Purpose: To explore the effects of 3 doses of caffeine on muscle strength and muscle endurance. Methods: Twenty-eight resistance-trained men completed the testing sessions under 5 conditions: no-placebo control, placebo control, and with caffeine doses of 2, 4, and 6 mg·kg−1. Muscle strength was assessed using the 1-repetition-maximum test; muscle endurance was assessed by having the participants perform a maximal number of repetitions with 60% 1-repetition maximum. Results: In comparison with both control conditions, only a caffeine dose of 2 mg·kg−1 enhanced lower-body strength (d = 0.13–0.15). In comparison with the no-placebo control condition, caffeine doses of 4 and 6 mg·kg−1 enhanced upper-body strength (d = 0.07–0.09) with a significant linear trend for the effectiveness of different doses of caffeine (P = .020). Compared with both control conditions, all 3 caffeine doses enhanced lower-body muscle endurance (d = 0.46–0.68). For upper-body muscle endurance, this study did not find significant effects of caffeine. Conclusions: This study revealed a linear trend between the dose of caffeine and its effects on upper-body strength. The study found no clear association between the dose of caffeine and the magnitude of its ergogenic effects on lower-body strength and muscle endurance. From a practical standpoint, the magnitude of caffeine’s effects on strength is of questionable relevance. A low dose of caffeine (2 mg·kg−1)—for an 80-kg individual, the dose of caffeine in 1–2 cups of coffee—may produce substantial improvements in lower-body muscle endurance with the magnitude of the effect being similar to that attained using higher doses of caffeine.

This review aimed to perform a meta-analysis examining the following: (a) acute effects of adopting an internal focus vs. external focus of attention on muscular strength; and (b) long-term effects of adopting an internal focus vs. external focus of attention during resistance training on gains in muscular strength. We searched through five databases to find eligible studies. Random-effects meta-analyses of standardized mean differences were conducted to analyze the data. Ten studies were included. In the meta-analysis for the acute effects, there was a significant positive effect of external focus on muscular strength (standardized mean difference: 0.34; 95% confidence interval: 0.22, 0.46). In the meta-analysis for the long-term effects, there was no significant difference between training with an internal focus and external focus on muscular strength gains (standardized mean difference: 0.32; 95% confidence interval: –0.08, 0.73). In the subgroup analysis for lower-body exercises, we found a significant positive effect of training with an external focus on muscular strength gains (standardized mean difference: 0.47; 95% confidence interval: 0.07, 0.87). In summary, our findings indicate an acute increase in muscular strength when utilizing an external focus of attention. When applied over the long-term, using an external focus of attention may also enhance resistance training-induced gains in lower-body muscular strength.

Children in schools are facing many academic challenges. Moreover, there is constant pressure on children and parents to maximize academic achievement. We aimed to determine the relationship between motor competence, physical fitness, and academic achievement in young school-aged children. Participants were 130 elementary school children ( mean ± SD 8.60 ± 0.61 years; 51 boys and 79 girls) from Serbia. The KTK (Körperkoordinations Test für Kinder) battery of tests was used to assess the motor competence in children; children’ physical fitness was assessed using the EUROFIT battery of tests, while academic achievement was assessed based on the children’s GPA (grade point average) scores at the end of the school year. Pearson’s r showed the weak to moderate relationships between the GPA and motor competence and physical fitness measures. The GPA correlates positively and significantly with almost all motor competence and physical fitness measures, but negatively with BMI ( p ≤ 0.05 ). However, the hierarchical linear regression indicated only the plate tapping and sit and reach as the significant predictors of the GPA. Although both tests positively affect the GPA, the plate tapping ( B = − 0.22 , p = 0.02 ) tends to influence the GPA more than the sit and reach test ( B = 0.18 , p = 0.04 ) after adjusting for effects of motor competence ( B = 0.19 , p = 0.03 ), age ( B = − 0.01 , p = 0.89 ), and BMI ( B = − 0.19 , p = 0.03 ). This study provides evidence demonstrating that academic achievement is generally associated with physical fitness and motor competence in children. However, plate taping and sit and reach were accounted as the most important predictors for academic achievement.

We aimed to examine the effects of mental fatigue on the Yo-Yo test and Loughborough soccer passing and shooting tests performance using a meta-analysis. The search for studies was performed through eight bibliographic databases (Academic Search Elite, AUSPORT, Cochrane Library, PsycInfo, PubMed/MEDLINE, Scopus, SPORTDiscus, and Web of Science). The methodological quality of the included studies was assessed using the PEDro checklist. A random-effects meta-analysis was performed for data analysis. After reviewing 599 search results, seven studies with a total of ten groups were included in the review. All studies were classified as being of good methodological quality. Mental fatigue reduced the distance covered in the Yo-Yo test (Cohen’s d: −0.49; 95% confidence interval [CI]: −0.66, −0.32). In the Loughborough soccer passing test, mental fatigue increased the original time needed to complete the test (Cohen’s d: −0.24; 95% CI: −0.46, −0.03), increased penalty time (Cohen’s d: −0.39; 95% CI: −0.46, −0.31), and decreased performance time (Cohen’s d: −0.52; 95% CI: −0.80, −0.24). In the Loughborough soccer shooting test, mental fatigue decreased points per shot (Cohen’s d: −0.37; 95% CI: −0.70, −0.04) and shot speed (Cohen’s d: −0.35; 95% CI: −0.64, −0.06). Overall, the findings presented in this review demonstrated that mental fatigue negatively impacts endurance-based running performance as well as soccer passing and shooting skills.

This study presents an overview of current scientific articles that address the reliability and validity of the 30–15 intermittent fitness test (30–15 IFT) as an assessment of aerobic capacity, as well as its use in terms of training programming. The search for and analysis of papers was conducted in accordance with PRISMA guidelines. A database search was performed through PubMed, PMC, Med Line, Cochrane Library and ScienceDirect, as well as directly from the author who first presented the IFT 30–15. Type of study: research was included in this paper on condition that (i) the original scientific paper was available in its entirety; (ii) the IFT 30–15 was used to evaluate or verify validity and reliability; and (iii) the IFT 30–15 was used for the purpose of evaluation of training programming. Of the 213 relevant studies identified, 21 were included in the quantitative analysis. All research was conducted on a sample of athletes who are exclusively engaged in team sports. As for the use of the subject test when it comes to programming individualized intermittent training to strengthen aerobic capacity, it seems that the IFT 30–15 test is appropriate and extremely useful for team sports. Regarding the reliability of tests identified in the reviewed literature, all studies indicate that the 30–15 IFT is a reliable test for assessment of aerobic capacity.