Acute caffeine intake increases muscle oxygen saturation during a maximal incremental exercise test.

AIMS: The main mechanism behind caffeine's ergogenicity lies in its tendency to bind to adenosine receptors, although other mechanisms might be involved. The aim of this investigation was to analyse the effects of caffeine on muscle oxygen saturation during exercise of increasing intensity. METHODS: Thirteen healthy and active individuals volunteered to participate in a randomized, double blind, placebo-controlled crossover trial. During 2 different trials, participants either ingested a placebo (cellulose) or 3 mg/kg of caffeine. After waiting for 60 min to absorb the substances, participants underwent a maximal ramp cycle ergometer test (25 W/min). Near infrared spectrometers were positioned on each leg's vastus lateralis to monitor tissue O2 saturation. Blood lactate concentration was measured 1 min after the end of the exercise test. RESULTS: In comparison to the placebo, the ingestion of caffeine improved the maximal wattage (258 ± 50 vs 271 ± 54 W, respectively, P < .001, effect size [ES] = 0.27; 95% confidence interval [CI] 0.14-0.35) and blood lactate concentration (11.9 ± 3.8 vs 13.7 ± 3.5 mmol/L, P = .029, ES = 0.38; 95% CI 0.14-0.75) at the end of the test. Caffeine increased muscle oxygen saturation at several exercise workloads with a main effect found in respect to the placebo (F = 6.28, P = .029; ES = 0.30 to 0.54; 95% CI 0.01-0.78). Peak pulmonary ventilation (124 ± 29 vs 129 ± 23 L/min, P = 0.035, ES = 0.25; 95% CI 0.07-0.40) and peak oxygen uptake (3.18 ± 0.70 vs 3.33 ± 0.88 L/min, P = 0.032, ES = 0.26; 95% CI 0.08-0.51) were also increased with caffeine. CONCLUSION: Acute ingestion of 3 mg/kg of caffeine improved peak aerobic performance and increased peak pulmonary ventilation. In addition, caffeine induced changes in muscle oxygen saturation during submaximal workloads, suggesting that this mechanism might also contribute to caffeine's ergogenic effect.

Time course of tolerance to adverse effects associated with the ingestion of a moderate dose of caffeine.

PURPOSE: This study aimed to identify and describe the time course of tolerance to the most common caffeine-induced side effects. METHODS: Eleven participants took part in a crossover, double-blind placebo-controlled experimental design. In one phase, participants ingested 3 mg/kg/day of caffeine for 20 days, while in another phase, they ingested a placebo. Resting heart rate and blood pressure were measured three times per week during each 20-day phase and a quantitative survey was used to categorise the magnitude of side effects. RESULTS: In the pairwise comparison with the placebo, the ingestion of caffeine increased systolic (+ 7.8 ± 10.1%, P < 0.05) and diastolic blood pressure (+ 6.4 ± 12.9% P < 0.05) for the first 8 days of ingestion, but then this effect became attenuated for both outcomes (on day 20, - 1.1 ± 4.3% and + 0.9 ± 9.6%, respectively). The ingestion of caffeine did not affect heart rate at any time point. Caffeine increased the feelings of nervousness and vigour and the rating of gastrointestinal complaints, insomnia and diuresis at several time points in the treatment (P < 0.05) and they did not disappear after 20 days of ingestion. CONCLUSIONS: The daily intake of 3 mg/kg of caffeine induced a meaningful elevation in arterial blood pressure that disappeared after 8 days. However, other caffeine-induced effects such as increased nervousness and vigour, irritability, insomnia and diuresis remained after 20 days of consecutive caffeine ingestion. Although there was clear tolerance to the effect of caffeine on blood pressure, the persistence of other side effects suggests the inconvenience of maintaining a chronic caffeine intake, at least at the dose of 3 mg/kg/day.

How Positional Constraints Affect Footedness in Football: A Notational Analysis of Five Leagues in Europe.

In elite-level soccer, the ability to take shots with both limbs from different positions in the pitch may be key to success. This research aimed to: 1) analyze footedness of elite-football players in European leagues during shooting by computing frequency of right- and left-foot use and accuracy; and 2) investigate whether an athlete's distance from the target (goal, penalty, and outside penalty area) and pitch zone (center, left, or right from the goal) can constrain foot selection during shooting. We analyzed 1826 games from the 2017/18 season, divided between: Spanish LaLiga (380 matches); Italian Serie A (380 matches); English Premier League (380 matches); German Bundesliga (306 matches); and French Ligue 1 (380 matches). Results revealed asymmetrical proportions of foot selection, favoring the preferred foot for right- and left-footed athletes. Frequency of preferred foot selection increased as a function of distance from the target (i.e., the farther the athlete, higher the percentage of preferred foot selection). Shots taken from the left side were more often performed with the right foot and vice-versa, for both left- and right-footed athletes. Interestingly, asymmetries were observed only in foot selection, but not in performance, as success rate did not vary between limbs in any position.

Running Patterns in LaLiga Before and After Suspension of the Competition Due to COVID-19.

In the first wave of the COVID-19 outbreak (spring 2020), the first division of professional soccer in Spain (LaLiga) was suspended for 12 weeks as part of the lockdown imposed by the Spanish health authorities. Professional soccer players were confined to home for 8 weeks and then a retraining period of 4 weeks was set before the first competitive match. When competition was resumed, professional soccer teams competed in a congested calendar (11 matchdays in 39 days) while some in-game regulations were altered (up to 5 substitutions, refreshment pauses). The current research presents an analysis of running patterns before suspension and after resumption of LaLiga to determine how the lockdown affected players' physical performance. To aid in this purpose, a pairwise comparison was performed of running patterns of the 2019-2020 vs. 2018-2019 season (i.e., control season). Using a two-way ANOVA (season x matchday), it was found that there was no main effect of the season on total running distance per match (P = 0.288) nor in the distances covered < 14.0 km/h (P = 0.294), at 21.0-23.9 km/h (P = 0.266), and at ≥ 24.0 km/h (P = 0.112). Only the distance at 14.0-20.9 km/h was affected by the season (P = 0.019) with a lower running distance on matchday 34 in the 2019-2020 vs. 2018-2019 season. The number of substitutions (from 2.9 to 4.5 substitutions per game; P < 0.001) and match duration (96 vs. 100 min; P < 0.001) significantly increased after resumption respect to the previous season. These data suggest that high-intensity running performance of professional soccer teams was maintained after the resumption of the competition while the alterations likely aided in the in-game regulations facilitated the maintenance of soccer physical performance.

Gender Differences in Prevalence and Patterns of Dietary Supplement Use in Elite Athletes.

Purpose: Dietary supplement use by athletes has been the topic of previous research; however, the lack of homogeneity among published studies makes it difficult to analyze the differences, if any, in the patterns of use between male and female athletes. The aim of this study was to determine gender differences in the patterns of dietary supplement use by elite athletes. Methods: A total of 504 elite athletes (329 males and 175 females) participating in individual and team sports completed a validated questionnaire on dietary supplement use during the preceding season. The dietary supplements were categorized according to the latest IOC consensus statement. Results: A higher proportion of male versus female athletes (65.3 versus 56.5%, p < .05) consumed dietary supplements. Both male and female athletes reported a similar mean consumption of dietary supplements (3.2 ± 2.1 versus 3.4 ± 2.3 supplements/season, respectively; p = .45). Protein supplements were the most commonly consumed supplements in male athletes (49.8%) and their prevalence was higher than in female athletes (29.3%, p < .01). In females, multivitamins (39.4%) and branched-chain amino acids (39.4%) were the most commonly consumed supplements and iron supplementation was more prevalent than in males (22.2% versus 10.2%, p = .01). A higher proportion of male athletes relied on themselves to plan dietary supplements use (48.0%), while female appeared to rely more on doctors (34.0%, p < .01). Conclusion: In summary, male athletes had a slightly higher prevalence in the use of supplements than their female counterparts, specifically regarding protein supplements, and were more involved in the self-prescription of supplements.

Effect of ambient temperature on fat oxidation during an incremental cycling exercise test.

Aim: The objective of this current research was to compare fat oxidation rates during an incremental cycling exercise test in a temperate vs. hot environment.Methods: Twelve healthy young participants were recruited for a randomised crossover experimental design. Each participant performed a VO2max test in a thermoneutral environment followed by two cycling ramp test trials, one in a temperate environment (18.3°C) and another in a hot environment (36.3°C). The ramp test consisted of 3-min stages of increasing intensity (+10% of VO2max) while gas exchange, heart rate and perceived exertion were measured.Results: During exercise, there was a main effect of the environment temperature on fat oxidation rate (F = 9.35, P = 0.014). The rate of fat oxidation was lower in the heat at 30% VO2max (0.42 ± 0.15 vs.0.37 ± 0.13 g/min; P = 0.042), 60% VO2max (0.37 ± 0.27 vs.0.23 ± 0.23 g/min; P = 0.018) and 70% VO2max (0.22 ± 0.26 vs.0.12 ± 0.26 g/min; P = 0.007). In addition, there was a tendency for a lower maximal fat oxidation rate in the heat (0.55 ± 0.2 vs.0.48 ± 0.2 g/min; P = 0.052) and it occurred at a lower exercise intensity (44 ± 14 vs.38% ± 8% VO2max; P = 0.004). The total amount of fat oxidised was lower in the heat (5.8 ± 2.6 vs 4.6 ± 2.8 g; P = 0.002). The ambient temperature also produced main effects on heart rate (F = 15.18, P = 0.005) and tympanic temperature (F = 25.23, P = 0.001) with no effect on energy expenditure (F = 0.01, P = 0.945).Conclusion: A hot environment notably reduced fat oxidation rates during a ramp exercise test. Exercising in the heat should not be recommended for those individuals seeking to increase fat oxidation during exercise.

Influence of Players' Maximum Running Speed on the Team's Ranking Position at the End of the Spanish LaLiga.

The maximum running speed that a football player can attain during match play has become one of the most popular variables to assess a player's physical talent. However, the influence of a player's maximum running speed on football performance has not yet been properly investigated. The aim of this study was to determine the influence of a player's peak/maximum running speed on the team's ranking position at the end of a national league. A second aim was to investigate differences in maximum running speed among playing positions. To fulfil this aim, the peak/maximum running speeds of 475 male professional football players were recorded for 38 fixtures of the Spanish first-division league (LaLiga) from the 2017-2018 season (7838 data points). Players' peak running speeds in each match were assessed with a validated multicamera tracking system and associated software (Mediacoach®). Players' maximum running speed was established as the fastest running speed they attained during the entire season. Most players (53.5% of the total) had a maximum running speed in the range of 32.0-33.9 km/h, with only three players (0.6%) with a maximum running speed of over 35.0 km/h. Overall, forwards were faster than defenders and both types of players were faster than midfielders (33.03 ± 1.35 > 32.72 ± 1.32 > 32.08 ± 1.63 km/h; p < 0.001). There was no association between teams' maximum running speed and ranking position at the end of the league (r = -0.356, p = 0.135). The correlations between teams' maximum speeds and ranking position were low for defenders (r = -0.334, p = 0.163), midfielders (r = 0.125, p = 0.610), and forwards (r = -0.065, p = 0.791). As a result, the variance in the ranking position at the end of the season explained by a team's maximum speed was of only 7.5%. Finally, as an average for all teams, players' peak running speeds remained stable at ~30.7 ± 0.6 km/h throughout the whole season. These results suggest that successful and less successful football teams have squads with players able to obtain similar maximum running speeds during match play throughout the season. Hence, players' maximum running speeds have a poor association with the team's ranking position at the end of the Spanish professional national league.

Prevalence and patterns of dietary supplement use in elite Spanish athletes.

BACKGROUND: Dietary supplementation is a common strategy to achieve a specific health status or performance benefit. Several investigations have focused on the prevalence of dietary supplement use by athletes. However, information on how athletes manage the use and purchase of dietary supplements is scarce. METHODS: Five hundred and twenty-seven high-performance athletes (346 males and 181 females), participating in individual and team sports, completed a validated questionnaire about use and purchase patterns of dietary supplements. The dietary supplements were categorized according to the International Olympic Committee (IOC) consensus. RESULTS: Sixty four percent of the athletes (n = 337) used dietary supplements (median = 3; range 1 to 12). Age, sex, type of sport, level of competition, and professionalism influenced the prevalence of dietary supplement use (all p < 0.05). The most prevalent dietary supplement consumed was proteins (41%; n = 137), followed by amino acids/BCAA-based supplements (37%; n = 124). Additionally, as per group of supplements according to IOC consensus, 18% of the supplements were rated as having a low level of scientific evidence (e.g., glutamine, HMB, L-carnitine, etc). Most athletes (45%, n = 152) purchased dietary supplements in a store and 24% (n = 81) obtained them from a sponsor. Most athletes also (42%, n = 141) reported a self-organization of supplementation and did not consult with any professional. Last, 81% (n = 273) of athletes consuming supplements did not know any platform to check supplement safety/quality. For those who do not use dietary supplements (36% of the total sample, n = 190), most reported that they do not consider supplements necessary (72%, n = 137). CONCLUSION: Dietary supplementation appears to be widely used in sport with a considerable proportion of athletes consuming supplements with low level of scientific evidence. Additionally, athletes seem to rely on inadequate sources of information and may be largely unaware of sources to detect supplement contamination.

An Extensive Comparative Analysis of Successful and Unsuccessful Football Teams in LaLiga.

The characterization of the in-game actions with the strongest influence on victory in football might be useful for designing playing styles that enhance teams' performance. The aim of this study was to analyze in-game match statistics on the top-3 and bottom-3 teams ranked in LaLiga. Accumulated offensive and defensive match statistics when playing at home and away were obtained from LaLiga for 8 consecutive seasons. Data extraction was performed by computerized video-analysis. The top-3 and bottom-3 teams were compared using independent t-test analysis and the magnitude of the difference was cataloged with effect sizes. Overall, the offensive variable with the greatest magnitude of difference in the top-3 vs. bottom-3 comparison was shooting accuracy (ES ± 90% confidence interval = 4.15 ± 0.52) followed by the number of offsides (2.25 ± 0.60) and corners (2.14 ± 0.61). However, when playing away, the offensive variable with the greatest magnitude of difference in the top-3 vs bottom-3 comparison was the number of shots (3.30 ± 0.44). The defensive variables that best differentiated top 3 - bottom 3 teams were the number of corners (2.16 ± 0.43) and shots conceded (2.04 ± 0.39). In conclusion, the match statistics that best discriminated successful from unsuccessful football teams were shooting accuracy while attacking and the number of shots conceded while defending.