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1.
Caffeine improved cycling trial performance in mentally fatigued cyclists, regardless of alterations in prefrontal cortex activation.
Franco-Alvarenga, PE, Brietzke, C, Canestri, R, Goethel, MF, Hettinga, F, Santos, TM, Pires, FO
Physiology & behavior. 2019;:41-48
Abstract
PURPOSE To verify whether caffeine (CAF) could increase the prefrontal cortex (PFC) activation and improve 20 km cycling time trial (TT20km) performance in mentally fatigued cyclists. METHODS After preliminary TT20km, twelve recreational cyclists (VO2MAX of 58.9 ± 6.2 mL kg min-1) performed a familiarization with a cognitive test to induce mental fatigue (MF) and psychological scales. Thereafter, they performed: 2) a baseline TT20km; 3) a mentally fatigued TT20km (MF); 4 and 5) a mentally fatigued TT20km after CAF (MF + CAF) or placebo (MF + PLA) ingestion, in a double-blind, counterbalanced design. Performance and psychological responses were obtained throughout the TT20km, while PFC electroencephalography (EEG) theta wave was obtained before and after the mental fatigue test. RESULTS The mental fatigue-induced increase in EEG theta wave (↑ ~ 4.8%) was reverted with CAF (↓ 8.8%) and PLA ingestion (↓ 4.8%). CAF improved TT20km performance in mentally fatigued cyclists by reducing time (p = .00; ↓ ~ 1.7%) and increasing WMEAN (p = .00; ↑ ~ 3.6%), when compared to MF + PLA. The RPE-power output ratio was lower (p = .01), but affect (p = .018), motivation (p = .033) and emotional arousal (p = .001) were greater throughout the TT20km in MF + CAF than in MF + PLA. CONCLUSIONS CAF ingestion improved TT20km performance and psychological responses in mentally fatigued cyclists, despite the unaltered PFC activation.
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2.
Acute Caffeine Ingestion did not Enhance Punch Performance in Professional Mixed-Martial Arts Athletes.
de Azevedo, AP, Guerra, MA, Caldas, LC, Guimarães-Ferreira, L
Nutrients. 2019;(6)
Abstract
Mixed martial arts (MMA) is a combat sport where competitors utilize strikes (punches, kicks, knees, and elbows) and submission techniques to defeat opponents in a cage or ring. The aim of this study was to investigate the effect of acute caffeine ingestion on punching performance by professional MMA athletes. The study used a double-blind, counterbalanced, crossover design. Eleven professional MMA competitors (27.6 ± 4.3 years and 83.5 ± 7.8 kg of body weight) ingested a dose of caffeine (5 mg·kg-1) or placebo 60 min prior to three sets of punching. Each set consisted of 15 s, at which participants were asked to perform straight punches with maximum strength and frequency with his dominant arm. After each set, a 45 s recovery time was applied. Using a force transducer attached to a cushioned plate, the punch frequency, and mean and maximal punch force was measured. The readiness to invest in both physical (RTIPE) and mental (RTIME) effort was assessed prior to the protocol, and the rating of perceived exertion (RPE) was recorded after. Caffeine ingestion did not result in increased punching frequency, mean and maximum punch force, RTIPE, RTIME, and RPE when compared to the placebo condition. Based on these results, acute caffeine ingestion did not improve punching performance in professional MMA athletes.
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3.
Caffeine alters the dynamics of ocular accommodation depending on the habitual caffeine intake.
Redondo, B, Vera, J, Molina, R, Luque-Casado, A, Jiménez, R
Experimental eye research. 2019;:107663
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4.
Challenging the Myth of Non-Response to the Ergogenic Effects of Caffeine Ingestion on Exercise Performance.
Del Coso, J, Lara, B, Ruiz-Moreno, C, Salinero, JJ
Nutrients. 2019;(4)
Abstract
The ergogenicity of caffeine on several exercise and sport situations is well-established. However, the extent of the ergogenic response to acute caffeine ingestion might greatly vary among individuals despite using the same dosage and timing. The existence of one or several individuals that obtained minimal ergogenic effects or even slightly ergolytic effects after caffeine intake (i.e., non-responders) has been reported in several previous investigations. Nevertheless, the concept non-responding to caffeine, in terms of physical performance, relies on investigations based on the measurement of one performance variable obtained once. Recently it has been suggested that correct identification of the individual ergogenic effect induced by caffeine intake requires the repeated measurement of physical performance in identical caffeine⁻placebo comparisons. In this communication, we present data from an investigation where the ergogenic effect of acute caffeine intake (3 mg/kg) was measured eight times over a placebo in the same individuals and under the same conditions by an incremental cycling test to volitional fatigue and an adapted version of the Wingate cycling test. The ergogenic response to caffeine varied from 9% to 1% among individuals, but all participants increased both cycling power in the incremental test and Wingate mean power at least three to eight times out of eight the caffeine⁻placebo comparisons. These data expand the suggestion of a minimal occurrence of caffeine non-responders because it shows that all individuals responded to caffeine when caffeine is compared to a placebo on multiple and repeated testing sessions.
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5.
Establishing a relationship between the effect of caffeine and duration of endurance athletic time trial events: A systematic review and meta-analysis.
Shen, JG, Brooks, MB, Cincotta, J, Manjourides, JD
Journal of science and medicine in sport. 2019;(2):232-238
Abstract
OBJECTIVES Caffeine has well-documented benefits on endurance athletic performance. Because of caffeine's ergogenic effects of reducing perceived fatigue, it is hypothesized that as duration of athletic event increases, so will the effect size of caffeine upon performance. This study aims to examine the relationship between duration of endurance athletic event and the effect size of caffeine compared to placebo for athletic performance. DESIGN A systematic review and meta-analysis of placebo-controlled trials assessing the effects of caffeine in adults performing endurance athletic events. METHODS We searched MedLine, Web of Science, and review article references published through March 2016. We performed meta-analyses on placebo-controlled trials to determine the effect of the duration of an endurance athletic event on the standardized mean difference (Cohen's d) between the caffeine and placebo groups for athletic performance. RESULTS Forty articles including 56 unique comparison groups were included. Pooled results showed a Cohen's d of 0.33 (95% CI=0.21, 0.45; p=1.00; I2=0%). The effect of the duration of athletic event was significantly associated with Cohen's d (Relative Risk: 0.005; 95% CI=0.001, 0.009; p=0.024). For a 30min increase in duration of the athletic event, Cohen's d will increase by 0.150. CONCLUSIONS This study is the first to report on the statistical finding that the effect size of caffeine increases along with the increasing duration of the time trial event. Endurance athletes may especially benefit from caffeine for performance enhancement.
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6.
Can caffeine supplementation reverse the effect of time of day on repeated-sprint exercise performance?
Lopes-Silva, JP, Santos, JFDS, Franchini, E
Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme. 2019;(2):187-193
Abstract
The aim of this study was to evaluate if caffeine can reduce the negative influence of diurnal variations on repeated-sprint performance, in addition to investigating if caffeine in the afternoon would potentiate performance compared with the morning. Thirteen physically active men took part in this randomized, double-blind, placebo-controlled and crossover study. All participants underwent a repeated-sprint ability test (10 × 6 s cycle sprints, with 30 s of rest) at 60 min after ingestion of either 5 mg·kg-1 or placebo under 4 different conditions: morning with caffeine ingestion, morning with placebo ingestion, afternoon with caffeine ingestion, and afternoon with placebo ingestion. Total work, peak power (PP) and anaerobic power reserve (APR) were assessed. Oxygen uptake, heart rate, lactate concentration, and rating of perceived exertion were also measured during the repeated-sprint test. Total work (+8%, d = 0.2, small), PP (+6%, d = 0.2), and APR (+9%, d = 0.2) were significantly higher in the afternoon when compared with morning. However, physiological responses were not different between caffeine and placebo conditions. Repeated-sprint (10 × 6 s cycle sprint) performance was influenced by time of day, with lower performance in the morning compared with the afternoon. However, caffeine supplementation did not prevent the reduction in performance in the morning or improve performance in the afternoon.
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7.
High-versus low-dose caffeine in preterm infants: a systematic review and meta-analysis.
Brattström, P, Russo, C, Ley, D, Bruschettini, M
Acta paediatrica (Oslo, Norway : 1992). 2019;(3):401-410
Abstract
AIM: Though caffeine is a consolidated treatment in preterm infants, the efficacy and safety of a higher dose have not been systematically appraised. METHODS A systematic review was conducted to compare high (loading dose >20 mg/kg and maintenance >10 mg/kg/day) versus low dose of caffeine. MEDLINE, EMBASE, Central and conference proceedings for randomised controlled trials (RCTs) and quasi-RCTs were searched. Two authors independently screened the records, extracted the data and assessed the risk of bias. RESULTS As only six RCTs enrolling a total of 816 preterm infants were included, the required information size was not reached. The loading and maintenance doses varied between 20 and 80 mg/kg/day and 3 and 20 mg/kg/day, respectively. The use of high dose had no impact on mortality (RR: 0.85; 95% CI: 0.53-1.38; RCTs = 4). However, it resulted in fewer cases of extubation failure, apnoeas and bronchopulmonary dysplasia (RR: 0.76; 95% CI: 0.60-0.96; studies = 4) and shorter duration of mechanical ventilation. The quality of the evidence was low due to imprecision of the estimates. CONCLUSION Due to imprecision, it is not possible to determine whether high-dose caffeine is more effective and safe than a low dose. High dose might improve short-term respiratory function and reduce bronchopulmonary dysplasia.
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8.
Effects of lisdexamfetamine on plasma steroid concentrations compared with d-amphetamine in healthy subjects: A randomized, double-blind, placebo-controlled study.
Strajhar, P, Vizeli, P, Patt, M, Dolder, PC, Kratschmar, DV, Liechti, ME, Odermatt, A
The Journal of steroid biochemistry and molecular biology. 2019;:212-225
Abstract
The novel d-amphetamine prodrug lisdexamfetamine is applied to treat attention-deficit/hyperactivity disorder (ADHD). d-Amphetamine releases dopamine and norepinephrine and stimulates the hypothalamic-pituitary-adrenal (HPA) axis, which may contribute to its reinforcing effects and risk of abuse. However, no data is currently available on the effects of lisdexamfetamine on circulating steroids. This randomized, double-blind, placebo-controlled, cross-over study evaluated the effects of equimolar doses of d-amphetamine (40 mg) and lisdexamfetamine (100 mg) and placebo on circulating steroids in 24 healthy subjects. Plasma steroid and d-amphetamine levels were determined up to 24 h. Delayed increase and peak levels of plasma d-amphetamine concentrations were observed following lisdexamfetamine treatment compared with d-amphetamine administration, however the maximal concentrations and total exposure (area under the curve [AUC]) were similar. Lisdexamfetamine and d-amphetamine significantly enhanced plasma levels of adrenocorticotropic hormone, glucocorticoids (cortisol, cortisone, corticosterone, 11-dehydrocorticosterone, and 11-deoxycortisol), androgens (dehydroepiandrosterone, dehydroepiandrosterone sulfate, and Δ4-androstene-3,17-dione [androstenedione]), and progesterone (only in men) compared with placebo. Steroid concentration-time curves were shifted to later time points due to a non-significantly later onset following lisdexamfetamine administration than after d-amphetamine, however maximal plasma steroid concentrations and AUCs did not differ between the active treatments. None of the active treatments altered plasma levels of the mineralocorticoids aldosterone and 11-deoxycorticosterone or the androgen testosterone compared with placebo. The effects of the amphetamines on glucocorticoid production were similar to those that were previously reported for methylphenidate (60 mg) but weaker than those for the serotonin releaser 3,4-methylenedioxymethamphetamine (MDMA; 125 mg) or direct serotonin receptor agonist lysergic acid diethylamide (LSD; 0.2 mg). Lisdexamfetamine produced comparable HPA axis activation and had similar pharmacokinetics than d-amphetamine, except for a delayed time of onset. Thus, serotonin (MDMA, LSD) may more effectively stimulate the HPA axis than dopamine and norepinephrine (D-amphetamine).
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9.
Are low doses of caffeine as ergogenic as higher doses? A critical review highlighting the need for comparison with current best practice in caffeine research.
Pickering, C, Kiely, J
Nutrition (Burbank, Los Angeles County, Calif.). 2019;:110535
Abstract
Caffeine is a popular and widely consumed sporting ergogenic aid. Over the years, the effects of different caffeine doses have been researched, with the general consensus being that 3 to 6 mg/kg of caffeine represents the optimal dose for most people. Recently, there has been increased attention placed on lower (≤3 mg/kg) caffeine doses, with some research suggesting these doses are also ergogenic. However, a critical consideration for athletes is not merely whether caffeine is ergogenic at a given dose, but whether the consumed dose provides an optimized performance benefit. Following this logic, the aim of this review was to identify a potential oversight in the current research relating to the efficacy of lower caffeine doses. Although low caffeine doses do appear to bestow ergogenic effects, these effects have not been adequately compared with the currently accepted best practice dose of 3 to 6 mg/kg. This methodological oversight limits the practical conclusions we can extract from the research into the efficacy of lower doses of caffeine, as the relative ergogenic benefits between low and recommended doses remains unclear. Here, we examine existing research with a critical eye, and provide recommendations both for those looking to use caffeine to enhance their performance, and those conducting research into caffeine and sport.
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10.
The effect of CYP1A2 genotype on the ergogenic properties of caffeine during resistance exercise: a randomized, double-blind, placebo-controlled, crossover study.
Rahimi, R
Irish journal of medical science. 2019;(1):337-345
Abstract
AIM: The purpose of this study was to examine the effect of CYP1A2 -163C>A polymorphism on the ergogenic effects of caffeine supplementation during a resistance exercise (RE) session. METHODS In a randomized, double-blind, placebo (PL)-controlled, crossover study, 30 resistance-trained men took part in two RE sessions (three sets to failure at 85% of one repetition maximum, 2-min rest between sets), including bench press (BP), leg press (LP), seated cable row, and shoulder press (SP) following caffeine (CAF) (6 mg kg-1) or PL (6 mg kg-1 of maltodextrin) ingestion 1 h prior to the trial. The number of repetitions was recorded after each set, along with calculation of total number of repetitions for each exercise. Genomic DNA was isolated from the whole blood samples for analyzing the CYP1A2 -163C>A polymorphism through amplification refractory mutation system-polymerase chain reaction (ARMS-PCR). Subjects were classified as either AA (n = 14) or AC/CC genotypes (n = 16). RESULTS The two-way ANOVA with repeated measures revealed differences between AAs and AC/CCs under CAF conditions for repetitions performed in sets 1, 2, and 3 of BP (F(1, 28) = 14.84, P = 0.001, ƞ2 = 0.34), LP (F(1, 28) = 8.92, P = 0.006, ƞ2 = 0.24), SR (F(1, 28) = 17.38, P = 0.0001, ƞ2 = 0.38), and SP (F(1, 28) = 3.76, P = 0.063, ƞ2 = 0.11). CAF also increased the total number of repetitions performed for all three sets in AAs versus AC/CCs for BP (F(1, 28) = 8.72, P = 0.006, ƞ2 = 0.23), LP (F(1, 28) = 4.67, P = 0.03, ƞ2 = 0.14), SR (F(1, 28) = 5.54, P = 0.02, ƞ2 = 0.16), and SP (F(1, 28) = 3.89, P = 0.058, ƞ2 = 0.12) in athletes who were homozygous carriers of the A allele, compared to the C allele carriers. Therefore, AA homozygotes were able to carry out a greater total volume of RE work under CAF but not PL conditions, compared to the C allele carriers. CONCLUSION In conclusion, acute ingestion of CAF significantly enhanced RE performance in resistance-trained men who were homozygous for the A allele, but not for C allele carriers. Further studies are needed to replicate the potential role of the CYP1A2 -163C>A polymorphism on the ergogenic effects of CAF in other modes of exercise and in other populations.