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Abstract

Purpose:: Inconsistent results among studies examining the effects of caffeine on exercise performance are potentially due to inter-individual variability in biological responses to caffeine ingestion. The aims, therefore, of the present study were to identify high and low caffeine responders and compare the influence of caffeine on exercise performance and biological responses between groups during a simulated soccer-game protocol on treadmill. Methods:: Well-trained soccer-players were distinguished as high (n = 11) and low (n = 9) caffeine responders based on resting blood pressure, plasma glycerol, non-esterified fatty acid and epinephrine responses to caffeine. Participants underwent two simulated soccer-game protocols on treadmill after caffeine (6 mg∙kg-1) or placebo ingestion. Exercise performance and several biological responses were evaluated. Results:: Exercise performance was not different between the high (H) and low (L) responders to caffeine (P > 0.05). However, time-to-fatigue (H, caffeine: 797±201 s vs placebo: 487±258 s; L, caffeine: 625±357 s vs placebo 447±198 s) and countermovement jumps (H, caffeine: 42.1±5.5 cm vs placebo: 40.5±5.7 cm; L, caffeine: 41.0±3.8 cm vs placebo: 38.8±4.6 cm) improved with caffeine relative to placebo (P < 0.001). Rating of perceived exertion was lower (P < 0.001) in H (13.4±2.3) compared to L (14.3±2.4) with caffeine ingestion. Conclusions:: Caffeine improved aerobic endurance and neuromuscular performance in well-trained soccer-players regardless of their responsiveness to caffeine at rest. Since no changes in substrate utilization were found with caffeine supplementation, performance improvements could be attributed to positive effects on the central nervous system and/or neuromuscular function, although the precise mechanism remains unclear.

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... Caffeine is one of the most popular ergogenic aids used by athletes from various sports in an attempt to improve endurance and/or anaerobic exercise performance; for recent reviews, see [1,2]. Several studies have revealed performance improvement after caffeine supplementation during time trials in cycling [3,4] and running [5]; in team sports, such as volleyball [6], handball [7] and soccer [8]; and during game simulation in controlled laboratory environment [9,10]. Recently, caffeine was also found to improve repeated sprint ability at a speed corresponding to 110% of VO 2 max, but not at higher speeds [11], and anaerobic endurance performance in both men and women [12]. ...
... Because of the mixed findings cited above, it is not clear whether habitual and non-habitual caffeine consumers exhibit different metabolic and performance responses to pre-exercise acute caffeine ingestion. The aim, therefore, of the present study was to compare lower and higher caffeine consumers with respect to the effect of acute caffeine ingestion on biological responses and exercise performance using the same simulated soccer-game protocol and study participants as in our previous study [10]. We hypothesized that caffeine ingestion would elicit dissimilar biological responses to exercise and dissimilar performance effects in well-trained soccer players with different levels of habitual caffeine consumption. ...
... During the participants' first visit to the laboratory, the experimental procedures of the study were explained, followed by their written consent to take part. Medical history, lifestyle [29,30], and habitual caffeine consumption questionnaires [31] were then completed, followed by measurement of anthropometric characteristics and maximum oxygen uptake (VO 2 max) as described [10]. ...
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Purpose Research on whether caffeine habituation reduces its ergogenicity is scarce and conflicting. The purpose of the present study was to examine the influence of habitual caffeine consumption on exercise performance and biological responses during a simulated soccer-game protocol following acute caffeine ingestion. Methods Twenty professional male soccer players were categorized as higher (n = 9) or lower caffeine consumers (n = 11) after answering a validated questionnaire. Participants performed a simulated treadmill soccer-game protocol on treadmill following either caffeine (6 mg kg⁻¹) or placebo ingestion, during which several variables were evaluated. Results Time to exhaustion, countermovement jump height, mean arterial pressure, heart rate, plasma glucose, and lactate were higher (P ≤ 0.001), while rating of perceived exertion (RPE) was lower (P = 0.002), following caffeine compared to placebo ingestion, with no differences between groups (P > 0.05). Plasma non-esterified fatty acids exhibited a higher response to caffeine in the higher vs lower caffeine consumers. Reaction time, plasma glycerol and epinephrine, carbohydrate and fat oxidation, and energy expenditure were not affected by caffeine (P > 0.05). Conclusion Caffeine ingestion largely improved cardiovascular and neuromuscular performance, while reducing RPE, in both higher and lower caffeine consuming athletes during prolonged intermitted exercise to exhaustion.
... To estimate power level, the equation proposed by Sayers et al. (25) was used: P max =60.7 x jump height (cm) + 45.3 x body mass (kg) -2055. The equation is similarly used for research in which muscle power is calculated on the basis of the CMJ (22,(26)(27)(28)(29)(30)(31)(32)(33)(34). The implemented motor trials are not specific to speed climbing. ...
... 2. Simple reaction time, understood as the period from the moment of stimulus presentation to the end of a strictly defined movement. The test was carried out according to the protocol proposed by Apostolidis et al. (27), with author modifications. In the research by Apostolidis et al. (27), the athletes performed jumps at a visual signal, while in this study, bearing in mind that the start in speed climbing takes place at the sound emitted from a device, the attempt was modified by introducing auditory stimulus. ...
... The test was carried out according to the protocol proposed by Apostolidis et al. (27), with author modifications. In the research by Apostolidis et al. (27), the athletes performed jumps at a visual signal, while in this study, bearing in mind that the start in speed climbing takes place at the sound emitted from a device, the attempt was modified by introducing auditory stimulus. The applied test consisted of performing 5 SJs (squat jump with arms folded over the hips) per auditory signal. ...
Article
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Study aim. The main aim of research was to verify which of the countermovement jumps (CMJ) provides the most accurate information on the possibility of obtaining the best result in a climbing run and to assess the coexistence (correlation) of the running result as well as the reaction time to an auditory signal. Material and methods. The study was conducted among a group of male climbers at the average age of 20.5 years (n=6). At the time of the measurements, the competitors presented the highest sports level and were members of the Polish National Team in the speed climbing competition. Somatic measurements were carried out successively, followed by measurements of simple reaction time and various jumps. Results. Correlations between the studied variables characteristic of somatic features as well as motor skills with climbing time were, in most cases, not significant. Statistically significant correlations at the level of p<0.05 were found between running time and the following trials: CMJb (cm) (rx,y: -0.88); PmaxCMJb (W/kg) (rx,y: -0.88) and PmaxCMJb (W/LBMkg) (rx,y: -0.86). Conclusions. CMJ without arm swing is a valuable tool in assessing the motor potential of a sprinting climber and is a test of great informative value in the context of the possibility to obtain high results in a speed climbing competition. The applied test to assess the level of response time to the auditory signal was a trial, which to a moderate extent, allows to diagnose the possibility of achieving high results in a speed climbing sprint.
... Other studies, however, have failed to support a carbohydrate sparing effect of caffeine [7] or a positive effect on endurance performance [8,9]. In wellcontrolled studies in which endurance performance improved following caffeine ingestion, fuel oxidation [10] and physiological responses to exercise were not significantly altered by caffeine [11], which questions even further the existence of a metabolic basis for the ergogenic effect of caffeine despite the finding that this effect increases with event duration [12]. Although an expectancy effect on physical performance cannot be excluded, it might be that caffeine's ergogenicity can be best explained by a reduction in rating of perceived exertion (RPE), probably due to adenosine antagonism in the central nervous system [12]. ...
... The use of homogeneous groups of athletes in terms of training status may assist to better examine this question. The purpose, therefore, of the present study was to examine whether the effects of caffeine supplementation on biological responses and exercise performance depend on levels of cardiorespiratory or neuromuscular fitness by using the same protocol and study participants as in our previous study [10]. We hypothesized that caffeine ingestion would provoke dissimilar biological responses to exercise and have dissimilar performance effects between athletes with different cardiorespiratory and/or neuromuscular fitness levels. ...
... Following explanation of tests and procedures, as well as the nature, benefits and risks of the study during a preliminary session, the participants gave their written consent, after which medical history, lifestyle, and caffeine consumption questionnaires were completed. Anthropometric characteristics and VO 2 max were measured as described [10]. ...
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Background: Equivocal findings examining the influence of caffeine on performance and biological responses to exercise may be due to inter-individual variability in cardiorespiratory or neuromuscular fitness. This study examined whether the effects of caffeine ingestion on exercise performance and biological responses to prolonged intermittent exercise to exhaustion depend on cardiorespiratory or neuromuscular fitness. Methods: Twenty male soccer players, separated according to either cardiorespiratory fitness (high vs medium) or neuromuscular fitness (high vs medium) underwent two trials simulating the cardiovascular demands of a soccer game to exhaustion on treadmill after ingesting either caffeine (6 mg∙kg- 1) or placebo. Physical performance, cardiorespiratory and metabolic parameters and blood metabolites were evaluated. Results: Time to exhaustion (719 ± 288 vs 469 ± 228 s), jump height (42.7 ± 4.2 vs 38.6 ± 4.4 cm), heart rate (163 ± 12 vs 157 ± 13 b∙min- 1), mean arterial blood pressure (98 ± 8 vs 92 ± 10 mmHg), plasma glucose (5.6 ± 0.7 vs 5.3 ± 0.6 mmol∙l- 1) and lactate (3.3 ± 1.2 vs 2.9 ± 1.2 mmol∙l- 1) were higher, while rating of perceived exertion (12.6 ± 1.7 vs 13.3 ± 1.6) was lower with caffeine vs placebo (p < 0.01), independent of cardiorespiratory or neuromuscular fitness level. Reaction time; plasma glycerol, non-esterified fatty acids and epinephrine; carbohydrate and fat oxidation rates; and energy expenditure were not affected by caffeine (p > 0.05). Conclusions: Caffeine was effective in improving endurance and neuromuscular performance in athletes with either high or medium cardiorespiratory and neuromuscular fitness. Cardiorespiratory and neuromuscular fitness do not appear to modulate the ergogenic effects of caffeine supplementation in well-trained athletes.
... Therefore, 16 RCTs (reported in 17 references) were included in this review. [1][2][3][4][5]7,10,12,14,19,22,[25][26][27]29,38,41 Figure 1 details the study selection process. ...
... Anaerobic power: countermovement jump. Seven studies 1,3,12,14,19,22,41 assessed countermovement jump as total height (in centimeters). Two studies 1,19 provided only graph results and it was not clear if they reported standard deviation, standard error, or confidence intervals. ...
... Rating of perceived exertion. Six studies measured this outcome using the Borg 6-to 20-point scale 3,7,14,22,25 and 15-point scale 1 after test completion. Three of them 1,7,14 did not provide numerical data to pool in a meta-analysis, but individual studies reported that there were no differences between trials for participants' RPE. ...
Article
Context Caffeine is 1 of the most popular supplements consumed by athletes, and the evidence for improving soccer performance remains limited. Objective To investigate and update the effects (benefits and harms) of caffeine to improve performance on soccer players. Data Sources Electronic search in Medline (via PubMed), CENTRAL, Embase, SPORTDiscus, and LILACS, from inception to March 28, 2020. Study Selection Randomized clinical trials (RCTs) assessing the effects of caffeine on the performance of soccer players. Study Design Systematic review with meta-analysis. Level of Evidence Level 1. Data Extraction Data extraction was conducted independently by 2 authors using a piloted form. We assessed methodological quality (Cochrane risk-of-bias [RoB] table) and the certainty of the evidence (GRADE [Grading of Recommendations Assessment, Development and Evaluation] approach). Results Sixteen RCTs were included. Overall methodological quality was classified as unclear to low risk of bias. When assessing aerobic endurance, meta-analyses did not demonstrate the differences between caffeine and placebo (mean difference [MD], 44.9 m; 95% confidence interval [CI], −77.7 to 167.6). Similarly, no difference was observed during time to fatigue test (MD, 169.8 seconds; 95% CI, −71.8 to 411.6). Considering anaerobic power, meta-analyses also did not find differences for vertical jump (MD, 1.01 cm; 95% CI, −0.68 to 2.69) and repeated sprint tests (MD, −0.02 seconds; 95% CI, −0.09 to 0.04), as well as reaction time agility test (MD, 0.02 seconds; 95% CI, −0.01 to 0.04) and rating of perceived exertion (MD, 0.16 points; 95% CI, −0.55 to 0.87). Regarding safety, a few minor adverse events were reported. Based on the GRADE approach, the certainty of this evidence was classified as very low to low. Conclusions We found no significant improvement in soccer-related performance with caffeine compared with placebo or no intervention. However, caffeine appears to be safe.
... With this background, one might suppose that caffeine is also ergogenic in soccer although the information regarding this sport has not been summarized. In the last few years, several studies have investigated the effects of caffeine intake on soccer physical performance [14][15][16][17][18][19][20][21] and in the opinion of the authors, the results of these investigations need to be objectively reviewed and summarized. Therefore, the objective of this systematic review was to critically evaluate the effectiveness of a moderate dose of caffeine on soccer physical performance, muscle damage and perception of fatigue in order to provide more objective and comprehensive information about the positive and negative impact of caffeine on soccer players. ...
... 2018 [19] 20 well-trained male players High (n = 11) and low (n = 9) responders ( ...
... In this line, Apostolidis et al., [19] showed that 6 mg/kg of caffeine ingested 60 min previous to a battery of tests improved aerobic endurance (time to fatigue) and neuromuscular performance (CMJ) in 20 well-trained soccer players (age: 21.5 ± 4 years). Since these authors did not find any change in substrate oxidation with caffeine, measured by indirect calorimetry during the testing, they commented that performance improvements could only be attributed to positive effects on the central nervous system and/or neuromuscular function, although the precise mechanism of caffeine ergogenicity was not indicated in this investigation. ...
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Soccer is a complex team sport and success in this discipline depends on different factors such as physical fitness, player technique and team tactics, among others. In the last few years, several studies have described the impact of caffeine intake on soccer physical performance, but the results of these investigations have not been properly reviewed and summarized. The main objective of this review was to evaluate critically the effectiveness of a moderate dose of caffeine on soccer physical performance. A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines in the Medline/PubMed and Web of Science databases from January 2007 to November 2018. The search included studies with a cross-over and randomized experimental design in which the intake of caffeine (either from caffeinated drinks or pills) was compared to an identical placebo situation. There were no filters applied to the soccer players’ level, gender or age. This review included 17 articles that investigated the effects of caffeine on soccer-specific abilities (n = 12) or on muscle damage (n = 5). The review concluded that 5 investigations (100% of the number of investigations on this topic) had found ergogenic effects of caffeine on jump performance, 4 (100%) on repeated sprint ability and 2 (100%) on running distance during a simulated soccer game. However, only 1 investigation (25%) found as an effect of caffeine to increase serum markers of muscle damage, while no investigation reported an effect of caffeine to reduce perceived fatigue after soccer practice. In conclusion, a single and moderate dose of caffeine, ingested 5–60 min before a soccer practice, might produce valuable improvements in certain abilities related to enhanced soccer physical performance. However, caffeine does not seem to cause increased markers of muscle damage or changes in perceived exertion during soccer practice.
... Thus, in the opinion of the authors of this manuscript, the concept of non-responders to the ergogenic effects of caffeine should be revisited. Figure 2 offers further insights on this topic because it presents individual data on caffeine-induced changes on resting systolic and diastolic blood pressure, measured before exercise, which is a variable also employed to categorize individual responses to acute caffeine ingestion [17]. As it happens with the ergogenic effect of caffeine, the outcomes of caffeine on blood pressure had great inter-and intraindividual variability. ...
... The black dashed line represents the natural variation of the graded exercise test (± 2.4%) and the 15-second Wingate test (± 2.7%) measured during the placebo treatment. Figure 2 offers further insights on this topic because it presents individual data on caffeineinduced changes on resting systolic and diastolic blood pressure, measured before exercise, which is a variable also employed to categorize individual responses to acute caffeine ingestion [17]. As it happens with the ergogenic effect of caffeine, the outcomes of caffeine on blood pressure had great inter-and intraindividual variability. ...
Article
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The ergogenicity of caffeine on several exercise and sport situations is well-established. However, the extent of the ergogenic response to acute caffeine ingestion might greatly vary among individuals despite using the same dosage and timing. The existence of one or several individuals that obtained minimal ergogenic effects or even slightly ergolytic effects after caffeine intake (i.e., non-responders) has been reported in several previous investigations. Nevertheless, the concept non-responding to caffeine, in terms of physical performance, relies on investigations based on the measurement of one performance variable obtained once. Recently it has been suggested that correct identification of the individual ergogenic effect induced by caffeine intake requires the repeated measurement of physical performance in identical caffeine–placebo comparisons. In this communication, we present data from an investigation where the ergogenic effect of acute caffeine intake (3 mg/kg) was measured eight times over a placebo in the same individuals and under the same conditions by an incremental cycling test to volitional fatigue and an adapted version of the Wingate cycling test. The ergogenic response to caffeine varied from 9% to 1% among individuals, but all participants increased both cycling power in the incremental test and Wingate mean power at least three to eight times out of eight the caffeine–placebo comparisons. These data expand the suggestion of a minimal occurrence of caffeine non-responders because it shows that all individuals responded to caffeine when caffeine is compared to a placebo on multiple and repeated testing sessions.
... The Yerkes-Dobson law states that performance increases with higher levels of arousal up to a certain point and then decreases, in an "inverted U shape" [38]. The effects of caffeine on arousal levels are known [39,40], but the importance of different arousal levels in different tactical and decision-making actions in soccer is not yet fully understood. Although speculative, one hypothesis is that different levels of arousal are required for different tactical actions during the game and that the effects of caffeine are different according to this relationship. ...
Article
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In soccer, physical, tactical, and decision-making processes are highly important facets of successful performance. Caffeine has well established effects for promoting both physical and cognitive performance, but the translation of such benefits specifically for soccer match play is not well established. This study examined the effects of acute caffeine ingestion on tactical performance during small-sided games (SSG) in professional soccer players. Nineteen soccer players (22 ± 4 yrs) underwent a randomized, counterbalanced, crossover, double-blind placebo-controlled trial. The protocol consisted of 5 bouts of 5-min SSG with 3 players plus a goalkeeper in each team (3 + GK × 3 + GK) with each SSG separated by 1 min rest intervals. Tactical performance was assessed using the system of tactical assessment in soccer (FUT-SAT). Prior to each experimental trial, participants ingested caffeine (5 mg·kg −1) or a placebo 60 min before the protocol. Overall, caffeine ingestion resulted in an increased ball possession time when compared to the placebo. When the offensive and defensive core principles were analyzed, the results were equivocal. Caffeine resulted in positive effects on some tactical decisions during the protocol, but it was deleterious or promoted no observed effect on other of the core tactical principles. Caffeine ingestion resulted in less offensive (during SSG3) and defensive (SSG 2, SSG3, and SSG4) errors. Caffeine ingestion also resulted in higher total offensive success during SSG 1 and SSG2, but it was detrimental during SSG3. Additionally, total defensive success was lower for the caffeine conditions during SSG 2 and SSG5 when compared to the placebo. In conclusion, caffeine influenced aspects of tactical decisions in soccer, resulting in fewer offensive and defensive errors, although it may be deleterious considering other tactical parameters. Future studies may clarify the effects of caffeine ingestion on specific decision-making parameters in soccer.
... In SJ, the performance of the players after taking caffeine was significantly better than the other two conditions (placebo and nitrate). A review of the literature on the effects of caffeine shows that our findings are consistent with the findings of previous research [7,13,23]. ...
Article
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Caffeine and nitrates have both been reported to enhance performance in power efforts; however, it is not clear which supplement is most effective. The aim of this study was to compare the effects of caffeine and nitrates on the performance of semi-professional soccer players during different fitness tests. Ten male soccer players in a randomized crossover design were assigned to receive caffeine (5 mg/kg body mass) (CG), nitrate ((250 mL/150 mg of NO3−) (NG), or a placebo (PG) on three different occasions. In each treatment, the participants performed the following tests: 10 m and 30 m sprints, the Illinois agility test, a countermovement jump test, a squat jump test, and a repeated sprint test (6 × 40 m). Caffeine boosted performance in jumps (CMJ: CGvsPG, p = 0.018; SJ: CGvsPG, p = 0.045 and CGvsNG, p = 0.001) and limited the decrease in performance in the RSA test (CGvsPG, p = 0.012). Nitrates limited the decrease in performance in the RSA test (NGvsPG, p = 0.035). In conclusion, the two supplements limited the decrease in performance in the test of repeated sprints, with caffeine showing a greater effect. Among the other tests, only caffeine improved performance, and only in the jumps. Thus, we can conclude that supplementation with caffeine 1 h before these kinds of activities at a dosage of 5 mg/kg of body weight can enhance performance.
... anaerobic sprint running test). Contrary to the two previous cited studies, players supplemented by CAF (six mgkg -1 ) decreased CMJ height (1.1 cm) after two simulated soccer-game protocols on a treadmill (Apostolidis, et al., 2019). These contradictory results could be explained by the nature and characteristics of the neuromuscular tests or by the increase in performance in the condition prior to fatigue, seeing the attenuated effect of the administration of CAF in the post assessment. ...
Article
The aim of this study was to analyze the effect of different supplementation conditions on the flywheel half-squat fatigue and performance. Sixteen active males participated in the experimental intervention during a 4-week period. Four experimental conditions were stablished in a double-blind manner as follows: placebo, caffeine (CAF), beetroot juice (BRJ) and combined BRJ+CAF. Before (Pre), 30 s after (Post-30s) and 180 s after (Post-180s) a flywheel half-squat power protocol based on 4 sets of 8 all-out repetitions with 3-min rest using different inertial loads (i.e., 0.025, 0.050, 0.075 and 0.100 kg·m-2) in each set and a CMJ test were performed. In addition, the total mean power outcomes during the flywheel half-squat exercise was recorded attending to each supplementation condition. Repeated measured ANOVA showed greater mean power (~1000 W, p < 0.001) in flywheel exercise when participants were supplemented with CAF, BRJ and BRJ+CAF in comparison to placebo condition. Moreover, a two-way ANOVA test reported lower CMJ performance at Post-180s (p = 0.003-0.087; ES = -0.39/-0.49) after the flywheel half-squat power test in comparison to Pre in placebo, CAF and BRJ. However, no significant differences (p = 0.087) were reported with BRJ+CAF consumption at Post-180s. In conclusion, while the supplementation by CAF, BRJ and BRJ+CAF produced greater total mean power in a flywheel half-squat power test, this supplementation did not imply higher exercise-related fatigue. In addition,
... However, the results of the current study are inconsistent with most of the previous findings, which indicated an improvement of power output in lower body ballistic tasks after acute CAF intake [8,9,34]. Although, acute CAF intake has been shown to improve CMJ performance, previous studies mostly involved male subjects [31,[35][36][37] or both sexes [8,38], thus indicating that the gender may have an impact on CAF ergogenicity during ballistic tasks, such as CMJ. To the best of the authors' knowledge, only few studies examined CAF impact on CMJ performance in women [16,34,39]. ...
Article
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Introduction. The main goal of this study was to examine the effect of acute intake of 3 mg/kg/body mass (b.m.) of caffeine (CAF) on countermovement jump (CMJ) performance in recreationally trained women habituated to CAF. Material and Methods. 17 healthy recreationally trained women habitually using CAF participated in the study. The experiment followed randomized, cross-over, double-blind design under three different conditions: control test (CONT) or consumed placebo (PLAC) or consumed 3 mg/kg/b.m. of CAF (CAF-3). Each participant performed 2 sets of 2 CMJ. The following variables were recorded: concentric peak velocity (PV), peak power (PP) and jump height (JH). Results. The two-way repeated measure ANOVA (substance × set) revealed no statistically significant interaction and main effects for all measured variables between conditions. In comparison to the CONT and PLAC, the intake of CAF-3 was not effective at increasing PV (p = 0.533), JH (p = 0.417) and PP (p = 0.871) during 2 sets of the CMJ. Conclusions. This study suggests that 3 mg/kg/b.m. of CAF did not improve CMJ height in recreationally trained women habituated to CAF. Furthermore, the level of athletic performance might be considered a factor in regard to CAF ergogenicity.
... Caffeine is a central nervous system stimulant that regardless of mode, intensity, or duration results in an alteration in participants' perceptual response during exercise testing [2]. Recent studies have demonstrated that caffeine ingestion prior to aerobic bouts of exercise has positive ergogenic effects by delaying fatigue and increasing time to exhaustion [3,4]. In addition, caffeine is an adenosine receptor antagonist and has a documented exercise-related hypoalgesic effect [5,6]. ...
Article
Caffeine has documented hypoalgesic effects during exercise. However, there is a lack of research focusing on caffeine's potential analgesic effects to ameliorate delayed onset muscle soreness. A placebo controlled randomized cross-over trial was carried out to determine if 5 mg/kg of body weight (mg/kgBW) of caffeine attenuates muscle pain and improves 5 k running performance following delayed onset muscle soreness. Prior to participating, eleven runners (9 male; 2 female; age, 24.5 ± 6.3 years; height, 173.6 ± 7.8 cm; body mass, 66.3 ± 7.5 kg; BMI, 23.18 kg/m 2 ± 1.6; VO 2max 61.0 ± 6.1 ml/kg/min À1), were asked to discontinue supplement use for 72 hours and abstain from caffeine consumption for 48 hours. Participants performed a 30-minute downhill run on a treadmill set at À10% grade at 70% VO 2max to induce delayed onset of muscle soreness. Participants then returned 48 hours after to complete a 5 k time trial run where they consumed either 5 mg/kgBW of caffeine or a placebo. Rate of perceived exertion and heart rate were taken every two minutes during the trial. There was no detectable statistical difference between 5 k performance between caffeine (1074.9 ± 119.7 sec) or placebo (1053.8 ± 86.8 sec) (p = .41). Algometer readings were similar between both treatments for muscle soreness in the rectus femoris (p = .791) and the vastus medialis oblique (p = .371). Muscle soreness ratings were found to be greater in the caffeine condition compared to the placebo condition (p = .030). There was no effect of treatment on rating of perceived exertion between conditions (p = .574). The present study suggests that caffeine is not effective at reducing muscle soreness, rating of perceived exertion, or improving running performance in a time trial in the presence of muscle soreness.
... Caffeine is a central nervous system stimulant that regardless of mode, intensity, or duration results in an alteration in participants' perceptual response during exercise testing [2]. Recent studies have demonstrated that caffeine ingestion prior to aerobic bouts of exercise has positive ergogenic effects by delaying fatigue and increasing time to exhaustion [3,4]. In addition, caffeine is an adenosine receptor antagonist and has a documented exercise-related hypoalgesic effect [5,6]. ...
Article
Objective: No study has analyzed the effects of caffeine ingestion on performance during a multidirectional high-intensity intermittent exercise. Thus, we aimed to investigate the effects of caffeine ingestion during a novel repeated agility test in futsal athletes. Methods: Using a double-blind, counterbalanced, and repeated-measures design, ten athletes (mass 71.2 ± 8.7 kg, height 1.77 ± 0.05 m, body mass index 22.7 ± 1.9 km/m2, body fat percentage 10.2 ± 3.7%) performed a novel repeated-bout agility test 60 min after ingesting 6 mg · kg-1 of caffeine or cellulose (placebo). Results: Performance time decreased progressively throughout the trial in both conditions (P = 0.01; ηp2 = 0.66), with a significant interaction effect (P = 0.01; ηp2 = 0.35) showing a potential beneficial effect of caffeine at the beginning, followed by a decrease at the end of the test. Furthermore, magnitude of decrease in performance was more pronounced in caffeine (-9.0 ± 5.7%) compared with placebo (-4.7 ± 3.9%, P = 0.01; d = 0.88). Interestingly, magnitude-based inferences revealed a possible benefit (70%) of caffeine at the beginning, followed by likely (93%) to very likely (96%) impairments in performance during the last third of the test. Heart rate and rating of perceived effort increased in both conditions over the time (P < 0.05), with similar values between experimental conditions (P > 0.05). Conclusion: Caffeine seems to have a potential beneficial effect at the beginning, with an impaired performance during the final third of a new multidirectional high-intensity intermittent exercise in futsal athletes.
Article
Caffeine has documented hypoalgesic effects during exercise. However, there is a lack of research focusing on caffeine's potential analgesic effects to ameliorate delayed onset muscle soreness. A placebo controlled randomized cross-over trial was carried out to determine if 5 mg/kg of body weight (mg/kgBW) of caffeine attenuates muscle pain and improves 5 k running performance following delayed onset muscle soreness. Prior to participating, eleven runners (9 male; 2 female; age, 24.5 ± 6.3 years; height, 173.6 ± 7.8 cm; body mass, 66.3 ± 7.5 kg; BMI, 23.18 kg/m2 ± 1.6; VO2max 61.0 ± 6.1 ml/kg/min-1), were asked to discontinue supplement use for 72 hours and abstain from caffeine consumption for 48 hours. Participants performed a 30-minute downhill run on a treadmill set at -10% grade at 70% VO2max to induce delayed onset of muscle soreness. Participants then returned 48 hours after to complete a 5 k time trial run where they consumed either 5 mg/kgBW of caffeine or a placebo. Rate of perceived exertion and heart rate were taken every two minutes during the trial. There was no detectable statistical difference between 5 k performance between caffeine (1074.9 ± 119.7 sec) or placebo (1053.8 ± 86.8 sec) (p = .41). Algometer readings were similar between both treatments for muscle soreness in the rectus femoris (p = .791) and the vastus medialis oblique (p = .371). Muscle soreness ratings were found to be greater in the caffeine condition compared to the placebo condition (p = .030). There was no effect of treatment on rating of perceived exertion between conditions (p = .574). The present study suggests that caffeine is not effective at reducing muscle soreness, rating of perceived exertion, or improving running performance in a time trial in the presence of muscle soreness.
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Background: Fatigue is one of the major health conditions induced by excessive stress or abnormal immune function or defective antioxidant systems. Placental extract has been reported to have various effects such as immune modulation and cellular regeneration. Fermented porcine placenta (FPP) is a safe nontoxic material, which is highly valuable as a functional food. The aim of this study was to investigate the anti-fatigue effects of FPP supplementation compared with a placebo product. Methods: In this double-blind, parallel, randomized, and placebo-controlled trial 84 healthy males and females, aged between 30 and 60 years were randomized to 320 mg of FPP once daily or placebo. The main outcome measures included efficacy of fatigue-inducing treadmill exercise on physical fatigue and fatigue-related parameters based on the questionnaire administered. Results: The IL-1β mRNA expression and fatigue severity scale were changed significantly after 8 weeks of treatment with fermented porcine placenta compared with placebo (p < 0.05). Cortisol levels were significantly improved in participants younger than 45 years following treatment with FPP compared with placebo. Furthermore, the lactate and myoglobin levels were improved significantly in participants with BMI ≥ 23 kg/m2 (p = 0.045 and p = 0.011, respectively) following treatment with FPP versus placebo. Conclusions: Our study showed that FPP supplementation significantly ameliorated fatigue-related parameters and subjective symptoms in healthy adults. Therefore, our results indicate that FPP supplementation induced anti-fatigue effect by regulating the inflammatory response.
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Objectives To examine the efficacy of caffeine on athletic performance, also to establish the most effective dose and form of caffeine intake that is needed to bring about a positive effect in performance. News Studies were searched in various electronic databases, including Web of Science, PubMed, Pedro, and CINAHL. Studies were excluded if: 1) it was conducted before January 2010; 2) caffeine was given along with other substance/exercise; 3) only abstract was available; 4) it included non-healthy athlete; 5) the population was not involved in any kind of sports; 6) Pedro score < 7. Thirty articles were included in this review after the removal of duplicates and applying exclusion criteria. A random-effect model was used in this meta-analysis to analyze the effect of caffeine on athletic performance using the standardized mean difference with a 95% confidence interval. Our meta-analysis showed that there is a significant effect, immediately (SMD: 0.82; 95% confidence interval: 0.27, 1.37; P = 0.003) and after 60 minutes (SMD: 0.26; 95% confidence interval: 0.05, 0.47; P = 0.02) of caffeine intake on jump height favouring the placebo group. There was a significant effect on reaction time (SMD: −0.40; 95% confidence interval: −0.76, −0.04; P = 0.03) and agility (SMD: −0.36; 95% confidence interval: −0.66, −0.07; P = 0.02) after 60 minutes of caffeine intake favouring the experimental group. Prospects and projects To back up the results presented in this study, more research into the effects of caffeine supplementation on non-athlete performance is required. Conclusion Caffeine supplementation is efficient in improving the reaction time and agility of an athlete. Agility and reaction time is seen to improve when an athlete is supplemented with caffeine at a dosage of 3 mg/kg of body mass and 6 mg/kg of body mass, respectively. Also, improvement in agility and reaction time favoring caffeine-supplemented group occurs after 60 minutes of caffeine ingestion.
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Purpose: Many studies have examined the effect of caffeine on exercise performance, but findings have not always been consistent. The objective of this study was to determine whether variation in the CYP1A2 gene, which affects caffeine metabolism, modifies the ergogenic effects of caffeine in a 10-km cycling time trial. Methods: Competitive male athletes (n=101; age: 25 ± 4 years) completed the time trial under three conditions: 0, 2 or 4 mg of caffeine per kg body mass, using a split-plot randomized, double-blinded, placebo-controlled design. DNA was isolated from saliva and genotyped for the -163A>C polymorphism in the CYP1A2 gene (rs762551). Results: Overall, 4 mg/kg caffeine decreased cycling time by 3% (mean ± SEM) versus placebo (17.6 ± 0.1 vs. 18.1 ± 0.1 min, p = 0.01). However, a significant (p <0.0001) caffeine-gene interaction was observed. Among those with the AA genotype, cycling time decreased by 4.8% at 2 mg/kg (17.0 ± 0.3 vs. 17.8 ± 0.4 min, p = 0.0005) and by 6.8% at 4 mg/kg (16.6 ± 0.3 vs. 17.8 ± 0.4 min, p < .0001). In those with the CC genotype, 4 mg/kg increased cycling time by 13.7% versus placebo (20.8 ± 0.8 vs. 18.3 ± 0.5 min, p = 0.04). No effects were observed among those with the AC genotype. Conclusion: Our findings show that both 2 and 4 mg/kg caffeine improve 10-km cycling time, but only in those with the AA genotype. Caffeine had no effect in those with the AC genotype and diminished performance at 4 mg/kg in those with the CC genotype. CYP1A2 genotype should be considered when deciding whether an athlete should use caffeine for enhancing endurance performance.
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Background The aim of this study was to examine the influence of caffeine supplementation on knee flexor and knee extensor strength before, during and after intermittent running exercise in female team-sport players taking oral contraceptive steroids (OCS). Method Ten healthy females (24 ± 4 years; 59.7 ± 3.5 kg; undertaking 2–6 training sessions per week) taking low-dose monophasic oral contraceptives of the same hormonal composition took part in a randomised, double-blind, placebo-controlled crossover-design trial. Sixty minutes following the ingestion of a capsule containing 6 mg∙kg−1 body mass anhydrous caffeine or artificial sweetener (placebo), participants completed a 90-min intermittent treadmill-running protocol. Isometric strength performance and eccentric and concentric strength and power of the knee flexors and knee extensors (using isokinetic dynamometer), as well as countermovement jump (CMJ), was measured before, during and after the exercise protocol, as well as ~12 h post-exercise. Blood samples were taken before, during and post-exercise to measure glucose, insulin and free fatty acids (FFA). ResultsCaffeine supplementation significantly increased eccentric strength of the knee flexors (P < 0.05) and eccentric power of both the knee flexors (P < 0.05) and extensors (P < 0.05). However, there was no effect on isometric or concentric parameters, or CMJ performance. FFA was elevated with caffeine supplementation over time (P < 0.05) while levels of glucose and insulin were not affected by caffeine intake. Conclusion Caffeine supplementation increased eccentric strength and power in female team-sport players taking OCS both during an intermittent running protocol and the following morning.
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Caffeine is consumed by over 80% of U.S. adults. This review examines the effects caffeine has on cognitive and physical function, since most real-world activities require complex decision making, motor processing and movement. Caffeine exerts its effects by blocking adenosine receptors. Following low (∼40mg or ∼0.5 mg·kg(-1)) to moderate (∼300mg or 4 mg·kg(-1)) caffeine doses, alertness, vigilance, attention, reaction time and attention improve, but less consistent effects are observed on memory and higher-order executive function, such as judgement and decision making. Effects on physical performance on a vast array of physical performance metrics such as time-to-exhaustion, time-trial, muscle strength and endurance, and high-intensity sprints typical of team sports are evident following doses that exceed about 200mg (∼3mg·kg(-1)). Many occupations, including military, first responders, transport workers and factory shift workers, require optimal physical and cognitive function to ensure success, workplace safety and productivity. In these circumstances, that may include restricted sleep, repeated administration of caffeine is an effective strategy to maintain physical and cognitive capabilities.
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Caffeine is a popular work-enhancing supplement that has been actively researched since the 1970s. The majority of research has examined the effects of moderate to high caffeine doses (5-13 mg/kg body mass) on exercise and sport. These caffeine doses have profound effects on the responses to exercise at the whole-body level and are associated with variable results and some undesirable side effects. Low doses of caffeine (<3 mg/kg body mass, ~200 mg) are also ergogenic in some exercise and sport situations, although this has been less well studied. Lower caffeine doses (1) do not alter the peripheral whole-body responses to exercise; (2) improve vigilance, alertness, and mood and cognitive processes during and after exercise; and (3) are associated with few, if any, side effects. Therefore, the ergogenic effect of low caffeine doses appears to result from alterations in the central nervous system. However, several aspects of consuming low doses of caffeine remain unresolved and suffer from a paucity of research, including the potential effects on high-intensity sprint and burst activities. The responses to low doses of caffeine are also variable and athletes need to determine whether the ingestion of ~200 mg of caffeine before and/or during training and competitions is ergogenic on an individual basis.
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The FIFA 11+ is a structured warm-up programme specially designed to prevent injuries among football players from age 14 years and above. However, studies to prove its efficacy are generally few and it is yet to be tested in male youth footballers and among African players. The purpose of the study was to examine the efficacy of the FIFA 11+ programme in reducing the risk of injuries among male youth football players of the Lagos Junior League. A cluster randomised controlled trial was conducted. All the 20 teams (414 players aged 14 -19 years) in the Premier League division were block-randomised into either an intervention (INT) or a control (CON) group. The INT group performed the FIFA 11+ exercises as warm-up during training sessions and the CON group performed usual warm-up. Participating teams were prospectively followed through an entire league season of 6 months in which they were visited every week to assess injured players for time-loss injuries in both groups. The primary outcomes were any injury to the players, injuries by type of exposure and injuries specific to the lower extremities. The secondary outcomes were injuries reported by body location, aetiology, mechanism and severity. In total, 130 injuries were recorded affecting 104 (25%) of the 416 players. Team and player compliance with the INT was 60% and 74% respectively. Based on the primary outcome measures of the study, the FIFA 11+ programme significantly reduced the overall rate of injury in the INT group by 41% [RR = 0.59 (95% CI: 0.40 - 0.86; p = 0.006)] and all lower extremity injuries by 48% [RR = 0.52 (95% CI: 0.34 - 0.82; p = 0.004)]. However, the rate of injury reduction based on secondary outcomes mostly did not reach the level of statistical significance. The FIFA 11+ programme is effective in reducing the rates of injuries in male youth football players.
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There is little information about the effects of caffeine intake on female team-sport performance. The aim of this study was to investigate the effectiveness of a caffeine-containing energy drink to improve physical performance in female soccer players during a simulated game. A double-blind, placebo controlled and randomized experimental design was used in this investigation. In two different sessions, 18 women soccer players ingested 3 mg of caffeine/kg in the form of an energy drink or an identical drink with no caffeine content (placebo). After 60 min, they performed a countermovement jump (CMJ) and a 7 × 30 m sprint test followed by a simulated soccer match (2 × 40 min). Individual running distance and speed were measured using GPS devices. In comparison to the placebo drink, the ingestion of the caffeinated energy drink increased the CMJ height (26.6 ± 4.0 vs 27.4 ± 3.8 cm; P < 0.05) and the average peak running speed during the sprint test (24.2 ± 1.6 vs 24.5 ± 1.7 km/h; P < 0.05). During the simulated match, the energy drink increased the total running distance (6,631 ± 1,618 vs 7,087 ± 1,501 m; P < 0.05), the number of sprints bouts (16 ± 9 vs 21 ± 13; P < 0.05) and the running distance covered at >18 km/h (161 ± 99 vs 216 ± 103 m; P < 0.05). The ingestion of the energy drink did not affect the prevalence of negative side effects after the game. An energy drink with a dose equivalent to 3 mg of caffeine/kg might be an effective ergogenic aid to improve physical performance in female soccer players.
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This study compared fat oxidation rate from a graded exercise test (GXT) with a moderate-intensity interval training session (MIIT) in obese men. Twelve sedentary obese males (age 29 ± 4.1 years; BMI 29.1 ± 2.4 kg·m(-2); fat mass 31.7 ± 4.4 %body mass) completed two exercise sessions: GXT to determine maximal fat oxidation (MFO) and maximal aerobic power (VO2max), and an interval cycling session during which respiratory gases were measured. The 30-min MIIT involved 5-min repetitions of workloads 20% below and 20% above the MFO intensity. VO2max was 31.8 ± 5.5 ml·kg(-1)·min(-1) and all participants achieved ≥ 3 of the designated VO2max test criteria. The MFO identified during the GXT was not significantly different compared with the average fat oxidation rate in the MIIT session. During the MIIT session, fat oxidation rate increased with time; the highest rate (0.18 ± 0.11 g·min(- 1)) in minute 25 was significantly higher than the rate at minute 5 and 15 (p ≤ 0.01 and 0.05 respectively). In this cohort with low aerobic fitness, fat oxidation during the MIIT session was comparable with the MFO determined during a GXT. Future research may consider if the varying workload in moderate-intensity interval training helps adherence to exercise without compromising fat oxidation. Key PointsFat oxidation during interval exercise is not com-promised by the undulating exercise intensityPhysiological measures corresponding with the MFO measured during the GXT correlated well to the MIITThe validity of exercise intensity markers derived from a GXT to reflect the physiological responses during MIIT.
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The aim of this study was to investigate the effects of caffeine on reaction time during a specific taekwondo task and athletic performance during a simulated taekwondo contest. Ten taekwondo athletes ingested either 5 mg·kg-1 body mass caffeine or placebo and performed two combats (spaced apart by 20 min). The reaction-time test (five kicks "Bandal Tchagui") was performed immediately prior to the first combat and immediately after the first and second combats. Caffeine improved reaction time (from 0.42 ± 0.05 to 0.37 ± 0.07 s) only prior to the first combat (P = 0.004). During the first combat, break times during the first two rounds were shorter in caffeine ingestion, followed by higher plasma lactate concentrations compared with placebo (P = 0.029 and 0.014, respectively). During the second combat, skipping-time was reduced, and relative attack times and attack/skipping ratio was increased following ingestion of caffeine during the first two rounds (all P < 0.05). Caffeine resulted in no change in combat intensity parameters between the first and second combat (all P > 0.05), but combat intensity was decreased following placebo (all P < 0.05). In conclusion, caffeine reduced reaction time in non-fatigued conditions and delayed fatigue during successive taekwondo combats.
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To investigate the effects of a caffeine-containing energy drink on soccer performance during a simulated game. A second purpose was to assess the post-exercise urine caffeine concentration derived from the energy drink intake. Nineteen semiprofessional soccer players ingested 630 ± 52 mL of a commercially available energy drink (sugar-free Red Bull®) to provide 3 mg of caffeine per kg of body mass, or a decaffeinated control drink (0 mg/kg). After sixty minutes they performed a 15-s maximal jump test, a repeated sprint test (7 × 30 m; 30 s of active recovery) and played a simulated soccer game. Individual running distance and speed during the game were measured using global positioning satellite (GPS) devices. In comparison to the control drink, the ingestion of the energy drink increased mean jump height in the jump test (34.7 ± 4.7 v 35.8 ± 5.5 cm; P<0.05), mean running speed during the sprint test (25.6 ± 2.1 v 26.3 ± 1.8 km · h(-1); P<0.05) and total distance covered at a speed higher than 13 km · h(-1) during the game (1205 ± 289 v 1436 ± 326 m; P<0.05). In addition, the energy drink increased the number of sprints during the whole game (30 ± 10 v 24 ± 8; P<0.05). Post-exercise urine caffeine concentration was higher after the energy drink than after the control drink (4.1 ± 1.0 v 0.1 ± 0.1 µg · mL(-1); P<0.05). A caffeine-containing energy drink in a dose equivalent to 3 mg/kg increased the ability to repeatedly sprint and the distance covered at high intensity during a simulated soccer game. In addition, the caffeinated energy drink increased jump height which may represent a meaningful improvement for headers or when players are competing for a ball.
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The aim of this investigation was to determine the use of caffeine by athletes after its removal from the World Anti-Doping Agency list. For this purpose, we measured the caffeine concentration in 20 686 urine samples obtained for doping control from 2004 to 2008. We utilized only urine samples obtained after official national and international competitions. Urine caffeine concentration was determined using alkaline extraction followed by gas chromatography-mass spectrometry. The limit of detection (LOD) was set at 0.1 µg·mL(-1). The percentage of urine samples below the LOD was 26.2%; the remaining 73.8% of the urine samples contained caffeine. Most urine samples (67.3%) had urinary caffeine concentrations below 5 µg·mL(-1). Only 0.6% of urine samples exceeded the former threshold for caffeine doping (12 µg·mL(-1)). Triathlon (3.3 ± 2.2 µg·mL(-1)), cycling (2.6 ± 2.0 µg·mL(-1)), and rowing (1.9 ± 1.4 µg·mL(-1)) were the sports with the highest levels of urine caffeine concentration; gymnastics was the sport with the lowest urine caffeine concentration (0.5 ± 0.4 µg·mL(-1)). Older competitors (>30 y) had higher levels of caffeine in their urine than younger competitors (<20 y; p < 0.05); there were no differences between males and females. In conclusion, 3 out of 4 athletes had consumed caffeine before or during sports competition. Nevertheless, only a small proportion of these competitors (0.6%) had a urine caffeine concentration higher than 12 µg·mL(-1). Endurance sports were the disciplines showing the highest urine caffeine excretion after competition.
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The present study examined putative modulators and indices of brain serotonergic and dopaminergic function, perceptual responses, and endurance exercise performance following caffeine co-ingested with a high fat meal. Trained humans (n = 10) performed three constant-load cycling tests at 73% of maximal oxygen uptake (VO2max) until exhaustion at 10 degrees C remove space throughout. Prior to the first test, subjects consumed a 90% carbohydrate meal (Control trial) and for the remaining two tests, a 90% fat meal with (FC trial) and without (F trial) caffeine. Time to exhaustion was not different between the F and FC trials (P > 0.05); [Control trial: 116(88-145) min; F trial: 122(96-144) min; FC trial: 127(107-176) min]. However, leg muscular discomfort during exercise was significantly lower on the FC relative to F trial (P < 0.01). There were no significant differences between F and FC trials in key modulators and indices of brain serotonergic (5-HT) and dopaminergic (DA) function [(i.e. plasma free and total tryptophan (Trp), tyrosine (Tyr), large neutral amino acids (LNAA), Trp:LNAA ratio, free-Trp:Tyr ratio, total Trp:Tyr ratio, and plasma prolactin] (P > 0.05) with the exception of plasma free-Trp:LNAA ratio which was higher at 90 min and at exhaustion during the FC trial (P < 0.05). Neither brain 5-HT nor DA systems would appear to be implicated in the fatigue process when exercise is performed without significant thermoregulatory stress, thus indicating fatigue development during exercise in relatively cold temperatures to occur predominantly due to glycogen depletion.
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Caffeine, an adenosine receptor antagonist, has been studied for decades as a putative ergogenic aid. In the past 2 decades, the information has overwhelmingly demonstrated that it indeed is a powerful ergogenic aid, and frequently theories have been proposed that this is due to alterations in fat and carbohydrate metabolism. While caffeine certainly mobilizes fatty acids from adipose tissue, rarely have measures of the respiratory exchange ratio indicated an increase in fat oxidation. However, this is a difficult measure to perform accurately during exercise, and small changes could be physiologically important. The few studies examining human muscle metabolism directly have also supported the fact that there is no change in fat or carbohydrate metabolism, but these usually have had a small sample size. We combined the data from muscle biopsy analyses of several similar studies to generate a sample size of 16-44, depending on the measure. We examined muscle glycogen, citrate, acetyl-CoA, glucose-6-phosphate, and cyclic adenosine monophosphate (cAMP) in resting samples and in those obtained after 10-15 min of exercise at 70%-85% maximal oxygen consumption. Exercise decreased (p < 0.05) glycogen and increased (p < 0.05) citrate, acetyl-CoA, and glucose-6-phosphate. The only effects of caffeine were to increase (p < 0.05) citrate in resting muscle and cAMP in exercise. There is very little evidence to support the hypothesis that caffeine has ergogenic effects as a result of enhanced fat oxidation. Individuals may, however, respond differently to the effects of caffeine, and there is growing evidence that this could be explained by common genetic variations.
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In this study the effects of acute caffeine ingestion on exercise performance, hormonal (epinephrine, norepinephrine, insulin), and metabolic (free fatty acids, glycerol, glucose, lactate, expired gases) parameters during short-term withdrawal from dietary caffeine were investigated. Recreational athletes who were habitual caffeine users (n = 6) (maximum oxygen uptake 54.5 +/- 3.3 ml x kg-1 x min-1 and daily caffeine intake 761.3 +/- 11.8 mg/day) were tested under conditions of no withdrawal and 2-day and 4-day withdrawal from dietary caffeine. There were seven trials in total with a minimum of 10 days between trials. On the day of the exercise trial, subjects ingested either dextrose placebo or 6 mg/kg caffeine in capsule form 1 h before cycle ergometry to exhaustion at 80-85% of maximum oxygen uptake. Test substances were assigned in a random, double-blind manner. A final placebo control trial completed the experiment. There was no significant difference in any measured parameters among days of withdrawal after ingestion of placebo. At exhaustion in the 2- and 4-day withdrawal trials, there were significant increases in plasma norepinephrine in response to caffeine ingestion. Caffeine-induced increases in serum free fatty acids occurred after 4 days and only at rest. Subjects responded to caffeine with increases in plasma epinephrine (P < 0.05) at exhaustion and prolonged exercise time in all caffeine trials compared with placebo, regardless of withdrawal from caffeine. It is concluded that increased endurance is unrelated to hormonal or metabolic changes and that it is not related to prior caffeine habituation in recreational athletes.
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Competitive athletes completed two studies of 2-h steady-state (SS) cycling at 70% peak O(2) uptake followed by 7 kJ/kg time trial (TT) with carbohydrate (CHO) intake before (2 g/kg) and during (6% CHO drink) exercise. In Study A, 12 subjects received either 6 mg/kg caffeine 1 h preexercise (Precaf), 6 x 1 mg/kg caffeine every 20 min throughout SS (Durcaf), 2 x 5 ml/kg Coca-Cola between 100 and 120 min SS and during TT (Coke), or placebo. Improvements in TT were as follows: Precaf, 3.4% (0.2-6.5%, 95% confidence interval); Durcaf, 3.1% (-0.1-6.5%); and Coke, 3.1% (-0.2-6.2%). In Study B, eight subjects received 3 x 5 ml/kg of different cola drinks during the last 40 min of SS and TT: decaffeinated, 6% CHO (control); caffeinated, 6% CHO; decaffeinated, 11% CHO; and caffeinated, 11% CHO (Coke). Coke enhanced TT by 3.3% (0.8-5.9%), with all trials showing 2.2% TT enhancement (0.5-3.8%; P < 0.05) due to caffeine. Overall, 1) 6 mg/kg caffeine enhanced TT performance independent of timing of intake and 2) replacing sports drink with Coca-Cola during the latter stages of exercise was equally effective in enhancing endurance performance, primarily due to low intake of caffeine (approximately 1.5 mg/kg).
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In soccer, the players perform intermittent work. Despite the players performing low-intensity activities for more than 70% of the game, heart rate and body temperature measurements suggest that the average oxygen uptake for elite soccer players is around 70% of maximum (VO(2max). This may be partly explained by the 150 - 250 brief intense actions a top-class player performs during a game, which also indicates that the rates of creatine phosphate (CP) utilization and glycolysis are frequently high during a game. Muscle glycogen is probably the most important substrate for energy production, and fatigue towards the end of a game may be related to depletion of glycogen in some muscle fibres. Blood free-fatty acids (FFAs) increase progressively during a game, partly compensating for the progressive lowering of muscle glycogen. Fatigue also occurs temporarily during matches, but it is still unclear what causes the reduced ability to perform maximally. There are major individual differences in the physical demands of players during a game related to physical capacity and tactical role in the team. These differences should be taken into account when planning the training and nutritional strategies of top-class players, who require a significant energy intake during a week.
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This study examined the effects of caffeine, co-ingested with a high fat meal, on perceptual and metabolic responses during incremental (Experiment 1) and endurance (Experiment 2) exercise performance. Trained participants performed three constant-load cycling tests at approximately 73% of maximal oxygen uptake (VO2max) for 30 min at 20 degrees C (Experiment 1, n = 8) and to the limit of tolerance at 10 degrees C (Experiment 2, n = 10). The 30 min constant-load exercise in Experiment 1 was followed by incremental exercise (15 W . min-1) to fatigue. Four hours before the first test, the participants consumed a 90% carbohydrate meal (control trial); in the remaining two tests, the participants consumed a 90% fat meal with (fat + caffeine trial) and without (fat-only trial) caffeine. Caffeine and placebo were randomly assigned and ingested 1 h before exercise. In both experiments, ratings of perceived leg exertion were significantly lower during the fat + caffeine than fat-only trial (Experiment 1: P < 0.001; Experiment 2: P < 0.01). Ratings of perceived breathlessness were significantly lower in Experiment 1 (P < 0.01) and heart rate higher in Experiment 2 (P < 0.001) on the fat + caffeine than fat-only trial. In the two experiments, oxygen uptake, ventilation, blood [glucose], [lactate] and plasma [glycerol] were significantly higher on the fat + caffeine than fat-only trial. In Experiment 2, plasma [free fatty acids], blood [pyruvate] and the [lactate]:[pyruvate] ratio were significantly higher on the fat + caffeine than fat-only trial. Time to exhaustion during incremental exercise (Experiment 1: control: 4.9, s = 1.8 min; fat-only: 5.0, s = 2.2 min; fat + caffeine: 5.0, s = 2.2 min; P > 0.05) and constant-load exercise (Experiment 2: control: 116 (88 - 145) min; fat-only: 122 (96 - 144) min; fat + caffeine: 127 (107 - 176) min; P > 0.05) was not different between the fat-only and fat + caffeine trials. In conclusion, while a number of metabolic responses were increased during exercise after caffeine ingestion, perception of effort was reduced and this may be attributed to the direct stimulatory effect of caffeine on the central nervous system. However, this caffeine-induced reduction in effort perception did not improve exercise performance.
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After 13 days of weight maintenance diet (13,720 ± 620 kJ/day, 40% fat, 15% protein, and 45% carbohydrate), five young men (71.3 ± 7.1 kg, 181 ± 8 cm; means ± SD) were overfed for 9 days at 1.6 times their maintenance requirements (i.e., +8,010 kJ/day). Twenty-four-hour energy expenditure (24-h EE) and basal metabolic rate (BMR) were measured on three occasions, once after 10 days on the weight-maintenance diet and after 2 and 9 days of overfeeding. Physical activity was monitored throughout the study, body composition was measured by underwater weighing, and nitrogen balance was assessed for 3 days during the two experimental periods. Overfeeding caused an increase in body weight averaging 3.2 kg of which 56% was fat as measured by underwater weighing. After 9 days of overfeeding, BMR increased by 622 kJ/day, which could explain one-third of the increase in 24-h EE (2,038 kJ/day); the remainder was due to the thermic effect of food (which increased in proportion with excess energy intake) and the increased cost of physical activity, related to body weight gain. This study shows that approximately one-quarter of the excess energy intake was dissipated through an increase in EE, with 75% being stored in the body. Under our experimental conditions of mixed overfeeding in which body composition measurements were combined with those of energy balance, it was possible to account for all of the energy ingested in excess of maintenance requirements.
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This study investigated effects of caffeine ingestion (8 mg/kg) on maximum voluntary torque (MVT) and voluntary activation of the quadriceps during isometric, concentric and eccentric contractions. Fourteen subjects ingested caffeine and placebo in a randomized, controlled, counterbalanced, double-blind crossover design. Neuromuscular tests were performed before and 1 h after oral caffeine and placebo intake. MVTs were measured and the interpolated twitch technique was applied during isometric, concentric and eccentric contractions to assess voluntary activation. Furthermore, normalized root mean square of the EMG signal was calculated and evoked spinal reflex responses (H-reflex evoked at rest and during weak isometric voluntary contraction) as well as twitch torques were analyzed. Caffeine increased MVT by 26.4 N m (95%CI: 9.3-43.5 N m, P = 0.004), 22.5 N m (95%CI: 3.1-42.0 N m, P = 0.025) and 22.5 N m (95%CI: 2.2-42.7 N m, P = 0.032) for isometric, concentric
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Preclinical studies suggest that cost/benefit decision-making involves interactions between adenosine and dopamine (DA). In rats, DA depletion decreases willingness to incur effort costs, while adenosine antagonism reverses these effects, likely by increasing DA transmission. Caffeine is a non-selective adenosine antagonist commonly used to facilitate effortful tasks, and thus may affect decisions involving effort costs in humans. The current study examined acute effects of 200 mg of caffeine on willingness to exert effort for monetary rewards at varying levels of reward value and reward probability, in young adult light caffeine users. Based on previous findings with amphetamine, we predicted that caffeine would increase willingness to exert effort. At separate sessions, 23 healthy normal adults received placebo or 200 mg caffeine under counterbalanced double-blind conditions, then completed the effort expenditure for rewards task (EEfRT). Measures of subjective and cardiovascular effects were obtained at regular intervals. Caffeine produced small but significant subjective and cardiovascular effects, and sped psychomotor performance on the EEfRT. Caffeine did not alter willingness to exert effort, except in high cardiovascular responders to caffeine, in whom it decreased willingness to exert effort. These results were contrary to our predictions, but consistent with rodent studies suggesting that moderate doses of caffeine alone do not affect effort, but rather only influence effort in the context of DA antagonism. Our results demonstrate that psychomotor speeding and decisional effects on the EEfRT are dissociable, providing additional evidence for the EEfRT as a specific measure of effort-based decision-making. This study provides a starting point for exploring contributions of the adenosine system to motivation in humans.
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The effect of oral caffeine ingestion on intense intermittent exercise performance and muscle interstitial ion concentrations was examined. The study consists of two studies (S1 and S2). In S1, 12 subjects completed the Yo-Yo intermittent recovery level 2 (Yo-Yo IR2) test with prior caffeine (6 mg/kg body wt; CAF) or placebo (PLA) intake. In S2, 6 subjects performed one low-intensity (20 W) and three intense (50 W) 3-min (separated by 5 min) one-legged knee-extension exercise bouts with (CAF) and without (CON) prior caffeine supplementation for determination of muscle interstitial K(+) and Na(+) with microdialysis. In S1 Yo-Yo IR2 performance was 16% better (P < 0.05) in CAF compared with PLA. In CAF, plasma K(+) at the end of the Yo-Yo IR2 test was 5.2 ± 0.1 mmol/l with no difference between the trials. Plasma free fatty acids (FFA) were higher (P < 0.05) in CAF than PLA at rest and remained higher (P < 0.05) during exercise. Peak blood glucose (8.0 ± 0.6 vs. 6.2 ± 0.4 mmol/l) and plasma NH(3) (137.2 ± 10.8 vs. 113.4 ± 13.3 μmol/l) were also higher (P < 0.05) in CAF compared with PLA. In S2 interstitial K(+) was 5.5 ± 0.3, 5.7 ± 0.3, 5.8 ± 0.5, and 5.5 ± 0.3 mmol/l at the end of the 20-W and three 50-W periods, respectively, in CAF, which were lower (P < 0.001) than in CON (7.0 ± 0.6, 7.5 ± 0.7, 7.5 ± 0.4, and 7.0 ± 0.6 mmol/l, respectively). No differences in interstitial Na(+) were observed between CAF and CON. In conclusion, caffeine intake enhances fatigue resistance and reduces muscle interstitial K(+) during intense intermittent exercise.
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Breathing has inherent irregularities that produce breath-to-breath fluctuations ("noise") in pulmonary gas exchange. These impair the precision of characterizing nonsteady-state gas exchange kinetics during exercise. We quantified the effects of this noise on the confidence of estimating kinetic parameters of the underlying physiological responses and hence of model discrimination. Five subjects each performed eight transitions from 0 to 100 W on a cycle ergometer. Ventilation, CO2 output, and O2 uptake were computed breath by breath. The eight responses were interpolated uniformly, time aligned, and averaged for each subject; and the kinetic parameters of a first-order model (i.e., the time constant and time delay) were then estimated using three methods: linear least squares, nonlinear least squares, and maximum likelihood. The breath-by-breath noise approximated an uncorrelated Gaussian stochastic process, with a standard deviation that was largely independent of metabolic rate. An expression has therefore been derived for the number of square-wave repetitions required for a specified parameter confidence using methods b and c; method a being less appropriate for parameter estimation of noisy gas exchange kinetics.
Article
The aim of this study was to evaluate the reproducibility and validity of a 61-item semiquantitative food frequency questionnaire used in a large prospective study among women. This form was administered twice to 173 participants at an interval of approximately one year (1980-1981), and four one-week diet records for each subject were collected during that period. Intraclass correlation coefficients for nutrient intakes estimated by the one-week diet records (range = 0.41 for total vitamin A without supplements to 0.79 for vitamin B6 with supplements) were similar to those computed from the questionnaire (range = 0.49 for total vitamin A without supplements to 0.71 for sucrose), indicating that these methods were generally comparable with respect to reproducibility. With the exception of sucrose and total carbohydrate, nutrient intakes from the diet records tended to correlate more strongly with those computed from the questionnaire after adjustment for total caloric intake. Correlation coefficients between the mean calorie-adjusted intakes from the four one-week diet records and those from the questionnaire completed after the diet records ranged from 0.36 for vitamin A without supplements to 0.75 for vitamin C with supplements. Overall, 48% of subjects in the lowest quintile of calorie-adjusted intake computed from the diet records were also in the lowest questionnaire quintile, and 74% were in the lowest one of two questionnaire quintiles. Similarly, 49% of those in the highest diet record quintile were also in the highest questionnaire quintile, and 77% were in the highest one or two questionnaire quintiles. These data indicate that a simple self-administered dietary questionnaire can provide useful information about individual nutrient intakes over a one-year period.
Article
There is a great demand for perceptual effort ratings in order to better understand man at work. Such ratings are important complements to behavioral and physiological measurements of physical performance and work capacity. This is true for both theoretical analysis and application in medicine, human factors, and sports. Perceptual estimates, obtained by psychophysical ratio-scaling methods, are valid when describing general perceptual variation, but category methods are more useful in several applied situations when differences between individuals are described. A presentation is made of ratio-scaling methods, category methods, especially the Borg Scale for ratings of perceived exertion, and a new method that combines the category method with ratio properties. Some of the advantages and disadvantages of the different methods are discussed in both theoretical-psychophysical and psychophysiological frames of reference.
Article
The aim of this study was to devise a laboratory-based protocol for a motorized treadmill that was representative of work rates observed during soccer match-play. Selected physiological responses to this soccer-specific intermittent exercise protocol were then compared with steady-rate exercise performed at the same average speed. Seven male university soccer players (mean ± s: age 24 ± 2 years, height 1.78 ± 0.1 m, mass 72.2 ± 5.0 kg, V̇O(2max) 57.8 ± 4 ml/kg-1/min-1) completed a 45-min soccer-specific intermittent exercise protocol on a motorized treadmill. They also completed a continuous steady-rate exercise session for an identical period at the same average speed. The physiological responses to the laboratory-based soccer-specific protocol were similar to values previously observed for soccer match-play (oxygen consumption approximately 68% of maximum, heart rate 168 ± 10 beats/min-1). No significant differences were observed in oxygen consumption, heart rate, rectal temperature or sweat production rate between the two conditions. Average minute ventilation was greater (P < 0.05) in intermittent exercise (81.3 ± 0.2 l/min-1) than steady-rate exercise (72.4 ± 11.4 l/min-1). The rating of perceived exertion for the session as a whole was 15 ± 2 during soccer-specific intermittent exercise and 12 ± 1 for continuous exercise (P < 0.05). The physiological strain associated with the laboratory-based soccer-specific intermittent protocol was similar to that associated with 45 min of soccer match-play, based on the variables measured, indicating the relevance of the simulation as a model of match-play work rates. Soccer-specific intermittent exercise did not increase the demands placed on the aerobic energy systems compared to continuous exercise performed at the same average speed, although the results indicate that anaerobic energy provision is more important during intermittent than during continuous exercise at the same average speed.
Article
1. Skinfold thickness, body circumferences and body density were measured in samples of 308 and ninety-five adult men ranging in age from 18 to 61 years. 2. Using the sample of 308 men, multiple regression equations were calculated to estimate body density using either the quadratic or log form of the sum of skinfolds, in combination with age, waist and forearm circumference. 3. The multiple correlations for the equations exceeded 0.90 with standard errors of approximately +/-0.0073 g/ml. 4. The regression equations were cross validated on the second sample of ninety-five men. The correlations between predicted and laboratory-determined body density exceeded 0.90 with standard errors of approximately 0.0077 g/ml. 5. The regression equations were shown to be valid for adult men varying in age and fatness.
Article
The purpose of this study was to use the meta-analytic approach to examine the effects of caffeine ingestion on ratings of perceived exertion (RPE). Twenty-one studies with 109 effect sizes (ESs) met the inclusion criteria. Coding incorporated RPE scores obtained both during constant load exercise (n=89) and upon termination of exhausting exercise (n=20). In addition, when reported, the exercise performance ES was also computed (n=16). In comparison to placebo, caffeine reduced RPE during exercise by 5.6% (95% CI (confidence interval), -4.5% to -6.7%), with an equivalent RPE ES of -0.47 (95% CI, -0.35 to -0.59). These values were significantly greater (P<0.05) than RPE obtained at the end of exercise (RPE % change, 0.01%; 95% CI, -1.9 to 2.0%; RPE ES, 0.00, 95% CI, -0.17 to 0.17). In addition, caffeine improved exercise performance by 11.2% (95% CI; 4.6-17.8%). Regression analysis revealed that RPE obtained during exercise could account for approximately 29% of the variance in the improvement in exercise performance. The results demonstrate that caffeine reduces RPE during exercise and this may partly explain the subsequent ergogenic effects of caffeine on performance.
Caffeine ingestion and muscle metabolism during prolonged exercise in humans
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Association between habitual coffee consumption and blood pressure
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Vitamins, minerals and water
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McArdle WD, Katch FI, Katch VL. Vitamins, minerals and water. In: Frank I, Katch FI, Victor L, Katch VL, eds. Exercise Physiology: Energy, Nutrition and Human Performance. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2007:42-78.
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PubMed ID: 21836046 doi:10.1152/japplphysiol.01028.2010