Lívia de Souza Gonçalves

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.

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.

Chronic lactate supplementation does not improve blood buffering capacity and repeated high‐intensity exercise

Since there is conflicting data on the buffering and ergogenic properties of calcium lactate (CL), we investigated the effect of chronic CL supplementation on blood pH, bicarbonate, and high‐intensity intermittent exercise performance. Sodium bicarbonate (SB) was used as a positive control. Eighteen athletes participated in this double‐blind, placebo‐controlled, crossover, fully counterbalanced study. All participants underwent three different treatments: placebo (PL), CL, and SB. The dose was identical in all conditions: 500 mg/kg BM divided into four daily individual doses of 125 mg/kg BM, for five consecutive days, followed by a 2–7‐day washout period. On the fifth day of supplementation, individuals undertook four 30‐s Wingate bouts for upper body with 3‐min recovery between bouts. Total mechanical work (TMW) for the overall protocol and for the initial (1st+2nd) and final (3rd+4th) bouts was determined at each session. Blood pH, bicarbonate, and lactate levels were determined at rest, immediately and 5 min after exercise. CL supplementation did not affect performance (P > 0.05 for the overall TMW as well for initial and final bouts), nor did it affect blood bicarbonate and pH prior to exercise. SB supplementation improved performance by 2.9% for overall TMW (P = 0.02) and 5.9% in the 3rd+4th bouts (P = 0001). Compared to the control session, SB also promoted higher increases in blood bicarbonate than CL and PL (+0.03 ± 0.04 vs +0.009 ± 0.02 and +0.01 ± 0.03, respectively). CL supplementation was not capable of enhancing high‐intensity intermittent performance or changing extracellular buffering capacity challenging the notion that this dietary supplement is an effective buffering agent.

Does brain creatine content rely on exogenous creatine in healthy youth? A proof-of-principle study.

It has been hypothesized that dietary creatine could influence cognitive performance by increasing brain creatine in developing individuals. This double-blind, randomized, placebo-controlled, proof-of-principle study aimed to investigate the effects of creatine supplementation on cognitive function and brain creatine content in healthy youth. The sample comprised 67 healthy participants aged 10 to 12 years. The participants were given creatine or placebo supplementation for 7 days. At baseline and after the intervention, participants undertook a battery of cognitive tests. In a random subsample of participants, brain creatine content was also assessed in the regions of left dorsolateral prefrontal cortex, left hippocampus, and occipital lobe by proton magnetic resonance spectroscopy (1H-MRS) technique. The scores obtained from verbal learning and executive functions tests did not significantly differ between groups at baseline or after the intervention (all p > 0.05). Creatine content was not significantly different between groups in left dorsolateral prefrontal cortex, left hippocampus, and occipital lobe (all p > 0.05). In conclusion, a 7-day creatine supplementation protocol did not elicit improvements in brain creatine content or cognitive performance in healthy youth, suggesting that this population mainly relies on brain creatine synthesis rather than exogenous creatine intake to maintain brain creatine homeostasis.

Reply to Areta et al.: Time to withdraw and let the myth rest

to the editor: It is undisputable that caffeine variation in coffee—which is not as dramatic in Brazil as reported elsewhere ([2][1])—is a potential bias pertaining to our, and any, study assessing its habitual dietary intake. In fact, such variability exists in any natural food due to