Rafael Pires da Silva

Pre-game hydration status, sweat loss, and fluid intake in elite Brazilian young male soccer players during competition

Abstract In this study, we assessed the pre-game hydration status and fluid balance of elite young soccer players competing in a match played in the heat (temperature 31.0 ± 2.0°C, relative humidity 48.0 ± 5.0%) for an official Brazilian soccer competition. Fluid intake was measured during the match, as were urine specific gravity and body mass before and after the game to estimate hydration status. Data were obtained from 15 male players (age 17.0 ± 0.6 years, height 1.78 ± 0.06 m, mass 65.3 ± 3.8 kg); however, data are only analysed for 10 players who completed the full game. The mean (±s) sweat loss of players amounted to 2.24 ± 0.63 L, and mean fluid intake was 1.12 ± 0.39 L. Pre-game urine specific gravity was 1.021 ± 0.004, ranging from 1.010 to 1.025. There was no significant correlation between sweat loss and fluid intake (r = 0.504, P = 0.137) or between urine specific gravity and fluid intake (r = −0.276, P = 0.440). We conclude that young, native tropical soccer players started the match hypohydrated and replaced about 50% of the sweat lost. Thus, effective strategies to improve fluid replacement are needed for players competing in the heat.

Dispelling the myth that habitual caffeine consumption influences the performance response to acute caffeine supplementation

This study investigates the influence of habitual caffeine intake on aerobic exercise-performance responses to acute caffeine supplementation. A double-blind, crossover, counterbalanced study was performed. Forty male endurance-trained cyclists were allocated into tertiles, according to their daily caffeine intake: low (58 ± 29 mg/d), moderate (143 ± 25 mg/d), and high (351 ± 139 mg/d) consumers. Participants completed three trials in which they performed simulated cycling time trials (TTs) in the fastest time possible following ingestion of the following: caffeine (CAF: 6 mg/kg body mass), placebo (PLA), and no supplement (CON). A mixed-model analysis revealed that TT performance was significantly improved in CAF compared with PLA and CON (29.92 ± 2.18 vs. 30.81 ± 2.67 and 31.14 ± 2.71 min, respectively; P = 0.0002). Analysis of covariance revealed no influence of habitual caffeine intake as a covariate on exercise performance (P = 0.47). TT performance was not significantly different among tertiles (P = 0.75). No correlation was observed between habitual caffeine intake and absolute changes (CAF - CON) in TT performance with caffeine (P = 0.524). Individual analysis showed that eight, seven, and five individuals improved above the variation of the test in CAF in the low, moderate, and high tertiles, respectively. A Fishers exact test did not show any significant differences in the number of individuals who improved in CAF among the tertiles (P > 0.05). Blood lactate and ratings of perceived exertion were not different between trials and tertiles (P > 0.05). Performance effects of acute caffeine supplementation during an ~30-min cycling TT performance were not influenced by the level of habitual caffeine consumption.NEW & NOTEWORTHY There has been a long-standing paradigm that habitual caffeine intake may influence the ergogenicity of caffeine supplementation. Low, moderate, and high caffeine consumers showed similar absolute and relative improvements in cycling time-trial performance following acute supplementation of 6 mg/kg body mass caffeine. Performance effects of acute caffeine were not influenced by the level of habitual caffeine consumption, suggesting that high habitual caffeine intake does not negate the benefits of acute caffeine supplementation.

An undergraduate level experiment on the synthesis of Au nanoparticles and their size-dependent optical and catalytic properties

The synthesis of gold nanoparticles (Au NPs) 15, 26, and 34 nm in diameter, followed by the investigation of their size-dependent optical and catalytic properties, is described herein as an undergraduate level experiment. The proposed experiment covers concepts on the synthesis, stabilization, and characterization of Au NPs, their size-dependent optical and catalytic properties at the nanoscale, chemical kinetics, and the role of a catalyst. The experiment should be performed by groups of two or three students in three lab sessions of 3 h each and organized as follows: i) synthesis of Au NPs of different sizes and investigation of their optical properties; ii) evaluation of their catalytic activity; and iii) data analysis and discussion. We believe that this activity enables students to integrate these multidisciplinary concepts in a single experiment as well as to become introduced/familiarized with an active research field and current literature in the areas of nanoparticle synthesis and catalysis.

Twenty-four Weeks of β-alanine Supplementation on Carnosine Content, Related Genes, and Exercise.

Introduction Skeletal muscle carnosine content can be increased through &bgr;-alanine (BA) supplementation, but the maximum increase achievable with supplementation is unknown. No study has investigated the effects of prolonged supplementation on carnosine-related genes or exercise capacity. Purpose This study aimed to investigate the effects of 24 wk of BA supplementation on muscle carnosine content, gene expression, and high-intensity cycling capacity (CCT110%). Methods Twenty-five active males were supplemented with 6.4 g·d−1 of sustained release BA or placebo for a 24 wk period. Every 4 wk participants provided a muscle biopsy and performed the CCT110%. Biopsies were analyzed for muscle carnosine content and gene expression (CARNS, TauT, ABAT, CNDP2, PHT1, PEPT2, and PAT1). Results Carnosine content was increased from baseline at every time point in BA (all P < 0.0001; week 4 = +11.37 ± 7.03 mmol·kg−1 dm, week 8 = +13.88 ± 7.84 mmol·kg−1 dm, week 12 = +16.95 ± 8.54 mmol·kg−1 dm, week 16 = +17.63 ± 8.42 mmol·kg−1 dm, week 20 = +21.20 ± 7.86 mmol·kg−1 dm, and week 24 = +20.15 ± 7.63 mmol·kg−1 dm) but not placebo (all P > 0.05). Maximal increases were +25.66 ± 7.63 mmol·kg−1 dm (range = +17.13 to +41.32 mmol·kg−1 dm), and absolute maximal content was 48.03 ± 8.97 mmol·kg−1 dm (range = 31.79 to 63.92 mmol·kg−1 dm). There was an effect of supplement (P = 0.002) on TauT; no further differences in gene expression were shown. Exercise capacity was improved in BA (P = 0.05) with possible to almost certain improvements across all weeks. Conclusions Twenty-four weeks of BA supplementation increased muscle carnosine content and improved high-intensity cycling capacity. The downregulation of TauT suggests it plays an important role in muscle carnosine accumulation with BA supplementation, whereas the variability in changes in muscle carnosine content between individuals suggests that other determinants other than the availability of BA may also bear a major influence on muscle carnosine content.

The Effects of Two Different Doses of Calcium Lactate on Blood pH, Bicarbonate, and Repeated High-Intensity Exercise Performance

We investigated the effects of low- and high-dose calcium lactate supplementation on blood pH and bicarbonate (Study A) and on repeated high-intensity performance (Study B). In Study A, 10 young, physically active men (age: 24 ± 2.5 years; weight: 79.2 ± 9.45 kg; height: 1.79 ± 0.06 m) were assigned to acutely receive three different treatments, in a crossover fashion: high-dose calcium lactate (HD: 300 mg · kg(-1) body mass), low-dose calcium lactate (LD: 150 mg · kg(-1) body mass) and placebo (PL). During each visit, participants received one of these treatments and were assessed for blood pH and bicarbonate 0, 60, 90, 120, 150, 180, and 240 min following ingestion. In Study B, 12 young male participants (age: 26 ± 4.5 years; weight: 82.0 ± 11.0 kg; height: 1.81 ± 0.07 m) received the same treatments of Study A. Ninety minutes after ingestion, participants underwent 3 bouts of the upper-body Wingate test and were assessed for blood pH and bicarbonate 0 and 90 min following ingestion and immediately after exercise. In Study A, both HD and LD promoted slight but significant increases in blood bicarbonate (31.47 ± 1.57 and 31.69 ± 1.04 mmol · L(-1, respectively) and pH levels (7.36 ± 0.02 and 7.36 ± 0.01, respectively), with no effect of PL. In Study B, total work done, peak power, mean power output were not affected by treatments. In conclusion, low- and high-dose calcium lactate supplementation induced similar, yet very discrete, increases in blood pH and bicarbonate, which were not sufficiently large to improve repeated high-intensity performance.

Beta-alanine supplementation enhances judo-related performance in highly-trained athletes

OBJECTIVES In official judo competitions, athletes usually engage in 5-7 matches in the same day, performing numerous high-intensity efforts interspersed by short recovery intervals. Thus, glycolytic demand in judo is high and acidosis may limit performance. Carnosine is a relevant intracellular acid buffer whose content is increased with beta-alanine supplementation. Thus, we hypothesized that beta-alanine supplementation could attenuate acidosis and improve judo performance. DESIGN Twenty-three highly-trained judo athletes were randomly assigned to receive either beta-alanine (6.4gday-1) or placebo (dextrose, same dosage) for 4 weeks. METHODS Performance was assessed before (PRE) and after (POST) supplementation through a 5-min simulated fight (randori) followed by 3 bouts of the Special Judo Fitness Test (SJFT). Blood samples were collected for blood pH, bicarbonate (HCO3-) and lactate determination. RESULTS Beta-alanine supplementation improved the number of throws per set and the total number of throws (both p<0.05). Placebo did not change these variables (both p>0.05). Blood pH and HCO3- reduced after exercise (all p<0.001), with no between-group differences (all p>0.05). However, the lactate response to exercise increased in the beta-alanine group as compared to placebo (p<0.05). CONCLUSIONS In conclusion, 4 weeks of beta-alanine supplementation effectively enhance judo-related performance in highly-trained athletes.

Cafeína no altera los niveles de imunoglobulina salivar, en jugadores de voleibol

Se avalio la influencia de la ingestion de cafeina en la respuesta de a inmunoglobulina A salivar (IgA-s) en atletas de voleibol se uso el modelo crossover y doble-cego. Nueve atletas participaran de dos sesiones de entrenamiento y ingirieron cafeina (6 mg de peso corporal) o placebo. Se analizo la concentracion de IgA-s antes y despues de la sesion. Los resultados mostraron que no hubo diferencia significativa (P > 0,05) en los niveles de (IgA-s) pre e pos entrenamiento en los atetas que ingirieron CAF (8,54 ± 4,03 mg/dL e 7,45 ± 4,72 mg/dL, respectivamente) como en aquellos que tomaron PLA (6,88 ± 3,17 mg/dL e 9,76 ± 5,81 mg/dL, respectivamente). Se concluyo que la suplementacion adoptada no afecto la respuesta de la IgA-s durante las sesiones del entrenamiento realizados por los atletas de voleibol.

Caffeine does not change Salivary Immunoglobulin A (s-IgA) levels in volleyball players

Se avalio la influencia de la ingestion de cafeina en la respuesta de a inmunoglobulina A salivar (IgA-s) en atletas de voleibol se uso el modelo crossover y doble-cego. Nueve atletas participaran de dos sesiones de entrenamiento y ingirieron cafeina (6 mg de peso corporal) o placebo. Se analizo la concentracion de IgA-s antes y despues de la sesion. Los resultados mostraron que no hubo diferencia significativa (P > 0,05) en los niveles de (IgA-s) pre e pos entrenamiento en los atetas que ingirieron CAF (8,54 ± 4,03 mg/dL e 7,45 ± 4,72 mg/dL, respectivamente) como en aquellos que tomaron PLA (6,88 ± 3,17 mg/dL e 9,76 ± 5,81 mg/dL, respectivamente). Se concluyo que la suplementacion adoptada no afecto la respuesta de la IgA-s durante las sesiones del entrenamiento realizados por los atletas de voleibol.