Journal of caffeine and adenosine research

Journal of Caffeine and Adenosine ResearchVol. 11, No. 4 EditorialThe Closing of a ChapterSergi FerréSergi FerréEditor-in-Chief, Journal of Caffeine and Adenosine Research.Search for more papers by this authorPublished Online:15 Dec 2021https://doi.org/10.1089/caff.2021.29029.sfAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"The Closing of a Chapter." Journal of Caffeine and Adenosine Research, 11(4), pp. 79–80FiguresReferencesRelatedDetails Volume 11Issue 4Dec 2021 InformationCopyright 2021, Mary Ann Liebert, Inc., publishersTo cite this article:Sergi Ferré.The Closing of a Chapter.Journal of Caffeine and Adenosine Research.Dec 2021.79-80.http://doi.org/10.1089/caff.2021.29029.sfPublished in Volume: 11 Issue 4: December 15, 2021Online Ahead of Print:December 1, 2021PDF download

Background: We investigated the effects of caffeine ingestion on autonomic modulation at rest and after a high-intensity intermittent exercise (HITE). Methods: Seven handball athletes performed a HIIE 60 minutes after ingesting caffeine (5 mg .kg(-1)) or placebo. We analyzed the heart rate at rest (HRrest) and both time (standard deviation of normal-to-normal interval time series [SDNN]; the root mean square of successive differences [RMSSD] in the normal-to-normal intervals) and frequency (low frequency ELF]; high frequency [HF]; low frequency-to-high frequency ratio [LF/HF]) domains of heart rate variability. Furthermore, we analyzed the RMSSD in the R-R intervals during successive 30-second segments (RMSSD30s) and heart rate recovery (HRR30s) after the exercise. Results: Caffeine ingestion did not influence the HR at rest (p > 0.05) and during the exercise (p > 0.05) but delayed the HRR30s (p = 0.05; eta(2)(p) = 0.48) and RMSSD30s (p = 0.01; eta(2)(p) = 0.03) after the HITE. Conclusion: Our results suggest that autonomic control of handball players is influenced by caffeine during recovery of the HITE.

Background: Coffee includes some potentially bioactive components that can interfere with platelets, which can influence coagulation, despite generating controversy. The aim of this systematic review is to verify whether coffee or its components can influence platelet regulators and/or aggregation. Materials and Methods: The research was conducted on July 29, 2021, in PubMed, Scopus, and Web of Science, using the following mesh-terms: (caffeine)) OR (coffee)) AND (platelets). Eligibility criteria were: studies carried out in humans, referring to the effects of coffee consumption, or one of its components, on platelets or their regulators. We exclude in vitro or animal studies, reviews, editorials, and non-English written studies. From a total of 836 publications, 17 articles were included from which we extracted the relationship between coffee consumption and changes in blood platelets and performed a subjective assessment of bias. Results: Ten articles refer to the non-interference of coffee or its components with platelets, nine affirm results that support the increase in platelet aggregation, and eight articles observe the decrease in platelet aggregation when coffee is consumed. Some articles presented the lack of data regarding the sample collection location, age group, or classification as to the type of study, which is limiting. Conclusions: The heterogeneity of results makes it difficult to correctly interpret the possible interaction of coffee or its components with platelets or their regulators. For better interpretation, further studies on this topic should be carried out considering the individualization of coffee components, different platelet regulators, and the size of the sample used.

Journal of Caffeine and Adenosine ResearchVol. 11, No. 3 EditorialFree AccessCoffee and Platelets: An Unsolved ProblemAnna Vittoria MattioliAnna Vittoria MattioliAddress correspondence to: Anna Vittoria Mattioli, MD, PhD, Surgical, Medical and Dental Department of Morphological Sciences related to Transplant, Oncology and Regenerative Medicine, University of Modena and Reggio Emilia, Via del pozzo, 71, Modena 41100, Italy E-mail Address: annavittoria.mattioli@unimore.itSurgical, Medical and Dental Department of Morphological Sciences related to Transplant, Oncology and Regenerative Medicine, University of Modena and Reggio Emilia, Modena, Italy.Search for more papers by this authorPublished Online:17 Sep 2021https://doi.org/10.1089/caff.2021.29023.aviAboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail Coffee is the most popular beverage worldwide, is an important component in diet, and contains several ingredients that interact with health status.1The clinical importance of the systematic review carried out by Gache and Almeida-de-Souza2 is related to the increasing spread of antiplatelet drugs that are used in the therapy of cardiovascular diseases and, in particular, of ischemic heart disease. This raises questions about whether there may be an interrelation between coffee and platelets that can influence the effectiveness of the therapy as occurs for anticoagulants, vitamin K inhibitors.The systematic review by Gache and Almeida-de-Souza analyzed many articles without reaching a final conclusion.2 They found that some articles detect a positive effect on platelet activity and others, on the contrary, demonstrated that neither coffee nor caffeine affected platelet aggregation.This dichotomy is caused by several factors.It is well known that the different ways of preparing coffee affect the concentration of active components. For instance, the increase in plasmatic lipids level is attributed to diterpene esters, kahweol, and cafestol, which are naturally present in coffee oils. Kahweol and cafestol increased the activity levels of cholesteryl ester transfer protein and phospholipid transfer protein while decreasing the activity level of lecithin–cholesterol acyltrans-ferase, contributing to a rise in low density lypoprotein cholesterol (LDL-C). The method of coffee preparation is an important factor in the amount of kahweol and cafestol in the beverage because these esters are removed when coffee is brewed through a paper filter. Espresso machines, which use high pressure to force very hot water through the coffee beans to extract the flavor and coffee oils, do not use paper filters. However, the low volumes of coffee that characterize the espresso coffee greatly limit the amount of kahweol and cafestol included in the beverage, leading to very limited effects on plasmatic levels of LDL-C.3Different aspects of lifestyle (physical activity, diet, sleep quality, and smoking) can directly affect platelets. Interference with other foods consumed with the diet can modify the effects of coffee on platelet activity.4Gache and Almeida-de-Souza emphasized this aspect that emerged in the articles they examined. This is a fundamental point because dietary habits and lifestyle influence the absorption and bioavailability of the active ingredients contained in the coffee. For example, in the countries of the Mediterranean basin, espresso coffee and mocha coffee are often taken after a meal and this can determine a synergy with the foods eaten.4Coffee consumption might be associated with unhealthy lifestyle habits, such as smoking, and the beneficial effect of coffee consumption on coronary heart disease risk in men could be attenuated by the negative effects of unhealthy behaviors. Woodward and Tunstall-Pedoe found that a higher coffee consumption was associated with a lower risk of cardiovascular disease in men but not in women.5Moreover, the different components present in coffee have some effects on platelets. Coffee could be an excellent functional beverage, containing many polyphenolic compounds that display high antioxidant activity. Several studies suggested that polyphenols have a protective effect in the early stages of atherosclerosis development. Polyphenols improve endothelial function, modulate inflammation, and protect against platelet aggregation.6An important issue is whether the antioxidants derived from coffee are bioactive and bioavailable. Several studies demonstrated bioactivity of coffee and support coffee contribution to antioxidant process and platelet's function.7In addition to the effects of coffee on platelets, Gache and Almeida-de-Souza also analyzed the effects of caffeine on platelets. However, when we analyze the effects of caffeine, we must remember that there are several factors influencing caffeine intake, absorption, metabolism, and physiological and functional effects, which all could affect caffeine plasma levels, such as age, gender, hormonal status, diet, smoking, exposure to drugs, and genetic background.7That is, grapefruit juice decreases caffeine clearance by 23% and prolongs caffeine half-life by 31%. The flavonoid quercetin affects the metabolism of caffeine and paraxanthine and mainly decreases the urinary excretion of the latter compound by 32%; it changes also the excretion of several other metabolites of caffeine.Furthermore, gender differences exert an important influence on the response of biological functions to food and beverages including coffee. The effects of food components on biological function are influenced by hormones and metabolism.8–10 Obesity is an important cardiovascular risk factor in women, especially visceral obesity that develops during menopause and is associated with high levels of inflammation. Obesity differs in different genders and seems to interact with platelets and also with coffee.9,10Several studies confirm the efficacy of coffee extract's application for weight loss and treatment of some metabolic disorders (diabetes, obesity, etc.). The differences in lifestyle between the genders can also influence the effects of coffee on platelet activity.6,8,10 The most obvious example is the complex relationship between smoking, coffee, and platelet aggregation. This association must be deepened with a view to gender differences.In conclusion, Gache and Almeida-de-Souza2 dealt with a topic of extreme importance even though they did not reach a conclusion. However, they highlighted the interference and interactions of lifestyle and food on health. Further studies will lead to elucidate the effects of coffee and caffeine on platelets.Author's ContributionA.V.M. conceived of the idea at the basis of the article, developed the different parts of the article, and performed the final supervision.Author Disclosure StatementNo competing financial interests exist.Funding InformationNo funding was received for this article.References1. Mattioli AV. Effects of caffeine and coffee consumption on cardiovascular disease and risk factors. Future Cardiol. 2007;3:203–212. Crossref, Medline, Google Scholar2. Gache L, Almeida-de-Souza J. Systematic review of the effects of coffee or its components on platelets and their regulators. J Caffeine Adenosine. 2021 (in press). Google Scholar3. Cheung RJ, Gupta EK, Ito MK. Acute coffee ingestion does not affect LDL cholesterol level. Ann Pharmacother. 2005;39:1209–1213. Crossref, Medline, Google Scholar4. Truzzi ML, Ballerini Puviani M, Tripodi A, et al. Mediterranean diet as a model of sustainable, resilient and healthy diet. Prog Nutr. 2020;22:388–394. Google Scholar5. Woodward M, Tunstall-Pedoe H. Coffee and tea consumption in the Scottish Heart Health Study follow-up: Conflicting relations with coronary risk factors, coronary disease, and all cause mortality. J Epidemiol Community Health. 1999;53:481–487. Crossref, Medline, Google Scholar6. Mattioli AV, Migaldi M, Farinetti A. Coffee in hypertensive women with asymptomatic peripheral arterial disease: A potential nutraceutical effect. J Cardiovasc Med (Hagerstown). 2018;19:183–185. Crossref, Medline, Google Scholar7. Hutachok N, Angkasith P, Chumpun C, et al.. Anti-platelet aggregation and anti-cyclooxygenase activities for a range of coffee extracts (Coffea arabica). Molecules. 2020;26:10. Crossref, Google Scholar8. Mattioli AV, Sciomer S, Moscucci F, et al.. Cardiovascular prevention in women: A narrative review from the Italian Society of Cardiology working groups on 'cardiovascular prevention, hypertension and peripheral circulation' and on 'women disease.' J Cardiovasc Med. 2019;20:575–583. Crossref, Google Scholar9. Sirotkin AV, Kolesárová A. The anti-obesity and health-promoting effects of tea and coffee. Physiol Res. 2021;70:161–168. Crossref, Medline, Google Scholar10. Purdy JC, Shatzel JJ. The hematologic consequences of obesity. Eur J Haematol. 2021;106:306–319. Crossref, Medline, Google ScholarFiguresReferencesRelatedDetails Volume 11Issue 3Sep 2021 InformationCopyright 2021, Mary Ann Liebert, Inc., publishersTo cite this article:Anna Vittoria Mattioli.Journal of Caffeine and Adenosine Research.Sep 2021.49-50.http://doi.org/10.1089/caff.2021.29023.aviPublished in Volume: 11 Issue 3: September 17, 2021PDF download

Journal of Caffeine and Adenosine ResearchVol. 11, No. 3 InterviewsA Conversation with Francisco Ciruela AlférezFrancisco Ciruela AlférezFrancisco Ciruela AlférezSearch for more papers by this authorPublished Online:17 Sep 2021https://doi.org/10.1089/caff.2021.29026.fcaAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View articleFiguresReferencesRelatedDetails Volume 11Issue 3Sep 2021 InformationCopyright 2021, Mary Ann Liebert, Inc., publishersTo cite this article:Francisco Ciruela Alférez.A Conversation with Francisco Ciruela Alférez.Journal of Caffeine and Adenosine Research.Sep 2021.65-68.http://doi.org/10.1089/caff.2021.29026.fcaPublished in Volume: 11 Issue 3: September 17, 2021PDF download

Journal of Caffeine and Adenosine ResearchVol. 11, No. 3 InterviewsA Conversation with Luísa V. LopesLuísa V. LopesLuísa V. LopesSearch for more papers by this authorPublished Online:17 Sep 2021https://doi.org/10.1089/caff.2021.29025.lvlAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View articleFiguresReferencesRelatedDetails Volume 11Issue 3Sep 2021 InformationCopyright 2021, Mary Ann Liebert, Inc., publishersTo cite this article:Luísa V. Lopes.A Conversation with Luísa V. Lopes.Journal of Caffeine and Adenosine Research.Sep 2021.69-74.http://doi.org/10.1089/caff.2021.29025.lvlPublished in Volume: 11 Issue 3: September 17, 2021PDF download

Background: The present study collected benchmark data on alternative methods for collecting quantity and frequency information about caffeine, alcohol, and caffeine and alcohol combined (CAFF+ALC) use. Materials and Methods: Participants were N = 50 college students who completed computer-administered survey (COMPSURVEY) and Timeline Followback (TLFB) interviews in randomized order. COMPSURVEY and TLFB data were compared using t-tests, McNemar's tests, and Spearman's correlations. Results: For alcohol, COMPSURVEY underestimated quantity consumed compared to TLFB. Similar patterns were found for caffeine, with every participant having >= 1 COMPSURVEY-TLFB self-report difference and 65.5% having a CAFF+ALC inconsistency. Over half (56%) of participants had >= 1 caffeine misreport, with 46% misclassifying a beverage as containing/not containing caffeine. Moderate to strong relationships were found for caffeine and alcohol quantity and frequency of use, but associations for CAFF+ALC were weak. Conclusions: The largest inconsistencies were found for CAFF+ALC use, indicating that more research is needed to identify methods for collecting reliable and valid CAFF+ALC use data.

Background: The present study aimed to determine whether energy drink (ED) formulas containing 140 and 100 mg of caffeine have the potential to alter excess postexercise oxygen consumption (EPOC) responses after an incremental exercise test in males and females. Materials and Methods: Participants were submitted to incremental tests to exhaustion after receiving EDs containing 140 and 100 mg of caffeine and a placebo in a randomized order. Results: EPOC was greater in ED containing 140 mg of caffeine (9.47 +/- 0.37 L; p < 0.05), but not in 100 mg (9.20 +/- 0.374.4 L; p = 0.31) in relation to placebo (8.84 +/- 0.37 L). Conclusion: Ingesting an ED containing 140 mg of caffeine may affect EPOC after an incremental exercise to exhaustion. ED containing 100 mg of caffeine, ingested 2 hours before exercise, may not promote changes in EPOC following an incremental exercise to exhaustion protocol and could be acceptable before exercise testing in caffeine habituated young adults. This study was registered with clinicaltrials.gov under the identifier NCT04455009.

Background: Caffeine's influence on numerous physical functions indicates that it has more than a simple stimulating effect. The aim of this study is to investigate the effects of caffeine on well-being, taking into account physical activity, anxiety, and depression as mediators. Materials and Methods: A sample of 160 subjects 50 years of age and older were recruited for this study. Five standardized questionnaires and an extension of the simple mediatized regression with three mediators made it possible to check the model relationships. Research was conducted in accordance with the 2013 revised Declaration of Helsinki. Results: The results could demonstrate no indirect effect through one or a combination of the mediator variables, but a direct effect of caffeine on well-being (p = 0.01, beta = 0.16), provided that the three variables were taken into account. Conclusion: Due to the fact that individual compounds, and especially, the direct effect of caffeine on well-being in this model, were found to be significant, these findings could be the foundation for future research.

Introduction: We assessed motor function after chronic caffeine ingestion and examined brain regions controlling them: the sensorimotor cortex, striatum, and cerebellar cortex. Materials and Methods: Twenty-four adult male albino mice received caffeine 20 mg/kg (low dose), 60 mg/kg (high dose), or water (control) daily by gavage for eight weeks. Motor function was assessed by open field, pole, and inverted square grid tests. The sensorimotor cortex, striatum, and cerebellum were processed for hematoxylin and eosin, Nissl, and Golgi staining. Results: Reduced body weight gain in the high-dose group, a dose-dependent increase in locomotion, but not muscular strength; increased cerebellar Purkinje cell density, increased apical dendrite length in the pyramidal neurons of the sensorimotor cortex, and increased dendritic arborization in the sensorimotor cortex pyramidal neurons and striatal medium spiny neurons in both low-dose and high-dose groups were observed. Conclusion: Prolonged caffeine intake improves motor function possibly through promoting the growth of dendrites and an increase in the neuronal population.

Pharmacokinetic and pharmacodynamic properties of caffeine as the most and widely consumed beverage in the globe were examined. Forty-three articles published between 1980 and 2016 were selected with a list of keywords that represent the most relevant pharmacokinetic and pharmacodynamic properties of caffeine. Findings show that the oral route is the most common route of administration of caffeine. The complete caffeine absorption takes place in the small intestine and it needs around 45 minutes to get 99% bioavailability with no significant first pass effect of caffeine. Caffeine absorption rate constant K01 is around 0.33 minute−1, volume of distribution is ranging between 0.5 and 0.75 L/kg, plasma-protein binding about 10–30%, half-life is around 4 hours, clearance is ranging between 1 and 3 mg/kg/min, and elimination rate constant is ranging between 0.09 and 0.33 hour−1. Caffeine elimination takes place by first-order kinetics and is effectively explained by a one-compartment open model system. Ninety-five percent of the caffeine primary metabolism is done in the liver by CYP1A2, and 3% or less is excreted unchanged in urine. Caffeine is metabolized through phase I oxidation reactions mainly to paraxanthine, theobromine, and theophylline followed by phase II conjugation. 1-Methylxanthine, 1-methyluric acid, 5-acetylamino-6-formylamino-3-methyluracil, and 1,7-dimethyluric acid are the main caffeine metabolites in the urine. Caffeine fatal dose ranges between 5 and 10 g/day.

Purpose: To develop and validate a questionnaire to evaluate caffeine consumption habits in adults. Methods: A caffeine habits and consumption questionnaire (CaffCo) was developed in three stages. First, focus groups explored factors influencing consumption of various caffeine-containing products. Second, thematic analysis (reported elsewhere) was used to develop a draft CaffCo. Third, pilot testing of this draft examined comprehensibility, ease of use, and test-retest reliability among students (n = 227). Content validity and construct validity were assessed. Results: The CaffCo questionnaire items explored four main themes: social drivers, environmental opportunity, functional expectations, and individual experiences. Pilot testing reflected influences of caffeinated product consumption. CaffCo demonstrates good content validity and construct validity. The test-retest showed good interrater reliability (Cronbach's alpha >0.70). Conclusion: CaffCo shows good validity and reliability. It can be used, or adapted for use, to identify patterns of caffeine consumption for a range of caffeinated products.

Background: Caffeine is the most consumed psychoactive substance in the world. More importantly, caffeine evokes symptoms, which allow for its classification among substances of abuse. However, caffeine consumption is often neglected in the clinical context, particularly during treatment. Methods and Materials: The aim of the current study is to use Item Response Theory (IRT) to develop a caffeine dependency inventory according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), while also recording participant knowledge about the caffeine content in various foods and beverages. Results: Within a sample of n = 188 participants, none of the subjects displayed an entirely caffeine-free consumption behavior. Rather, a lower degree of knowledge regarding caffeine content in various caffeinated drinks correlated with a higher level of caffeine consumption (r = -0.15). A majority showed a low to moderate degree of caffeine use disorder (CUD) (M = 4.36 +/- 4.18 [CI 3.75 to 4.96], range 0-16; Md = 3.0, IQR 1-7; skewness z = 4.78). Conclusions: To our knowledge, this has been the first German language study to apply an IRT approach to examining CUD, proposed by DSM-5 for clinical use.

Journal of Caffeine and Adenosine ResearchVol. 10, No. 3 Call for PapersFree AccessCall for Papers: Adenosine in the Central Nervous SystemEditor-in-Chief: Sergi FerréEditor-in-Chief: Sergi FerréIntegrative Neurobiology Section, National Institute on Drug AbuseSearch for more papers by this authorPublished Online:16 Sep 2020https://doi.org/10.1089/caff.2019.29017.cfp2AboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail The Journal of Caffeine and Adenosine Research has extended its scope beyond caffeine research to include original research related to adenosine and adenosine receptors in physiology and disease. In the central nervous system, adenosine is a ubiquitous neuromodulator involved in many physiological functions. While caffeine is an adenosine receptor antagonist, adenosine is the endogenous agonist which promotes sleep homeostasis and is actively released following cellular insult as a distress signal that modulates tissue damage and repair, a role that extends beyond the central nervous system. Adenosine and ATP are important messengers in neuronal and glial interactions and function. The role of adenosine and purines has been well established in neurodegeneration, cognition, and psychiatric disorders. Journal of Caffeine and Adenosine Research aims to showcase novel original adenosine research from around the world.The journal is specifically looking for original research investigating the role of adenosine in central nervous system physiology and pathogenesis. We will consider manuscripts in the following categories: Adenosine in neurophysiologyAdenosine in epilepsy and movement disordersAdenosine in cognition and neurodegenerative disordersAdenosine in psychiatric disordersAdenosine in sleep and sleep disordersAdenosine in addiction physiologyAdenosine and the circadian clock in addiction and alcohol useAdvantages of publishing in the Journal of Caffeine and Adenosine Research include:Fast and user-friendly electronic submissionRapid, high-quality peer reviewMaximum exposure: accessible in 170 countries worldwideOpen Access options availablePlease address any questions to Managing Editor Dr. Karen Cloud-Hansen (kch.editor@gmail.com) and our Editor-in-Chief Dr. Sergi Ferré (sferre@intra.nida.nih.gov).Submit your paper for peer review online:https://mc.manuscriptcentral.com/caffeineFiguresReferencesRelatedDetails Volume 10Issue 3Sep 2020 InformationCopyright 2020, Mary Ann Liebert, Inc., publishersTo cite this article:Editor-in-Chief: Sergi Ferré.Call for Papers: Adenosine in the Central Nervous System.Journal of Caffeine and Adenosine Research.Sep 2020.93-93.http://doi.org/10.1089/caff.2019.29017.cfp2Published in Volume: 10 Issue 3: September 16, 2020PDF download

It is well known that the neuromodulator adenosine, acting through the adenosine A1 receptor subtype, can limit or stop seizures. In 2008, adenosine was proposed as a key component of the anticonvulsant mechanism of the ketogenic diet (KD), a very low carbohydrate diet that can be highly effective in drug-refractory epilepsy. In this study, we review the accumulated data on the intersection among adenosine, ketosis, and anticonvulsant/antiepileptogenic effects. In several rodent models of epilepsy and seizures, antiseizure effects of ketogenic treatments (the KD itself, exogenous ketone bodies, medium-chain triglycerides or fatty acids) are reversed by administration of an adenosine A1 receptor antagonist. In addition, KD treatment elevates extracellular adenosine and tissue adenosine content in brain. Efforts to maintain or mimic a ketogenic milieu in brain slices reveal a state of reduced excitability produced by pre- and postsynaptic adenosine A1 receptor-based effects. Long-lasting seizure reduction may be due to adenosine-based epigenetic effects. In conclusion, there is accumulating evidence for an adenosinergic anticonvulsant action in the ketogenic state. In some cases, the main trigger is mildly but consistently lowered glucose in the brain. More research is needed to investigate the importance of adenosine in the antiepileptogenic and neuroprotective effects of these treatments. Future research may begin to investigate alternative adenosine-promoting strategies to enhance the KD or to find use as treatments themselves.

Background:Because cardiac events are a major cause of in-line deaths in firefighters and caffeine use is common in this population, we sought to examine the effects of caffeine on the hemostatic response to firefighting drills. Materials and Methods:Twelve firefighters completed two trials of firefighting drills after consuming caffeine (6 mg/kg) or placebo. Factor VIII, tissue plasminogen activator (tPA), and plasminogen activator inhibitor-1 (PAI-1) were analyzed from pre- and post-exercise blood samples. Results:Factor VIII increase was larger (p < 0.05) in the caffeine trial (Pre = 0.20 +/- 0.13 IU/mL, Post = 0.43 +/- 0.15 IU/mL) than the placebo trial (Pre = 0.21 +/- 0.11 IU/mL, Post = 0.38 +/- 0.15 IU/mL). tPA activity significantly (p < 0.05) increased and PAI-1 activity significantly decreased (p < 0.05) by the same magnitude in both conditions. Conclusions:Results suggest that caffeine elicits a higher coagulation response during firefighting drills.