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

The present study aimed to investigate the concomitant effects of Ramadan intermittent fast (RIF) and muscle fatigue on neuromuscular performances and reaction times in young trained athletes. Eight karate players (17.2 ± 0.5 years) were tested on three sessions: during a control period (S1: one week before Ramadan), and during the first (S2) and the fourth week of RIF (S3). Dietary intake and anthropometric measurements were assessed before each session. During each test session, participants performed maximal voluntary isometric contractions (MVC) and a submaximal contraction at 75 % MVC until exhaustion (T lim ) of the right elbow flexors. Surface electromyography was recorded from biceps brachii muscle during MVC and T lim . Simple (SRT) and choice (CRT) reaction times were evaluated at rest and just after T lim in a random order. The total daily energy (S2: +19.5 %, p < 0.05; S3: +27.4 %, p < 0.01) and water (S2: +26.8 %, p < 0.01; S3: +23.2 %, p < 0.05) intake were significantly increased during RIF. However, neither body mass nor body mass index was altered by RIF (F (2,14) = 0.80, p = 0.47 and F (2,14) = 0.78, p = 0.48, respectively). In addition, T lim (F (2,14) = 2.53, p = 0.12), MVC (F (2,14) = 0.51, p = 0.61) and associated electrical activity (F (2,14) = 0.13, p = 0.88) as well as neuromuscular efficiency (F (2,14) = 0.27, p = 0.76) were maintained during RIF. Moreover, neither SRT nor CRT was affected by RIF (F (2,14) = 1.82, p = 0.19 and F (2,14) = 0.26, p = 0.78, respectively) or neuromuscular fatigue (F (1,7) = 0.0002, p = 0.98 and F (1,7) = 3.78, p = 0.09, respectively). The present results showed that RIF did not adversely affect the neuromuscular performances and anthropometric parameters of elite karate athletes who were undertaking their usual training schedule. In addition, neither RIF nor neuromuscular fatigue poorly affects reaction times in elite karate athletes.

The aim of this study was to investigate the acute effects of whole-body vibration (WBV) on Repeated Sprint Ability (RSA). Seventeen male soccer players (16.71±0.47 y) performed three RSA tests (Randomized crossover study design). The second RSA test was done with WBV (RSA2) to assess the effect of WBV. The studied variables were: best time (BT), worst time (WT), total time (TT), the fatigue index (FI) of RSA, and post-test blood lactate (BLa). ANOVA with repeated measures showed no differences between RSA1 and RSA3, while there were significant differences in all variables studied. TT= [RSA2 0.93% and 1.68% lower than RSA1 and RSA3 respectively; p<0.05], BLa= [RSA2 16.97% and 14.73% greater than RSA1 and RSA3 respectively; p<0.001], WT= [RSA2 1.90% and 2.93% lower than RSA1 and RSA3 respectively; p<0.01], and FI = [RSA2 30.64% and 40.15% lower than RSA1 and RSA3 respectively; p<0.0001]. When comparing individual sprints, WBV showed a significant effect at the 5^th sprint: RSA2 2.29 % and 2.95% lower than RSA1 and RSA3 respectively (p<0.005), while at the 6^th sprint: RSA2 2.75% and 4.09% lower than RSA1 and RSA3 respectively; p<0.005. In conclusion, when applying WBV during the recovery periods of Repeated Sprint Ability efforts, most of the performance variables improved.

There is a conflict in the literature with regard to effects of the Ramadan intermittent fasting (RIF) on body composition and neuromuscular performance. The purpose of this pilot study was to examine the effect of the RIF on body mass/composition and neuromuscular performance during maximal voluntary contraction (MVC) and a muscle endurance exercise (T_lim ) of the knee extensors. Eight adolescents (17.2 ± 0.5 years) karate players were tested. Anthropometric variables (i.e. body mass, body mass index, fat mass and lean body mass) were evaluated 7 days before Ramadan (T1), and on days 7 (T2) and 28 (T3) of Ramadan. Each subject performed three MVC and a T_lim at 75% of MVC at T1, T2, and T3. Surface electromyographic (EMG) activity of vastus lateralis and vastus medialis was recorded during these neuromuscular tests. The anthropometric variables were unaltered by RIF. Likewise, there was no significant effect of RIF on the MVC (P = 0.29) and the T_lim (P = 0.22). This result was in accordance with the absence of change in both EMG activity level during MVC and in the rate of changes in EMG parameters (EMG activity level and frequency content) during T_{li m} . The results of the present study suggest that RIF does not impair maximal force generating capacity and muscle endurance at 75% of MVC. Therefore, Muslim experienced athletes could maintain their neuromuscular performance level by undertaking usual training loads during RIF.

The objective of this study was to determine and compare leg asymmetry between preferred dominant and non-dominant legs in muscular power and balance among sub-elite soccer (football) players in Qatar. Thirty-two professional local soccer players from the Qatar Stars League (Second Division) participated in the study (23.1 ± 6.1 years). They were classified according to their preferred dominant leg (preferred leg to kick the ball). Twenty-two players had a right dominant leg, and the remaining ten had a left dominant leg. Countermovement jump (CMJ) was used to measure unilateral and bilateral vertical jump performances. The Y-balance test (YBT) was used to assess dynamic balance. No significant differences were found between the dominant and non-dominant leg for CMJ flight height (p > 0.05; asymmetry index (AI) = 1.83 ± 11.46) or the relative and absolute reach distance derived from the YBT (p > 0.05; AI (relative) = −0.45 ± 9.68, AI (absolute) = −0.60 ± 12.3). Bilateral asymmetry in dynamic balance was not significant for any of the anterior, posteromedial, or the posterolateral reaching directions (p > 0.05). The selected football players demonstrated an acceptable level of leg symmetry for power and dynamic balance. These findings may prove helpful for the assessment and evaluation of talents and should help to develop and optimize training regimes.