Nicola Luigi Bragazzi, Kayvan Khoramipour, Anis Chaouachi, and Karim Chamari
Wissem Dhahbi, Anis Chaouachi, Anis Ben Dhahbi, Jodie Cochrane, Laurence Chèze, Angus Burnett, and Karim Chamari
To examine differences between ground-reaction-force (GRF)-based parameters collected from 5 types of plyometric push-ups. Between-trials reliability and the relationships between parameters were also assessed.
Thirty-seven highly active commando soldiers performed 3 trials of 5 variations of the plyometric push-up in a counterbalanced order: standard countermovement push-up (SCPu), standard squat push-up (SSPu), kneeling countermovement push-up (KCPu), kneeling squat push-up (KSPu), and drop-fall push-up (DFPu). Vertical GRF was measured during these exercises using a portable Kistler force plate. The GRF applied by the hands in the starting position (initial force supported), peak GRF and rate of force development during takeoff, flight time, impact force, and rate of force development impact on landing were determined.
During standard-position exercises (SCPu and SSPu) the initial force supported and impact force were higher (P < .001) than with kneeling exercises (KCPu, KSPu, and DFPu). The peak GRF and rate of force development during takeoff were higher (P < .001) in the countermovement push-up exercises ([CMP] SCPu, KCPu, and DFPu) than squat push-up exercises ([SP] SSPu and KSPu). Furthermore, the flight time was greater (P < .001) during kneeling exercises than during standard-position exercises. A significant relationship (P < .01) between impact force and the rate of force development impact was observed for CMP and SP exercises (r = .83 and r = .62, respectively). The initial force supported was also negatively related (P < .01) to the flight time for both CMP and SP (r = –.74 and r = –.80, respectively). It was revealed that the initial force supported and the peak GRF during takeoff had excellent reliability; however, other parameters had poor absolute reliability.
It is possible to adjust the intensity of plyometric push-up exercises and train athletes’ muscle power by correctly interpreting GRF-based parameters. However, caution is required as some parameters had marginal absolute reliability.
Aymen Ben Othman, Mehdi Chaouachi, Issam Makhlouf, Jonathan P. Farthing, Urs Granacher, David G. Behm, and Anis Chaouachi
Purpose: Whereas cross-education has been extensively investigated with adults, there are far fewer youth investigations. Two studies suggested that children had greater global responses to unilateral knee extensor fatigue and training, respectively, than adults. The objective of this study was to compare global training responses and cross-education effects after unilateral elbow flexion (EFlex) and leg press (LP) training. Methods: Forty-three prepubertal youths (aged 10–13 y) were randomly allocated into dominant LP (n = 15), EFlex (n = 15) training groups, or a control (n = 13). Experimental groups trained 3 times per week for 8 weeks and were tested pretraining and posttraining for ipsilateral and contralateral 1-repetition maximum LP; knee extensor, knee flexors, elbow flexors; and handgrip maximum voluntary isometric contractions (MVIC), and countermovement jump. Results:In comparison to no significant changes with the control group, dominant elbow flexors training demonstrated significant ( P < .001) improvements only with ipsilateral and contralateral upper body testing (EFlex MVIC [15.9–21.5%], EFlex 1-repetition maximum [22.9–50.8%], handgrip MVIC [5.5–13.8%]). Dominant LP training similarly exhibited only significant ( P < .001) improvements for ipsilateral and contralateral lower body testing (LP 1-repetition maximum [59.6–81.8%], knee extensor MVIC [12.4–18.3%], knee flexor MVIC [7.9–22.3%], and countermovement jump [11.1–18.1%]). Conclusions: The ipsilateral and contralateral training adaptations in youth were specific to upper or lower body training, respectively.
Hichem Souissi, Anis Chaouachi, Karim Chamari, Mohamed Dogui, Mohamed Amri, and Nizar Souissi
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 Ppeak and 6% for Pmean 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.
Raouf Hammami, Anis Chaouachi, Issam Makhlouf, Urs Granacher, and David G. Behm
Balance, strength and power relationships may contain important information at various maturational stages to determine training priorities.
The objective was to examine maturity-specific relationships of static/dynamic balance with strength and power measures in young male athletes.
Soccer players (N = 130) aged 10–16 were assessed with the Stork and Y balance (YBT) tests. Strength/power measures included back extensor muscle strength, standing long jump (SLJ), countermovement jump (CMJ), and 3-hop jump tests. Associations between balance with strength/power variables were calculated according to peak-height-velocity (PHV).
There were significant medium-large sized correlations between all balance measures with back extensor strength (r = .486–.791) and large associations with power (r = .511–.827). These correlation coefficients were significantly different between pre-PHV and circa PHV as well as pre-PHV and post-PHV with larger associations in the more mature groups. Irrespective of maturity-status, SLJ was the best strength/power predictor with the highest proportion of variance (12–47%) for balance (i.e., Stork eyes opened) and the YBT was the best balance predictor with the highest proportion of variance (43–78%) for all strength/power variables.
The associations between balance and muscle strength/power measures in youth athletes that increase with maturity may imply transfer effects from balance to strength/power training and vice versa in youth athletes.
Anis Chaouachi, Monoem Haddad, Carlo Castagna, Del P. Wong, Fathi Kaouech, Karim Chamari, and David G. Behm
The objective of this study was to examine the response and recovery to a single set of maximal, low and high angular velocity isokinetic leg extension-flexion contractions with boys. Sixteen boys (11–14 yrs) performed 10 isokinetic contractions at 60°.s−1 (Isok60) and 300°.s−1 (Isok300). Three contractions at both velocities, blood lactate and ratings of perceived exertion were monitored pretest and at 2, 3, 4, and 5 min of recovery (RI). Participants were tested in a random counterbalanced order for each velocity and recovery period. Only a single contraction velocity (300°.s−1 or 60°.s−1) was tested during recovery at each session to remove confounding influences between the recovery intervals. Recovery results showed no change in quadriceps’ power at 300°.s−1, quadriceps’ power, work and torque at 60°.s−1 and hamstrings’ power and work with 60°.s−1. There was an increase during the 2 min RI in hamstrings’ power, work and torque and quadriceps’
Hichem Souissi, Hamdi Chtourou, Anis Chaouachi, Mohamed Dogui, Karim Chamari, Nizar Souissi, and Mohamed Amri
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.
Wissem Dhahbi, Anis Chaouachi, Johnny Padulo, David G. Behm, and Karim Chamari
To examine the concurrent validity and absolute and relative reliabilities of a commando-specific power test.
21 antiterrorism commandos.
All participants were assessed on a 5-m rope-climbing test (RCT) and the following tests: pull-ups, push-ups, estimated-1-repetition-maximum (est-1RM), medicine-ball put, and handgrip-strength test. The stopwatch method related to the execution time (ET) was validated by comparison with video motion analysis. The best individual attempt of 3 trials was kept for analysis, and the performance was expressed in absolute power output (APO) and body-mass relative power output (RPO).
Stopwatch assessment had an excellent criterion validity (r = .99, P < .001), intraclass correlation coefficient (ICC3,1) of .98, standard errors of measurement (SEM%) of 1.19%, bias ± the 95% limits of agreement of 0.03 ± 0.26 s, and minimal detectable change (MDC95) of 0.51 s. The ET, APO, and RPO were significantly correlated (P < .05) with all cited tests (absolute-value r range .55−.98), while est-1RM was not significantly correlated with the other tests. Test-retest reliability coefficients were excellent for ET, APO, and RPO (ICC3,1 > .90). The SEM% values for the ET, APO, and RPO were all under 5% (range 3.73−4.52%), all being smaller than the corresponding smallest worthwhile change. The coefficients of variation for the ET, APO, and RPO were all under 10%. %MDC95 ranged from 10.37% to 12.53%.
Considering the strong concurrent validity and excellent test–retest reliability, the RCT is simple to administer, has ecological validity, and is a valid specific field test of upper-body power for commandos and, in addition, can be accurately assessed with a stopwatch.
Chaouachi Anis, John B. Leiper, Souissi Nizar, Aaron J. Coutts, and Chamari Karim
The month-long diurnal Ramadan fast imposes a major challenge to Islamic athletes. Sporting events are programmed throughout the year, with the result that training and competition are often scheduled during Ramadan. The small numbers of well-controlled studies that have examined the effects of Ramadan on athletic performance suggest that few aspects of physical fitness are negatively affected, and only modest decrements are observed. Whereas subjective feelings of fatigue and other mood indicators are often cited as implying additional stress on the athlete throughout Ramadan, most studies show these measures may not be reflected in decreases in performance. The development and early implementation of sensible eating and sleeping strategies can greatly alleviate the disruptions to training and competitiveness, thus allowing the athlete to perform at a high level while undertaking the religious intermittent fast. Nevertheless, further research is required to understand the mechanisms and energy pathways that allow athletes to maintain their performance capacities during Ramadan, and which factors are responsible for the observed decrements in performance of some individuals.
Olivier Galy, Olivier Hue, Karim Chamari, Alain Boussana, Anis Chaouachi, and Christian Préfaut
To study the relationship between performance and exercise-induced arterial hypoxemia (EIAH), 5 internationally ranked (INT) and 8 regionally ranked (REG) triathletes performed cycle-run successions (CR) and control runs (R) in competitionlike conditions: at ≍75% VO2max.
Ventilatory parameters and oxyhemoglo-bin saturation (SpO2) data were collected continuously. Arteriolized partial pressure in O2 (PaO2) and alveolar ventilation (VA) were measured before and after cycling (CRcycle), the successive run (CRrun), and R. Pulmonary diffusing capacity (DLco) was measured at rest and 10 minutes post-CR. Training and short-distance triathlon data were collected.
INT showed signifcantly greater experience than REG in competition years (P > .05), training regimen (P > .05), and swimming (P > .05), and cycling (P > .05) volumes; running showed a trend (P < .06). Cycling, running, and total triathlon performances were significantly higher in INT than REG (P > .01). SpO2 during CR dropped significantly more in INT than in REG. Both groups showed significant inverse correlations between the magnitude of the SpO2 change from CRcy-cle to CRrun and the triathlon running time (r = −0.784; P < .05 and r = −0.699; P < .05; respectively). When compared with CRcycle, PaO2 significantly decreased and VA significantly increased after CRrun and R in both groups (P < .01). DLco significantly dropped between pre- and postexercise in CR and R with no between-group difference (P < .05).
EIAH was aggravated in higher performers during simulated cycle-run segments, related to longer experience and heavier training regimens. Possibly, relative hypoventilation caused this aggravated EIAH in INT, although pulmonary diffusion limitation was observed in both groups. Beyond EIAH severity, the magnitude of SpO2 variations during the cycle-run transition may affect triathlon running performance.