Isolated but not combined ergogenic effects of caffeine and L-arginine during an isokinetic knee extension.

Introduction: The use of single supplements as ergogenic aids to enhance performance in strength-oriented sports is widespread among athletes (74%). The aim of this study was to increase knowledge about the combined effects of caffeine and L-arginine dietary supplements on performance. Methods: In this double-blind, randomized and counterbalanced crossover study, 29 participants (age: 23.2 ± 3.6 yr.; height: 181.0 ± 7.6 cm; weight: 77.0 ± 8.8 kg) each underwent six trials. In each trial performance tests were conducted to examine the effects of the supplement combinations on maximum (NmMax) and averaged torque (NmM), maximum (JMax) and averaged work (JM), the blockwise mean values of torque and work, and rate of perceived exertion (RPE) during an isokinetic leg extension task (90°·s-1) with the right leg for two sets of 40 repetitions and a set rest of 3 min on a dynamometer. The first and second trials were used to familiarize the participants with the movements in the dynamometer and no supplements were taken. After this 2-week pre-test trial, the supplement combinations of placebo/placebo, caffeine/placebo (5 mg·kg-1), L-arginine/placebo (0.15 g·kg-1), and caffeine/L-arginine (5 mg·kg-1 + 0.15 g·kg-1) were ingested. Results: The main finding of this study is the absence of an ergogenic effect of the combined supplements caffeine and L-arginine during voluntary maximal isokinetic leg extensions, although an increase of 3.5% was noted for Nmmax compared to the placebo trial. However, the administration of caffeine was able to increase the NmMax of the quadriceps femoris muscle about 5.1% (p = 0.043). In addition, caffeine (4.2%, p = 0.026) and also L-arginine (4.2%, p = 0.040) significantly increased NmM over a complete set. No single or combined supplement had an effect on muscle fatigue looking at the blockwise mean values of torque and work or RPE (all p > 0.05). Conclusion: The combination of caffeine and L-arginine was not superior to the isolated intake of both supplements in a strength-based exercise and a synergistic effect was absent.

In-season head-coach changes have positive short- and long-term effects on team perfor-mance in men's soccer-evidence from the Premier League, Bundesliga, and La Liga.

The study investigated effects of in-season head-coach changes (HCC) on the subsequent team performance in men's English, German, and Spanish premier soccer leagues. A pre-post matched-controls design involved 149 HCC-teams and 3,960 games in 2010-19. Analyses (paired t-test, repeated-measurement ANOVA) revealed five central findings. 1. An HCC was preceded by a spell of under-performance, with a particular performance collapse in the two last pre-HCC rounds. 2. Performance showed an instant, strong improvement in the first post-HCC game. 3. The performance remained increased up to 16 post-HCC rounds. 4. Post-HCC performance also exceeded teams' initial baseline performance earlier before the HCC. Accordingly, the summed performance through 8, 12, and 16 post-HCC rounds exceeded the performance through 8, 12, and 16 pre-HCC rounds (0.92 < Cohen's d < 1.17). 5. HCC-teams' pre-post performance development differed from matched non-HCC control teams. In sum, the present evidence suggests positive short, medium, and long-term HCC effects at the highest professional soccer level. Theoretical hypotheses discussed in the literature - the "common-sense," "ritual-scapegoating," "vicious-circle," and "mean-reversion" hypotheses - are partly inconsistent with the present evidence. However, the evidence is fully consistent with a new hypothesis introduced here: the hypothesis of relief from a coach's performance-suppressing factor (RCPSF).

Frequency-Dependent Reaction of the Triceps Surae Muscle of the Mouse During Electromyostimulation.

The difference in the efficacy of altered stimulation parameters in whole-body-electromyostimulation training (WB-EMS) has hardly been examined. Higher impulse frequencies (>50 Hz) might be most adequate for strength gains because of the force frequency relationship (FFR), which describes a greater force production by increasing the applied frequency. Frequencies below this value, however, also seem to have positive influences on muscle strength increases. Therefore, the aim of this study was to analyze possible muscle length changes to different stimulation frequencies of the dissected mouse triceps surae muscle. A bending rod transducer was used to measure and compare changes in muscle lengths at different frequencies in relation to the initial length in the prepared muscle. We found significant differences between the muscle shortening at different frequencies (p < 0.001). At 20 Hz the largest muscle shortening was observed (20 Hz = 3.32 ± 2.06, 60 Hz = 0.77 ± 0.58, 85 Hz = 0.32 ± 0.29, 100 Hz = 0.31 ± 0.29). From a frequency of 60 Hz, the muscle shortening decreased progressively, at stimulation frequencies above 60 Hz the lowest shortenings were recorded. The results demonstrate a different behavior of the isolated triceps surae muscle of the mouse in an ex vivo environment. Even if there is no FFR in this investigation, the results indicate a higher metabolic demand using higher frequencies in electromyostimulation, despite the experimental execution in ex vivo design. Therefore, future studies should take this faster fatigue into account when drawing up training protocols in order to counteract possible frequency modulations.

Sport activities differentiating match-play improvement in elite youth footballers - a 2-year longitudinal study.

This study examined contributions of different types of sport activities to the development of elite youth soccer performance. Match-play performance of 44 German male players was assessed by expert coaches twice, 24 months apart (age 11.1-13.1 years), based on videotaped 5v5 matches. Player pairs were matched by identical age and initial performance at t1. Each player was assigned to a group of either "Strong" or "Weak Responders" based on a higher or lower subsequent performance improvement at t2 within each pair (mean Δperformance 29% vs. 7%). A questionnaire recorded current and earlier amounts of organised practice/training and non-organised sporting play, in soccer and other sports, respectively. Group comparison revealed that "Strong Responders" accumulated more non-organised soccer play and organised practice/training in other sports, but not more organised soccer practice/training. Subsequent multivariate analyses (multiple linear regression analyses (MLR)) highlighted that higher resultant match-play performance at t2 was accounted for R2adj = 0.65 by performance at t1, together with more non-organised soccer play and organised engagement in other sports, respectively, and greater current, but less earlier volume of organised soccer. The findings suggest that variable early sporting experience facilitates subsequent soccer performance development in German elite youth footballers.