The Acute Effect of In Natura Beetroot Juice Intake on Intra-Session Exercise Sequences During Concurrent Training.

The purpose of this study was to analyze the acute effects of in natura beetroot juice intake on intra-session exercise sequences during concurrent training. Following a randomized double-blind placebo-controlled crossover design, 20 well-trained men (21.4 ± 2.9 years; 74.8 ± 6.3 kg; 175.7 ± 5.0 cm) performed two concurrent training sessions with different intra-session exercise sequences: CT1 (aerobic exercise + resistance exercises) and CT2 (resistance exercises + aerobic exercise). The resistance exercises were bench-press, lat-pull down, and shoulder-press (three sets to failure; 2 s cadence for the concentric and eccentric phases; 90 s rest interval between sets and exercises; 75% 1RM), and the aerobic exercise was 4-km running. Each concurrent training session was randomized to placebo, beetroot juice, and control (no substances), totaling six exercise sessions. The rate of perceived exertion (RPE) was reported at the end of each exercise in each session. The beetroot juice significantly increased plasma nitric oxide concentration from 14.5 ± 3.9 mmol/L to 140.2 ± 37.5 mmol/L (P < 0.01) and there was no significant change after placebo intake (13.8 ± 4.2 vs 15.1 ± 5.7 mmol/L). The 4-km running time was significantly less (P < 0.05) after beetroot juice intake in CT1 (17.0 ± 2.1 min) and CT2 (18.5 ± 1.9 min) than placebo (19.1 ± 3.2 and 22.2 ± 2.9 min, respectively) and control (19.4 ± 2.6 and 21.7 ± 3.0 min, respectively). No differences were identified in the total number of repetitions in resistance exercises and RPE. In conclusion, the acute intake of in natura beetroot juice decreased the 4-km running time independently of concurrent training exercise sequences. Our results may assist trainers in order to choose the supplement to increase performance.

Risk or benefit? Side effects of caffeine supplementation in sport: a systematic review.

PURPOSE: The aim of this study was to systematically review evidence on the prevalence and magnitude of side effects associated with caffeine supplementation in athletes. METHODS: Systematic searches through the PubMed, VHL, Scopus, and Web of Science databases were conducted according to the PRISMA guidelines. Peer-reviewed articles written in English that reported the prevalence/percentage or magnitude/effect size of side effects after caffeine supplementation in athletes in a sports context were included. Studies were grouped by the dose of caffeine administered as follows: low = ≤ 3.0 mg/kg; moderate = from 3.1 to 6.0 mg/kg; high = ≥ 6.1 mg/kg. The magnitude of the side effects was calculated with effect sizes. RESULTS: The search retrieved 25 studies that met the inclusion/exclusion criteria with a pooled sample of 421 participants. The supplementation with caffeine produced a higher prevalence or magnitude of all side effects under investigation when compared to placebo/control situations. The prevalence (magnitude) was between 6 and 34% (ES between 0.13 and 1.11) for low doses of caffeine, between 0 and 34% (ES between -0.13 and 1.20) for moderate doses of caffeine, and between 8 and 83% (ES between 0.04 and 1.52) with high doses of caffeine. The presence of tachycardia/heart palpitations and the negative effects on sleep onset had the highest prevalence and magnitude, in athletes using supplementation with caffeine. CONCLUSION: In summary, caffeine supplementation in the doses habitually used to enhance physical performance produces several side effects, both after exercise and at least 24 h after the ingestion. However, the prevalence and magnitude of side effects with high doses of caffeine were habitually higher than with low doses of caffeine. From a practical perspective, using ~3.0 mg/kg of caffeine may be the dose of choice to obtain the ergogenic benefits of caffeine with the lowest prevalence and magnitude of side effects.

Players' physical performance in LaLiga across the season: insights for competition continuation after COVID-19.

Due to the COVID-19 outbreak, professional football players competing in LaLiga were confined at home for ~8 weeks and then they were allowed to train to prepare the first competitive match for 4 weeks. As the duration of summer break in the prior four seasons of LaLiga (from 2015-2016 to 2018-2019) was of similar length to the suspension of the championship due to COVID-19 (~12 weeks), we have analysed the running performance of teams competing in LaLiga in these four seasons to anticipate players' physical performance after the resumption of the competition. The analysis includes the average running distance per game for each of the 38 matchdays that compose LaLiga. One-way ANOVA revealed that there was a main effect of the matchday on total running distance per match (p = 0.001), and in the distance covered between 14.0 and 20.9 km/h (p < 0.001), between 21.0 and 23.9 km/h (p < 0.001) and at above 24.0 km/h (p < 0.001). Overall, the post-hoc analysis revealed that the running patterns progressively increased during the first 8-10 matchdays and then reached a plateau which was significantly different to matchday-1 (p < 0.05). This analysis reveals that, in the prior four competitive seasons of LaLiga, players' physical performance was lower at the beginning of the season and the teams needed approximately 8-10 matchdays to reach a steady state running performance. These data suggest that football players will progressively increase their performance across the 11 matchdays remaining to complete LaLiga.

Caffeine and resistance exercise: the effects of two caffeine doses and the influence of individual perception of caffeine.

Although caffeine is a widely used ergogenic resource, some information regarding its effects on resistance exercises is still lacking. The objective of the present study was to verify the acute effect of the ingestion of two different doses of caffeine on performance during a session of resistance exercises and to analyze the perception of the subjects in relation to the intake of caffeine. Following a double-blind, randomised, cross-over, controlled, and non-placebo design, 14 trained and healthy men (24.7 ± 6.8 years; 79.8 ± 9.8 kg; 177.3 ± 8.5 cm) performed a training session in chest-press, shoulder-press, and biceps curl exercises (3 sets until exhaustion; 70% 1RM; 3 min rest interval; 2 s for each concentric and eccentric phase) on three non-consecutive days after ingestion of 3 mg.kg-1 caffeine (CAF3), 6 mg.kg-1 caffeine (CAF6), or no substance (CON). Subjects were informed that one of the caffeine doses would be placebo. The total number of repetitions performed in CON (93.6 ± 22.4) was significantly lower than in CAF3 (108.0 ± 19.9, P = 0.02) and in CAF6 (109.3 ± 19.8, P = 0.03) and there were no differences between caffeine doses. Eight subjects noticed that caffeine was in CAF3 and six in CAF6 and there were no differences in the number of repetitions between sessions in which the subjects perceived and did not perceive caffeine. In conclusion, caffeine doses of 3 or 6 mg.kg-1 similarly increased performance in resistance upper limb exercises, independent of the subject's perception of substance ingestion.