Mohamed Amri

Effect of Concurrent Endurance and Circuit Resistance Training Sequence on Muscular Strength and Power Development

Chtara, M, Chaouachi, A, Levin, GT, Chaouachi, M, Chamari, K, Amri, M, Laursen, PB. Effect of concurrent endurance and circuit resistance-training sequence on muscular strength and power development. J Strength Cond Res 22: 1037-1045, 2008-The purpose of this study was to examine the influence of the sequence order of high-intensity endurance training and circuit training on changes in muscular strength and anaerobic power. Forty-eight physical education students (ages, 21.4 ± 1.3 years) were assigned to 1 of 5 groups: no training controls (C, n = 9), endurance training (E, n = 10), circuit training (S, n = 9), endurance before circuit training in the same session, (E+S, n = 10), and circuit before endurance training in the same session (S+E, n = 10). Subjects performed 2 sessions per week for 12 weeks. Resistance-type circuit training targeted strength endurance (weeks 1-6) and explosive strength and power (weeks 7-12). Endurance training sessions included 5 repetitions run at the velocity associated with &OV0312;o2max (&OV0312;o2max) for a duration equal to 50% of the time to exhaustion at &OV0312;o2max; recovery was for an equal period at 60% &OV0312;o2max. Maximal strength in the half squat, strength endurance in the 1-leg half squat and hip extension, and explosive strength and power in a 5-jump test and countermovement jump were measured pre- and post-testing. No significant differences were shown following training between the S+E and E+S groups for all exercise tests. However, both S+E and E+S groups improved less than the S group in 1 repetition maximum (p < 0.01), right and left 1-leg half squat (p < 0.02), 5-jump test (p < 0.01), peak jumping force (p < 0.05), peak jumping power (p < 0.02), and peak jumping height (p < 0.05). The intrasession sequence did not influence the adaptive response of muscular strength and explosive strength and power. Circuit training alone induced strength and power improvements that were significantly greater than when resistance and endurance training were combined, irrespective of the intrasession sequencing.

Effect Of Ramadan Intermittent Fasting On Aerobic And Anaerobic Performance And Perception Of Fatigue In Male Elite Judo Athletes

Chaouachi, A, Coutts, AJ, Chamari, K, Wong, DP, Chaouachi, M, Chtara, M, Roky, R, and Amri, M. Effect of ramadan intermittent fasting on aerobic and anaerobic performance and perception of fatigue in male elite judo athletes. J Strength Cond Res 23(9): 2702-2709, 2009-The aim of the present study was to evaluate the influence of the Ramadan intermittent fast (RIF) on aerobic and anaerobic exercise performance in elite judo athletes (Judokas) maintaining their usual training loads. Physical performance tests (squat jump [SJ]), countermovement jump [CMJ], 30-second repeated jump, 30-m sprint, and the multistage fitness test) and fatigue scores were measured in 15 elite Judokas on 4 occasions: before Ramadan (T1), at the beginning of Ramadan (T2), at the end of Ramadan (T3) and 3 weeks after Ramadan. Results showed that 30-m sprint performance, multistage shuttle run test, SJ, and CMJ did not change during Ramadan. However, average power during the 30-second repeated jump test was slightly lower at the end of Ramadan (22.4 ± 2.3 W/kg; P < 0.05) than before Ramadan (23.4 ± 2.3 W/kg). There was a minor reduction of 1.3 kg in body mass and an increase in total fatigue scores (T2, 19 ± 5; T3, 16 ± 4; both P < 0.05) during Ramadan in comparison with the control period (T1, 12 ± 3). These results show that the RIF has little effect on aerobic performance and on very short duration sprinting and jumping test performance in elite Judokas. Additionally, experienced athletes can maintain both sufficient energy intake and normal training loads during the RIF. The slight reduction in the 30-second jump test may be associated with reduced central drive and body mass. Collectively, these results suggest that the RIF has little effect on the performance of experienced Judokas, but Muslim athletes who train during the RIF should carefully periodize their training load and monitor their food intake and fatigue levels to avoid performance decrements.

Haematological, inflammatory, and immunological responses in elite judo athletes maintaining high training loads during Ramadan

During Ramadan, Muslims abstain from food and fluid intake from dawn to sunset for 1 month. These behavioural changes that accompany Ramadan may impact upon Muslim athletes who continue to train intensely. The aim of the present study was to evaluate the effect of Ramadan intermittent fasting (RIF) on the haematological, inflammatory, and immunological measures in elite judo athletes maintaining their usual high training loads. Haematological markers of inflammation, hormones, and immune status were studied in 15 elite male judo athletes before, during, and after Ramadan. The RIF produced small but significant changes in inflammatory, hormonal, and immunological profiles in judo athletes. Serum C-reactive protein increased from 2.93 +/- 0.26 mg.L-1 pre-Ramadan to 4.60 +/- 0.51 mg.L-1 at the end of Ramadan. Haptoglobin and antitrypsin also significantly increased at different phases during Ramadan, whereas homocysteine and prealbumin remained relatively unchanged. Albumin decreased slightly by mid-Ramadan, then recovered. Immunoglobulin Aincreased from 1.87 +/- 0.56 g.L-1 before Ramadan to 2.49 +/- 0.75 g.L-1 at the end, and remained high 3 weeks after. There were no changes in the leucocyte cell counts throughout the study. The mean blood level of thyroid-stimulating hormone and free thyroxine increased significantly during RIF. Most of these changes were within the normal ranges. These results suggest that athletes who continue to train intensely during Ramadan are liable to experience a myriad of small fluctuations in hormones, immunoglobulins, antioxidants, and inflammatory responses.

Ten minutes of dynamic stretching is sufficient to potentiate vertical jump performance characteristics

Turki, O, Chaouachi, A, Drinkwater, EJ, Chtara, M, Chamari, K, Amri, M, and Behm, DG. Ten minutes of dynamic stretching is sufficient to potentiate vertical jump performance characteristics. J Strength Cond Res 25(9): 2453-2463, 2011—The current literature recommends dynamic rather than static stretching for the athletic warm-up. Dynamic stretching and various conditioning stimuli are used to induce potentiation in subsequent athletic performance. However, it is unknown as to which type of activity in conjunction with dynamic stretching within a warm-up provides the optimal potentiation of vertical jump performance. It was the objective of the study to examine the possible potentiating effect of various types of conditioning stimuli with dynamic stretching. Twenty athletes participated in 6 protocols. All the experimental protocols included 10 minutes of dynamic stretching. After the dynamic stretching, the subjects performed a (a) concentric (DS/CON): 3 sets of 3 repetition maximum deadlift exercise; (b) isometric (DS/ISOM): 3 sets of 3-second maximum voluntary contraction back squats; (c) plyometric (DS/PLYO): 3 sets of 3 tuck jumps; (d) eccentric (DS/ECC): 3 modified drop jumps; (e) dynamic stretching only (DS), and (f) control protocol (CON). Before the intervention and at recovery periods of 15 seconds, 4, 8, 12, 16, and 20 minutes, the participants performed 1-2 maximal countermovement jumps. The DS and DS/CON protocols generally had a 95-99% likelihood of exceeding the smallest worthwhile change for vertical jump height, peak power, velocity and force. However, the addition of the deadlift to the DS did not augment the potentiating effect. Time-to-peak potentiation was variable between individuals but was most consistent between 3 and 5 minutes. Thus, the volume and the intensity associated with 10 minutes of dynamic stretching were sufficient to provide the potentiation of vertical jump characteristics. Additional conditioning activities may promote fatigue processes, which do not permit further potentiation.

The Effect of Warm-Ups Incorporating Different Volumes of Dynamic Stretching on 10- and 20-m Sprint Performance in Highly Trained Male Athletes

Turki, O, Chaouachi, A, Behm, DG, Chtara, H, Chtara, M, Bishop, D, Chamari, K, and Amri, M. The effect of warm-ups incorporating different volumes of dynamic stretching on 10- and 20-m sprint performance in highly trained male athletes. J Strength Cond Res 26(1): 63–72, 2012—Recently, athletes have transitioned from traditional static stretching during warm-ups to incorporating dynamic stretching routines. However, the optimal volume of dynamic drills is yet to be identified. The aim of this repeated-measures study was to examine varying volumes (1, 2, and 3 sets) of active dynamic stretching (ADS) in a warm-up on 10- and 20-m sprint performance. With a within-subject design, 16 highly trained male participants (age: 20.9 ± 1.3 years; height: 179.7 ± 5.7 cm; body mass: 72.7 ± 7.9 kg; % body fat: 10.9 ± 2.4) completed a 5-minute general running warm-up before performing 3 preintervention measures of 10- to 20-m sprint. The interventions included 1, 2, and 3 sets of active dynamic stretches of the lower-body musculature (gastrocnemius, gluteals, hamstrings, quadriceps, and hip flexors) performed approximately 14 times for each exercise while walking (ADS1, ADS2, and ADS3). The active dynamic warm-ups were randomly allocated before performing a sprint-specific warm-up. Five minutes separated the end of the warm-up and the 3 postintervention measures of 10- to 20-m sprints. There were no significant time, condition, and interaction effects over the 10-m sprint time. For the 0- to 20-m sprint time, a significant main effect for the pre-post measurement (F = 10.81; p < 0.002), the dynamic stretching condition (F = 6.23; p = 0.004) and an interaction effect (F = 41.19; p = 0.0001) were observed. A significant decrease in sprint time (improvement in sprint performance) post-ADS1 (2.56%, p = 0.001) and post-ADS2 (2.61%, p = 0.001) was observed. Conversely, the results indicated a significant increase in sprint time (sprint performance impairment) post-ADS3 condition (2.58%, p = 0.001). Data indicate that performing 1–2 sets of 20 m of active dynamic stretches in a warm-up can enhance 20-m sprint performance. The results delineated that 3 sets of ADS repetitions could induce acute fatigue and impair sprint performance within 5 minutes of the warm-up.

Exercise-induced bronchoconstriction and atopy in Tunisian athletes

BackgroundThis study is a cross sectional analysis, aiming to evaluate if atopy is as a risk factor for exercise induced bronchoconstriction (EIB) among Tunisian athletes.MethodsAtopy was defined by a skin prick test result and EIB was defined as a decrease of at least 15% in forced expiratory volume in one second (FEV1) after 8-min running at 80–85% HRmaxTheo. The study population was composed of 326 athletes (age: 20.8 ± 2.7 yrs – mean ± SD; 138 women and 188 men) of whom 107 were elite athletes.ResultsAtopy was found in 26.9% (88/326) of the athletes. Post exercise spirometry revealed the presence of EIB in 9.8% of the athletes including 13% of the elite athletes. Frequency of atopy in athletes with EIB was significantly higher than in athletes without EIB [62.5% vs 23.1%, respectively].ConclusionThis study showed that atopic Tunisian athletes presented a higher risk of developing exercise induced bronchoconstriction than non-atopic athletes.

Greater effects of high- compared with moderate-intensity interval training on cardio-metabolic variables, blood leptin concentration and ratings of perceived exertion in obese adolescent females

This study examined the effects of high- vs. moderate-intensity interval training on cardiovascular fitness, leptin levels and ratings of perceived exertion (RPE) in obese female adolescents. Forty-seven participants were randomly assigned to one of three groups receiving either a 1:1 ratio of 15 s of effort comprising moderate-intensity interval training (MIIT at 80% maximal aerobic speed: MAS) or high-intensity interval training (HIIT at 100% MAS), with matched 15 s recovery at 50% MAS, thrice weekly, or a no-training control group. The HIIT and MIIT groups showed improved (p < 0.05) body mass (BM), BMI Z-score, and percentage of body fat (%BF). Only the HIIT group showed decreased waist circumference (WC) (p = 0.017). The effect of exercise on maximal oxygen uptake (VO2max) was significant (p = 0.019, ES = 0.48 and p = 0.010, ES = 0.57, HIIT and MIIT, respectively). The decrease of rate-pressure product (RPP) (p < 0.05, ES = 0.53 and ES = 0.46, HIIT and MIIT, respectively) followed the positive changes in resting heart rate and blood pressures. Blood glucose, insulin level and the homeostasis model assessment index for insulin decreased (p < 0.05) in both training groups. Significant decreases occurred in blood leptin (p = 0.021, ES = 0.67 and p = 0.011, ES = 0.73) and in RPE (p = 0.001, ES = 0.76 and p = 0.017, ES = 0.57) in HIIT and MIIT, respectively. In the post-intervention period, blood leptin was strongly associated with %BF (p < 0.001) and VO2max (p < 0.01) in the HIIT and MIIT groups, respectively, while RPE was strongly associated with BM (p < 0.01) in the HIIT group. The results suggest that high-intensity interval training may produce more positive effects on health determinants in comparison with the same training mode at a moderate intensity.

Plyometric exercise combined with high-intensity interval training improves metabolic abnormalities in young obese females more so than interval training alone

The aim of this study was to compare the effects of 12 weeks of high-intensity interval training (HIIT) with the effects of 12 weeks of plyometric exercise combined with HIIT (P+HIIT) on anthropometric, biochemical, and physical fitness data in young obese females. Sixty-eight participants (age, 16.6 ± 1.3 y; body mass, 82.8 ± 5.0 kg; body fat, 39.4% ± 3.3%; body mass index z score, 2.9 ± 0.4) were assigned to 1 of 3 groups: HIIT (2 blocks per session of 6-8 bouts of 30-s runs at 100% velocity at peak oxygen uptake, with 30-s active recovery between bouts at 50%velocity at peak oxygen uptake (n = 23)); P+HIIT (2 blocks per session of 3 different 15-s plyometric exercises with 15-s passive recoveries, totaling 2 min for each plyometric exercise + the same HIIT program (n = 26)); or control (no exercise (n = 19)). Anthropometric (body mass, body mass index z score, body fat, lean body mass, and waist circumference), biochemical (plasma glucose, insulin, leptin and adiponectin concentrations, leptin/adiponectin ratio, and homeostasis model assessment of insulin resistance (HOMA-IR)), physical fitness (peak oxygen uptake, velocity at peak oxygen uptake, squat jump, and countermovement jump performances), and energy intake data were collected. Both training programs improved the anthropometric, biochemical, and physical fitness variables. However, the P+HIIT program induced greater improvements than did the HIIT program in lean body mass (+3.0% ± 1.7%), plasma glucose and leptin concentrations (-11.0% ± 4.7% and -23.8% ± 5.8%, respectively), plasma leptin/adiponectin ratio (-40.9% ± 10.9%), HOMA-IR (-37.3% ± 6.2%), and squat jump performance (22.2% ± 7.5%). Taken together, these findings suggest that adding plyometric exercises to a HIIT program may be more beneficial than HIIT alone in obese female adolescents.

Eight weeks of dynamic stretching during warm-ups improves jump power but not repeated or single sprint performance

Abstract There is abundant research involving the acute effects of stretching on subsequent performance; however, there is little information on dynamic stretch training programmes on range of motion (ROM), power and speed measures. It was the objective of this research to examine the training consequences of active dynamic stretching (ADS) and static dynamic stretching (SDS). A repeated measures design compared the effects of 8 weeks of warm-ups incorporating two dynamic stretch modalities: ADS and SDS on squat jump (SJ), countermovement jump (CMJ), 20-m sprint performances and repeated sprint ability (RSA) and hip ROM in 37 male soccer players. SJ height (SDS: 4.6%; ADS: 5.3%; p <0.05), CMJ height (SDS: 5.3%; ADS: 3.4%; p<0.05), CMJ force (SDS: 7.2%; ADS: 12.7%; p<0.001) and CMJ peak power (SDS: 3.9%; ADS: 3.3%; p<0.05) increased significantly after SDS and ADS training compared to the control group (no significant change). Sprint performance and RSA were not affected by either of the dynamic stretch training regimens. The SDS and ADS training programmes elicited similar improvements in flexibility (SDS: 57.6%; ADS: 45.1%; p<0.01) compared to the non-significant changes in the control group. The inclusion of ADS and SDS within the regular warm-up of an 8-week training programme can improve not only flexibility but also jump power measures as well.

Exercise-induced bronchoconstriction in Tunisian elite athletes is underdiagnosed

Many studies have shown an increased risk of developing exercise-induced bronchoconstriction among the athletic population, particularly at the elite level. Subjective methods for assessing exercise-induced bronchoconstriction such as surveys and questionnaires have been used but have resulted in an underestimation of the prevalence of airway dysfunction when compared with objective measurements. The aim of the present study was to compare the prevalence of exercise-induced bronchoconstriction among Tunisian elite athletes obtained using an objective method with that using a subjective method, and to discuss the possible causes and implications of the observed discrepancy. As the objective method we used spirometry before and after exercise and for the subjective approach we used a medical history questionnaire. All of the recruited 107 elite athletes responded to the questionnaire about respiratory symptoms and medical history and underwent a resting spirometry testing before and after exercise. Post-exercise spirometry revealed the presence of exercise-induced bronchoconstriction in 14 (13%) of the elite athletes, while only 1.8% reported having previously been diagnosed with asthma. In conclusion, our findings indicate that medical history-based diagnoses of exercise-induced bronchoconstriction lead to underestimations of true sufferers.