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Cheng IS, Tsao JP, Bernard JR, Tsai TW, Chang CC, Liao SF. Oral post-exercise garlic extract supplementation enhances glycogen replenishment but does not up-regulate mitochondria biogenesis mRNA expression in human-exercised skeletal muscle. J Int Soc Sports Nutr 2024; 21:2336095. [PMID: 38576169 PMCID: PMC11000618 DOI: 10.1080/15502783.2024.2336095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 03/10/2024] [Indexed: 04/06/2024] Open
Abstract
PURPOSE Garlic extract (GA) is purported to enhance antioxidant and anti-inflammatory activity and glucose regulation in humans. The present study investigated the effects of post-exercise GA supplementation on GLUT4 expression, glycogen replenishment, and the transcript factors involved with mitochondrial biosynthesis in exercised human skeletal muscle. METHODS The single-blinded crossover counterbalanced study was completed by 12 participants. Participants were randomly divided into either GA (2000 mg of GA) or placebo trials immediately after completing a single bout of cycling exercise at 75% Maximal oxygen uptake (VO2max) for 60 minutes. Participants consumed either GA (2000 mg) or placebo capsules with a high glycemic index carbohydrate meal (2 g carb/body weight) immediately after exercise. Muscle samples were collected at 0-h and 3-h post-exercise. Muscle samples were used to measure glycogen levels, GLUT4 protein expression, as well as transcription factors for glucose uptake, and mitochondria biogenesis. Plasma glucose, insulin, glycerol, non-esterified fatty acid (NEFA) concentrations, and respiratory exchange ratio (RER) were also analyzed during the post-exercise recovery periods. RESULTS Skeletal muscle glycogen replenishment was significantly elevated during the 3-h recovery period for GA concurrent with no difference in GLUT4 protein expression between the garlic and placebo trials. PGC1-α gene expression was up-regulated for both GA and placebo after exercise (p < 0.05). Transcript factors corresponding to muscle mitochondrial biosynthesis were significantly enhanced under acute garlic supplementation as demonstrated by TFAM and FIS1. However, the gene expression of SIRT1, ERRα, NFR1, NFR2, MFN1, MFN2, OPA1, Beclin-1, DRP1 were not enhanced, nor were there any improvements in GLUT4 expression, following post-exercise garlic supplementation. CONCLUSION Acute post-exercise garlic supplementation may improve the replenishment of muscle glycogen, but this appears to be unrelated to the gene expression for glucose uptake and mitochondrial biosynthesis in exercised human skeletal muscle.
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Affiliation(s)
- I-Shiung Cheng
- National Taichung University of Education, Department of Physical Education, Taichung City, Taiwan
| | - Jung-Piao Tsao
- Department of Sports Medicine, China Medical University, Taichung City, Taiwan
| | - Jeffrey R. Bernard
- Department of Kinesiology and Public Health Promotion,California State University, Stanislaus, Turlock, USA
| | - Tsen-Wei Tsai
- Department of Nursing, Taichung, China Medical University Hospital, Taiwan
| | - Chia-Chen Chang
- College of HuilanNational Dong Hwa University, Physical Education Center, Hualien, Taiwan
| | - Su-Fen Liao
- Department of Physical Medicine and Rehabilitation, Changhua Christian Hospital, Changhua, Taiwan
- Department of Post-Baccalaureate Medicine, College of Medicine, National Chung Hsing University, Taichung, Taiwan
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2
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Caffeine does not change incremental test performance and autonomic recovery response in COPD patients. SPORT SCIENCES FOR HEALTH 2023. [DOI: 10.1007/s11332-022-01037-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Cintineo HP, Bello ML, Chandler AJ, Cardaci TD, McFadden BA, Arent SM. Effects of caffeine, methylliberine, and theacrine on vigilance, marksmanship, and hemodynamic responses in tactical personnel: a double-blind, randomized, placebo-controlled trial. J Int Soc Sports Nutr 2022; 19:543-564. [PMID: 36016763 PMCID: PMC9397462 DOI: 10.1080/15502783.2022.2113339] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Background Tactical athletes require fast reaction times (RT) along with high levels of vigilance and marksmanship performance. Caffeine has been shown to improve these measures but also results in increased blood pressure and jitteriness. Research on other purine alkaloids, such as methylliberine and theacrine, has suggested they do not increase blood pressure or jitteriness to the same extent, but their impact on tactical performance is unknown. Methods A between-subjects, randomized, placebo-controlled design was used to test the effects of placebo (PLA), 300 mg caffeine (CAF), and a combination of 150 mg caffeine, 100 mg methylliberine, and 50 mg theacrine (CMT) on RT and marksmanship along with hemodynamic and arousal measures following a sustained vigilance task in tactical personnel (n = 48). Following consumption of the supplement, participants underwent a 150-min protocol consisting of two rounds. Each round began with leisurely reading followed by a 30-min vigilance task before beginning two trials of movement and marksmanship tasks. Hemodynamics and felt arousal were assessed throughout the protocol. Composite Z-scores were calculated for overall performance measures at each timepoint, and mixed-effects models were used to assess differences in RT, accuracy, and composite Z-scores along with hemodynamics and felt arousal. An α-level of 0.05 was used to determine statistical significance, and Cohen’s d was used to quantify effect sizes. Results A Group-by-Time interaction for vigilance RT (P = 0.038) indicated improvements for both CAF and CMT from round 1 to round 2 (P < 0.01) while PLA did not change (P = 0.27). No Group main effects or Group-by-Time interactions were found for movement or marksmanship performance (P > 0.20). Group main effects for systolic (SBP; P = 0.001) and diastolic blood pressure (DBP; P = 0.028) indicated higher SBP in CAF (P = 0.003, d= 0.84) and CMT (P = 0.007, d= 0.79) compared to PLA but only higher DBP in CAF (P = 0.025, d= 0.74). No Group-by-Time interaction or Group main effect was found for felt arousal (P > 0.16). Conclusions These findings suggest similar benefits on RT during a vigilance task between CAF, containing 300 mg caffeine, and CMT above PLA, though CAF resulted in slightly less favorable hemodynamic changes. This study is the first to provide data showing similar efficacy of combined caffeine, methylliberine, and theacrine compared to double the caffeine dose consumed alone on vigilance RT but without a significant rise in DBP above PLA in tactical personnel.
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Affiliation(s)
- Harry P. Cintineo
- Department of Exercise Science, University of South Carolina, Columbia, SC, USA
| | - Marissa L. Bello
- Department of Kinesiology, Mississippi State University, Mississippi State, MS, USA
| | - Alexa J. Chandler
- Department of Exercise Science, University of South Carolina, Columbia, SC, USA
| | - Thomas D. Cardaci
- Department of Pathology, Microbiology, and Immunology, University of South Carolina School of Medicine, Columbia, SC, USA
| | - Bridget A. McFadden
- Department of Exercise Science, University of South Carolina, Columbia, SC, USA
| | - Shawn M. Arent
- Department of Exercise Science, University of South Carolina, Columbia, SC, USA
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Cristina-Souza G, Santos PS, Santos-Mariano AC, Coelho DB, Rodacki A, DE-Oliveira FR, Bishop DJ, Bertuzzi R, Lima-Silva AE. Caffeine Increases Endurance Performance via Changes in Neural and Muscular Determinants of Performance Fatigability. Med Sci Sports Exerc 2022; 54:1591-1603. [PMID: 35969166 DOI: 10.1249/mss.0000000000002944] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE In the present study, we tested the hypothesis that caffeine would increase endurance performance via attenuation of neural and muscular determinants of performance fatigability during high-intensity, whole-body exercise. METHODS Ten healthy males cycled until exhaustion (89% ± 2% of V̇O2max) after the ingestion of caffeine or placebo. During another four visits, the same exercise was performed after either caffeine or placebo ingestion but with exercise discontinued after completing either 50% or 75% of the duration of placebo trial. An additional trial with caffeine ingestion was also performed with interruption at the placebo time to exhaustion (isotime). Performance fatigability was measured via changes in maximal voluntary contraction, whereas neural and muscular determinants of performance fatigability were quantified via preexercise to postexercise decrease in quadriceps voluntary activation (VA) and potentiated twitch force, respectively. RESULTS Compared with the placebo, caffeine increased time to exhaustion (+14.4 ± 1.6%, P = 0.017, 314.4 ± 47.9 vs 354.9 ± 40.8 s). Caffeine did not change the rate of decline in maximal voluntary contraction (P = 0.209), but caffeine reduced the twitch force decline at isotime when stimulating at single twitch (-58.6 ± 22.4 vs -45.7 ± 21.9%, P = 0.014) and paired 10 Hz electrical stimuli (-37.3 ± 13.2 vs -28.2 ± 12.9%, P = 0.025), and reduced the amplitude of electromyography signal during cycling at isotime (P = 0.034). The decline in VA throughout the trial was lower (P = 0.004) with caffeine (-0.5 ± 4.2%) than with placebo (-5.8 ± 8.5%). Caffeine also maintained peripheral oxygen saturation at higher levels (95.0 ± 1.9%) than placebo (92.0 ± 6.2%, P = 0.016). CONCLUSIONS Caffeine ingestion improves performance during high-intensity, whole-body exercise via attenuation of exercise-induced reduction in VA and contractile function.
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Affiliation(s)
| | | | | | | | - Andre Rodacki
- Department of Physical Education, Federal University of Paraná, Paraná, BRAZIL
| | | | - David J Bishop
- Institute for Health and Sport, Victoria University, Melbourne, AUSTRALIA
| | - Romulo Bertuzzi
- Endurance Performance Research Group (GEDAE-USP), University of São Paulo, São Paulo, BRAZIL
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Marinho AH, Lopes-Silva JP, Cristina-Souza G, Sousa FADB, Ataide-Silva T, Lima-Silva AE, Araujo GGD, Silva-Cavalcante MD. Effects of caffeine ingestion on cardiopulmonary responses during a maximal graded exercise test: a systematic review with meta-analysis and meta-regression. Crit Rev Food Sci Nutr 2022; 64:127-139. [PMID: 35894639 DOI: 10.1080/10408398.2022.2104807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
While the effects of caffeine ingestion on endurance performance are well known, its effects on cardiopulmonary responses during a maximal graded exercise test have been less explored. This study systematically reviewed and meta-analyzed studies investigating the effects of caffeine ingestion on cardiopulmonary responses during a maximal graded exercise test. A search was performed in four databases, and study quality was assessed using the PEDro scale. Data reported by the selected studies were pooled using random-effects meta-analysis, with selected moderator effects assessed via meta-regression. Twenty-one studies with good and excellent methodological quality were included in this review. Compared to placebo, caffeine increased peak minute ventilation (SMD = 0.33; p = 0.01) and time to exhaustion (SMD = 0.41; p = 0.01). However, meta-regression showed no moderating effects of dosage and timing of caffeine ingestion, stage length, or total length of GXT (all p > 0.05). Caffeine ingestion did not affect peak oxygen uptake (SMD = 0.13; p = 0.42), peak heart rate (SMD = 0.27; p = 0.07), peak blood lactate concentration (SMD = 0.60; p = 0.09), peak tidal volume (SMD = 0.10; p = 0.69), peak breathing frequency (SMD =0.20; p = 0.23), or peak power output (SMD = 0.22; p = 0.28). The results of this systematic review with meta-analysis suggest that caffeine increases time to exhaustion and peak minute ventilation among the cardiopulmonary variables assessed during GXT.
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Affiliation(s)
- Alisson Henrique Marinho
- Laboratory of Applied Sports Science, Institute of Physical Education and Sports, Federal University of Alagoas, Maceió, Alagoas, Brazil
- Human Performance Research Group, Federal University of Technology Parana, Curitiba, Parana, Brazil
- Department of Physical Education, Federal University of Parana, Curitiba, Parana, Brazil
- Nutrition and Exercise Research Group, State University of Minas Gerais (UEMG), Passos, Minas Gerais, Brazil
| | - João Paulo Lopes-Silva
- Applied Research Group to Performance and Health, CESMAC University Center, Maceió, Alagoas, Brazil
| | - Gislaine Cristina-Souza
- Human Performance Research Group, Federal University of Technology Parana, Curitiba, Parana, Brazil
- Nutrition and Exercise Research Group, State University of Minas Gerais (UEMG), Passos, Minas Gerais, Brazil
| | - Filipe Antônio de Barros Sousa
- Laboratory of Applied Sports Science, Institute of Physical Education and Sports, Federal University of Alagoas, Maceió, Alagoas, Brazil
- Post-graduate Program in Nutrition, Faculty of Nutrition, Federal University of Alagoas, Maceió, Alagoas, Brazil
| | - Thays Ataide-Silva
- Laboratory of Applied Sports Science, Institute of Physical Education and Sports, Federal University of Alagoas, Maceió, Alagoas, Brazil
- Post-graduate Program in Nutrition, Faculty of Nutrition, Federal University of Alagoas, Maceió, Alagoas, Brazil
| | | | - Gustavo Gomes de Araujo
- Laboratory of Applied Sports Science, Institute of Physical Education and Sports, Federal University of Alagoas, Maceió, Alagoas, Brazil
- Post-graduate Program in Nutrition, Faculty of Nutrition, Federal University of Alagoas, Maceió, Alagoas, Brazil
| | - Marcos David Silva-Cavalcante
- Laboratory of Applied Sports Science, Institute of Physical Education and Sports, Federal University of Alagoas, Maceió, Alagoas, Brazil
- Post-graduate Program in Nutrition, Faculty of Nutrition, Federal University of Alagoas, Maceió, Alagoas, Brazil
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Naulleau C, Jeker D, Pancrate T, Claveau P, Deshayes TA, Burke LM, Goulet EDB. Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis. Sports Med 2022; 52:2431-2445. [PMID: 35616851 DOI: 10.1007/s40279-022-01692-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2022] [Indexed: 11/26/2022]
Abstract
BACKGROUND Heat is associated with physiological strain and endurance performance (EP) impairments. Studies have investigated the impact of caffeine intake upon EP and core temperature (CT) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat. OBJECTIVE To use a meta-analytical approach to determine the effect of pre-exercise caffeine intake on EP and CT in the heat. DESIGN Systematic review with meta-analysis. DATA SOURCES Four databases and cross-referencing. DATA ANALYSIS Weighted mean effect summaries using robust variance random-effects models for EP and CT, as well as robust variance meta-regressions to explore confounders. STUDY SELECTION Placebo-controlled, randomized studies in adults (≥ 18 years old) with caffeine intake at least 30 min before endurance exercise ≥ 30 min, performed in ambient conditions ≥ 27 °C. RESULTS Respectively six and 12 studies examined caffeine's impact on EP and CT, representing 52 and 205 endurance-trained individuals. On average, 6 mg/kg body mass of caffeine were taken 1 h before exercises of ~ 70 min conducted at 34 °C and 47% relative humidity. Caffeine supplementation non-significantly improved EP by 2.1 ± 0.8% (95% CI - 0.7 to 4.8) and significantly increased the rate of change in CT by 0.10 ± 0.03 °C/h (95% CI 0.02 to 0.19), compared with the ingestion of a placebo. CONCLUSION Caffeine ingestion of 6 mg/kg body mass ~ 1 h before exercise in the heat may provide a worthwhile improvement in EP, is unlikely to be deleterious to EP, and trivially increases the rate of change in CT.
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Affiliation(s)
- Catherine Naulleau
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Institut National du Sport du Québec, Montréal, P.Q., Canada
| | - David Jeker
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Institut National du Sport du Québec, Montréal, P.Q., Canada
| | - Timothée Pancrate
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
| | - Pascale Claveau
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
| | - Thomas A Deshayes
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada
- Research Center on Aging, University of Sherbrooke, Sherbrooke, P.Q., Canada
| | - Louise M Burke
- Mary MacKillop Institute for Health Research, Australian Catholic University, Melbourne, VIC, Australia
| | - Eric D B Goulet
- Performance, Hydration and Thermoregulation Laboratory, Faculty of Physical Activity Sciences, University of Sherbrooke, 2500 boul. de l'Université, Sherbrooke, P.Q., J1K 2R1, Canada.
- Research Center on Aging, University of Sherbrooke, Sherbrooke, P.Q., Canada.
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Holland MD, Morales A, Simmons S, Smith B, Misko SR, Jiang X, Hormuth DA, Christenson C, Koomullil RP, Morgan DE, Li Y, Xu J, Yankeelov TE, Kim H. Disposable point-of-care portable perfusion phantom for quantitative DCE-MRI. Med Phys 2021; 49:271-281. [PMID: 34802148 DOI: 10.1002/mp.15372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 10/12/2021] [Accepted: 11/05/2021] [Indexed: 12/30/2022] Open
Abstract
PURPOSE To develop a disposable point-of-care portable perfusion phantom (DP4) and validate its clinical utility in a multi-institutional setting for quantitative dynamic contrast-enhanced magnetic resonance imaging (qDCE-MRI). METHODS The DP4 phantom was designed for single-use and imaged concurrently with a human subject so that the phantom data can be utilized as the reference to detect errors in qDCE-MRI measurement of human tissues. The change of contrast-agent concentration in the phantom was measured using liquid chromatography-mass spectrometry. The repeatability of the contrast enhancement curve (CEC) was assessed with five phantoms in a single MRI scanner. Five healthy human subjects were recruited to evaluate the reproducibility of qDCE-MRI measurements. Each subject was imaged concurrently with the DP4 phantom at two institutes using three 3T MRI scanners from three different vendors. Pharmacokinetic (PK) parameters in the regions of liver, spleen, pancreas, and paravertebral muscle were calculated based on the Tofts model (TM), extended Tofts model (ETM), and shutter speed model (SSM). The reproducibility of each PK parameter over three measurements was evaluated with the intraclass correlation coefficient (ICC) and compared before and after DP4-based error correction. RESULTS The contrast-agent concentration in the DP4 phantom was linearly increased over 10 min (0.17 mM/min, measurement accuracy: 96%) after injecting gadoteridol (100 mM) at a constant rate (0.24 ml/s, 4 ml). The repeatability of the CEC within the phantom was 0.997 when assessed by the ICC. The reproducibility of the volume transfer constant, Ktrans , was the highest of the PK parameters regardless of the PK models. The ICCs of Ktrans in the TM, ETM, and SSM before DP4-based error correction were 0.34, 0.39, and 0.72, respectively, while those increased to 0.93, 0.98, and 0.86, respectively, after correction. CONCLUSIONS The DP4 phantom is reliable, portable, and capable of significantly improving the reproducibility of qDCE-MRI measurements.
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Affiliation(s)
- Martin D Holland
- Interdisciplinary Engineering, University of Alabama, Birmingham, Alabama, USA
| | - Andres Morales
- Engineering and Innovative Technology Development, University of Alabama, Birmingham, Alabama, USA
| | | | - Brandon Smith
- Engineering and Innovative Technology Development, University of Alabama, Birmingham, Alabama, USA
| | - Samuel R Misko
- Engineering and Innovative Technology Development, University of Alabama, Birmingham, Alabama, USA
| | - Xiaoyu Jiang
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - David A Hormuth
- The Oden Institute for Computational Engineering and Sciences, University of Texas, Austin, Texas, USA
| | - Chase Christenson
- The Oden Institute for Computational Engineering and Sciences, University of Texas, Austin, Texas, USA
| | - Roy P Koomullil
- Department of Mechanical Engineering, University of Alabama, Birmingham, Alabama, USA
| | - Desiree E Morgan
- Department of Radiology, University of Alabama, Birmingham, Alabama, USA
| | - Yufeng Li
- Department of Preventive Medicine, University of Alabama, Birmingham, Alabama, USA
| | - Junzhong Xu
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Thomas E Yankeelov
- The Oden Institute for Computational Engineering and Sciences, University of Texas, Austin, Texas, USA
| | - Harrison Kim
- Department of Radiology, University of Alabama, Birmingham, Alabama, USA
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Hunt LA, Hospers L, Smallcombe JW, Mavros Y, Jay O. Caffeine alters thermoregulatory responses to exercise in the heat only in caffeine-habituated individuals: a double-blind placebo-controlled trial. J Appl Physiol (1985) 2021; 131:1300-1310. [PMID: 34435513 DOI: 10.1152/japplphysiol.00172.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
To assess the impact of acute caffeine ingestion on thermoregulatory responses during steady-state exercise under moderate heat stress conditions in caffeine-habituated and nonhabituated individuals. Twenty-eight participants [14 habituated (HAB) (4 females) and 14 nonhabituated (NHAB) (6 females)] cycled at a fixed metabolic heat production (7 W·kg-1) for 60 min on two separate occasions 1 h after ingesting 1) 5 mg·kg-1 caffeine (CAF) or 2) 5 mg·kg-1 placebo (PLA), in a double-blinded, randomized, and counterbalanced order. Environmental conditions were 30.6 ± 0.9°C, 31 ± 1% relative humidity (RH). The end-exercise rise in esophageal temperature (ΔTes) from baseline was greater with CAF in the HAB group (CAF = 0.88 ± 0.29°C, PLA = 0.62 ± 0.34°C, P < 0.001), but not in the NHAB group (CAF = 1.00 ± 0.42°C, PLA = 1.00 ± 0.39°C, P = 0.94). For a given change in mean body temperature, rises in % of maximum skin blood flow were attenuated with CAF on the forearm (P = 0.015) and back (P = 0.021) in the HAB group, but not in the NHAB group (P ≥ 0.65). Dry heat loss was similar in the HAB (CAF = 31 ± 5 W·m-2, PLA = 33 ± 7 W·m-2) and NHAB groups (CAF = 31 ± 3 W·m-2, PLA 30 ± 4 W·m-2) (P ≥ 0.37). There were no differences in whole body sweat losses in both groups (HAB: CAF = 0.59 ± 0.15 kg, PLA = 0.56 ± 0.17 kg, NHAB:CAF = 0.53 ± 0.19 kg, PLA 0.52 ± 0.19 kg) (P ≥ 0.32). As the potential for both dry and evaporative heat loss was uninhibited by caffeine, we suggest that the observed ΔTes differences with CAF in the HAB group were due to alterations in internal heat distribution. Our findings support the common practice of participants abstaining from caffeine before participation in thermoregulatory research studies in compensable conditions.NEW & NOTEWORTHY We provide empirical evidence that acute caffeine ingestion exerts a thermoregulatory effect during exercise in the heat in caffeine-habituated individuals but not in nonhabituated individuals. Specifically, caffeine habituation was associated with a greater rise in esophageal temperature with caffeine compared with placebo, which appears to be driven by a blunted skin blood flow response. In contrast, no thermoregulatory differences were observed with caffeine in nonhabituated individuals. Caffeine did not affect sweating responses during exercise in the heat.
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Affiliation(s)
- Lindsey A Hunt
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - Lily Hospers
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - James W Smallcombe
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - Yorgi Mavros
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia.,Charles Perkins Centre, The University of Sydney, Camperdown, New South Wales, Australia
| | - Ollie Jay
- Thermal Ergonomics Laboratory, Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Camperdown, New South Wales, Australia.,Charles Perkins Centre, The University of Sydney, Camperdown, New South Wales, Australia
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9
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Lima-Silva AE, Cristina-Souza G, Silva-Cavalcante MD, Bertuzzi R, Bishop DJ. Caffeine during High-Intensity Whole-Body Exercise: An Integrative Approach beyond the Central Nervous System. Nutrients 2021; 13:2503. [PMID: 34444663 PMCID: PMC8400708 DOI: 10.3390/nu13082503] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 07/15/2021] [Accepted: 07/19/2021] [Indexed: 11/16/2022] Open
Abstract
Caffeine is one of the most consumed ergogenic aids around the world. Many studies support the ergogenic effect of caffeine over a large spectrum of exercise types. While the stimulatory effect of caffeine on the central nervous system is the well-accepted mechanism explaining improvements in exercise performance during high-intensity whole-body exercise, in which other physiological systems such as pulmonary, cardiovascular, and muscular systems are maximally activated, a direct effect of caffeine on such systems cannot be ignored. A better understanding of the effects of caffeine on multiple physiological systems during high-intensity whole-body exercise might help to expand its use in different sporting contexts (e.g., competitions in different environments, such as altitude) or even assist the treatment of some diseases (e.g., chronic obstructive pulmonary disease). In the present narrative review, we explore the potential effects of caffeine on the pulmonary, cardiovascular, and muscular systems, and describe how such alterations may interact and thus contribute to the ergogenic effects of caffeine during high-intensity whole-body exercise. This integrative approach provides insights regarding how caffeine influences endurance performance and may drive further studies exploring its mechanisms of action in a broader perspective.
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Affiliation(s)
- Adriano E. Lima-Silva
- Human Performance Research Group, Federal University of Technology Parana (UTFPR), Curitiba 81310900, PR, Brazil; (A.E.L.-S.); (G.C.-S.)
| | - Gislaine Cristina-Souza
- Human Performance Research Group, Federal University of Technology Parana (UTFPR), Curitiba 81310900, PR, Brazil; (A.E.L.-S.); (G.C.-S.)
- Nutrition and Exercise Research Group, State University of Minas Gerais (UEMG), Passos 37902092, MG, Brazil
| | - Marcos D. Silva-Cavalcante
- Postgraduate Program in Nutrition (PPGNUT), Faculty of Nutrition (FANUT), Federal University of Alagoas (UFAL), Maceio 57072900, AL, Brazil;
| | - Romulo Bertuzzi
- Endurance Sports Research Group (GEDAE-USP), University of São Paulo, Sao Paulo 05508030, SP, Brazil;
| | - David J. Bishop
- Institute for Health and Sport (IHES), Victoria University, Melbourne, VIC 8001, Australia
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Harber MP, McCurry A, Carlini N, Kistler B, Fleenor BS. Caffeine ingestion alters central hemodynamics following aerobic exercise in middle-aged men. Eur J Appl Physiol 2020; 121:435-443. [PMID: 33098463 DOI: 10.1007/s00421-020-04521-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 10/01/2020] [Indexed: 12/21/2022]
Abstract
PURPOSE To examine the acute influence of caffeine on post-exercise central blood pressures, arterial stiffness, and wave reflection properties. METHODS In a double-blind randomized placebo-controlled crossover study design, ten middle-aged males (55 ± 5 year) completed two exercise trials after ingestion of caffeine (400 mg) or placebo. Measurements were taken before and 30 min post-ingestion via cuff-based pulse wave analysis (PWA) and carotid-femoral pulse wave velocity (PWV). Participants performed a 40-min cycling bout at 70% HRmax with matched workloads between trials. PWA and PWV were reassessed 30 min post-exercise. RESULTS Prior to exercise, compared to placebo, caffeine increased brachial systolic blood pressure (bSBP) (+ 12.3 ± 2.4 mmHg; p = 0.004), brachial diastolic blood pressure (bDBP) (+ 7.7 ± 0.9 mmHg; p = 0.011), central systolic blood pressure (cSBP) (+ 11.1 ± 2.1 mmHg; p = 0.005) and central diastolic blood pressure (cDBP) (+ 7.6 ± 1.0 mmHg; p = 0.012). PWV was higher 30 min after pill ingestion (p = 0.021 for time) with a trend for a greater increase in caffeine (p = 0.074 for interaction). bSBP (p = 0.036) and cSBP (p = 0.007) were lower after exercise but remained higher (both p < 0.001) in caffeine compared to placebo. PWV remained higher (p = 0.023) after exercise in caffeine compared to placebo but was not influenced by exercise. At rest, augmentation pressure (AP) and index (AIx) were not influenced by caffeine ingestion. Conversely, AIx was lower (p = 0.009) after exercise in placebo only. CONCLUSION In healthy and active middle-aged men, pre-exercise caffeine ingestion led to higher central and peripheral systolic blood pressures, PWV and AIx at 30 min post-exercise, indicating an increased left ventricular workload which may have implications for cardiovascular event risk.
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Affiliation(s)
- Matthew P Harber
- Clinical Exercise Physiology, Human Performance Laboratory, Ball State University, Muncie, IN, 47306, USA.
| | - Allison McCurry
- Clinical Exercise Physiology, Human Performance Laboratory, Ball State University, Muncie, IN, 47306, USA
| | - Nicholas Carlini
- Clinical Exercise Physiology, Human Performance Laboratory, Ball State University, Muncie, IN, 47306, USA
| | - Brandon Kistler
- Nutrition and Dietetics, Ball State University, Muncie, IN, USA
| | - Bradley S Fleenor
- Clinical Exercise Physiology, Human Performance Laboratory, Ball State University, Muncie, IN, 47306, USA
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Lutsch DJ, Camic CL, Jagim AR, Stefan RR, Cox BJ, Tauber RN, Henert SE. Effects of a Multi-Ingredient Preworkout Supplement Versus Caffeine on Energy Expenditure and Feelings of Fatigue during Low-Intensity Treadmill Exercise in College-Aged Males. Sports (Basel) 2020; 8:sports8100132. [PMID: 32992830 PMCID: PMC7600984 DOI: 10.3390/sports8100132] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 09/18/2020] [Accepted: 09/23/2020] [Indexed: 11/27/2022] Open
Abstract
The primary purpose of this study was to examine the acute effects of a multi-ingredient (i.e., caffeine, green tea extract, Yohimbe extract, capsicum annum, coleus extract, L-carnitine, beta-alanine, tyrosine) preworkout supplement versus a dose of caffeine (6 mg·kg−1) on energy expenditure during low-intensity exercise. The effects of these treatments on substrate utilization, gas exchange, and psychological factors were also investigated. Twelve males (mean ± SD: age = 22.8 ± 2.4 years) completed three bouts of 60 min of treadmill exercise on separate days after consuming a preworkout supplement, 6 mg·kg−1 of caffeine, or placebo in a randomized fashion. The preworkout and caffeine supplements resulted in significantly greater energy expenditure (p < 0.001, p = 0.006, respectively), V˙O2 (p < 0.001, p = 0.007, respectively), V˙CO2 (p = 0.006, p = 0.049, respectively), and V˙E (p < 0.001, p = 0.007, respectively) compared to placebo (collapsed across condition). There were no differences among conditions, however, for rates of fat or carbohydrate oxidation or respiratory exchange ratio. In addition, the preworkout supplement increased feelings of alertness (p = 0.015) and focus (p = 0.005) 30-min postingestion and decreased feelings of fatigue (p = 0.014) during exercise compared to placebo. Thus, the preworkout supplement increased energy expenditure and measures of gas exchange to the same extent as 6 mg·kg−1 of caffeine with concomitant increased feelings of alertness and focus and decreased feelings of fatigue.
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Affiliation(s)
- Daniel J. Lutsch
- Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115, USA; (D.J.L.); (R.R.S.); (B.J.C.); (R.N.T.); (S.E.H.)
| | - Clayton L. Camic
- Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115, USA; (D.J.L.); (R.R.S.); (B.J.C.); (R.N.T.); (S.E.H.)
- Correspondence: ; Tel.: +1-815-753-3415
| | - Andrew R. Jagim
- Sports Medicine, Mayo Clinic Health System, Onalaska, WI 54650, USA;
| | - Riley R. Stefan
- Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115, USA; (D.J.L.); (R.R.S.); (B.J.C.); (R.N.T.); (S.E.H.)
| | - Brandon J. Cox
- Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115, USA; (D.J.L.); (R.R.S.); (B.J.C.); (R.N.T.); (S.E.H.)
| | - Rachel N. Tauber
- Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115, USA; (D.J.L.); (R.R.S.); (B.J.C.); (R.N.T.); (S.E.H.)
| | - Shaine E. Henert
- Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115, USA; (D.J.L.); (R.R.S.); (B.J.C.); (R.N.T.); (S.E.H.)
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12
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Kim H, Park J, Lee S, Lee SA, Park EC. Association between energy drink consumption, depression and suicide ideation in Korean adolescents. Int J Soc Psychiatry 2020; 66:335-343. [PMID: 32114878 DOI: 10.1177/0020764020907946] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND Suicide is the leading cause of death among adolescents in South Korea. Negative influences of the abuse of energy drinks on mental health problems have emerged. AIMS This study aimed to analyze the relationship between energy drink consumption, depression and suicide ideation. METHODS We analyzed the data of 26,346 boys and 26,966 girls who participated in the 2015 Korean Youth Risk Behavior Web-Based Survey. The independent variable was the frequency of energy drink consumption per week. Experience of depression and suicide ideation were considered as the dependent variables. Multiple logistic regression was performed. RESULTS An association was found between energy drink intake per week and depressive mood. Moreover, the most frequent energy drink intake (three times or more per week) group showed the highest association with depressive mood (odds ratios (ORs); boys: ORs = 1.40, 95% confidence interval (CI): 1.25-1.56; girls: ORs = 1.61, 95% CI: 1.44-1.79) and suicide ideation (boys: ORs = 1.46, 95% CI: 1.27-1.69; girls: ORs = 1.36, 95% CI: 1.20-1.55). CONCLUSION We observed that consumption of excessive amounts of energy drinks is associated with depression and suicide ideation. Therefore, appropriate regulation or education is needed to prevent adolescents from experiencing adverse outcomes.
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Affiliation(s)
- Hun Kim
- Premedical School, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Junha Park
- Premedical School, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Seungryul Lee
- Premedical School, Yonsei University College of Medicine, Seoul, Republic of Korea
| | - Sang Ah Lee
- Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.,Research and Analysis Team, National Health Insurance Service Ilsan Hospital, Goyang, Republic of Korea
| | - Eun-Cheol Park
- Institute of Health Services Research, Yonsei University, Seoul, Republic of Korea.,Department of Preventive Medicine, Institute of Health Services Research, Yonsei University College of Medicine, Seoul, Republic of Korea
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Effects of One Versus Two Doses of a Multi-Ingredient Pre-Workout Supplement on Metabolic Factors and Perceived Exertion during Moderate-Intensity Running in Females. Sports (Basel) 2020; 8:sports8040052. [PMID: 32331393 PMCID: PMC7240597 DOI: 10.3390/sports8040052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 04/03/2020] [Accepted: 04/20/2020] [Indexed: 12/18/2022] Open
Abstract
The primary purpose of this study was to examine the acute effects of one versus two doses of a multi-ingredient pre-workout supplement on energy expenditure during moderate-intensity treadmill running. In addition, our second aim was to investigate the responses of associated metabolic factors (i.e., substrate utilization, measures of gas exchange), perceived exertion, and resting cardiovascular variables with one and two doses of the pre-workout supplement. Twelve females (mean ± SD: age = 25.3 ± 9.4 years; body mass = 61.2 ± 6.8 kg) completed three bouts of 30 min of treadmill running at 90% of their ventilatory threshold on separate days after consuming one dose of the pre-workout supplement (1-dose), two doses (2-dose), and a placebo. There were no differences among conditions for energy expenditure, fat or carbohydrate oxidation, respiratory exchange ratio, oxygen consumption, or heart rate across exercise time. The two-dose group, however, had lower (p = 0.036) ratings of perceived exertion (11.8 ± 1.7) than the one-dose (12.6 ± 1.7) and the placebo (12.3 ± 1.2) at the 20-min time point of exercise as well as greater resting systolic blood pressure (110 ± 10 mmHg) compared to the one-dose (106 ± 10 mmHg) and the placebo (104 ± 10 mmHg) conditions. Both the one-dose and two-dose conditions had greater increases in diastolic blood pressure compared to the placebo. Thus, our findings indicated that the present pre-workout supplement had no performance-enhancing benefits related to energy metabolism but did attenuate feelings of exertion.
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14
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Effect of caffeine ingestion on competitive rifle shooting performance. PLoS One 2019; 14:e0224596. [PMID: 31671137 PMCID: PMC6822722 DOI: 10.1371/journal.pone.0224596] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 10/17/2019] [Indexed: 01/08/2023] Open
Abstract
PURPOSE The purpose of the present study was to test if caffeine ingestion affects rifle shooting accuracy in trained shooters. METHODS Twenty trained shooters performed 4 shooting tests in a randomized, double-blinded, placebo controlled crossover design; 2 identical tests after placebo ingestion and 2 after ingestion of 300 mg caffeine. The tests consisted of 30 shots in prone position and 30 in standing position on a 10 ring electronic target, on a distance of 50 metres, without any time limit, at rest. RESULTS Caffeine supplementation entailed a mean decrease in shooting performance by 11.8 points (95% CI: 6.7 to 17.0, effect size: 0.9). This was primarily a result of an 11.3 (95% CI: 7.2 to 15.4, effect size: 0.9) point decrease during shooting in standing position and not in prone position (0.6 point decrease, 95% CI: -2.1 to 3.2, effect size: 0.1). CONCLUSIONS We conclude that prior ingestion of 300 mg caffeine impairs rifle shooting accuracy in trained shooters when performed in standing but not in prone position.
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15
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Bello ML, Walker AJ, McFadden BA, Sanders DJ, Arent SM. The effects of TeaCrine® and caffeine on endurance and cognitive performance during a simulated match in high-level soccer players. J Int Soc Sports Nutr 2019; 16:20. [PMID: 30999897 PMCID: PMC6472067 DOI: 10.1186/s12970-019-0287-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 04/04/2019] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND Theacrine (1,3,7,9-tetramethyluric-acid) is a pure alkaloid with a similar structure to caffeine and acts comparably as an adenosine receptor antagonist. Early studies have shown non-habituating effects, including increases in energy and focus in response to Teacrine®, the compound containing pure theacrine. The purpose of this study was to determine and compare the effects of Teacrine® and caffeine on cognitive performance and time-to-exhaustion during a simulated soccer game in high-level male and female athletes. METHODS Male and female soccer players (N = 24; MAge = 20.96 ± 2.05y, MMaleVO2max = 55.31 ± 3.39 mL/O2/kg, MFemaleVO2max = 50.97 ± 3.90 mL/O2/kg) completed a 90-min simulated treadmill soccer match over four randomized sessions (TeaCrine®, caffeine, TeaCrine® + caffeine, placebo). Cognitive testing at halftime and end-of-game including simple reaction time (SRT), choice RT (CRT), and cognitive-load RT with distraction questions (COGRT/COGRTWrong) was performed, with a run time-to-exhaustion (TTE) at 85% VO2max following end-of-game cognitive testing. Session times and pre-exercise nutrition were controlled. RM-MANOVAs with univariate follow-ups were conducted and significance was set at P < 0.05. RESULTS TTE trended towards significance in TeaCrine® and TeaCrine® + caffeine conditions compared to placebo (P < 0.052). A condition main effect (P < 0.05) occurred with faster CRT in caffeine and TeaCrine® + caffeine compared to placebo. COGRTWrong showed a significant time main effect, with better accuracy at end-of-game compared to halftime (P < 0.05). A time x condition interaction in SRT (P < 0.05) showed placebo improved from halftime to end-of-game. CONCLUSIONS The 27-38% improvements in TTE reflect increased performance capacity that may have important implications for overtime scenarios. These findings suggest TeaCrine® favorably impacts endurance and the combination with caffeine provides greater benefits on cognitive function than either supplement independently.
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Affiliation(s)
- Marissa L Bello
- IFNH Center for Health and Human Performance, Rutgers University, 61 Dudley Rd, New Brunswick, NJ, 08901, USA
| | - Alan J Walker
- IFNH Center for Health and Human Performance, Rutgers University, 61 Dudley Rd, New Brunswick, NJ, 08901, USA
| | - Bridget A McFadden
- IFNH Center for Health and Human Performance, Rutgers University, 61 Dudley Rd, New Brunswick, NJ, 08901, USA
| | - David J Sanders
- IFNH Center for Health and Human Performance, Rutgers University, 61 Dudley Rd, New Brunswick, NJ, 08901, USA
| | - Shawn M Arent
- IFNH Center for Health and Human Performance, Rutgers University, 61 Dudley Rd, New Brunswick, NJ, 08901, USA.
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16
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da Silva Rolim P, da Costa Matos RA, Von Koenig Soares EDMK, Molina GE, da Cruz CJG. Caffeine increases parasympathetic reactivation without altering resting and exercise cardiac parasympathetic modulation: A balanced placebo design. Eur J Sport Sci 2018; 19:490-498. [PMID: 30326789 DOI: 10.1080/17461391.2018.1532532] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The sympathicotonic effect of caffeine is strongly evidenced in the literature. However, the effects of caffeine or caffeine expectancy on the cardiac parasympathetic modulation remain obscure. Thus, the aim of this study was to investigate the effects of caffeine consumption and expectancy of caffeine consumption on the cardiac parasympathetic modulation under different stress conditions. Twenty-one physically active men (22.3 ± 2.9 years, 25.2 ± 2.7 kg/m2) consumed ∼3 mg/kg of caffeine received as caffeine, caffeine as placebo, placebo as placebo and placebo as caffeine. Parasympathetic modulation was assessed by heart rate variability (HRV-Poincaré SD1 index) at supine and orthostatic positions, during a submaximal exercise (HRV threshold-HRVT) and during each 60 seconds (s) within 300 s of post-exercise active recovery. A factorial ANOVA for repeated measures (p < 0.05) was used to assess the effect of caffeine, expectancy and resting time after caffeine intake on the HRV. No significant effect of caffeine or expectancy was observed on the SD1 value at supine or standing positions (p = 0.47-0.53; p = 0.57-0.31, respectively), despite an increase in this variable after resting periods in both positions (p < 0.001). During exercise, caffeine and expectancy do not alter the HRVT (p = 0.51-0.39). However, higher SD1 values were observed after caffeine administration from 60 to 300 s post-exercise recovery (p = 0.01-0.05) but not for the effects of expectancy (p = 0.19-0.94). We concluded that low doses of caffeine or expectancy do not alter the resting cardiac parasympathetic modulation or HRVT. However, caffeine, but not expectancy, increases parasympathetic reactivation after a submaximal exercise test in young men.
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Affiliation(s)
- Paloma da Silva Rolim
- a Group of Studies and Research in Cardiac Autonomic Function (GEFAC) , Centro Universitário Euro Americano-UNIEURO , Brasilia , Brazil
| | - Raquel Adjafre da Costa Matos
- a Group of Studies and Research in Cardiac Autonomic Function (GEFAC) , Centro Universitário Euro Americano-UNIEURO , Brasilia , Brazil
| | | | - Guilherme Eckhardt Molina
- b Laboratory of Exercise Physiology, Faculty of Physical Education , Universidade de Brasília , Brasilia , Brazil
| | - Carlos Janssen Gomes da Cruz
- a Group of Studies and Research in Cardiac Autonomic Function (GEFAC) , Centro Universitário Euro Americano-UNIEURO , Brasilia , Brazil.,b Laboratory of Exercise Physiology, Faculty of Physical Education , Universidade de Brasília , Brasilia , Brazil
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Mercier J, Tang A, Morin M, Khalifé S, Lemieux MC, Reichetzer B, Dumoulin C. Test-retest reliability of clitoral blood flow measurements using color Doppler ultrasonography at rest and after a pelvic floor contraction task in healthy adult women. Neurourol Urodyn 2018; 37:2249-2256. [DOI: 10.1002/nau.23582] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 03/04/2018] [Indexed: 12/29/2022]
Affiliation(s)
- Joanie Mercier
- School of Rehabilitation; Faculty of Medicine; University of Montreal; Research Centre of the Institut Universitaire de Gériatrie de Montréal; Montreal Canada
| | - An Tang
- Department of Radiology; Radio-Oncology and Nuclear Medecine; Centre hospitalier de l'Université de Montréal; Montreal Canada
| | - Mélanie Morin
- Faculty of Medicine; School of Rehabilitation; University of Sherbrooke; Research Centre of the Centre hospitalier universitaire de Sherbrooke; Sherbrooke Canada
| | - Samir Khalifé
- Department of Obstetrics and Gynecology; Sir Mortimer B. Davis-Jewish General Hospital; McGill University; Montreal Quebec Canada
| | - Marie-Claude Lemieux
- Department of Obstetrics and Gynecology; Maisonneuve-Rosemont Hospital; Montreal Canada
| | - Barbara Reichetzer
- Department of Obstetrics and Gynecology; Centre hospitalier de l'Université de Montréal; Montreal Canada
| | - Chantale Dumoulin
- Faculty of Medicine; School of Rehabilitation; University of Montreal; Research Centre of the Institut Universitaire de Gériatrie de Montréal; Montreal Canada
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Li N, Zhang P, Kiang KMY, Cheng YS, Leung GKK. Caffeine Sensitizes U87-MG Human Glioblastoma Cells to Temozolomide through Mitotic Catastrophe by Impeding G2 Arrest. BIOMED RESEARCH INTERNATIONAL 2018; 2018:5364973. [PMID: 30050935 PMCID: PMC6046144 DOI: 10.1155/2018/5364973] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Accepted: 06/03/2018] [Indexed: 12/31/2022]
Abstract
Temozolomide (TMZ) is the first-line chemotherapeutic agent in the treatment of glioblastoma multiforme (GBM). Despite its cytotoxic effect, TMZ also induces cell cycle arrest that may lead to the development of chemoresistance and eventual tumor recurrence. Caffeine, a widely consumed neurostimulant, shows anticancer activities and is reported to work synergistically with cisplatin and camptothecin. The present study aimed to investigate the effects and the mechanisms of action of caffeine used in combination with TMZ in U87-MG GBM cells. As anticipated, TMZ caused DNA damage mediated by the ATM/p53/p21 signaling pathway and induced significant G2 delay. Concurrent treatment with caffeine repressed proliferation and lowered clonogenic capacity on MTT and colony formation assays, respectively. Mechanistic study showed that coadministration of caffeine and TMZ suppressed the phosphorylation of ATM and p53 and downregulated p21 expression, thus releasing DNA-damaged cells from G2 arrest into premature mitosis. Cell cycle analysis demonstrated that the proportion of cells arrested in G2 phase decreased when caffeine was administered together with TMZ; at the same time, the amount of cells with micronucleation and multipolar spindle poles increased, indicative of enhanced mitotic cell death. Pretreatment of cells with caffeine further enhanced mitotic catastrophe development in combined treatment and sensitized cells to apoptosis when followed by TMZ alone. In conclusion, our study demonstrated that caffeine enhanced the efficacy of TMZ through mitotic cell death by impeding ATM/p53/p21-mediated G2 arrest.
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Affiliation(s)
- Ning Li
- Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong
| | - Pingde Zhang
- Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong
| | - Karrie Mei Yee Kiang
- Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong
| | - Yin Stephen Cheng
- Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong
| | - Gilberto Ka Kit Leung
- Department of Surgery, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong
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Caffeine and Physiological Responses to Submaximal Exercise: A Meta-Analysis. Int J Sports Physiol Perform 2018; 13:402-411. [PMID: 28872376 DOI: 10.1123/ijspp.2017-0312] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The aim of this study was to carry out a systematic review and meta-analysis of the effects of caffeine supplementation on physiological responses to submaximal exercise. A total of 26 studies met the inclusion criteria of adopting double-blind, randomized crossover designs that included a sustained (5-30 min) fixed-intensity bout of submaximal exercise (constrained to 60-85% maximal rate of oxygen consumption) using a standard caffeine dose of 3-6 mg·kg-1 administered 30-90 min prior to exercise. Meta-analyses were completed using a random-effects model, and data are presented as raw mean difference (D) with associated 95% confidence limits (CLs). Relative to placebo, caffeine led to significant increases in submaximal measures of minute ventilation (D = 3.36 L·min-1; 95% CL, 1.63-5.08; P = .0001; n = 73), blood lactate (D = 0.69 mmol·L-1; 95% CL, 0.46-0.93; P < .00001; n = 208), and blood glucose (D = 0.42 mmol·L-1; 95% CL, 0.29-0.55; P < .00001; n = 129). In contrast, caffeine had a suppressive effect on ratings of perceived exertion (D = -0.8; 95% CL, -1.1 to -0.6; P < .00001; n = 147). Caffeine had no effect on measures of heart rate (P = .99; n = 207), respiratory exchange ratio (P = .18; n = 181), or oxygen consumption (P = .92; n = 203). The positive effects of caffeine supplementation on sustained high-intensity exercise performance are widely accepted, although the mechanisms to explain that response are currently unresolved. This meta-analysis has revealed clear effects of caffeine on various physiological responses during submaximal exercise, which may help explain its ergogenic action.
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Mercier J, Tang A, Morin M, Lemieux MC, Khalifé S, Reichetzer B, Dumoulin C. Test–retest reliability of internal pudendal artery blood flow using color Doppler ultrasound in healthy women. Int Urogynecol J 2018; 29:1817-1824. [DOI: 10.1007/s00192-018-3615-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 02/26/2018] [Indexed: 11/24/2022]
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Caffeine and cardiovascular health. Regul Toxicol Pharmacol 2017; 89:165-185. [DOI: 10.1016/j.yrtph.2017.07.025] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 07/21/2017] [Accepted: 07/23/2017] [Indexed: 02/07/2023]
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Martin JS, Mumford PW, Haun CT, Luera MJ, Muddle TWD, Colquhoun RJ, Feeney MP, Mackey CS, Roberson PA, Young KC, Pascoe DD, DeFreitas JM, Jenkins NDM, Roberts MD. Effects of a pre-workout supplement on hyperemia following leg extension resistance exercise to failure with different resistance loads. J Int Soc Sports Nutr 2017; 14:38. [PMID: 28959158 PMCID: PMC5615454 DOI: 10.1186/s12970-017-0195-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 09/20/2017] [Indexed: 01/24/2023] Open
Abstract
Background We sought to determine if a pre-workout supplement (PWS), containing multiple ingredients thought to enhance blood flow, increases hyperemia associated with resistance training compared to placebo (PBO). Given the potential interaction with training loads/time-under-tension, we evaluated the hyperemic response at two different loads to failure. Methods Thirty males participated in this double-blinded study. At visit 1, participants were randomly assigned to consume PWS (Reckless™) or PBO (maltodextrin and glycine) and performed four sets of leg extensions to failure at 30% or 80% of their 1-RM 45-min thereafter. 1-wk. later (visit 2), participants consumed the same supplement as before, but exercised at the alternate load. Heart rate (HR), blood pressure (BP), femoral artery blood flow, and plasma nitrate/nitrite (NOx) were assessed at baseline (BL), 45-min post-PWS/PBO consumption (PRE), and 5-min following the last set of leg extensions (POST). Vastus lateralis near infrared spectroscopy (NIRS) was employed during leg extension exercise. Repeated measures ANOVAs were performed with time, supplement, and load as independent variables and Bonferroni correction applied for multiple post-hoc comparisons. Data are reported as mean ± SD. Results With the 30% training load compared to 80%, significantly more repetitions were performed (p < 0.05), but there was no difference in total volume load (p > 0.05). NIRS derived minimum oxygenated hemoglobin (O2Hb) was lower in the 80% load condition compared to 30% for all rest intervals between sets of exercise (p < 0.0167). HR and BP did not vary as a function of supplement or load. Femoral artery blood flow at POST was higher independent of exercise load and treatment. However, a time*supplement*load interaction was observed revealing greater femoral artery blood flow with PWS compared to PBO at POST in the 80% (+56.8%; p = 0.006) but not 30% load condition (+12.7%; p = 0.476). Plasma NOx was ~3-fold higher with PWS compared to PBO at PRE and POST (p < 0.001). Conclusions Compared to PBO, the PWS consumed herein augmented hyperemia following multiple sets to failure at 80% of 1-RM, but not 30%. This specificity may be a product of interaction with local perturbations (e.g., reduced tissue oxygenation levels [minimum O2Hb] in the 80% load condition) and/or muscle fiber recruitment.
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Affiliation(s)
- Jeffrey S Martin
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA.,Department of Cell Biology and Physiology, Edward Via College of Osteopathic Medicine-Auburn Campus, 910 S. Donahue Drive, Auburn, AL 36832 USA
| | - Petey W Mumford
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA
| | - Cody T Haun
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA
| | - Micheal J Luera
- School of Kinesiology, Applied Health and Recreation, Oklahoma State University, Stillwater, OK 74078 USA
| | - Tyler W D Muddle
- School of Kinesiology, Applied Health and Recreation, Oklahoma State University, Stillwater, OK 74078 USA
| | - Ryan J Colquhoun
- School of Kinesiology, Applied Health and Recreation, Oklahoma State University, Stillwater, OK 74078 USA
| | - Mary P Feeney
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA
| | - Cameron S Mackey
- School of Kinesiology, Applied Health and Recreation, Oklahoma State University, Stillwater, OK 74078 USA
| | - Paul A Roberson
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA
| | - Kaelin C Young
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA.,Department of Cell Biology and Physiology, Edward Via College of Osteopathic Medicine-Auburn Campus, 910 S. Donahue Drive, Auburn, AL 36832 USA
| | - David D Pascoe
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA
| | - Jason M DeFreitas
- School of Kinesiology, Applied Health and Recreation, Oklahoma State University, Stillwater, OK 74078 USA
| | - Nathaniel D M Jenkins
- School of Kinesiology, Applied Health and Recreation, Oklahoma State University, Stillwater, OK 74078 USA
| | - Michael D Roberts
- School of Kinesiology, Auburn University, Auburn, AL 36849 USA.,Department of Cell Biology and Physiology, Edward Via College of Osteopathic Medicine-Auburn Campus, 910 S. Donahue Drive, Auburn, AL 36832 USA
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Production of theobromine by N-demethylation of caffeine using metabolically engineered E . coli. BIOCATALYSIS AND AGRICULTURAL BIOTECHNOLOGY 2017. [DOI: 10.1016/j.bcab.2017.06.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Jones MD, Taylor JL, Barry BK. Occlusion of blood flow attenuates exercise-induced hypoalgesia in the occluded limb of healthy adults. J Appl Physiol (1985) 2017; 122:1284-1291. [DOI: 10.1152/japplphysiol.01004.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 01/19/2017] [Accepted: 02/07/2017] [Indexed: 12/21/2022] Open
Abstract
Animal studies have demonstrated an important role of peripheral mechanisms as contributors to exercise-induced hypoalgesia (EIH). Whether these same mechanisms contribute to EIH in humans is not known. In the current study, pain thresholds were assessed in healthy volunteers ( n = 36) before and after 5 min of high-intensity leg cycling exercise and an equivalent period of quiet rest. Pressure pain thresholds (PPTs) were assessed over the rectus femoris muscle of one leg and first dorsal interosseous muscles (FDIs) of both arms. Blood flow to one arm was occluded by a cuff throughout the 5-min period of exercise (or rest) and postexercise (or rest) assessments. Ratings of pain intensity and pain unpleasantness during occlusion were also measured. Pain ratings during occlusion increased over time (range, 1.5 to 3.5/10, all d > 0.63, P < 0.001) similarly in the rest and exercise conditions ( d < 0.35, P > 0.4). PPTs at all sites were unchanged following rest (range, −1.3% to +0.9%, all d < 0.05, P > 0.51). Consistent with EIH, exercise significantly increased PPT at the leg (+29%, d = 0.69, P < 0.001) and the nonoccluded (+23%, d = 0.56, P < 0.001) and occluded (+8%, d = 0.19, P = 0.003) unexercised arms. However, the increase in the occluded arm was significantly smaller ( d = −1.03, P < 0.001). These findings show that blocking blood flow to a limb during exercise attenuates EIH, suggesting that peripheral factors contribute to EIH in healthy adults. NEW & NOTEWORTHY This is the first demonstration in humans that a factor carried by the circulation and acting at the periphery is important for exercise-induced hypoalgesia. Further understanding of this mechanism may provide new insight to pain relief with exercise as well as potential interactions between analgesic medications and exercise.
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Affiliation(s)
- Matthew D. Jones
- School of Medical Sciences, University of New South Wales, Sydney, Australia; and
- Neuroscience Research Australia, Sydney, Australia
| | - Janet L. Taylor
- School of Medical Sciences, University of New South Wales, Sydney, Australia; and
- Neuroscience Research Australia, Sydney, Australia
| | - Benjamin K. Barry
- School of Medical Sciences, University of New South Wales, Sydney, Australia; and
- Neuroscience Research Australia, Sydney, Australia
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Cheung M, Quach J, Chan A, Nguyen NN, Shah SA. Effects of Energy Shots on Blood Pressure in Caffeine-Naive Versus Caffeine-Consuming Healthy Volunteers. JOURNAL OF CAFFEINE RESEARCH 2016. [DOI: 10.1089/jcr.2016.0013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Michael Cheung
- Department of Pharmacy Practice, University of the Pacific, Thomas J. Long School of Pharmacy and Health Sciences, Stockton, California
| | - Joanna Quach
- Department of Pharmacy Practice, University of the Pacific, Thomas J. Long School of Pharmacy and Health Sciences, Stockton, California
| | - Amanda Chan
- Department of Pharmacy Practice, University of the Pacific, Thomas J. Long School of Pharmacy and Health Sciences, Stockton, California
| | - Nancy N. Nguyen
- Department of Pharmacy Practice, University of the Pacific, Thomas J. Long School of Pharmacy and Health Sciences, Stockton, California
| | - Sachin A. Shah
- Department of Pharmacy Practice, University of the Pacific, Thomas J. Long School of Pharmacy and Health Sciences, Stockton, California
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Clemente-Suarez VJ, Robles-Pérez JJ. Acute effects of caffeine supplementation on cortical arousal, anxiety, physiological response and marksmanship in close quarter combat. ERGONOMICS 2015; 58:1842-1850. [PMID: 25848703 DOI: 10.1080/00140139.2015.1036790] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
UNLABELLED Previous studies have researched the ergogenic effect of caffeine in different shooting actions, but none of them in a stressful combat action. This study aimed to analyse the effect of a dose of 400 mg of caffeine monohydrate on the psycho-physiological response and marksmanship of soldiers in close quarter combat (CQC). We analysed the heart rate, blood lactate concentration, cortical arousal, state anxiety and marksmanship of 19 soldiers in the Spanish Army (38.9 ± 4.1 years; 177.4 ± 5.3 cm; 78.8 ± 7.6 kg) before and after a CQC simulation in a double-blind procedure. Caffeine intake did not improve shooting performance in CQC; however, it increased cognitive and somatic anxiety levels. PRACTITIONER SUMMARY According to the previous literature, the ingestion of caffeine could help soldiers in operations conducted in sleep deprivation conditions, but in stressful combat situations it does not improve the marksmanship of soldiers.
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Affiliation(s)
- Vicente Javier Clemente-Suarez
- a Center for Higher Studies in Applied Combat , Toledo , Spain
- b Faculty of Sport Sciences, Department of Motricity , Human Performance and Sport Management , Calle Tajo, s/n, 28670 Villaviciosa de Odón, Madrid , Spain
| | - José Juan Robles-Pérez
- a Center for Higher Studies in Applied Combat , Toledo , Spain
- c Light Forces Head Quarter of the Spanish Army , Madrid , Spain
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Gurley BJ, Steelman SC, Thomas SL. Multi-ingredient, Caffeine-containing Dietary Supplements: History, Safety, and Efficacy. Clin Ther 2015; 37:275-301. [DOI: 10.1016/j.clinthera.2014.08.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Revised: 08/19/2014] [Accepted: 08/23/2014] [Indexed: 02/07/2023]
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Kim BJ, Seo Y, Kim JH, Lee DT. Effect of caffeine intake on finger cold-induced vasodilation. Wilderness Environ Med 2014; 24:328-36. [PMID: 24238217 DOI: 10.1016/j.wem.2013.06.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 04/25/2013] [Accepted: 06/19/2013] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The purpose of the study was to investigate the effect of caffeine intake on finger cold-induced vasodilation (CIVD). METHODS Ten healthy men underwent 6 experimental trials characterized by control (NCAFF) or caffeine intake (CAFF) via chewing gum (300 mg of caffeine) while resting on a chair or performing submaximal (70% maximal oxygen consumption) or maximal (100% maximal oxygen consumption) treadmill exercise (Bruce protocol) followed by immersion of the middle finger in a water bath (5°C) for 20 minutes. Finger temperature (Tf ) and time parameters of the first CIVD cycle and post-test norepinephrine were measured. RESULTS Exercise duration for submaximal and maximal exercise was 8.9 ± 0.9 and 12.4 ± 0.8 minutes, respectively. CAFF had no effect on Tf, but exercise increased minimal Tf in NCAFF (9.08 ± 1.27°C, 13.02 ± 2.13°C, and 13.25 ± 1.63°C in rest, submaximal, and maximal exercise, respectively) and CAFF (8.76 ± 1.39°C, 12.50 ± 1.91°C, and 12.79 ± 1.20°C). Maximal Tf was significantly higher in NCAFF (15.98 ± 1.04°C, 16.18 ± 1.56°C, and 15.14 ± 1.52°C) than in CAFF (13.56 ± 1.19°C, 15.52 ± 1.31°C, and 14.39 ± 1.43°C), resulting in a significant difference between minimal and maximal Tf in rest (NCAFF, 6.89 ± 1.56°C and CAFF, 4.79 ± 1.23°C), but not in exercise conditions. CAFF had no effect on CIVD time responses, but exercise significantly shortened CIVD onset and peak time compared with rest in both NCAFF and CAFF. Norepinephrine concentration was significantly greater in CAFF (290.6 ± 113.0 pg/mL, 278.1 ± 91.4 pg/mL, and 399.8 ± 125.5 pg/mL) than NCAFF (105.6 ± 29.5 pg/mL, 199.6 ± 89.6 pg/mL, and 361.5 ± 171.3 pg/mL). CONCLUSIONS Caffeine intake before finger immersion in cold water does not result in a thermogenic effect and adversely affects CIVD responses, whereas exercise modifies CIVD temperature and time responses.
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Affiliation(s)
- Byeong Jo Kim
- College of Physical Education, Kookmin University, Seoul, South Korea
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El Agaty SMT, Seif AA. Cardiovascular effects of long-term caffeine administration in aged rats. Ir J Med Sci 2014; 184:265-72. [PMID: 24639015 DOI: 10.1007/s11845-014-1098-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Accepted: 02/26/2014] [Indexed: 01/13/2023]
Abstract
AIM To evaluate the possible beneficial effect of long-term caffeine administration on cardiovascular system in aged rats. METHODS This study was carried out on 20 senile male albino rats, aged 18-20 months. Rats were divided into caffeine-treated group, which received 25 mg/kg caffeine by gavage daily for 6 weeks, and control group. All rats were subjected to the following in vivo measurements: body weight, arterial blood pressure, heart rate and ECG recording. In vitro measurements included studying isolated hearts in a Langendorff apparatus for their intrinsic properties as well as plasma levels of lipids, malondialdehyde and nitrate. RESULTS Caffeine administration to aged rats significantly enhanced the baseline and maximum values achieved in response to isoproterenol infusion in isolated heart preparation for both maximum rate of tension development (dT/dt max) and time to peak tension (TPT). The responses of hearts isolated from caffeine group to the three doses of isoproterenol infusion also showed a significantly higher dT/dt max with shorter TPT and half relaxation time (1/2 RT) compared to controls. Plasma nitrate was significantly increased and ECG recording was nonsignificantly affected in caffeine group. The plasma levels of total cholesterol, LDL cholesterol as well as in vivo heart rate and systolic, diastolic and mean arterial blood pressures were all significantly increased associated with a significant decrease in HDL cholesterol in caffeine group. CONCLUSION Long-term caffeine administration in aged rats increased cardiac inotropy, lusitropy and preserved NO level, which points to a promising potential favorable effect on cardiac intrinsic properties.
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Affiliation(s)
- S M T El Agaty
- Physiology Department, Faculty of Medicine, Ain Shams University, 74 Abbassiya Street, Abdou Pasha Square, Cairo, Egypt,
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Higgins JP, Babu KM. Caffeine reduces myocardial blood flow during exercise. Am J Med 2013; 126:730.e1-8. [PMID: 23764265 DOI: 10.1016/j.amjmed.2012.12.023] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 12/17/2012] [Accepted: 12/17/2012] [Indexed: 12/25/2022]
Abstract
Caffeine consumption has been receiving increased interest from both the medical and lay press, especially given the increased amounts now available in energy products. Acute ingestion of caffeine usually increases cardiac work; however, caffeine impairs the expected proportional increase in myocardial blood flow to match this increased work of the heart, most notably during exercise. This appears to be mainly due to caffeine's effect on blocking adenosine-induced vasodilatation in the coronary arteries in normal healthy subjects. This review summarizes the available medical literature specifically relating to pure caffeine tablet ingestion and reduced exercise coronary blood flow, and suggests possible mechanisms. Further studies are needed to evaluate this effect for other common caffeine-delivery systems, including coffee, energy beverages, and energy gels, which are often used for exercise performance enhancement, especially in teenagers and young athletes.
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Affiliation(s)
- John P Higgins
- Memorial Hermann Ironman Sports Medicine Institute, The University of Texas Medical School at Houston, Houston, TX 77030-1501, USA.
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Endothelial function acutely worse after drinking energy beverage. Int J Cardiol 2013; 168:e47-9. [PMID: 23876461 DOI: 10.1016/j.ijcard.2013.06.114] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 06/30/2013] [Indexed: 12/18/2022]
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ETEHADTAVAKOL MAHNAZ, NG EDDIEYK. BREAST THERMOGRAPHY AS A POTENTIAL NON-CONTACT METHOD IN THE EARLY DETECTION OF CANCER: A REVIEW. J MECH MED BIOL 2013. [DOI: 10.1142/s0219519413300019] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This review paper discusses recent research achievements in medical thermography with concerns about the possibility of early breast cancer detection. With the advancements in infrared (IR) technology, image processing methods, and the pathophysiological-based knowledge of thermograms, IR screening is sufficiently mature to be utilized as a first-line complement to both health managing and clinical prognosis. In addition, it explains the performance and environmental conditions in identifying thermography for breast tumor imaging under strict indoor controlled environmental circumstances. An irregular thermogram is indicated as a significant biological risk marker for the presence or growth of breast tumors. Breast thermography is completely non-contact, with no form of radiation and compression. It is useful for all women of all ages, for pregnant and breastfeeding women, for women with implants, for women with dense or fibrocystic breasts, for women on hormone replacement therapy, and for pre or post menopausal women. Breast thermography is specifically worthwhile during the early stages of fast tumor growth, which is not yet recognizable by mammography as thermography is a physiological test while mammography is an anatomical one. Often, physiological changes precede anatomical changes. This early detection of irregular tissue liveliness gives breast thermography the potential to be greatly useful and economical as an imaging program and provides the opportunity to apply non-invasive treatment to reform breast tissue activity. The non-radiating nature of thermography also permits repeated images. Thus, changes can be compared over time and the results of protective approaches can be observed to ensure utmost care of breast cells.
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Affiliation(s)
- MAHNAZ ETEHADTAVAKOL
- Medical Image and Signal Processing Research Centre, Isfahan University of Medical Sciences, Isfahan 81745-319, Iran
| | - EDDIE Y. K. NG
- School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
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Optimized exercise load control system based on Heart Rate Variability. Biomed Eng Lett 2011. [DOI: 10.1007/s13534-011-0037-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
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Ganio MS, Armstrong LE. Effect of caffeine on internal temperature. Eur J Appl Physiol 2011; 112:1977-8. [DOI: 10.1007/s00421-011-2125-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 08/12/2011] [Indexed: 11/24/2022]
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Bloomer RJ, Harvey IC, Farney TM, Bell ZW, Canale RE. Effects of 1,3-dimethylamylamine and caffeine alone or in combination on heart rate and blood pressure in healthy men and women. PHYSICIAN SPORTSMED 2011; 39:111-20. [PMID: 22030947 DOI: 10.3810/psm.2011.09.1927] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND The use of 1,3-dimethylamylamine (geranamine), alone and in combination with caffeine, is becoming widespread within the dietary supplement industry. To our knowledge, no data are available concerning the effects of oral geranamine intake on heart rate (HR) and blood pressure in individuals. METHODS Ten young healthy men and women ingested 1 of 5 conditions on different days using a double-blind, randomized, crossover design. The following were ingested after a 10-hour overnight fast: 250 mg caffeine (C), 50 mg geranamine (G 50 mg), 75 mg geranamine (G 75 mg), 250 mg caffeine + 50 mg geranamine (C + G 50 mg), and 250 mg caffeine + 75 mg geranamine (C + G 75 mg). Heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), and rate pressure product (RPP) were measured pre-ingestion and at 30, 60, 90, and 120 minutes post-ingestion. Plasma norepinephrine (NE) and epinephrine (EPI) were measured pre-ingestion and at 60 and 120 minutes post-ingestion. RESULTS Heart rate was unaffected by treatment, but blood pressure and RPP were higher with geranamine, generally in a dose-dependent manner. The peak percent change from pre-ingestion in SBP (~20%), DBP (~17%), and RPP (~9%) was noted with C + G 75 mg at 60 minutes post-ingestion. Plasma NE and EPI were relatively unaffected by treatment. CONCLUSION We report for the first time that acute ingestion of 1,3-dimethylamylamine alone and in combination with caffeine results in an increase in SBP, DBP, and RPP without an increase in HR. The largest increase is observed at 60 minutes post-ingestion of C + G 75 mg. These changes cannot be explained by circulating NE and EPI.
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Affiliation(s)
- Richard J Bloomer
- Department of Health and Sport Sciences, The University of Memphis, Memphis, TN, USA.
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Abstract
In the concentration range that is normally achieved in humans, e.g., after the drinking of coffee or in patients treated with theophylline, the cardiovascular effects of methylxanthines are primarily due to antagonism of adenosine A(1) and A(2) receptors. Inhibition of phosphodiesterases or mobilization of intracellular calcium requires much higher concentrations. In conscious humans, acute exposure to caffeine results in an increase in blood pressure by an increased total peripheral resistance, and a slight decrease in heart rate. This overall hemodynamic response is composed of direct effects of caffeine on vascular tone, on myocardial contractility and conduction, and on the sympathetic nervous system. Caffeine is the most widely consumed methylxanthine, mainly derived from coffee intake. Regular coffee consumption can affect various traditional cardiovascular risk factors, including a slight increase in blood pressure, an increase in plasma cholesterol and homocysteine levels, and a reduced incidence of type 2 diabetes mellitus. Although most prospective studies have not reported an association between coffee consumption and coronary heart disease, these findings do not exclude that the acute hemodynamic and neurohumoral effects of coffee consumption could have an adverse effect in selected patient groups who are more vulnerable for these effects, based on their genetic profile or medication use.
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Affiliation(s)
- Niels P Riksen
- Department of Pharmacology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
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Cazé RF, Franco GAM, Porpino SKP, Souza AAD, Padilhas OP, Silva AS. Influência da cafeína na resposta pressórica ao exercício aeróbio em sujeitos hipertensos. REV BRAS MED ESPORTE 2010. [DOI: 10.1590/s1517-86922010000500001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A redução da pressão arterial (PA) promovida pelo exercício físico é evidente segundo a literatura atual. Mecanismos neuro-humorais explicam essa resposta hipotensora, em que a diminuição da atividade simpática apresenta-se como um dos principais mecanismos. Porém, a ingestão de alimentos ricos em cafeína (CA) pode suprimir esta atenuação simpática. O objetivo desse estudo foi elucidar o impacto da ingestão de CA na resposta pressórica ao exercício em pessoas hipertensas. Sete hipertensos (52,3 ± 3,3 anos), sendo cinco mulheres, realizaram duas sessões de caminhada com 40 minutos de duração, em dois dias de treinamento, tendo previamente ingerido CA (4mg/kg de peso corporal) ou placebo (PL). A PA e a frequência cardíaca foram verificadas anteriormente a ingestão, após 15, 30, 45, 60 minutos da ingestão em estado de repouso e com 10, 20 e 30 minutos após o exercício. Os dados foram tratados por meio de estatística descritiva, e pelo teste não paramétrico de Wilcoxon (p < 0,05). A média da PA aumentou de 124,9/80,9mmHg antes da ingestão de CA para 129,4/84,3mmHg 60 minutos após, ainda no repouso (p < 0,05). Trinta minutos após o exercício observou-se resposta hipotensora no procedimento PL (queda da PA de 122,6/79,4mmHg para 115,7/78,6mmHg), enquanto que no procedimento com CA, a PA mostrou-se significativamente mais alta em relação aos valores de repouso (aumento de 124,9/80,9mmHg para 136,9/90,9mmHg, p < 0,05). Conclui-se que a ingestão de CA não só suprime a resposta hipotensora do exercício, como provoca uma hipertensão pós-exercício.
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DEL COSO JUAN, ESTEVEZ EMMA, MORA-RODRIGUEZ RICARDO. Caffeine during Exercise in the Heat. Med Sci Sports Exerc 2009; 41:164-73. [DOI: 10.1249/mss.0b013e318184f45e] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Cibicek N, Zivna H, Cibicek J, Cermakova E, Vorisek V, Malakova J, Micuda S, Palicka V. CAFFEINE DOES NOT MODULATE NUTRITIVE BLOOD FLOW TO RAT GASTRIC SUBMUCOSA - A MICRODIALYSIS STUDY. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 2008; 152:83-90. [DOI: 10.5507/bp.2008.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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George SE, Ramalakshmi K, Mohan Rao LJ. A Perception on Health Benefits of Coffee. Crit Rev Food Sci Nutr 2008; 48:464-86. [DOI: 10.1080/10408390701522445] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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TURLEY KENNETHR, BLAND JUSTINR, EVANS WILLIAMJ. Effects of Different Doses of Caffeine on Exercise Responses in Young Children. Med Sci Sports Exerc 2008; 40:871-8. [DOI: 10.1249/mss.0b013e318165984c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Giacomin E, Palmerini E, Ballo P, Zacà V, Bova G, Mondillo S. Acute effects of caffeine and cigarette smoking on ventricular long-axis function in healthy subjects. Cardiovasc Ultrasound 2008; 6:9. [PMID: 18318902 PMCID: PMC2288591 DOI: 10.1186/1476-7120-6-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2007] [Accepted: 03/04/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Few data exist regarding the direct effects of caffeine and smoking on cardiac function. We sought to explore the acute effects of caffeine assumption, cigarette smoking, or both on left ventricular (LV) and right ventricular (RV) function in a population of young normal subjects. METHODS Forty-five healthy subjects aged 25 +/- 2 years underwent echocardiography. Fifteen of them were non-smokers and habitual coffee consumers (group 1), 15 were smokers and not habitual coffee consumers (group 2), and 15 were smokers and habitual coffee consumers (group 3). Peak systolic (Sa), early diastolic Ea, and late diastolic (Aa) velocity of mitral annulus were measured by pulsed Tissue Doppler, and left atrioventricular plane displacement was determined by M-mode. Tricuspid annular velocities and systolic excursion (TAPSE) were also determined. Measurements were performed at baseline and after oral assumption of caffeine 100 mg in group 1, one cigarette smoking in group 2, and both in group 3. RESULTS No changes in ventricular function were observed in group 1 after caffeine administration. In group 2, cigarette smoking yielded an acute increase in mitral Aa (+12.1%, p = 0.0026), tricuspid Sa (+9.8%, p = 0.012) and TAPSE (+7.9%, p = 0.017), and a decrease in the mitral Ea/Aa ratio (-8.5%, p = 0.0084). Sequential caffeine assumption and cigarette smoking in group 3 was associated with an acute increase in mitral Aa (+13.0%, p = 0.015) and tricuspid Aa (+11.6%, p < 0.0001) and a reduction in mitral Ea/Aa ratio (-8.5%, p = 0.0084) tricuspid Ea (-6.6%, p = 0.048) and tricuspid Ea/Aa ratio (-9.6%, p = 0.0003). In a two-way ANOVA model controlling for hemodynamic confounding factors, changes in the overall population remained significant for mitral Aa and Ea/Aa ratio, and for tricuspid Aa and Ea/Aa ratio. CONCLUSION In young healthy subjects, one cigarette smoking is associated to an acute impairment in LV diastolic function and a hyperdynamic RV systolic response. Caffeine assumption alone does not exert any acute effect on ventricular long-axis function, but potentiates the negative effect of cigarette smoking by abolishing RV supernormal response and leading to a simultaneous impairment in both LV and RV diastolic function.
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Affiliation(s)
- Elisa Giacomin
- Department of Cardiovascular Disease, University of Siena, Italy
| | | | - Piercarlo Ballo
- Cardiology Operative Unit, S. Andrea Hospital, La Spezia, Italy
| | - Valerio Zacà
- Department of Cardiovascular Disease, University of Siena, Italy
| | - Giovanni Bova
- Department of Cardiovascular Disease, University of Siena, Italy
| | - Sergio Mondillo
- Department of Cardiovascular Disease, University of Siena, Italy
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Blank MD, Kleykamp BA, Jennings JM, Eissenberg T. Caffeine's influence on nicotine's effects in nonsmokers. Am J Health Behav 2007; 31:473-83. [PMID: 17555378 PMCID: PMC3209967 DOI: 10.5555/ajhb.2007.31.5.473] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022]
Abstract
OBJECTIVE To determine if nicotine's effects are influenced by caffeine in nonsmoking, moderate-caffeine consuming individuals (N=20). METHODS The first 3 sessions included one of 3 randomly ordered, double-blind caffeine doses (0, 75, or 150 mg, oral [po]) and 2 single-blind nicotine gum doses (2 and 4 mg) in ascending order. The fourth session (single blind) repeated the 0 mg caffeine condition. RESULTS Nicotine increased heart rate and subjective ratings indicative of aversive effects, and decreased reaction times. These effects were independent of caffeine dose and reliable across sessions. CONCLUSIONS In nonsmokers, nicotine effects are not influenced by moderate caffeine doses.
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Affiliation(s)
- Melissa D Blank
- Virginia Commonwealth University, Department of Psychology, Richmond, VA 23298-0205, USA.
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McClaran SR, Wetter TJ. Low doses of caffeine reduce heart rate during submaximal cycle ergometry. J Int Soc Sports Nutr 2007; 4:11. [PMID: 17925021 PMCID: PMC2164943 DOI: 10.1186/1550-2783-4-11] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Accepted: 10/09/2007] [Indexed: 11/26/2022] Open
Abstract
Background The purpose of this study was to examine the cardiovascular effects of two low-levels of caffeine ingestion in non habitual caffeine users at various submaximal and maximal exercise intensities. Methods Nine male subjects (19–25 yr; 83.3 ± 3.1 kg; 184 ± 2 cm), underwent three testing sessions administered in a randomized and double-blind fashion. During each session, subjects were provided 4 oz of water and a gelatin capsule containing a placebo, 1.5 mg/kg caffeine, or 3.0 mg/kg caffeine. After thirty minutes of rest, a warm-up (30 Watts for 2 min) the pedal rate of 60 rpm was maintained at a steady-state output of 60 watts for five minutes; increased to 120 watts for five minutes and to 180 watts for five minutes. After a 2 min rest the workload was 180 watts for one minute and increased by 30 watts every minute until exhaustion. Heart rate (HR) was measured during the last 15-seconds of each minute of submaximal exercise. Systolic blood pressure (BP) was measured at rest and during each of the three sub-maximal steady state power outputs. Minute ventilation (VE), Tidal volume (VT), Breathing frequency (Bf), Rating of perceived exertion (RPE), Respiratory exchange ratio (RER), and Oxygen consumption (VO2) were measured at rest and during each minute of exercise. Results Caffeine at 1.5 and 3.0 mg/kg body weight significantly lowered (p < 0.05) HR during all three submaximal exercise intensities compared to placebo (range – 4 to 7 bpm lower) but not at rest or maximal exercise. BP was significantly higher (p < 0.05) at rest and after the 3 mg/kg caffeine vs placebo (116 ± 13 vs 123 ± 10 mm Hg). Neither dose of caffeine had any effect on BP during submaximal exercise. Caffeine had no effect on VE, VT, VO2, RPE, maximal power output or time to exhaustion. Conclusion In non habitual caffeine users it appears that consuming a caffeine pill (1.5 & 3.0 mg/kg) at a dose comparable to 1–3 cups of coffee lowers heart rate during submaximal exercise but not at near maximal and maximal exercise. In addition, this caffeine dose also only appears to affect systolic blood pressure at rest but not during cycling exercise.
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Affiliation(s)
- Steven R McClaran
- Department of Kinesiology& Health, University of Wisconsin Oshkosh, Oshkosh, WI 54901, USA.
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Abstract
Caffeine is one of the most widely consumed drugs in the world, taken socially and for its alertness- and performance-promoting actions. Extensive reports assert that caffeine increases alertness and cognitive performance levels and, when taken before exercise, demonstrates ergogenic properties. Caffeine ingestion has been associated with increased performance during endurance submaximal, and acute, high-intensity exercise. The exact mechanism of action for the performance effects of caffeine is unknown, although several physiologically and psychologically based theories exist as to how caffeine achieves increased performance capabilities. This paper outlines the known sites of caffeine activity in the body,and discusses these with respect to the effects of caffeine observed during performance assessments.
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Affiliation(s)
- Naomi L Rogers
- Woolcock Institute of Medical Research, P.O. Box M77, Missenden Road, Camperdown, NSW 2050, Australia.
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Ballard TLP, Halaweish FT, Stevermer CL, Agrawal P, Vukovich MD. NARINGIN DOES NOT ALTER CAFFEINE PHARMACOKINETICS, ENERGY EXPENDITURE, OR CARDIOVASCULAR HAEMODYNAMICS IN HUMANS FOLLOWING CAFFEINE CONSUMPTION. Clin Exp Pharmacol Physiol 2006; 33:310-4. [PMID: 16620293 DOI: 10.1111/j.1440-1681.2006.04367.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
1. Naringin, a grapefruit constituent interacts with many medications including caffeine, a popular weight loss supplement. The purpose of the current study was to identify changes in caffeine pharmacokinetics, resting energy expenditure (REE), oxygen consumption (VO(2)) and respiratory exchange ratio (RER) after an acute dosage of caffeine and naringin. 2. Using a double-blinded, counterbalanced design, REE, VO(2), and RER were measured before and systematically for 8 h after a single dosage of caffeine (CAF, 200 mg) with and without naringin (100 mg (CN100) or 200 mg (CN200)) in 10 apparently healthy individuals. A standardized meal was provided following 240-minute measurements (400 kcals; 35 g carbohydrate; 27 g protein; 7 g fat). 3. Caffeine, CN100, CN200 did not alter VO(2) or VO(2) area under the curve (137 301 +/- 8318, 139 729 +/- 9300, 134 297 +/- 8318, mL/480 min). Resting energy expenditure (k/cals) was 10.0 +/- 1.4% higher with CAF versus CN200 (6.0 +/- 1.4%) and CN100 (6 +/- 1.5%) at 240 min (P = 0.07) which was then negated following a standardized meal. Percent change in RER from pre to 240 min and pre to 480 min was not different between the CAF, CN100, or CN200 (-0.2 +/- 1.7%, 1.7 +/- 1.7%, -2.8 +/- 1.9%). 4. Although caffeine alone suggests a trend of increased REE, the results of the present study indicate that concurrent consumption of caffeine with naringin in acute dosages does not affect RER, VO(2), and prevents the increase of REE in adult humans. The results suggest that the interaction of grapefruit juice and caffeine may be due to constituents of grapefruit juice other than naringin or in addition to naringin.
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Affiliation(s)
- Tasha L P Ballard
- South Dakota Health Promotion and Research Program, Applied Physiology Laboratory, South Dakota State University, Brookings 57007, USA
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Turley KR, Gerst JW. Effects of Caffeine on Physiological Responses to Exercise in Young Boys and Girls. Med Sci Sports Exerc 2006; 38:520-6. [PMID: 16540840 DOI: 10.1249/01.mss.0000191189.40436.73] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE To describe the influence of caffeine on physiological responses to exercise in young children and determine whether sex differences in these responses exist. METHODS Twenty-six healthy 7- to 9-yr-old boys and 26 healthy 7- to 9-yr-old girls volunteered to participate in a double-blind, randomized, double crossover study design. Each child randomly received both the placebo (PL) and caffeinated (5 mg x kg(-1)) drink (CAF) twice each on four separate days. Following a 1-h wash-in period and resting measures, each child rode a cycle ergometer at 25 and then 50 W for 8 min each, while HR, blood pressure (BP), and oxygen consumption (VO2) were measured. RESULTS HR (bpm) was significantly (P < 0.05) lower at rest and at 25 and 50 W in CAF versus PL in both boys and girls. Diastolic BP (mm Hg) was significantly (P </= 0.05) higher at rest, 25 W in both boys and girls, and at 50 W in boys, in CAF versus PL. Systolic BP (mm Hg) was significantly (P </= 0.05) higher at rest in both boys and girls, at 25 W in boys, and at 50 W in girls. During exercise, VO2 (L x min(-1) or mL x kg(-1) x min(-1)) and RER were not different in CAF versus PL in either boys or girls. CONCLUSIONS A moderate dose of caffeine (5 mg.kg) does not affect metabolism (VO2 or RER) in young children at low-moderate intensities of exercise. However, CAF causes a significantly lower HR (bpm) and higher BP (mm Hg) in both young boys and girls.
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Affiliation(s)
- Kenneth R Turley
- Human Performance Laboratory, Department of Kinesiology, Harding University, Searcy, AR, USA.
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Kalmar JM, Del Balso C, Cafarelli E. Increased spinal excitability does not offset central activation failure. Exp Brain Res 2006; 173:446-57. [PMID: 16506005 DOI: 10.1007/s00221-006-0383-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2005] [Accepted: 01/27/2006] [Indexed: 11/30/2022]
Abstract
We hypothesized that if reduced spinal excitability contributes to central activation failure, then a caffeine-induced increase in spinal excitability would enhance postfatigue maximal voluntary activation and maximal voluntary contraction (MVC). Ten male volunteer subjects attended two laboratory sessions separated by at least 1 week. Contractile and electrical properties were assessed before, and 1 h after oral administration of caffeine (6 mg/kg) or placebo (all-purpose flour), and again following a fatigue protocol. The slope of the H reflex recruitment curve, normalized to that of the M wave (H(slp)/M(slp)), was used to estimate spinal excitability. Maximal voluntary activation was assessed using maximal EMG (EMG(max)) and twitch interpolation. Postfatigue, MVC torque declined (P<0.05) to 75.2+/-12.7 and 70.2+/-9.3% of the prefatigue values in the placebo (PL) and caffeine (CF) trials, respectively, and remained depressed throughout the recovery period. This was accompanied by a decline in % activation (P<0.05) from 99.6+/-0.3% (PL) and 99.8+/-0.3% (CF) to 94.8+/-3.5% (PL) and 95.3+/-5.0% (CF), indicating the presence of central activation failure. Caffeine offset the decline in H(slp)/M(slp )observed in the placebo trial (P<0.05), but it did not prevent the decline in maximal voluntary activation or MVC torque. Furthermore, although the decline in spinal excitability was correlated to the decline in EMG(max) (r=0.55, P<0.05) it was not correlated with the decline in % activation or MVC torque. Thus a fatigue-induced decline in spinal excitability did not limit maximal activation.
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Affiliation(s)
- J M Kalmar
- Department of Biology, Rm 346 Bethune College, York University, Toronto, ON, Canada
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