength variation observed between the morning and evening.

Introduction: Power laws (Dlim=ktlimγ) are applied to the study of world records. Indices derived... more Introduction: Power laws (Dlim=ktlimγ) are applied to the study of world records. Indices derived from hyperbolic (critical speed, SCrit) and logarithmic (Endurance Index, Péronnet and Thibault 1989) models are often used in the study of individual performances. Materials and Methods: Endurance Index, SCrit and γ have been applied to the individual performances of two exceptional runners (ER, Nurmi and Gebrselassie) and 11 physical education students (PES) during running exercises at constant (CS) and sinusoidal speeds (SS). Results: Exponent γ is close to 1 in ER and was equal to 0.790±0.089 (PES-CS) and 0.779±0.075 (PES-SS). In contrast with ER, Endurance Index depends on the range of tlim in PES whose γ is low. Endurance index and SCrit are linearly correlated provided that they are computed from the same range of tlim. Endurance Index, SCrit and γ were not different for PES-CS and PES-SS when normalized to the maximal speed sustainable during 7 min at CS or SS. Endurance Index, ...

PLOS ONE, 2015

The aim of the present study was to examine whether listening to music during warming-up might in... more The aim of the present study was to examine whether listening to music during warming-up might influence short-term maximal performance (STMP), cognitive anxiety, self-confidence, and enjoyment during Ramadan, and whether these affects might predict STMP. Nine male physical education students (age: 21 ± 1.1 years; height: 1.8 ± 0.04 m; body mass: 83 ± 5 kg) volunteered to participate in the present study. A within-subjects design consisted of four experimental sessions: Two sessions occurred one week before Ramadan and two others took place during Ramadan. They were scheduled at 5 p.m. and were conducted as follows: After a 10-minute warm-up either with or without listening to music, each participant performed a 5-m multiple shuttle run test, after which he was asked to answer items intended to assess his affective state during the experimental task. Our findings revealed that STMP was lower during Ramadan than before Ramadan in the no-music condition. Additionally, it was found that STMP was higher in the music condition than in the no-music condition during Ramadan, and that STMP measured before Ramadan did not differ from that measured during Ramadan in the music condition. Regarding affects, the findings revealed that enjoyment was lower during Ramadan than before Ramadan in the music condition, and that cognitive anxiety was lower in the music condition than in the no-music condition before Ramadan. Self-confidence was not influenced by the experimental conditions. This study showed that listening to music during warming-up not only would be beneficial for STMP in Ramadan fasters, but also would counteract the negative effects of Ramadan observance on STMP.

The Journal of Strength and Conditioning Research

European Journal of Applied Physiology, 2001

The present investigation has been designed to confirm the effect of instruction (hard-and-fast i... more The present investigation has been designed to confirm the effect of instruction (hard-and-fast instruction compared to fast instruction) upon maximal voluntary isometric force (MVF) and maximal rate of force development (MRFD) in muscle groups which differ with regards to muscle mass and usage. In addition, we took advantage of the force data collected during unilateral and bilateral leg extension, to compare the instruction effects on the indices of the bilateral deficits (BI, the differences between the data collected during bilateral extensions and the sum of the data collected during unilateral left and right extensions) with regard to MVF (BIMVF) and MRFD (BIMRFD). Force-time curves were recorded during maximal isometric contractions of the elbow flexors, the leg extensors of the take-off and lead legs and during bilateral leg extension in 26 healthy young male volunteers from the track-and-field national team of Tunisia. In the first protocol, the subjects were instructed to produce MFV as hard-and-fast as possible (instruction I). In the second protocol (instruction II) the subjects were instructed to provide MFRD, that is the most explosive force, by concentrating on the fastest contraction without concern for achieving maximal force. The present study confirmed the importance of an appropriate instruction for the measurement of MRDF. The MRFD (F=40.8, PF=52.1; PANOVA, F=0.562; P=0.454). Moreover, the results of the present study suggested that the effect of instruction was significantly larger for BIMRFD than forBIMVF.

The Journal of sports medicine and physical fitness, Jan 11, 2016

To evaluate the effect of two types of partial sleep deprivation (PSD) on biomarkers of muscle an... more To evaluate the effect of two types of partial sleep deprivation (PSD) on biomarkers of muscle and cardiac injuries in response to acute intermittent exercise in professional athletes. In a counterbalanced order, Ten healthy male Taekwondo athletes were asked to perform the Yo-Yo Intermittent Recovery Test (YYIRT) in three conditions, allowing a 36 h recovery period in between: i) following a full night of habitual sleep known as a reference sleep night (RN); ii) following PSD in the beginning of the night (PSDBN), and iii) following PSD in the end of the night (PSDEN). Heart rate (HR) and arterial oxygen saturation (SaO2) were measured during exercise. Blood samples were taken just before and 3 min after the YYIRT to measure biomarkers related to muscle and cardiac injuries. No significant effect of PSD was observed for physiological parameters (i.e., HR and SaO2). However, a significant alteration of resting ultra-sensitive C-reactive protein (P < 0.05) and myoglobin (MYO) (P &...

Journal of Exercise Rehabilitation, 2016

Athletes and coaches believe that adequate sleep is essential for peak performance. There is ampl... more Athletes and coaches believe that adequate sleep is essential for peak performance. There is ample scientific evidence which support the conclusion that sleep loss seems to stress many physiological functions in humans. The aim of this study was to determine the effect of one night&amp;amp;amp;amp;#39;s sleep deprivation on intermittent exercise performance in the evening of the following day. Ten male Taekwondo players performed the Yo-Yo intermittent recovery test (YYIRT) in three sleep conditions (reference sleep night [RN], partial sleep deprivation at the beginning of night [PSDBN], partial sleep deprivation at the end of night [PSDEN]) in a counterbalanced order, allowing a recovery period ≥36 hr in between them. Heart rate peak (HRpeak), plasma lactate concentrations (Lac) and rating of perceived exertion (RPE) were measured during the test. A significant effect of sleep restriction was observed on the total distance covered in YYIRT (P&amp;amp;amp;amp;lt;0.0005) and Lac (P&amp;amp;amp;amp;lt;0.01) in comparison with the RN. In addition, performance more decreased after PSDEN (P&amp;amp;amp;amp;lt;0.0005) than PSDBN (P&amp;amp;amp;amp;lt;0.05). Also, Lac decreased significantly only after PS-DEN (P&amp;amp;amp;amp;lt;0.05) compared with RN. However, there were no significant changes in HRpeak and RPE after the two types of partial sleep deprivation compared to RN. The present study indicates that short-term sleep restriction affect the intermittent performance, as well as the Lac levels of the Taekwondo players in the evening of the following day, without alteration of HRpeak and RPE.

Http Dx Doi Org 10 1080 23311916 2015 1029237, Apr 13, 2015

The first friction-cycle ergometers of the end of the nineteenth century and the beginning of the... more The first friction-cycle ergometers of the end of the nineteenth century and the beginning of the 20th century are presented before the description of more recent ergometers such as Fleisch ergometer (1954), Ergoméca TM (1985), sinusbalance ergometer, and weight-basket loaded ergometer. The limits of each ergometer are debated. The interest of friction-loaded ergometers was renewed with the proposal of different protocols enabling the assessment of maximal power during short all-out sprints on a cycle ergometer. These protocols are succinctly presented: corrected peak power protocol, force-speed test during repeated all-out sprints against different loads, torque-velocity relationship during a single all-out sprint. The different calibration procedures (static, dynamic, and physiological calibrations) of friction-loaded ergometers are described before the presentation of their results in the literature. Some improvements for the future friction-loaded ergometers are presented at the end of the paper.

Proceedings of the 3rd International Congress on Sport Sciences Research and Technology Support, 2015

Qatar Foundation Annual Research Conference, Nov 13, 2014

Http Dx Doi Org 10 1080 02640414 2013 865253, Jan 30, 2014

This study investigated the interaction between emotion-eliciting pictures and power output durin... more This study investigated the interaction between emotion-eliciting pictures and power output during a repetitive supra-maximal task on a cycle ergometre. Twelve male participants (mean (±SD) age, height and weight: 28.58 ± 3.23 years, 1.78 ± 0.05 m and 82.41 ± 13.29 kg) performed 5 repeated sprint tests on a cycle ergometre in front of neutral, pleasant or unpleasant pictures. For each sprint, mechanical (peak power and work), physiological (heart rate) and perceptual (affective load) indices were analysed. Affective load was calculated from the ratings of perceived exertion, which reflected the amount of pleasant and unpleasant responses experienced during exercise. The results showed that peak power, work and heart rate values were significantly lower (P &amp;amp;amp;amp;lt; 0.05) for unpleasant pictures (9.18 ± 0.20 W ∙ kg(-1); 47.69 ± 1.08 J ∙ kg(-1); 152 ± 4 bpm) when compared with pleasant ones (9.50 ± 0.20 W ∙ kg(-1); 50.11 ± 0.11 J ∙ kg(-1); 156 ± 3 bpm). Furthermore, the affective load was found to be similar for the pleasant and unpleasant sessions. All together, these results suggested that the ability to produce maximal power output depended on whether the emotional context was pleasant or unpleasant. The fact that the power output was lower in the unpleasant versus pleasant session could reflect a regulatory process aimed at maintaining a similar level of affective load for both sessions.

European Journal of Applied Physiology, Aug 1, 2001

The present investigation has been designed to con®rm the eect of instruction (hard-and-fast inst... more The present investigation has been designed to con®rm the eect of instruction (hard-and-fast instruction compared to fast instruction) upon maximal voluntary isometric force (MVF) and maximal rate of force development (MRFD) in muscle groups which dier with regards to muscle mass and usage. In addition, we took advantage of the force data collected during unilateral and bilateral leg extension, to compare the instruction eects on the indices of the bilateral de®cits (BI, the dierences between the data collected during bilateral extensions and the sum of the data collected during unilateral left and right extensions) with regard to MVF (BI MVF ) and MRFD (BI MRFD ). Force-time curves were recorded during maximal isometric contractions of the elbow¯exors, the leg extensors of the take-o and lead legs and during bilateral leg extension in 26 healthy young male volunteers from the track-and-®eld national team of Tunisia. In the ®rst protocol, the subjects were instructed to produce MFV as hard-and-fast as possible (instruction I). In the second protocol (instruction II) the subjects were instructed to provide MFRD, that is the most explosive force, by concentrating on the fastest contraction without concern for achieving maximal force. The present study con®rmed the importance of an appropriate instruction for the measurement of MRDF.

Http Dx Doi Org 10 1080 02640414 2013 805238, Jan 2, 2014

The present investigation verified that strength is improved by a training programme consisting o... more The present investigation verified that strength is improved by a training programme consisting of repetitions of maximal isometric voluntary co-contractions without increasing co-activations during contractions against external resistances. Ten participants performed 12 training sessions (four sets of 6 × 4 second maximal isometric co-contraction of the elbow flexor and extensors, 3 days a week for 4 weeks). Surface electromyograms of triceps and biceps brachii were collected during maximal voluntary isometric elbow flexion and extension against a force transducer. Maximal voluntary isometric force increased significantly after training, by 13.8 ± 6.0% (extension) and 9.6 ± 9.5% (flexion), but the observed increases in EMG of agonist muscles during maximal voluntary contraction were not significant. No significant changes in the levels of co-activation of the elbow flexors and extensors were observed. No significant change was observed for all the parameters in a control group of ten participants. These results indicated that the strength improvements after co-contraction training occur without increases in co-activation level.

BioMed Research International, 2015

The present study examined the reliability of the force-velocity relationship during cycling and ... more The present study examined the reliability of the force-velocity relationship during cycling and arm cranking exercises in active males and females. Twenty male and seventeen female physical education students performed three-session tests with legs and three-session tests with arms on a friction-loaded ergometer on six different sessions in a randomized order. The reliability of maximal power ( max ), maximal pedal rate ( 0 ), and maximal force ( 0 ) were studied using the coefficient of variation (CV), the intraclass correlation coefficient (ICC) and the test-retest correlation coefficient ( ). Reliability indices were better for men (1.74 ≤ CV ≤ 4.36, 0.82 ≤ ICC ≤ 0.97, and 0.81 ≤ r ≤ 0.97) compared with women (2.34 ≤ CV ≤ 7.04, 0.44 ≤ ICC ≤ 0.98, and 0.44 ≤ r ≤ 0.98) and in cycling exercise (1.74 ≤ CV ≤ 3.85, 0.88 ≤ ICC ≤ 0.98, and 0.90 ≤ r ≤ 0.98) compared with arm exercise (2.37 ≤ CV ≤ 7.04, 0.44 ≤ ICC ≤ 0.95, and 0.44 ≤ r ≤ 0.95). Furthermore, the reliability indices were high for max and 0 whatever the expression of the results (raw data or data related to body dimensions). max and 0 could be used in longitudinal physical fitness investigations. However, further studies are needed to judge 0 reliability.

PLOS ONE, 2015

The aim of this study was to examine the impact of emotional eliciting pictures on neuromuscular ... more The aim of this study was to examine the impact of emotional eliciting pictures on neuromuscular performance during repetitive supramaximal cycling exercises (RSE). In a randomized order, twelve male participants were asked to perform five 6-s cycle sprints (interspaced by 24 s of recovery) on a cycle ergometer in front of neutral, pleasant or unpleasant pictures. During each RSE, mean power output (MPO) and electromyographic activity [root mean square (RMS) and median frequency (MF)] of the vastus lateralis and vastus medialis muscles were analyzed. Neuromuscular efficiency (NME) was calculated as the ratio of MPO to RMS. Higher RMS (232.17 ± 1.17 vs. 201.90 ± 0.47 µV) and MF (68.56 ± 1.78 vs. 64.18 ± 2.17 Hz) were obtained in pleasant compared to unpleasant conditions (p < 0.05). This emotional effect persisted from the first to the last sprint. Higher MPO was obtained in pleasant than in unpleasant conditions (690.65 ± 38.23 vs. 656.73 ± 35.95 W, p < 0.05). However, this emotional effect on MPO was observed only for the two first sprints.

Several studies have shown the importance of the instruction on maximal voluntary force (MVF) and... more Several studies have shown the importance of the instruction on maximal voluntary force (MVF) and maximal rate of force development (MRFD) (Bemben et al., 1990; Christ et al., 1993; Sahaly et al., 2001, 2003). MRFD is slower when the subjects are instructed to produce their “maximal peak force as fast as possible” than when they are instructed “to focus on MRFD” (Sahaly et al., 2001). The reliability of isometric strength indices is high (Viitasalo et al., 1980; Bemben et al., 1990; Sleivert et al., 1994; Mirkov et al., 2004). However, the effect of instruction on the reliability of explosive force indices has not been studied. We compared the reliability of MRFD and MVF measured with Hard-and-Fast instruction (INST 1) vs. Fast instruction (INST2) in 11 men and 12 women. MVF and MRFD were measured in 3 sessions at one week intervals at the same hour with both protocols. The force time curve was recorded during unilateral maximal isometric knee extensions. After familiarization, the ...

Journal of Strength and Conditioning Research, 2015

Zbidi, S, Zinoubi, B, Vandewalle, H, and Driss, T. Diurnal rhythm of muscular strength depends on... more Zbidi, S, Zinoubi, B, Vandewalle, H, and Driss, T. Diurnal rhythm of muscular strength depends on temporal specificity of self-resistance training. J Strength Cond Res 30(3): 717-724, 2016-The study investigated the effect of the time-of-day at which maximal isometric voluntary co-contraction (MIVCC) training is conducted on the adaptation and diurnal variation of maximal and explosive force production. Twenty active men underwent a 6-week (3 times per week) MIVCC training of the right elbow joint. The participants were randomly assigned to a morning training group (MTG, 07:00-08:00 hours) and evening training group (ETG, 17:00-18:00 hours). The maximal voluntary force (MVF) and maximal rate of force development (MRFD) during isometric elbow flexion (MVFF and MRFDF) and extension (MVFE and MRFDE) were recorded before (T0) and after (T1) training in the morning and evening. At T0, MVF and MRFD were higher in the evening compared with those in the morning for the MTG and ETG (p ≤ 0.05). At T1, MVFF and MVFE increased in the morning and evening for both groups (p &amp;amp;lt; 0.001). The MRFDF and MRFDE increased only if training and test session were scheduled at the same time. The relative increase of MVF was greater at the specific time of training for the MTG (12 and 17.6% in MVFF and MVFE, respectively) and ETG (9.8 and 13.4% in MVFF and MVFE, respectively). The diurnal variations in MVF and MRFD during flexion and extension disappeared in the MTG and persisted in the ETG. Maximal isometric voluntary co-contraction training enhanced muscle strength whatever the time-of-day at which the training was scheduled without alteration of explosive force. In contrast, to optimize the muscle strength, our results suggested that morning training may be accompanied by the greatest muscle strength gain and blunted muscle strength variation observed between the morning and evening.

Introduction: Power laws (Dlim=ktlimγ) are applied to the study of world records. Indices derived... more Introduction: Power laws (Dlim=ktlimγ) are applied to the study of world records. Indices derived from hyperbolic (critical speed, SCrit) and logarithmic (Endurance Index, Péronnet and Thibault 1989) models are often used in the study of individual performances. Materials and Methods: Endurance Index, SCrit and γ have been applied to the individual performances of two exceptional runners (ER, Nurmi and Gebrselassie) and 11 physical education students (PES) during running exercises at constant (CS) and sinusoidal speeds (SS). Results: Exponent γ is close to 1 in ER and was equal to 0.790±0.089 (PES-CS) and 0.779±0.075 (PES-SS). In contrast with ER, Endurance Index depends on the range of tlim in PES whose γ is low. Endurance index and SCrit are linearly correlated provided that they are computed from the same range of tlim. Endurance Index, SCrit and γ were not different for PES-CS and PES-SS when normalized to the maximal speed sustainable during 7 min at CS or SS. Endurance Index, ...

PLOS ONE, 2015

The aim of the present study was to examine whether listening to music during warming-up might in... more The aim of the present study was to examine whether listening to music during warming-up might influence short-term maximal performance (STMP), cognitive anxiety, self-confidence, and enjoyment during Ramadan, and whether these affects might predict STMP. Nine male physical education students (age: 21 ± 1.1 years; height: 1.8 ± 0.04 m; body mass: 83 ± 5 kg) volunteered to participate in the present study. A within-subjects design consisted of four experimental sessions: Two sessions occurred one week before Ramadan and two others took place during Ramadan. They were scheduled at 5 p.m. and were conducted as follows: After a 10-minute warm-up either with or without listening to music, each participant performed a 5-m multiple shuttle run test, after which he was asked to answer items intended to assess his affective state during the experimental task. Our findings revealed that STMP was lower during Ramadan than before Ramadan in the no-music condition. Additionally, it was found that STMP was higher in the music condition than in the no-music condition during Ramadan, and that STMP measured before Ramadan did not differ from that measured during Ramadan in the music condition. Regarding affects, the findings revealed that enjoyment was lower during Ramadan than before Ramadan in the music condition, and that cognitive anxiety was lower in the music condition than in the no-music condition before Ramadan. Self-confidence was not influenced by the experimental conditions. This study showed that listening to music during warming-up not only would be beneficial for STMP in Ramadan fasters, but also would counteract the negative effects of Ramadan observance on STMP.

The Journal of Strength and Conditioning Research