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Simple Summary: This study explored the effects of different caffeine doses on nutrient digestion and fermentation in a simulated rumen environment. The main goal was to improve our understanding of how caffeine might influence these important metabolic processes in the rumen when a lactating cow diet is used. Here, we report that a dose of caffeine (50 ppm) improved the digestibility of dry/organic matter and starch while reducing the protozoa numbers and ammonia concentration, which are related to ruminal protein metabolism. However, higher caffeine doses (above 50 ppm) began to negatively impact these parameters. Our observations suggest that caffeine, a naturally occurring compound in several plants such as coffee, cacao, and tea, could potentially be used to enhance digestion and fermentation in ruminants. This research is valuable to our understanding of anaerobic fermentation in the rumen as it demonstrates the use of this plant secondary metabolite to enhance nutrient utilization and milk production and other benefits to management and the environment. Caffeine is a plant secondary metabolite, commonly known for its bioactivity properties. This molecule increases microbial activity during anaerobic digestion. The aim of this study was to determine the effects of caffeine doses on the rumen fermentation profile and nutrient digestibility when continuous culture fermenters were fed a lactating cow's diet. We hypothesize that adding caffeine doses into continuous culture fermenters with a rumen fluid inoculum will not affect anaerobic fermentation or nutrient utilization. Fermenters were fed twice a day (at 0800 and 2000 h) with an experimental diet of high-producing dairy cows (53.55 g/DM day; Forage:Concentrate ratio, F:C of 40:60). Four levels of caffeine (0 ppm, 50 ppm, 100 ppm, and 150 ppm) were added to the diets as a treatment. The experiment was arranged in a randomized complete block design. Two blocks of four fermenters were run in two replicated periods of ten days. Statistical analyses were conducted in SAS version 9.4 for Windows (SAS Institute Inc., Cary, NC, USA) using the GLIMMIX procedure. The addition of caffeine at a 50 ppm dose on continuous culture fermentation decreased the protozoal counts (Diplodinium spp.) (p = 0.03) and ammonia concentrations (p < 0.05). A treatment of 50 ppm of caffeine increased the DM, OM, and starch digestibility (p < 0.05). When caffeine doses increased further than 50 ppm, the OM, DM, and starch digestibility decreased linearly (p = 0.01). The total volatile fatty acids and fatty acid proportions were unaffected. However, the acetate-to-propionate ratio (A:P) tended to decrease linearly among treatments (p = 0.07). The means of pH measurements and maximum pH had a significantly linear decrease effect (p < 0.01). Caffeine may represent a potential rumen fermentation modifier for use in lactating cow diets. [ABSTRACT FROM AUTHOR]

Caffeine is the world's most popular stimulant and is consumed daily by a significant portion of the world's population through coffee, tea, soda, and energy drinks. Consumers often shop online and in physical stores immediately after or while consuming caffeine. This is further facilitated by the increasing prevalence of coffee shops and by the phenomenon of some retail stores having in-store coffee bars and offering complimentary caffeinated beverages. This research examines how caffeine consumption before shopping influences purchase behavior. The results of a series of experiments conducted in the field (at multiple retail stores across different countries) and in the lab show that consuming a caffeinated (vs. noncaffeinated) beverage before shopping enhances impulsivity in terms of more items purchased and higher spending. This effect is stronger for "high-hedonic" products and attenuated for "low-hedonic" products. These findings are important for managers to understand how a seemingly unrelated behavior (i.e., caffeine consumption) in and/or around the store affects spending. From a consumer perspective, although moderate amounts of caffeine consumption can have positive health benefits, there can be unintended negative financial consequences of caffeine intake on spending. Thus, consumers trying to control impulsive spending should avoid consuming caffeinated beverages before shopping. [ABSTRACT FROM AUTHOR]

Although the positive effects of caffeine supplementation on individual and team-sports have been widely described, the literature evaluating the effect of caffeine supplementation on athletic performance in ice hockey players is almost non-existent. Therefore, the aim of the present study was to evaluate the effect of acute caffeine ingestion (3 mg/kg body mass). Thirteen elite adult ice hockey male players participated in this double-blind, randomized, counterbalanced, placebo-controlled crossover trial. A 35-m sprint, an agility test (Weave agility-slalom with puck), and a reaction test were performed twice in two separate days. On both occasions players ingested 330 ml of water with lemon isotonic drink (86 kcal/19 g of carbohydrates). On one of the days the drink included 3 mg/kg body mass of anhydrous caffeine. The randomization was performed by a researcher who was not involved in the register of main outcomes. No differences were found between the placebo and the caffeine condition for the 35-m sprint (4.223 vs. 4.188 s respectively, P = 0.516), Weave agility test (22.492 vs. 22.341 s respectively, P = 0.534) and reaction test (4.869 vs. 4.837 s respectively, P = 0.570). When analyzing individual results, three players showed improvements in the 35-m sprint while two showed decreases in performance after ingesting caffeine. Caffeine consumption did not improve athletic performance in ice hockey players. Clinicaltrial.gov (NCT05170139). [ABSTRACT FROM AUTHOR]

The study aimed to examine the combined effects of caffeine and aerobic exercise on leptin levels and some indices of insulin resistance in diabetics Thirty-two males with type 2 diabetes participated in a quasi-experimental and double-blind design. All participants were divided into four homogeneous groups of 8 individuals, including placebo (P), caffeine supplementation (C), aerobic training (AT), and aerobic training and caffeine (AT + C). The design protocol included eight weeks of aerobic exercise and caffeine consumption. Blood samples were taken to measure serum levels of leptin, glucose, insulin, HbA1c, HOMA-IR, and insulin sensitivity (QUICKI) indices at two phases. Data were analyzed by repeated measure ANOVA, Bonferroni posthoc, and independent T-test at a significant level of α ≤ 0.05. The results showed that the levels of leptin, glucose, insulin, HbA1c, and HOMA-IR in the three intervention groups significantly decreased compared to the placebo group (P = 0.001). In addition, QUICKI was significantly increased in the three groups of caffeine (C), aerobic training (AT), and aerobic training + caffeine (AT + C) compared to the placebo group (P = 0.001). Also, the AT+C group has double effects on the investigated indices compared to the caffeine (C) group (P = 0.001). Regular aerobic exercise and caffeine supplementation may be more effective treatments for improving insulin resistance indicators associated with type 2 diabetes. [ABSTRACT FROM AUTHOR]

The Adenosine A2A Receptor, ADORA2A, is a protein-coding gene that plays a crucial role in neuromodulatory functions. High expression of the A2A receptor in human brain cells is one of the known stress biomarkers in the human brain. Furthermore, a high dose of caffeine can cause brain diseases like stroke and dementia. However, the effect of a high dose of caffeine on ADORA2A gene expression in human brain cells has never been investigated. Therefore, we hypothesized that caffeine might induce stress through an increased intracellular H2O2 level, which overexpresses ADORA2A in brain cells. First, when A172 human brain cells were incubated with various concentrations of caffeine, the caffeine-treated A172 cells showed a significantly higher ADORA2A expression level than the no caffeine-treated control sample. Second, when A172 human brain cells were treated with 0 µM caffeine and 20 µM caffeine, the 20 µM caffeine sample had a 3-fold increase in its H2O2 levels, demonstrating that caffeine increases intracellular H2O2 levels in A172 cells. Third, 30 µM and 50 µM of H2O2 treatment significantly increased the ADORA2A expression level, indicating that a higher H2O2 concentration leads to a higher ADORA2A expression level. Overall, we found that high doses of caffeine significantly augmented the ADORA2A expression levels through increased intracellular H2O2 in human brain cells. The application of this novel molecular mechanism may contribute to the development of therapeutic drugs for caffeine-induced stress in human brain cells.. [ABSTRACT FROM AUTHOR]

Caffeine has a stimulating effect on the central nervous system, which can reduce fatigue and drowsiness. In addition, it has been shown to improve sports performance. In this current study, researchers used a randomized, placebo-controlled single-blind parallel groups trial to investigate the effects of caffeine on the sprint performance of male university football players aged 18 to 25 years in the Multan zone of South Punjab, Pakistan. A total of 120 players were divided into four groups of 30 each, with each group receiving a different dose of caffeine in capsule form. Group A received 3 mg-kg-1, Group B received 6 mg-kg-1 and Group C received 9 mg-kg-1, while Group D was given a placebo 0mg-kg-1 . Sprint performance were measured through 20m Sprint test before and after the administration of caffeine and data analysis was conducted using GraphPad Prism version 6.0 software, with statistical tests like paired sample ‘‘t’’-test, ANOVA and Pearson correlation being applied to determine the relationship of each dose of caffeine on sprint performance. In our study, all three study groups 3, 6 and 9 mg/kg-1 presented conspicuous effects of caffeine on the 20-m sprint test. Overall results of this study showed that high doses 9 mg/kg-1 had prominent effects on the Sprint performance of university football players. Pearson correlation coefficient results showed that there was a positive significant correlation between Group B 6mg Pre and Group C 9mg Post. Moreover, high doses of caffeine do more to improve the sprint performance of university football players. [ABSTRACT FROM AUTHOR]

Rationale: Caffeine is the most consumed stimulant worldwide, and there is great interest in understanding its neurophysiological effects. Resting-state electroencephalography (EEG) studies suggest that caffeine enhances arousal, which suppresses the spectral power of alpha frequencies associated with reduced alertness. However, it is unclear whether caffeine's neurophysiological effects vary across the human menstrual cycle. Objective: The objective of our study was to test whether caffeine's effect on EEG activity differs across the human menstrual cycle. Methods: Fifty-six female participants were randomly assigned to complete the experiment while in either their menstrual (n = 21), follicular (n = 19), or luteal (n = 16) phase. Each participant completed two study sessions in the same menstrual phase, approximately 1 month apart, during which they were administered either a caffeine pill (200 mg, oral) or a placebo pill in a counterbalanced order using a randomized double-blinded procedure. We measured their eyes-closed resting-state EEG approximately 30 min after pill administration and conducted a spectral power analysis at different frequency bands. Results: Caffeine reduced EEG power in the alpha1 frequency band (8–10 Hz), but only for participants who self-reported higher weekly caffeine consumption. Importantly, caffeine's effects did not differ by menstrual phase. Conclusions: We conclude that when studying caffeine's effects on resting-state EEG, participants' baseline caffeine consumption is more influential than their menstrual cycle phase. This study has important implications for the inclusion of menstruating individuals in neurophysiological studies of caffeine. [ABSTRACT FROM AUTHOR]

Aims: Osteoporosis is a metabolic bone disease characterized by low bone mass and deteriorated bone tissue. There is ongoing debate about the effect of caffeine intake on bone metabolism due to inconsistent study results. This study aimed to assess the association between caffeine intake and bone mineral density (BMD). Methods: This single center cross-sectional study, prospectively enrolled postmenopausal women aged between 41 and 65 years who underwent bone mineral density measurement by dual-energy X-ray absorptiometry (DXA) at the lumbar spine and femoral neck. Caffeine intake was estimated using a food frequency questionnaire (FFQ) and a caffeine-specific FFQ. Patients consuming more than 260 mg/day caffeine were classified as high consumers. Results: The study included 80 subjects (mean age: 57.1±5.6 years). Daily caffeine intake was 229.7±119.5 mg, and 36.3% (n=29) of the patients was classified as high consumers. The mean total T-score was -1.4±0.9 at the lumbar spine and -1.7±0.9 at femoral neck. High and low caffeine consumers had similar mean total T-score at the lumbar spine (-1.4±1.1 vs. -1.4±0.8, p=0.849). However, femoral neck mean T-score was significantly lower in high caffeine consumers (-2.0±0.9 vs. -1.5±0.7, p=0.033). The amount of daily caffeine intake showed a negative, moderate correlation with femoral neck T-score (r=-0.251, p=0.025). Conclusions: The results of this study suggest that higher caffeine intake may be associated with lower T-scores on DXA of the femoral neck. [ABSTRACT FROM AUTHOR]

The ergogenic effects of caffeine supplementation on repeated-sprint ability (RSA) have produced equivocal results. This study aimed to examine the effects of 200 mg of caffeine during repeated-sprint running on heart rate (HR), rating of perceived exertion (RPE), blood lactate (BLa) concentration, and sprint time (ST). Thirty-two individuals (males: n = 17, females: n = 15; age: 22 ± 1 years) participated in the study. The study followed a double-blind, randomized, placebo-controlled, crossover design, in which each participant ingested 200 mg of caffeine or placebo on separate visits 60 minutes prior to repeated-sprinting exercise. The repeated-sprint protocol consisted of three sets of six maximal-effort 30-meter sprints with 20 seconds and 5 minutes of active recovery in between sprints and sets, respectively. During each set, HR, RPE, BLa, and ST were recorded. Caffeine supplementation did not significantly (set 1: p = 0.535; set 2: p = 0.602; set 3: p = 0.189) impact HR during exercise. Similarly, RPE was not statistically (p = 0.052) altered between conditions during any of the sprint sets. The caffeine trials elicited greater BLa values after all three sets compared to the placebo trials (p < 0.001). Moreover, the caffeine trials demonstrated significantly reduced total STs during all sets compared to the placebo trials (p < 0.001). Thus, our findings suggested that 200 mg of caffeine supplementation elicited an increase in RSA in young, healthy non-athletes. These findings are accompanied by a blunted perceived exertion relative to an increase in exercise intensity during repeated-sprint exercise. [ABSTRACT FROM AUTHOR]

The placebo effect of caffeine has been poorly investigated in endurance exercise. Therefore, the aim of this study was to analyze the placebo effect of caffeine on 4 km running performance in amateur runners. Twenty-two healthy and recreational male runners (25.5 ± 8.4 yrs; 75.0 ± 7.1 kg; 173.7 ± 6.3 cm) underwent a deceptive experimental design consisting of three different sessions: a) control (CON) in which participants did not ingest any substance; b) placebo (PLA) in which participants ingested a capsule filled with maltodextrin but they were informed that they would receive caffeine; c) caffeine (CAF) in which participants were informed that they would receive caffeine and actually received caffeine. After 60 min for substances absorption, participants performed a 4-km test and they completed the distance as fast as possible. The time employed to cover the distance was lower in PLA (17.4 ± 1.5 min) and CAF (17.4 ± 1.4 min) than CON sessions (18.6 ± 2.8 min; P<0.05). There were no differences in the 4-km times between PLA and CAF (P>0.05) and no differences were reported between treatments for RPE (P>0.05). In conclusion, there was a placebo effect of caffeine on a 4-km maximal running trial which entailed that believing to have ingested caffeine improved performance to a similar extent than actually receiving caffeine. Therefore, the expectancy induced by caffeine may be one of the mechanisms behinds the ergogenic effect of this stimulant on endurance exercise. [ABSTRACT FROM AUTHOR]

Caffeine may impact post-exercise heart rate variability (HRV); although, studies have yielded inconsistent findings. We examined the effects of low dose caffeine on post-exercise HRV. Healthy, college-aged adults [n = 18; age: 22.1 ± 2.6 years; BMI: 26.9 ± 4.3 kg/m2; estimated maximal oxygen consumption (VO2max): 45.1 ± 8.3 ml·kg-1·min-1] participated in a repeated-measures, double-blind, placebo-controlled trial. During the experimental trials, participants were fitted with a heart rate monitor and a mouthpiece with a one-way nonrebreathing valve and then rested for 10 min during baseline HRV and expired gas assessments. Participants chewed either caffeine (~170mg) or placebo gum for 5 min. Following expectoration and a 5 min warmup, participants walked on a treadmill for 20 min at 60% of estimated VO2max and then rested for 30 min. HRV indices were calculated from 10 min measurements during baseline and post-exercise (post 1, 2, and 3). A main effect of treatment was found for standard deviation of RR intervals (SDNN), absolute power of low frequency band (LF), absolute power of high frequency band (HF), and the standard deviation perpendicular to the line-of-identity in Poincaré plot (SD1) (p < 0.05). Further, a trend for higher root mean square of successive RR interval differences (RMSSD) with caffeine was observed (p = 0.066). Post hoc t-tests revealed that post-exercise SDNN, LF, HF, and SD1 were higher with caffeine compared to placebo (p = 0.012). Results demonstrated that low dose caffeine did not delay the recovery of HRV indices reflective of parasympathetic nervous system activity following an acute bout of moderate exercise. [ABSTRACT FROM AUTHOR]

Aim: To evaluate the effect of excessive caffeine intake on the inflammation/resorption processes associated with periapical periodontitis (PP) in rats. Methodology: Sixteen Wistar rats were used. Periapical periodontitis was induced in the four first molars in each animal. The animals were arranged into two groups: control (C)—rats with periapical periodontitis; and caffeine (CAF)—rats with periapical periodontitis under caffeine administration protocol. The CAF animals received 10 mg/100 g of body weight/day of caffeine via gavage starting fifteen days before PP induction and continuing for thirty more days until euthanasia. On the 30th day, the animals were euthanized and the jaws removed for microcomputed tomography, histological and immunohistochemical analysis for RANKL, OPG, TRAP, IL‐10, TNF‐⍺ and IL‐1β. The Mann–Whitney test was performed for nonparametric data, and Student's t test was performed for parametric data, using p <.05. Results: There was no significant difference in the weight change between the groups. The median score of the inflammatory process was significantly greater in the CAF group (3) compared with the C group (2), p =.0256. Bone resorption was greater in the group consuming caffeine (1.08 ± 0.15 mm3) compared with the C group (0.88 ± 0.10 mm3), p =.0346. The immunolabelling for RANKL, TRAP and IL‐1β was significantly higher in the CAF group when compared to the control, p <.05. No differences were found for the OPG, IL‐10 and TNF‐⍺ immunolabelling. Conclusion: Excessive caffeine exposure via gavage in rats was able to exacerbate the volume of periapical bone destruction, and the inflammatory pattern deriving from periapical periodontitis altering the expression of RANKL, IL‐1β and TRAP. [ABSTRACT FROM AUTHOR]

Background: In this study, we evaluate the available evidence regarding caffeine communication and its effect on cognitive function in people with ADHD. This systematic review examined various articles on this topic. Methods: In this systematic review, the selection of studies was carried out using the PubMed, Scopus databases, with a focus on articles published from 2000 to 2024. The search utilized keywords and MeSH terms such as "attention deficit disorder with hyperactivity" (ADHD) and "caffeine." Specifically, randomized control trial articles that investigated the use of caffeine as an intervention for individuals with ADHD were included in the present study. The comparison was made between participants who received caffeine as an intervention and those who did not, in order to assess the potential impact of caffeine on individuals with ADHD. Result: The research initially encompassed 121 articles containing 52 file attachments, identifying 2 final studies conducted in the USA and UK between 2019 and 2020. The studies reported using caffeine as an intervention, with a dosage of 2mg/kg for children aged 6-17 and 4mg/kg for adults aged 19-47. Specifically, the study by Kahathuduwa et al., involved 6 children, while the study by Hampsey et al., involved 27 adults. The findings from the studies indicated that the combination of caffeine and L-Theanine demonstrated improvements in Cognition composite, 11.4(p = 0.040). points greater than the mean cognition composite in placebo for children, and a decrease in the mean count of microsaccades in adults, had a 0.22(p:0.00027) decreasing effect In comparison with control group. Both studies were deemed to have acceptable methodological quality. Conclusion: This systematic review showed that caffeine supplementation could be a beneficial intervention in this disorder, however further research is needed to complete our view of this valuable field. [ABSTRACT FROM AUTHOR]

OBJECTIVE Preterm infants often require caffeine for the treatment of apnea. While the maintenance dose of caffeine citrate is usually administered once daily per FDA labeling, many providers administer the maintenance dose in two divided doses. This study evaluated the effectiveness of a twice daily dosing regimen of caffeine for apnea of prematurity. METHODS This was a retrospective analysis conducted from 2013-2018 that included preterm infants who received caffeine that was dosed both once and twice daily respectively. The primary outcome of our study was a composite of the number of apneic and bradycardic events for five 24-hour periods prior to switching to twice daily dosing of caffeine and five 24-hour periods after switching to twice daily dosing of caffeine. RESULTS The median five-day average incidence of apnea and bradycardia during the once and twice daily dosing periods was 6.2 events and 6.4 events respectively (p=0.09). CONCLUSIONS There is little benefit of twice daily dosing of caffeine for apnea of prematurity. ABBREVIATIONS FDA, US Food and Drug Administration [ABSTRACT FROM AUTHOR]

The main goal of this study was to evaluate the effectiveness of an acute dose of caffeine (6 mg/kg body mass (b.m.)) on power output and bar velocity during a bench press multiple-set resistance training session in participants with mild daily caffeine consumption (in the range of 1 to 3 mg/kg/b.m). Thirteen recreationally active male participants (age: 21.9 ± 1.2 years, body mass: 74.4 ± 5.3 kg, body mass index: 23.1 ± 1.6 kg/m2, bench press onerepetition maximum (1RM): 79.2 ± 14.9 kg), with daily caffeine ingestion of 1.56 ± 0.56 mg/kg/b.m., participated in the study with a randomized double-blind experimental design. Each participant performed two identical experimental sessions, 60 min after the intake of a placebo (PLAC) or 6 mg/kg/b.m. of caffeine (CAF-6). In each experimental session, participants performed 5 sets of 5 repetitions of the bench press exercise with a load equivalent to 70% 1RM. The eccentric and concentric phases of the bench press exercise were performed at maximal possible velocity in each repetition. Bar velocity was recorded with a linear position transducer and power output was calculated using velocity and load data. A two-way repeated measures ANOVA indicated no significant substance x set interaction for mean power output (MP), mean bar velocity (MV), peak power output (PP) and peak bar velocity (PV). However, there was a significant main effect of substance on MP (p < 0.01; η2 = 0.47) and MV (p < 0.01; η2 =0.45). Post hoc analysis for main effect revealed that MP and MV values in the CAF-6 group were higher than in the PLAC group in all 5 sets of the exercise (p < 0.05). In conclusion, this study demonstrated that an acute dose of caffeine before resistance exercise increased mean power output and mean bar velocity during a multiple-set bench press exercise protocol among mild caffeine users. [ABSTRACT FROM AUTHOR]

Extraverts are active and talkative, while introverts are quiet and calm. This difference has been attributed to the cortical activation level (arousal), which is low in extraverts and high in introverts. Thus, to reach an optimal level of arousal, extraverts seek stimulation and introverts avoid it. As caffeine increases arousal levels, our primary aim was to investigate the effect of caffeine on the performance of extraverted and introverted university students in the execution of stability, manipulative, and locomotor tasks. Considering the above, we evaluated side effects, such as restlessness and trembling of hands, we also analyzed the individual's perception regarding caffeine intake and the placebo. Forty two volunteers were classified as 21 extraverts and 21 introverts by the Eysenck Personality Questionnaire. Participants performed three tasks on two different days, having previously ingested caffeine and a placebo in counterbalanced order. A double-blind technique was employed. The dependent variable was the execution time to perform the tasks. The analyses of variance [2 (extraversion/introversion) x 2 (caffeine x placebo)] for each task did not show significant differences. Regarding the secondary aim, the chi-square test showed that introverts had a better perception of the substance they had ingested than did extraverts. Our findings indicate that in the execution of stability, manipulative, and locomotor tasks, either caffeine or the placebo produced the same effect, regardless of the participants' extraversion score. In addition, introverts were more sensitive to perceive which substance was ingested, caffeine or the placebo, than extraverts. [ABSTRACT FROM AUTHOR]

Hepatic encephalopathy is a pathophysiological complication of acute liver failure, which may be triggered by hepatotoxic drugs such as acetaminophen (APAP). Although APAP is safe in therapeutic concentration, APAP overdose may induce neurotoxicity, which is mainly associated with oxidative stress. Caffeine is a compound widely found in numerous natural beverages. However, the neuroprotective effect of caffeine remains unclear during APAP intoxication. The present study aimed to investigate the possible modulatory effects of caffeine on brain after APAP intoxication. Mice received intraperitoneal injections of APAP (250 mg/kg) and/or caffeine (20 mg/kg) and, 4 h after APAP administration, samples of brain and blood were collected for the biochemical analysis. APAP enhanced the transaminase activity levels in plasma, increased oxidative stress biomarkers (lipid peroxidation and reactive oxygen species), promoted an imbalance in endogenous antioxidant system in brain homogenate and increased the mortality. In contrast, APAP did not induce dysfunction of the mitochondrial bioenergetics. Co-treatment with caffeine modulated the biomarkers of oxidative stress as well as antioxidant system in brain. Besides, survival assays demonstrated that caffeine protective effects could be dose- and time-dependent. In addition, caffeine promoted an increase of mitochondrial bioenergetics response in brain by the enhancement of the oxidative phosphorylation, which could promote a better energy supply necessary for brain recovery. In conclusion, caffeine prevented APAP-induced biochemical alterations in brain and reduced lethality in APAP-intoxicated mice, these effects may relate to the preservation of the cellular antioxidant status, and these therapeutic properties could be useful in the treatment of hepatic encephalopathy induced by APAP intoxication. [ABSTRACT FROM AUTHOR]

Aims: The long‐term impact of coffee or tea consumption on subclinical left ventricular (LV) systolic or diastolic function has not been previously studied. We examined the association between coffee or tea consumption beginning in early adulthood and cardiac function in midlife. Methods and results: We investigated 2735 Coronary Artery Risk Development in Young Adults (CARDIA) study participants with long‐term total caffeine intake, coffee, and tea consumption data from three visits over a 20 year interval and available echocardiography indices at the CARDIA Year‐25 exam (2010–2011). Linear regression models were used to assess the association between caffeine intake, tea, and coffee consumption (independent variables) and echocardiography outcomes [LV mass, left atrial volume, and global longitudinal strain (GLS), LV ejection fraction (LVEF), and transmitral Doppler early filling velocity to tissue Doppler early diastolic mitral annular velocity (E/e´)]. Models were adjusted for standard cardiovascular risk factors, socioeconomic status, physical activity, alcohol use, and dietary factors (calorie intake, whole and refined grain intake, and fruit and vegetable consumption). Mean (standard deviation) age was 25.2 (3.5) years at the CARDIA Year‐0 exam (1985–1986), 57.4% were women, and 41.9% were African‐American. In adjusted multivariable linear regression models assessing the relationship between coffee consumption and GLS, beta coefficients when comparing coffee drinkers of <1, 1–2, 3–4, and >4 cups/day with non‐coffee drinkers were β = −0.30%, P < 0.05; β = −0.35%, P < 0.05; β = −0.32%, P < 0.05; β = −0.40%, P > 0.05; respectively (more negative values implies better systolic function). In adjusted multivariable linear regression models assessing the relationship between coffee consumption and E/e´, beta coefficients when comparing coffee drinkers of <1, 1–2, 3–4, and >4 cups/day with non‐coffee drinkers were β = −0.29, P < 0.05; β = −0.38, P < 0.01; β = −0.20, P >.05; and β = −0.37, P > 0.05, respectively (more negative values implies better diastolic function). High daily coffee consumption (>4 cups/day) was associated with worse LVEF (β = −1.69, P < 0.05). There were no associations between either tea drinking or total caffeine intake and cardiac function (P > 0.05 for all). Conclusions: Low‐to‐moderate daily coffee consumption from early adulthood to middle age was associated with better LV systolic and diastolic function in midlife. High daily coffee consumption (>4cups/day) was associated with worse LV function. There was no association between caffeine or tea intake and cardiac function. [ABSTRACT FROM AUTHOR]

Caffeine is a drug, which is consumed by the majority of the world population. It is available in various ingestible forms which makes it easier to consume. Caffeine is considered to be one of the major and most widely consumed stimulating drugs in this world. The effects of caffeine on the human body include cardiovascular diseases, insomnia, high blood pressure, diabetes mellitus and cancer lines etc. The withdrawal symptoms of caffeine include headache, flu like symptoms, fatigue etc. A questionnaire was distributed through an online google forms link to about 100 people of South Indian population belonging to all age groups. The study population were asked to fill out the forms. The results were collected and the data was analysed using SPSS version 20. When the study population was asked if they were aware about caffeine addiction and its effects, about 79.21% of the total respondents answered positively. 61% respondents were not aware of the fact that increased caffeine consumption might lead to diseases such as coronary heart disease, insomnia, high blood pressure etc. Conclusion: By this survey it is concluded that a more severe approach on the awareness of caffeine addiction and its various ill effects could be administered among the South Indian population for the betterment of lifestyle and health. [ABSTRACT FROM AUTHOR]

Carbohydrate and caffeine are known to independently improve certain aspects of athletic performance. However, less is understood about physiological and performance outcomes when these compounds are coingested in a rehydration and carbohydrate-replacement strategy. The aim of this study was to examine the influence of adding a moderate dose of caffeine to a carbohydrate solution during prolonged soccer activity. Fifteen male soccer players performed two 90-min intermittent shuttle-running trials. They ingested a carbohydrateelectrolyte solution (CON) providing a total of 1.8 g/kg body mass (BM) of carbohydrate or a similar solution with added caffeine (CAF; 3.7 mg/kg BM). Solutions were ingested 1 hr before exercise and every 15 min during the protocol. Soccer passing skill and countermovement-jump height (CMJ) were quantified before exercise and regularly during exercise. Sprinting performance, heart rate, blood lactate concentration (La) and the subjective experiences of participants were measured routinely. Mean 15-m sprint time was faster during CAF (p = .04); over the final 15 min of exercise mean sprint times were CAF 2.48 ± 0.15 s vs. CON 2.59 ± 0.2 s. Explosive leg power (CMJ) was improved during CAF (52.9 ± 5.8 vs. CON 51.7 ± 5.7 cm, p = .03). Heart rate was elevated throughout CAF, and ratings of pleasure were significantly enhanced. There were no significant differences in passing skill, rating of perceived exertion, La, or body-mass losses between trials. The addition of caffeine to the carbohydrate-electrolyte solution improved sprinting performance, countermovement jumping, and the subjective experiences of players. Caffeine appeared to offset the fatigue-induced decline in self-selected components of performance. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to evaluate the effects of caffeine ingestion before a resistance exercise session on markers of muscle damage (CK, LDH, ALT, AST) and leukocyte levels. Methods: Fifteen soccer athletes completed two resistance exercise sessions that differed only in the ingestion of caffeine or a placebo preworkout. Results: CK concentration increased significantly following the caffeine session (415.8 ± 62.8 to 542.0 ± 73.5) and the placebo session (411.5 ± 43.3 to 545.8 ± 59.9), with no significant differences between sessions. Similarly, LDH concentration increased significantly following the caffeine session (377.5 ± 18.0 to 580.5 ± 36.1) and the placebo session (384.8 ± 13.9 to 570.4 ± 36.1), with no significant differences between sessions. Both sessions resulted in significant increases in the total leukocyte count (caffeine = 6.24 ± 2.08 to 8.84 ± 3.41; placebo = 6.36 ± 2.34 to 8.77 ± 3.20), neutrophils (caffeine = 3.37 ± 0.13 to 5.15 ± 0.28; placebo = 3.46 ± 0.17 to 5.12 ± 0.24), lymphocytes (caffeine = 2.19 ± 0.091 to 2.78 ± 0.10; placebo = 2.17 ± 0.100 to 2.75 ± 0.11), and monocytes (caffeine = 0.53 ± 0.02 to 0.72 ± 0.06; placebo = 0.56 ± 0.03 to 0.69 ± 0.04), with no significant differences between sessions. Conclusion: Ingestion of caffeine at 4.5 mg·kg-1 did not augment markers of muscle damage or leukocyte levels above that which occurs through resistance exercise alone. [ABSTRACT FROM AUTHOR]

Purpose: This study examined the placebo effect of caffeine on number of repetitions (reps), rating of perceived exertion (RPE), blood pressure (BP), and peak heart rate (PHR) during resistance-training exercise with repetitions (reps) performed to volitional failure. Methods: Following determination of 1-rep maximum in single-leg leg extension, 15 males performed reps to failure at 60% 1-RM in 3 conditions: control, perceived caffeine condition, and perceived placebo condition presented in a randomized order. Participants were informed they would ingest 250 mL of solution that contained either 3 mg·kg-1 caffeine or 3 mg·kg-1 placebo 1 h before each exercise trial. A deceptive protocol was employed and subjects consumed a placebo solution in both conditions. During each condition, total reps, RPE for the active muscle and overall body, and PHR were recorded. Results: Subjects completed 2 more reps when they perceived they had ingested caffeine. RPE was significantly (P = .04) lower in the perceived caffeine and control conditions and RPE for the active muscle was significantly higher across all conditions compared with RPE for the overall body. No substantial differences were evident in PHR across conditions. Conclusions: Results of this study are similar to studies of actual caffeine ingestion. However, the perception of consuming a substance that purportedly enhances performance is sufficient enough to enable individuals to complete a greater number of reps to failure during short-term resistance exercise. [ABSTRACT FROM AUTHOR]

The study's objective was to determine whether orally ingested caffeine could help overcome excitation-contraction-coupling failure, which has been suggested to explain part of the strength loss associated with eccentric-contraction-induced muscle injury. A sample of 13 college students (4 men and 9 women) was used in a double-blind, repeated-measures experimental design. Each participant performed 2 experimental trials, 1 with each leg, with each trial lasting 4 consecutive days. On a given day, each participant was randomly assigned to ingest a capsule containing 6 mg/kg of either caffeine or flour (placebo). On the day of and the first 2 days after a bout of 50 injurious eccentric contractions done by the knee extensors, the interpolated-twitch technique was used to assess electrically evoked strength, maximal voluntary isometric contraction (MVIC) strength, and percent muscle activation during MVIC both before and after capsule ingestion. These variables were also measured before and after capsule ingestion the day before the eccentric-contraction bout—when the muscle was uninjured. In injured muscle, caffeine had no effect on any variable. In uninjured muscle, caffeine also had no effect on electrically evoked strength but increased MVIC strength by 10.4% compared with placebo (p = .00002), and this was attributed to an increase in muscle activation (6.2%; p = .01). In conclusion, the data provide no evidence that caffeine ingestion can help overcome excitation-contraction-coupling failure, if it exists, in injured human muscle. The data do indicate that caffeine ingestion can increase MVIC strength and activation in uninjured muscle but not in injured muscle. [ABSTRACT FROM AUTHOR]

The purpose of this experiment was to learn whether low doses of caffeine have ergogenic, perceptual, and metabolic effects during cycling. To determine the effects of 1, 2, and 3 mg/kg caffeine on cycling performance, differentiated ratings of perceived exertion (D-RPE), quadriceps pain intensity, and metabolic responses to cycling exercise, 13 cyclists exercised on a stationary ergometer for 15 min at 80% VO2peak, then, after 4 min of active recovery, completed a 15-min performance ride 60 min after ingesting caffeine or placebo. Work done (kJ/kg) during the performance ride was used as a measure of performance. D-RPE, pain ratings, and expired-gas data were obtained every 3 min, and blood lactate concentrations were obtained at 15 and 30 min. Compared with placebo, caffeine doses of 2 and 3 mg/kg increased performance by 4% (95% CI: 1.0-6.8%, p = .02) and 3% (95% CI: -0.4% to 6.8%, p = .077), respectively. These effects were ergogenic, on average, but varied considerably in magnitude among individual cyclists. There were no effects of caffeine on D-RPE or pain throughout the cycling task. Selected metabolic variables were affected by caffeine, consistent with its known actions. The authors conclude that caffeine preparations of 2 and 3 mg/kg enhanced performance, but future work should aim to explain the considerable interindividual variability of the drug's ergogenic properties. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this work was to determine the effects of caffeine on high intensity time trial (TT) cycling performance in well-trained subjects. Subjects: Six male cyclists with the following physical characteristics (mean ± SD) age 30.7 ± 12, height 179.3 ± 7.5 cm, mass 70.0 ± 7.5 kg, VO2max 65.0 ± 6.3 mL·kg-1·min-1 undertook three 1-h TT performances, control (C), placebo (P) and caffeine (CAF), on a Velotron cycle ergometer conducted in a double-blind, random fashion. Subjects rested for 60 min and were then given CAF or P in a dose of 6 mg·kg-1 body mass and then commenced exercise after another 60 min of rest. Before ingestion, 60 min postingestion, and at the end of the TT, finger-prick blood samples were analyzed for lactate. Results: The cyclists rode significantly further in the CAF trial (28.0 ± 1.3 km) than they did in the C (26.3 ± 1.5 km, P < .01) or P (26.4 ± 1.5 km, P < .02) trials. No differences were seen in heart rate data throughout the TT (P > .05). Blood lactate levels were significantly higher at the end of the trials than either at rest or postingestion (P < .0001), but there were no differences between the three trial groups. Conclusion: On the basis of the data, we concluded that performance was improved with the use of a caffeine supplement. [ABSTRACT FROM AUTHOR]

Introduction: Interest in the use of caffeine as an ergogenic aid has increased since the International Olympic Committee lifted the partial ban on its use. Caffeine has beneficial effects on various aspects of athletic performance, but its effects on training have been neglected. Purpose: To investigate the acute effect of caffeine on the exercise-associated increases in testosterone and cortisol in a double-blind crossover study. Methods: Twenty-four professional rugby-league players ingested caffeine doses of 0, 200, 400, and 800 mg in random order 1 hr before a resistance-exercise session. Saliva was sampled at the time of caffeine ingestion, at 15-min intervals throughout each session, and 15 and 30 min after the session. Data were log-transformed to estimate percent effects with mixed modeling, and effects were standardized to assess magnitudes. Results: Testosterone concentration showed a small increase of 15% (90% confidence limits, ± 19%) during exercise. Caffeine raised this concentration in a dose-dependent manner by a further small 21% (± 24%) at the highest dose. The 800-mg dose also produced a moderate 52% (± 44%) increase in cortisol. The effect of caffeine on the testosterone:cortisol ratio was a small decline (14%; ± 21%). Conclusion: Caffeine has some potential to benefit training outcomes via the anabolic effects of the increase in testosterone concentration, but this benefit might be counteracted by the opposing catabolic effects of the increase in cortisol and resultant decline in the testosterone:cortisol ratio. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effects of sodium bicarbonate (NaHCO3), caffeine, and their combination on repeated 200-m freestyle performance. Six elite male freestyle swimmers ingested NaHCO3 (0.3 g/kg; B), caffeine (6.2 ± 0.3 mg/kg; C), a combination of both (B+C), and placebo (P) on 4 separate occasions before completing 2 maximal 200-m freestyle time trials (TT1 and TT2) separated by 30 min. No significant differences (p = .06) were observed for performance in TT1 (B 2:03.01 ± 0:03.68 min, C 2:02.42 ± 0:03.17 min, B+C 2:01.69 ± 0:03.19 min, P 2:03.77 ± 0:03.21 min) or TT2 (B 2:02.62 ± 0:04.16 min, C 2:03.90 ± 0:03.58 min, B+C 2:01.70 ± 0:02.84 min, P 2:04.22 ± 0:03.75 min). The drop-off in performance time from TT1 to TT2, however, was significantly greater when C was ingested than with B (-1.5%, p = .002) or B+C (-1.2%, p = .024). This is likely because of the lower blood pH and slower recovery of blood HCO3 post-TT1 after C ingestion. These findings suggest that the ergogenic benefit of taking C alone for repeated 200-m swimming performance appears limited. When combined with NaHCO3, however, its negative impact on repeated maximal exercise performance is reversed. [ABSTRACT FROM AUTHOR]

This experiment examined the effect of a moderate dose of caffeine on perceptions of leg-muscle pain during a bout of high-intensity cycling exercise and the role of anxiety sensitivity in the hypoalgesic effect of caffeine on muscle pain during exercise. Sixteen college-age women ingested caffeine (5 mg/kg body weight) or a placebo and 1 hr later completed 30 min of cycling on an ergometer at 80% of peak aerobic capacity. The conditions were completed in a counterbalanced order, and perceptions of leg-muscle pain were recorded during the bouts of exercise. Caffeine resulted in a large reduction in leg-muscle pain-intensity ratings compared with placebo (d = -0.95), and the reduction in leg-muscle pain-intensity ratings was larger in those with lower anxiety-sensitivity scores than those with higher anxiety-sensitivity scores (d = -1.28 based on a difference in difference scores). The results support that caffeine ingestion has a large effect on reducing leg-muscle pain during high-intensity exercise, and the effect is moderated by anxiety sensitivity. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effects of prolonged simulated tennis on performance and the ergogenic potential of caffeine, carbohydrates, and cooling. Methods: Twelve highly trained male tennis players (age 18.3 ± 3.0 y, height 178.8 ± 8.5 cm, body mass 73.95 ± 12.30 kg, mean ± SD) performed 4 simulated matches (2 h 40 min) against a ball machine on an indoor hard court. The counterbalanced experimental trials involved caffeine supplementation (3 mg/kg), carbohydrate supplementation (6% solution), precooling and intermittent cooling, and placebo control. Physiological markers (core temperature, heart rate, blood lactate, and blood glucose), subjective responses (ratings of perceived exertion and thermal sensation), stroke velocity and accuracy, serve kinematics, and tennis-specific perceptual skill quantified the efficacy of interventions. Results: Significant effects of time (P < .01) reflected increased physiological demand, reduced serve velocity and ground-stroke velocity and accuracy, and a slowing of the serve racket-arm acceleration phase. Caffeine increased serve velocity (165 ± 15 km/h) in the final set of the match (P = .014) compared with placebo (159 ± 15 km/h, P = .008) and carbohydrate (158 ± 13 km/h, P = .001) conditions. Carbohydrate and cooling conditions afforded physiological advantage (increased blood glucose, P < .01, and reduced preexercise thermal sensation, P < .01) but did not affect performance relative to the placebo condition. Conclusions: Prolonged simulated tennis induced significant decrements in tennis skills. Caffeine supplementation partly attenuated the effects of fatigue and increased serve velocity. In contrast, carbohydrate and cooling strategies had little ergogenic effect on tennis performance. [ABSTRACT FROM AUTHOR]

We compared the influence of caffeine on physiological responses to exercise between boys and men. Fifty-two participants (26 boys and 26 men) participated in a double blind, randomized, double crossover study. Each participant received the caffeinated (5 mg/kg) drink (CAF) and placebo (PL) twice each on 4 separate days. One hour after drink consumption preexercise heart rate (HR) and blood pressure (BP) were measured. Then while the participants rode stationary cycle ergometers at two different exercise intensities, HR, BP, and oxygen consumption (VO2) were measured. Blood pressure was not significantly affected by CAF, although on average it was always higher in boys for diastolic BP (3 mmHg) and systolic BP (3-4 mmHg) and men for diastolic BP (2-3 mmHg) and systolic BP (1-6 mmHg) both at rest and during exercise. HR was significantly (p < .05) lower at rest, 25W and 50W in CAF versus PL in boys, with no change in adults. During exercise, VO2 and respiratory exchange ratio (RER) were not different in CAF versus PL in either group. In conclusion, metabolism is not affected by a moderate caffeine dose in children or adults. The same dose has a similar effect on BP in both groups. The effect on HR was different, however, with a significant (p < .05) lowering in children in CAF versus PL, with no adult effects. [ABSTRACT FROM AUTHOR]

Caffeine (CAF) exerts a pressor effect both at rest and during exercise, as blood pressure is higher than with placebo. The effect of acute CAF ingestion combined with intense resistance training on cardiovascular function is unknown, however. The primary aim of the study was to examine changes in cardiovascular function after completion of fatiguing bench-press and leg-press exercise after CAF or placebo ingestion. Twenty-two resistance-trained men ingested CAF (6 mg/kg) or placebo 1 h preexercise in a randomized, double-blind crossover design. They refrained from CAF intake and strenuous exercise 48 and 24 h pretrial, respectively. Heart rate and blood pressure were measured preexercise. After a standardized warm-up, 1-repetition-maximum (1-RM) on the barbell bench press and leg press was tested. When it had been determined, a load equivalent to 60% of 1-RM was placed on the bar, and the subject completed repetitions to failure. Measurements of heart rate and blood pressure were immediately completed, and mean arterial pressure and rate-pressure product were calculated. Results showed significant (P < 0.05) increases in heart rate (+ 10 beats/min), systolic blood pressure (+ 8-10 mmHg), and rate-pressure product with acute CAF ingestion versus placebo. No change (P > 0.05) in diastolic blood pressure across time or treatment was shown. To prevent elevated blood pressure and potential enhanced risk of heart disease, CAF intake should be monitored in at-risk men who participate in resistance training. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effects of Red Bull energy drink on Wingate cycle performance and muscle endurance. Healthy young adults (N = 15, 11 men, 4 women, 21 ± 5 y old) participated in a crossover study in which they were randomized to supplement with Red Bull (2 mg/kg body mass of caffeine) or isoenergetic, isovolumetric, noncaffeinated placebo, separated by 7 d. Muscle endurance (bench press) was assessed by the maximum number of repetitions over 3 sets (separated by 1-min rest intervals) at an intensity corresponding to 70% of baseline 1-repetition maximum. Three 30-s Wingate cycling tests (load = 0.075 kp/kg body mass), with 2 min recovery between tests, were used to assess peak and average power output. Red Bull energy drink significantly increased total bench-press repetitions over 3 sets (Red Bull = 34 ± 9 vs. placebo = 32 ± 8, P < 0.05) but had no effect on Wingate peak or average power (Red Bull = 701 ± 124 W vs. placebo = 700 ± 132 W, Red Bull = 479 ± 74 W vs. placebo = 471 ± 74 W, respectively). Red Bull energy drink significantly increased upper body muscle endurance but had no effect on anaerobic peak or average power during repeated Wingate cycling tests in young healthy adults. [ABSTRACT FROM AUTHOR]

Context: Ergogenic effects of caffeine on aerobic or endurance exercise are well documented. Conversely, the ergogenic value of caffeine on high-intensity, primarily anaerobic performance is not well understood even though the proposed mechanisms of action for caffeine permit a strong theoretical basis for application to this type of exercise. Purpose: This study examined effects of caffeine (Ca) on number repetitions (reps), ratings of perceived exertion (RPE), and peak heart rate (PHR) during resistance-training exercise with reps performed to volitional failure. Methods: Subjects (N = 17) were tested for 10-rep maximum in bench press (BP) and leg press (LP). In sessions 2 and 3, Ca (∼6 mg/kg) or placebo (Pl) was ingested 1 hr beforehand in a double-blind manner and counterbalanced order. Subjects performed 3 sets to failure (BP and LP) with reps, PHR, and RPE recorded each set. Repeated-measures ANOVAs, 2 (trial) × 3 (set), were used to analyze dependent measures with the Tukey honestly significant difference used when necessary as the post hoc test. Results: In BP, no significant differences (Ca vs Pl) were observed (reps, RPE, PHR). During set 3 of LP training, Ca was associated with significantly higher reps (12.5 ± 4.2 vs 9.9 ± 2.6) and PHR (158.5 ± 11.9 vs 151.8 ± 13.2). No significant RPE differences were found during LP. Conclusions: The findings of similar RPE concurrent with higher reps suggest that caffeine can blunt pain responses, possibly delaying fatigue in high-intensity resistance training. Ergogenic effects might be limited to the later sets in a resistance-training session. Further research is warranted regarding ergogenic effects of caffeine during resistance training and potential mechanisms of action. [ABSTRACT FROM AUTHOR]

This descriptive cross-sectional study assessed the perceptions, knowledge, and experiences of caffeine use by athletes competing at the 2005 Ironman Triathlon World Championships. Questionnaires were distributed to 140 athletes (105 men and 35 women, 40.3 ± 10.7 y old) representing 16 countries during prerace registration. A large proportion (73%) of these endurance athletes believe that caffeine is ergogenic to their endurance performance, and 84% believe it improves their concentration. The most commonly reported positive caffeine experiences related to in-competition use of cola drinks (65%) and caffeinated gels (24%). The athletes' ability to accurately quantify the caffeine content of common food items was limited. The most popular sources of caffeine information were self-experimentation (16%), fellow athletes (15%), magazines (13%), and journal articles (12%). Over half the athletes (53%) could not identify an amount of caffeine required to improve their triathlon performance. Mean (± standard deviation) suggested doses were 3.8 (± 3) mg/kg body weight. Few side effects associated with taking caffeine during exercise were reported. [ABSTRACT FROM AUTHOR]

Caffeine is regarded as a diuretic despite evidence that hydration is not impaired with habitual ingestion. The purpose of this study was to determine whether a caffeinated sports drink impairs fluid delivery and hydration during exercise in warm, humid conditions (28.5 °C, 60% relative humidity). Sixteen cyclists completed 3 trials: placebo (P), carbohydrate-electrolyte (CE), and caffeinated (195 mg/L) sports drink (CAF+CE). Subjects cycled for 120 min at 60-75% VO2max followed by 15 min of maximal-effort cycling. Heart rate and rectal temperature were similar until the final 15 min, when these responses and exercise intensity were higher with CAF+CE than with CE and P. Sweat rate, urine output, plasma-volume losses, serum electrolytes, and blood deuterium-oxide accumulation were not different. Serum osmolality was higher with CAF+CE vs. P but not CE. The authors conclude that CAF+CE appears as rapidly in blood as CE and maintains hydration and sustains cardiovascular and thermoregulatory function as well as CE during exercise in a warm, humid environment. [ABSTRACT FROM AUTHOR]

This double-blind experiment examined the effects of a caffeinated sports drink during prolonged cycling in a warm environment. Sixteen highly trained cyclists completed 3 trials: placebo, carbohydrate-electrolyte sports drink (CES), and caffeinated sports drink (CES+CAF). Subjects cycled for 135 min, alternating between 60% and 75% VO2max every 15 min for the first 120 min, followed by a 15-min performance ride. Maximal voluntary (MVC) and electrically evoked contractile properties of the knee extensors were measured before and after cycling. Work completed during the performance ride was 15-23% greater for CES+CAF than for the other beverages. Ratings of perceived exertion were lower with CES+CAF than with placebo and CES. After cycling, the MVC strength loss was two-thirds less for CES+CAF than for the other beverages (5% vs. 15%). Data from the interpolated-twitch technique indicated that attenuated strength loss with CES+CAF was explained by reduced intrinsic muscle fatigue. [ABSTRACT FROM AUTHOR]

People of all ages and fitness levels participate regularly in aerobic-dance bench stepping (ADBS) to increase fitness and control body weight. Any reasonable method for enhancing the experience or effectiveness of ADBS would be beneficial. This study examined the acute effects of a single dose of caffeine on physiological responses during ADBS in women. When compared with a placebo, neither a 3- nor a 6-mg/kg dose of caffeine altered physiological responses or rating of perceived exertion (RPE) in 20 women (age 19-28 y) of average fitness level, not habituated to caffeine, while they performed an ADBS routine. Since neither dose of caffeine had any effect on VO2, Vco2, minute ventilation, respiratory-exchange ratio, rate of energy expenditure, heart rate, or RPE during ADBS exercise, it would not be prudent for a group exercise leader to recommend caffeine to increase energy cost or decrease perception of effort in an ADBS session. Furthermore, caffeine ingestion should not interfere with monitoring intensity using heart rate or RPE during ADBS. [ABSTRACT FROM AUTHOR]

This study investigated the effects of caffeine on repeated, anaerobic exercise using a double-blind, randomized, crossover design. Seventeen subjects (five female) underwent cognitive (reaction time, number recall) and blood (glucose, potassium, catecholamines, lactate) testing before and after consuming caffeine (6 mg/kg), placebo, or nothing (control). An exercise test (two 60 s maximal cycling bouts) was conducted 90 min after caffeine/placebo consumption. Plasma caffeine concentrations significantly increased after caffeine ingestion, however, there were no positive effects on cognitive or blood parameters except a significant decrease in plasma potassium concentrations at rest. Potentially negative effects of caffeine included significantly higher blood lactate compared to control and significantly slower time to peak power in exercise bout 2 compared to control and placebo. Caffeine had no significant effect on peak power, work output, RPE, or peak heart rate. In conclusion, caffeine had no ergogenic effect on repeated, maximal cycling bouts and may be detrimental to anaerobic performance. [ABSTRACT FROM AUTHOR]

Context: Dieticians, physiologists, athletic trainers, and physicians have recommended refraining from caffeine intake when exercising because of possible fluid-electrolyte imbalances and dehydration. Objective: To assess how 16-hour rehydration is affected by caffeine ingestion. Design: Dose-response. Setting: Environmental chamber. Participants: 59 college-age men. Intervention: Sub-jects consumed a chronic caffeine dose of 0 (placebo), 3, or 6 mg · kg-1 · day-1 and performed an exercise heat-tolerance test (EHT) consisting of 90 minutes of walking on a treadmill (5.6 km/h) in the heat (37.7 °C). Outcome Measures: Fluid-electrolyte measures. Results: There were no between-group differences immediately after and 16 hours after EHT in total plasma protein, hematocrit, urine osmolality, specific gravity, color, and volume. Body weights after EHT and the following day (16 hours) were not different between groups (P > .05). Conclusion: Hydration status 16 hours after EHT did not change with chronic caffeine ingestion. [ABSTRACT FROM AUTHOR]

This investigation determined if 3 levels of controlled caffeine consumption affected fluid-electrolyte balance and renal function differently. Healthy males (mean ± standard deviation; age, 21.6 ± 3.3 y) consumed 3 mg caffeine · kg-1 · d-1 on days 1 to 6 (equilibration phase). On days 7 to 11 (treatment phase), subjects consumed either 0 mg (C0; placebo; n = 20), 3 mg (C3; n = 20), or 6 mg (C6; n = 19) caffeine · kg-1 · d-1 in capsules, with no other dietary caffeine intake. The following variables were unaffected (P > 0.05) by different caffeine doses on days 1, 3, 6, 9, and 11 and were within normal clinical ranges: body mass, urine osmolality, urine specific gravity, urine color, 24-h urine volume, 24-h Na+ and K+ excretion, 24-h creatinine, blood urea nitrogen, serum Na+ and K+, serum osmolality, hematocrit, and total plasma protein. Therefore, C0, C3, and C6 exhibited no evidence of hypohydration. These findings question the widely accepted notion that caffeine consumption acts chronically as a diuretic. [ABSTRACT FROM AUTHOR]

This study examined whether the prior consumption of coffee (COF) decreased the ergogenic effect of the subsequent ingestion of anhydrous caffeine (CAF). Thirteen subjects performed 6 rides to exhaustion at 80% VO2max 1.5 h after ingesting combinations of COF, decaffeinated coffee (DECOF), CAF, or placebo. The conditions were DECOF + placebo (A), DECOF + CAF (5 mg/kg) (B), COF (1.1 mg/kg caffeine) + CAF (5 mg/kg) (C), COF + CAF (3 mg/kg) (D), COF + CAF (7 mg/kg) (E), and colored water + CAF (5 mg/kg) (F). Times to exhaustion were significantly greater for all trials with CAF versus placebo (trial A). Exercise times (in minutes) were: 21.7 ± 8.1, 29.0 ± 7.4, 27.8 ± 10.8, 25.1 ± 7.9, 26.4 ± 8.0 and 26.8 ± 8.1 for trials A through F, respectively. In conclusion, the prior consumption of COF did not decrease the ergogenic effect of the subsequent ingestion of anhydrous CAF. [ABSTRACT FROM AUTHOR]

To examine the cognitive and physical changes associated with consuming an energy drink concurrent to video gaming, we examined a convenience sample of nine elite League of Legends (LoL) e-sport players (21 ± 2 y, BMI 25.6 ± 3.4 kg/m2) consuming an energy drink (ReloadTM) or placebo (Placebo) in a randomized, double-blind, placebo-controlled cross-over trial. Participants completed the same test battery prior to treatment consumption and after playing each of three competitive LoL games. Primary outcomes included measures of attention (Erikson Flanker Test), reaction time (Go/No-Go test) and working memory (n-back test). Secondary outcomes examined fatigue (hand grip strength and finger tap speed). Statistical analysis was performed by repeated-measures analysis of variance (RM-ANOVA) and reported as the mean (standard deviation [SD]) or mean change (95% confidence interval [CI]). Participants reported sleeping 8.1 (1.2) h/night, playing LoL 10.3 (2.1) h/d, playing other video games 1.8 (2.8) h/d, and exercising 4.2 (1.7) times per week. Overall, we observed no significant time, group, or group-by-time interactions for any measured performance index with the exception of a significant improvement for the n-back test, where the Reload group demonstrated a significant within-group improvement: Reload [-171 ms (95% CI, -327.91, -14.09), p < 0.004], Placebo [-92 ms (95% CI, -213.63, 29.63)]. However, no between-group differences were noted (38.50 ms, 95% CI, -141.89, 64.89, p = 0.803). Our findings suggest that elite eSport athletes do not demonstrate a mental or physical improvement in performance relative to the treatment supplement or indices measured in this study. [ABSTRACT FROM AUTHOR]

Caffeine, a popular psychostimulant that acts as an adenosine receptor antagonist, is the most widely used drug in history, consumed daily by people worldwide. Knowledge of the physiological and pathological effects of caffeine is crucial in improving public health because of its widespread use. We provide a summary of the current evidence on the effect of caffeine on the eye. Most of the research conducted to date is in relation to cataract and glaucoma, two of the most common eye diseases among the elderly. [ABSTRACT FROM AUTHOR]

This study examined the effects of a caffeine treatment to improve nuclear reprogramming in porcine cloned embryos. Embryonic development and the expression of genes related to pluripotency (POU5F1, SOX2, NANOG, and CDX2) were compared after caffeine supplementation during manipulation at different concentrations (0, 1.25, 2.5, and 5.0 mM) and after varying the delayed activation time (control, 1, 2, and 4 h) after fusion. Caffeine added to media during manipulation produced a higher rate of development to blastocysts in the 1.25 mM group than in the other concentration groups (22.8% vs. 16.1%, 16.2%, and 19.2%; p < 0.05). When caffeine was added during the 4 h delayed activation, the 1.25 mM caffeine concentration produced a significantly higher rate of development than those in the other 4 h-activation-delayed caffeine concentration groups (22.4% vs. 9.4%, 14.0%, and 11.1%; p < 0.05). On the other hand, no significant improvement over that in the control group was observed when caffeine was supplemented during both the manipulation period and delayed activation period (16.0% vs. 15.2%), respectively. The levels of POU5F1, SOX2, and NANOG expression in blastocysts were significantly higher in the delayed activation caffeine group (4 h, 1.25 mM) than in the control group (1 h, 0 mM; p < 0.05). In conclusion, a caffeine treatment at 1.25 mM during delayed activation for 4 h can improve the preimplantation development of porcine somatic cell nuclear transfer embryos by activating nuclear reprogramming. [ABSTRACT FROM AUTHOR]

Background: Caffeine use is highly prevalent among active duty military personnel and can be beneficial to performance in the short term. However, regular caffeine use has been found to contribute to sleep disturbances, which are elevated among the significant number of military personnel with posttraumatic stress disorder (PTSD). The current study is the first to examine caffeine use and its relationship with sleep disturbances in military personnel seeking treatment for PTSD. Participants: Active duty military personnel (N = 366) who had returned from deployments to Afghanistan or Iraq and were seeking treatment for PTSD. Methods: Pearson correlations were used to examine the relationships between caffeine use, sleep disturbances, and PTSD symptom clusters. Results: The majority of the sample (89%) reported some caffeine use, with coffee being the largest contributor to total caffeine intake. Contrary to hypotheses, higher caffeine use was associated with lower insomnia symptom severity; follow-up analysis indicated that this was due to elevated insomnia symptom severity in those reporting no caffeine use. Caffeine use was not associated with any other measures of sleep disturbance or with PTSD symptoms. Conclusions: Caffeine use was not associated with greater reported sleep disturbances in this sample, possibly because those with elevated insomnia symptom severity abstained from any caffeine, or because insomnia symptoms were elevated in this sample. [ABSTRACT FROM AUTHOR]

Background Coffee is one of the most widely consumed stimulants worldwide and is generally considered to be safe or even beneficial for health. However, increased risk of myocardial infarction and hypertension has been suggested for individuals who carry a functional variant at cytochrome P450 1A2 (CYP1A2), which makes them less effective at metabolizing caffeine. Objectives The aim of this study was to examine if the CYP1A2 genotype or a genetic score for caffeine metabolism (caffeine-GS) modifies the association between habitual coffee consumption and the risk of cardiovascular disease (CVD). Methods Genetic data and information on habitual coffee intake and relevant covariates were available for 347,077 individuals in the UK Biobank, including 8368 incident CVD cases. We used logistic regression to test for the association between coffee intake and CVD risk, and whether the association varies with CYP1A2 genotype or caffeine-GS. Results The association between habitual coffee intake and CVD risk was nonlinear, and, compared with participants drinking 1–2 cups/day, the risk of CVD was elevated for nondrinkers, drinkers of decaffeinated coffee, and those who reported drinking >6 cups/day (increase in odds by 11%, 7%, and 22%, respectively, P -curvature = 0.013). CYP1A2 genotype and caffeine-GS were not associated with CVD (P  ≥ 0.22 for all comparisons). There was no evidence for an interaction between the CYP1A2 genotype or caffeine-GS and coffee intake with respect to risk of CVD (P  ≥ 0.53). Conclusions Heavy coffee consumption was associated with a modest increase in CVD risk, but this association was unaffected by genetic variants influencing caffeine metabolism. [ABSTRACT FROM AUTHOR]

Among the factors that contribute to the onset and maintenance of depressive disorders, rhythmicity of symptoms and consumption of caffeine have recently gained attention. The current study aimed to examine the differential rhythmicity of relevant variables in a sample of young participants, considering the presence of depressive symptomatology and the frequency of caffeinated drinks consumption. A significant 24-hour differential rhythmicity of mood, cognitive and physiological variables was found indicating an evening peak pattern in the participants with depressive symptoms. Interestingly, caffeinated drinks consumption was differentially associated with self-perceived peaks, according to the presence of depressive symptomatology. Our findings are among the first reports about the potential association of the 24-hours rhythmicity of relevant mood-related variables, depressive symptoms, and caffeine intake. These results support the view that the identification of risk factors for depression, and the application of novel measurements and analysis methods in the development of new preventive strategies should be a public health priority. [ABSTRACT FROM AUTHOR]

Owing to the dynamic interaction between frog skin and the environment, xenobiotics in frog habitats are of particular concern, and knowledge of percutaneous absorption in frog skin is necessary for risk‐mitigation purposes. Baseline transdermal kinetics in adult aquatic and arboreal frog species have recently been reported; however, there is little information regarding absorption kinetics in adult terrestrial species. The present study investigated the in vitro absorption kinetics of 3 model chemicals—caffeine, benzoic acid, and ibuprofen—through different skin regions in the terrestrial toad Rhinella marina. Caffeine flux was consistently higher than that of the other 2 chemicals (p < 0.001), whereas the fluxes of the moderately and highly lipophilic chemicals (benzoic acid and ibuprofen) were similar, regardless of skin region. When considering individual chemicals, caffeine demonstrated increased flux through the ventral pelvic skin compared with the ventral thoracic or dorsal skin regions. Flux did not differ between skin regions for either benzoic acid or ibuprofen. These findings have implications for management of environmental contamination in frog habitats, as many environmental xenobiotics are of moderate to high lipophilicity and would be expected to be equally absorbed from all skin surfaces in terrestrial toads. Environ Toxicol Chem 2019;38:361–367. © 2018 SETAC [ABSTRACT FROM AUTHOR]

Objective: To investigate the effect of caffeine infusion on superior mesenteric artery (SMA) blood flow velocities (BFV) in preterm infants.Methods: Prospective observational study on 38 preterm neonates 28-33+6 weeks gestation, who developed apnea on their first day of life, and caffeine citrate infusion was initiated at a loading dose of 20 mg/kg, followed by a maintenance dose of 5-10 mg/kg/day. Duplex ultrasound measurements of SMA BFV were recorded: peak systolic velocity (PSV), end diastolic velocity (EDV) and resistive index (RI), at 15 min before, 1-, 2- and 6-h after caffeine loading dose, and 2 h after two maintenance doses.Results: There was a significant reduction in PSV 1-h (p = .008), a significant decrease in EDV 1- and 2-h (p = .000 and p = .005, respectively) and a significant increase in RI 1- and 2-h (p = .003 and p = .005, respectively) following caffeine loading dose, as compared to values before caffeine infusion. No significant effect of caffeine maintenance doses on SMA BFV was observed (p > .05).Conclusion: Blood flow in SMA is significantly reduced after caffeine citrate infusion at a loading dose of 20 mg/kg. This effect continues for at least 2 h. Meanwhile, SMA BFV seems not affected by maintenance doses. [ABSTRACT FROM AUTHOR]