Scientific information about the effects of caffeine intake on combat sport performance is scarce and controversial. The aim of this study was to investigate the effectiveness of caffeine to improve Brazilian Jiu-jitsu (BJJ)-specific muscular performance. Fourteen male and elite BJJ athletes (29.2 ± 3.3 years; 71.3 ± 9.1 kg) participated in a randomized double-blind, placebo-controlled and crossover experiment. In two different sessions, BJJ athletes ingested 3 mg kg(-1) of caffeine or a placebo. After 60 min, they performed a handgrip maximal force test, a countermovement jump, a maximal static lift test and bench-press tests consisting of one-repetition maximum, power-load, and repetitions to failure. In comparison to the placebo, the ingestion of the caffeine increased: hand grip force in both hands (50.9 ± 2.9 vs. 53.3 ± 3.1 kg; respectively p < .05), countermovement jump height (40.6 ± 2.6 vs. 41.7 ± 3.1 cm; p = .02), and time recorded in the maximal static lift test (54.4 ± 13.4 vs. 59.2 ± 11.9 s; p < .01).The caffeine also increased the one-repetition maximum (90.5 ± 7.7 vs. 93.3 ± 7.5 kg; p = .02), maximal power obtained during the power-load test (750.5 ± 154.7 vs. 826.9 ± 163.7 W; p < .01) and mean power during the bench-press exercise test to failure (280.2 ± 52.5 vs. 312.2 ± 78.3 W; p = .04). In conclusion, the pre-exercise ingestion of 3 mg kg(-1) of caffeine increased dynamic and isometric muscular force, power, and endurance strength in elite BJJ athletes. Thus, caffeine might be an effective ergogenic aid to improve physical performance in BJJ.

Caffeine might be an effective ergogenic aid for improving intensity and physical performance during successive elite BJJ combats.

This study compared the activity profile of national and international female rugby sevens players during competitive matches. Twenty rugby sevens female players were recruited, 10 were members of the Spanish National Team (26.27 ± 4.05 years, 65.39 ± 5.01 kg, 166.72 ± 6.70 cm) and 10 were amateur athletes from a Spanish rugby championship (32.12 ± 6.40 years, 66.48 ± 5.38 kg of body mass, 167.37 ± 3.02 cm). Data collection was conducted over 4 matches in each of the 2 tournaments, national and international. Distance, velocity, and heart rate (HR) were recorded using global positioning system devices for all participants throughout each match. There were significant differences (p < 0.01) in total distance (1642 ± 171 vs. 1363 ± 222 m), average speed (6.0 ± 0.3 vs. 5.2 ± 0.6 km·h-1), number of sprints (6.1 ± 3.1 vs. 1.9 ± 1.4 sprints), and distance covered in sprinting (118.8 ± 61.4 vs. 47.0 ± 38.8 m). Significant differences were found at >95% maximum HR (HRmax), both for the first (p < 0.01) and second half (p ≤ 0.05). The work-rest ratio was significantly different (p < 0.01) between international (1:0.3) and national players (1:0.4). Significant differences were found in accelerations above 2 m·s-2 in the first and second half between the 2 groups. These findings suggest that distance covered in a match and speed are considerably different between international and national rugby sevens players, and this is reflected as higher intensity of play with consequently higher HR. Coaches may use this information to design specific running drills for this athlete population to match the requirements of national or international game play.

Recognition of emotions is still an unresolved challenge, which could be helpful to improve current human-machine interfaces. Recently, nonlinear analysis of some physiological signals has shown to play a more relevant role in this context than their traditional linear exploration. Thus, the present work introduces for the first time the application of three recent entropy-based metrics: sample entropy (SE), quadratic SE (QSE) and distribution entropy (DE) to discern between emotional states of calm and negative stress (also called distress). In the last few years, distress has received growing attention because it is a common negative factor in the modern lifestyle of people from developed countries and, moreover, it may lead to serious mental and physical health problems. Precisely, 279 segments of 32-channel electroencephalographic (EEG) recordings from 32 subjects elicited to be calm or negatively stressed have been analyzed. Results provide that QSE is the first single metric presented to date with the ability to identify negative stress. Indeed, this metric has reported a discriminant ability of around 70%, which is only slightly lower than the one obtained by some previous works. Nonetheless, discriminant models from dozens or even hundreds of features have been previously obtained by using advanced classifiers to yield diagnostic accuracies about 80%. Moreover, in agreement with previous neuroanatomy findings, QSE has also revealed notable differences for all the brain regions in the neural activation triggered by the two considered emotions. Consequently, given these results, as well as easy interpretation of QSE, this work opens a new standpoint in the detection of emotional distress, which may gain new insights about the brain's behavior under this negative emotion.

The aim of this study was to examine the match physical demands and exercise intensity associated with men rugby union refereeing using global positioning system technology. Ten male rugby union referees (age, 37.1 ± 5.9 years; body mass, 83.7 ± 4.8 kg; height, 175.5 ± 6.2 cm) were analyzed 2-4 times during a total of 30 national level matches. The average total distance covered by the referees throughout the game was 6,322.2 ± 564.9 m. As a percentage of total distance, 37.3% (2,356.9 ± 291.3 m) was spent walking, 24.1% (1,524.4 ± 229.4 m) jogging, 10.4% (656.2 ± 130.7 m) running at low intensity, 17.6% (1,110.3 ± 212.2 m) at medium intensity, 5.5% (347.1 ± 27.1 m) at high intensity, and 5.2% (328.1 ± 230.3 m) at sprint. A significant decrease (p < 0.05) in running performance was observed between the first and the second halves in the last 3 speed zones. When the total distance traveled during consecutive 10-minute periods was compared, there was a significantly greater distance covered in the first 10 minutes of the game (876.3 ± 163 m) compared with 50-60 minutes (679.8 ± 117.6 m), 60-70 minutes (713.03 ± 122.3 m), and 70-80 minutes (694.2 ± 125.7 m; all p < 0.05). The average heart rate responses were similar (p > 0.05) in the first (157 ± 7 b · min; 85% HRmax) and second half (155 ± 7 b · min; 84% HRmax). This study provides evidence of reduced high-intensity running toward the end of the game. These findings offer important information to design better training strategies adapted to the requirements and demands of rugby union refereeing.