Article

Caffeine’s Ergogenic Effects on Cycling: Neuromuscular and Perceptual Factors

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Abstract

Unlabelled: Caffeine improves endurance exercise performance, but its ergogenic mechanism(s) remain unclear. Purpose: This investigation sought to examine the effects of caffeine on perceptual and physiological responses to endurance exercise. Methods: Two experiments were performed. In study A, 14 participants were tested. Maximal voluntary strength (MVC) and motor-unit recruitment (%ACT) of the knee extensors and elbow flexors were tested before and 60 min after ingestion of a 5-mg·kg⁻¹ dose of caffeine or placebo and after completion of 40 min of exercise (30 min of submaximal leg or arm cycling followed by a 10-min time-trial performance). Muscle pain, RPE, and cardiorespiratory variables were assessed throughout. To determine the effects of caffeine on muscle pain and RPE during high-intensity exercise, a second study (study B) was performed. Twelve participants exercised at 95% of their gas exchange threshold (GET) and at 70% of the difference between their GET and VO(2peak) (70%Δ) after caffeine and placebo ingestion. Results: Compared to placebo, caffeine improved MVC (6.3%, P = 0.014) and %ACT (5.5%, P = 0.013) in the knee extensors, but not the elbow flexors, and reduced muscle pain (P < 0.05) and RPE (P < 0.05) during both submaximal cycling modalities. Caffeine ingestion improved time-trial performance during leg cycling (4.9% ± 6.5%, P = 0.03), but not arm crank cycling (2.1% ± 8.2%, P = 0.28), but the effect on pain and RPE was eliminated. Caffeine ingestion had no effect on pain or RPE during cycling at 95% GET and 70%Δ. Conclusions: Our results suggest that augmented strength and motor-unit recruitment, rather than reductions in pain and effort, may underlie caffeine's ergogenic effect on endurance exercise.

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... Double-poling is considered primarily to be an UBE; however, the trunk and legs also play a role in the performance of this technique. On the other hand, when LBE and asynchronous UBE were directly compared in very low caffeine users (<40 mg/day) during a preloaded 10 min all-out performance trial (40 min total exercise time), caffeine (5 mg¨kg´1) improved LBE but failed to statistically impact UBE in a mixed AB group [16]. The opposing results may be linked to differences in the exercise testing protocols, caffeine dose, training status of the participants', or the participants' level of habitual caffeine consumption. ...
... It has been previously reported that caffeine increases muscular strength (maximal voluntary contraction) and motor unit recruitment in the knee extensors but not in the elbow flexors [15,16]. These observations may help to explain the lack of performance improvement during short-term UBE in AB participants [21]. ...
... These observations may help to explain the lack of performance improvement during short-term UBE in AB participants [21]. The influence of caffeine on longer UBE endurance performance, however, requires further investigation given the protocols of Stadheim et al. [12] and Black et al. [16] both allowed involvement of the trunk to some extent to produce force yet report opposing effects. Black et al. [16] also used a mixed male and female participant pool of very low caffeine users, which makes their findings less applicable to the many competitive athletes who consume caffeine regularly. ...
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Caffeine supplementation during whole-/lower-body exercise is well-researched, yet evidence of its effect during upper-body exercise is equivocal. The current study explored the effects of caffeine on cycling/handcycling 10 km time trial (TT) performance in habitual caffeine users. Eleven recreationally trained males (mean (SD) age 24 (4) years, body mass 85.1 (14.6) kg, cycling/handcycling peak oxygen uptake (9Vpeak) 42.9 (7.3)/27.6 (5.1) mL�kg�min�1, 160 (168) mg/day caffeine consumption) completed two maximal incremental tests and two familiarization sessions. During four subsequent visits, participants cycled/handcycled for 30 min at 65% mode-specific 9V peak (preload) followed by a 10 km TT following the ingestion of 4 mg�kg�1 caffeine (CAF) or placebo (PLA). Caffeine significantly improved cycling (2.0 (2.0)%; 16:35 vs. 16:56 min; p = 0.033) but not handcycling (1.8 (3.0)%; 24:10 vs. 24:36 min; p = 0.153) TT performance compared to PLA. The improvement during cycling can be attributed to the increased power output during the first and last 2 km during CAF. Higher blood lactate concentration (Bla) was reported during CAF compared to PLA (p < 0.007) and was evident 5 min post-TT during cycling (11.2 � 2.6 and 8.8 � 3.2 mmol/L; p = 0.001) and handcycling (10.6 � 2.5 and 9.2 � 2.9 mmol/L; p = 0.006). Lower overall ratings of perceived exertion (RPE) were seen following CAF during the preload (p < 0.05) but not post-TT. Lower peripheral RPE were reported at 20 min during cycling and at 30 min during handcycling, and lower central RPE was seen at 30 min during cycling (p < 0.05). Caffeine improved cycling but not handcycling TT performance. The lack of improvement during handcycling may be due to the smaller active muscle mass, elevated (Bla) and/or participants’ training status.
... 1,35 This is relevant to consider, given that caffeine ingestion has been reported to increase motor unit recruitment. 36 For example, in one study, motor unit F I G U R E 3 Forest plot presenting the results of the random-effects metaanalysis on the effects of caffeine vs. placebo on rate of force development (RFD) during resistance exercises. Data are reported as effect sizes (Hedges'g) and 95% confidence interval (CI). ...
... The plotted squares denote effect sizes, and the whiskers denote their 95% CIs recruitment of the knee extensors during maximal contractions increased following the ingestion of 5 mg/kg of caffeine. 36 Therefore, this caffeine-induced increase in motor unit recruitment may explain its ergogenic effects on RFD. 36 Interestingly, the increase in motor unit recruitment appears to be more pronounced in larger (eg, knee extensors) vs. smaller (eg, elbow flexors) muscle groups. ...
... 36 Therefore, this caffeine-induced increase in motor unit recruitment may explain its ergogenic effects on RFD. 36 Interestingly, the increase in motor unit recruitment appears to be more pronounced in larger (eg, knee extensors) vs. smaller (eg, elbow flexors) muscle groups. 8,36 Indeed, one of the included studies 19 evaluated RFD of the elbow flexors and did not report an ergogenic effect of caffeine. ...
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This review aimed to conduct a meta-analysis of studies examining the effects of caffeine on rate of force development (RFD). Ten databases were searched to find relevant studies. Risk of bias (RoB) of the included studies was evaluated. Data were analyzed in a random-effects meta-analysis. Eleven studies with “some concerns” regarding RoB were included. In the main meta-analysis, there was a significant ergogenic effect of caffeine ingestion on RFD (Hedges’ g = 0.37; 95% confidence interval [CI]: 0.21, 0.52; p < 0.0001). An ergogenic effect of caffeine was also found on RFD during resistance exercises (Hedges’ g = 0.49; 95% CI: 0.30, 0.67; p < 0.0001), but not during the countermovement jump test (Hedges’ g = 0.18; 95% CI: –0.02, 0.39; p = 0.08), with a significant difference between the subgroups (p = 0.03). Small-to-moderate (3–5 mg/kg; Hedges’ g = 0.25; 95% CI: 0.09, 0.41; p = 0.002) and moderate-to-high caffeine doses (6–10 mg/kg) enhanced RFD (Hedges’ g = 0.57; 95% CI: 0.30, 0.85; p < 0.0001), even though the effects were larger with higher caffeine doses (p = 0.04). Overall, caffeine ingestion increases RFD, which is relevant given that RFD is commonly associated with sport-specific tasks. From a practical perspective: (1) individuals interested in the acute enhancement of RFD in resistance exercise may consider supplementing with caffeine; and (2) given that evaluation of RFD is most commonly used for testing purposes, caffeine ingestion (3–10 mg/kg 60 min before exercise) should be standardized before RFD assessments.
... Numerous studies have reported that ingestion of 3-6 mg kg −1 of caffeine can improve time to exhaustion and time trial performance (Ganio et al. 2009;Mohr et al. 2011;Desbrow et al. 2012;Black et al. 2015) as well as short-term, high-intensity exercise performance (Collomp et al. 1992;Wiles et al. 2006;Jenkins et al. 2008;Simmonds et al. 2010). Caffeine ingestion can postpone the time to exhaustion during exercise (Gaesser and Rich 1985;Dodd et al. 1991;Doherty 1998;Simmonds et al. 2010); it, therefore, may influence the CP value. ...
... Previous studies have found that caffeine ingestion reduces both effort sense (Doherty and Smith 2005) and leg muscle pain (Motl et al. 2003(Motl et al. , 2006Gliottoni and Motl 2008;Gliottoni et al. 2009) during exercise. In addition, caffeine could improve the ability of muscle to generate force by increasing motor unit recruitment (Kalmar and Cafarelli 1999;Kalmar 2005;Warren et al. 2010;Black et al. 2015). The improved effort sensation and muscular strength might contribute to the ergogenic effects of caffeine during short-term, high-intensity exercise. ...
... Caffeine acts as an adenosine antagonist on the CNS and changes the perception of pain during exercise. Previous studies reported that caffeine ingestion reduces leg muscle pain (Motl et al. 2003(Motl et al. , 2006Gliottoni and Motl 2008;Gliottoni et al. 2009) during moderate and heavy cycling exercise, but this hypoalgesic effect disappeared with increases in performance during heavy to severe-intensity exercise (Jenkins et al. 2008;Black et al. 2015;Gonglach et al. 2016). Astorino et al. (2011) similarly determined that caffeine improved exercise performance during two sets of 40 repetitions of isokinetic knee extensions and flexions but did not change the RPE or pain perceptions in the leg. ...
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Purpose To investigate the effect of caffeine ingestion on the 3-min all-out test (3MT) performance and plasma electrolytes in athletes. Methods Fifteen collegiate male basketball players were recruited and completed two trials separated by at least 1 week in caffeine (CAF, 6 mg kg−1) and placebo conditions. During the first visit, participants performed an incremental cycling test to determine their 3MT resistance. After a familiarization trial, participants performed a CAF or PL trial according to a randomized crossover design. One hour after ingesting capsules, the participants performed the 3MT to estimate the end-test power (EP) and work done above EP (WEP). Blood samples for sodium (Na+), potassium (K+), pH, and lactate concentrations were drawn pretest, 1 h after ingestion, and posttest. Results Significant differences in WEP (CAF vs. PL, 13.4 ± 3.0 vs. 12.1 ± 2.7 kJ, P < 0.05) but not in EP (CAF vs. PL, 242 ± 37 vs. 244 ± 42 W, P > 0.05) were determined between the conditions. Compared with the PL condition, the CAF condition yielded significantly higher power outputs (60–150 s), a lower fatigue rate during the 3MT (CAF vs. PL, 0.024 ± 0.007 vs. 0.029 ± 0.006 s−1, P < 0.05), a significantly higher lactate concentration after the 3MT, and significantly lower K+ concentrations at 1 h after caffeine ingestion. There were no significant interaction effects for pH and Na+ concentrations. Conclusions Caffeine ingestion did not change EP but improved WEP and the rate of decline in power output during short-term, severe exercise.
... Research into the ergogenic properties of caffeine has revealed benefits across a range of exercise intensities and durations, with the greatest effects being displayed in sustained high-intensity aerobic activities [2,3]. Indeed, typical doses of 3-6 mgÁkg -1 ingested 30-90 minutes prior to exercise have produced positive effects (0.7-5.4%) in time trial events lasting 5-60 minutes [4][5][6][7][8][9][10][11][12][13][14][15]. Nevertheless, the mechanisms to explain the beneficial effects of caffeine supplementation on exercise performance remain unresolved. ...
... For example, whilst some studies have found no effect of caffeine on minute ventilation ( _ V E ) [18][19][20], others have reported a significant increase [4,7]. Similarly, many studies report no effect of caffeine on _ VO 2 [4,5,7,9,13,14,18,[20][21][22][23], though some have reported a significant increase [5,15]. ...
... For example, whilst some studies have found no effect of caffeine on minute ventilation ( _ V E ) [18][19][20], others have reported a significant increase [4,7]. Similarly, many studies report no effect of caffeine on _ VO 2 [4,5,7,9,13,14,18,[20][21][22][23], though some have reported a significant increase [5,15]. ...
Article
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Objectives: The aim of this study was to evaluate the effects of caffeine on physiological responses to submaximal exercise, with a focus on blood lactate concentration ([BLa]). Methods: Using a randomised, single-blind, crossover design; 16 endurance-trained, male cyclists (age: 38 ± 8 years; height: 1.80 ± 0.05 m; body mass: 76.6 ± 7.8 kg; [Formula: see text]: 4.3 ± 0.6 L∙min-1) completed four trials on an electromagnetically-braked cycle ergometer. Each trial consisted of a six-stage incremental test (3 minute stages) followed by 30 minutes of passive recovery. One hour before trials 2-4, participants ingested a capsule containing 5 mg∙kg-1 of either caffeine or placebo (maltodextrin). Trials 2 and 3 were designed to evaluate the effects of caffeine on various physiological responses during exercise and recovery. In contrast, Trial 4 was designed to evaluate the effects of caffeine on [BLa] during passive recovery from an end-exercise concentration of 4 mmol∙L-1. Results: Relative to placebo, caffeine increased [BLa] during exercise, independent of exercise intensity (mean difference: 0.33 ± 0.41 mmol∙L-1; 95% likely range: 0.11 to 0.55 mmol∙L-1), but did not affect the time-course of [BLa] during recovery (p = 0.604). Caffeine reduced ratings of perceived exertion (mean difference: 0.5 ± 0.7; 95% likely range: 0.1 to 0.9) and heart rate (mean difference: 3.6 ± 4.2 b∙min-1; 95% likely range: 1.3 to 5.8 b∙min-1) during exercise, with the effect on the latter dissipating as exercise intensity increased. Supplement × exercise intensity interactions were observed for respiratory exchange ratio (p = 0.004) and minute ventilation (p = 0.034). Conclusions: The results of the present study illustrate the clear, though often subtle, effects of caffeine on physiological responses to submaximal exercise. Researchers should be aware of these responses, particularly when evaluating the physiological effects of various experimental interventions.
... This study, which involved other conditions such as caffeine plus essential amino acids, presented a few moderating factors such as heat (30 °C) and prior ingestion of carbohydrates in addition to hypoxia (Eaton et al. 2016). Utilizing a similar testing protocol in normoxia, Black et al. (2015) investigated the effects of caffeine (5 mg kg −1 ) on MVC loss, central fatigue and peripheral fatigue after both arm and leg cycling exercise with a period of 30 min at a constant intensity (60% VO 2 max), followed by a 10-min time trial. Similar to our results, they found that caffeine reduced perception of effort and pain, and improved performance despite no effect on neuromuscular fatigue when compared to placebo. ...
... Similar to our results, they found that caffeine reduced perception of effort and pain, and improved performance despite no effect on neuromuscular fatigue when compared to placebo. It is noteworthy, however, that neuromuscular assessments were Fig. 5 Original torque recordings from one participant related to the measurements of central (superimposed doublet over the maximal voluntary contraction) and peripheral (potentiated doublet at rest) fatigue, both before the exercise task and after exhaustion made only 20 min after time-trial completion (Black et al. 2015). Interestingly, in their additional study, Black et al. (2015) found no differences in perception of effort, pain and time to exhaustion at exercise intensities closer to the ones used in the present study after caffeine ingestion. ...
... It is noteworthy, however, that neuromuscular assessments were Fig. 5 Original torque recordings from one participant related to the measurements of central (superimposed doublet over the maximal voluntary contraction) and peripheral (potentiated doublet at rest) fatigue, both before the exercise task and after exhaustion made only 20 min after time-trial completion (Black et al. 2015). Interestingly, in their additional study, Black et al. (2015) found no differences in perception of effort, pain and time to exhaustion at exercise intensities closer to the ones used in the present study after caffeine ingestion. This is unexpected, since the literature has shown a rather consistent effect of caffeine on perception of effort Doherty and Smith 2005) and on endurance performance Astorino and Roberson 2010). ...
Article
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Purpose: To investigate the effects of caffeine on performance, neuromuscular fatigue and perception of effort during high-intensity cycling exercise in moderate hypoxia. Methods: Seven adult male participants firstly underwent an incremental exercise test on a cycle ergometer in conditions of acute normobaric hypoxia (fraction inspired oxygen = 0.15) to establish peak power output (PPO). In the following two visits, they performed a time to exhaustion test (78 ± 3% PPO) in the same hypoxic conditions after caffeine ingestion (4 mg kg(-1)) and one after placebo ingestion in a double-blind, randomized, counterbalanced cross-over design. Results: Caffeine significantly improved time to exhaustion by 12%. A significant decrease in subjective fatigue was found after caffeine consumption. Perception of effort and surface electromyographic signal amplitude of the vastus lateralis were lower and heart rate was higher in the caffeine condition when compared to placebo. However, caffeine did not reduce the peripheral and central fatigue induced by high-intensity cycling exercise in moderate hypoxia. Conclusion: The caffeine-induced improvement in time to exhaustion during high-intensity cycling exercise in moderate hypoxia seems to be mediated by a reduction in perception of effort, which occurs despite no reduction in neuromuscular fatigue.
... The type of contraction does not seem to be a key factor because five other studies using isometric contractions reported ergogenic effects. 21,22,[26][27][28] The five studies that did not observe increased strength included volunteers not habituated to caffeine or with low caffeine consumption and four of them 20,24,29,30 evaluated the strength of smaller muscle groups. Hence, the ergogenic effects of CAFF were present in voluntary muscle contraction in eleven (68.8%) of the 16 analyzed studies. ...
... Four of these studies investigated isometric contractions. Similarly, Black et al. 27 did not observe any increases in strength when testing isometric contractions of elbow flexor muscles. Warren et al. 12 did not observe any differences when comparing isokinetic and isometric contractions in their meta-analysis; however the findings above mentioned indicate that this issue should be further investigated. ...
... Increased muscle activation seems to be related to the ergogenic effects of CAFF. 12 For example, Black et al. 27 observed increased activation after CAFF in knee extensors but not in elbow flexors. This observation correlated with an increase in strength, which only increased in the knee extensors. ...
Article
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The purpose of this review was to examine in the current literature the advances made in terms of the effects of caffeine supplementation on maximum strength and its associated mechanisms since the publication of two important papers in 2010. Searches were carried out in the PubMed, Medline, Scielo and Web of Science databases for articles published after 2010. Sixteen studies were included based on inclusion and exclusion criteria. Five studies did not report changes in maximal voluntary strength (31.3%). Four of them used isometric muscle contractions, although this may not be a key factor because five other studies also used isometric contractions and reported ergogenic effects. Furthermore, these four studies evaluated small muscle groups and volunteers were not accustomed to consuming caffeine. Caffeine produced ergogenic effects in eleven of the sixteen studies analyzed (68.8%). None of the doses were clearly related to ergogenic effects; however, a dose of at least 3 mg/kg of caffeine is probably necessary. Caffeine ergogenicity was affected by various factors. There was a lack of standardized protocols and controls for intervening factors (e.g., circadian cycles and nutritional states), which could affect results. An ideal caffeine supplementation protocol that is useful for future research, athletes, and physical activity practitioners, has yet to be defined. A small advance made since 2010 involved a possible lack of gender difference; it would appear that caffeine supplementation affects men and women equally. Level of Evidence I; Systematic Review of Level I Studies.
... RER, changes in blood lactate, glucose), also appear to deliver measurable ergogenic effects, offering strong support for the CNS as the origin of reported improvements [43,149,150]. As such, focus has shifted to the action of caffeine during exercise within the central and peripheral nervous systems, which could alter the rate of perceived exertion (RPE) [151][152][153][154], muscle pain [151,[155][156][157], and possibly the ability of skeletal muscle to generate force [151]. ...
... RER, changes in blood lactate, glucose), also appear to deliver measurable ergogenic effects, offering strong support for the CNS as the origin of reported improvements [43,149,150]. As such, focus has shifted to the action of caffeine during exercise within the central and peripheral nervous systems, which could alter the rate of perceived exertion (RPE) [151][152][153][154], muscle pain [151,[155][156][157], and possibly the ability of skeletal muscle to generate force [151]. ...
... RER, changes in blood lactate, glucose), also appear to deliver measurable ergogenic effects, offering strong support for the CNS as the origin of reported improvements [43,149,150]. As such, focus has shifted to the action of caffeine during exercise within the central and peripheral nervous systems, which could alter the rate of perceived exertion (RPE) [151][152][153][154], muscle pain [151,[155][156][157], and possibly the ability of skeletal muscle to generate force [151]. ...
Article
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Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: 1. Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. Small to moderate benefits of caffeine use include, but are not limited to: muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions. 2. Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use, although the magnitude of its effects differs between individuals. 3. Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3–6 mg/kg body mass. Minimal effective doses of caffeine currently remain unclear but they may be as low as 2 mg/kg body mass. Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. 4. The most commonly used timing of caffeine supplementation is 60 min pre-exercise. Optimal timing of caffeine ingestion likely depends on the source of caffeine. For example, as compared to caffeine capsules, caffeine chewing gums may require a shorter waiting time from consumption to the start of the exercise session. 5. Caffeine appears to improve physical performance in both trained and untrained individuals. 6. Inter-individual differences in sport and exercise performance as well as adverse effects on sleep or feelings of anxiety following caffeine ingestion may be attributed to genetic variation associated with caffeine metabolism, and physical and psychological response. Other factors such as habitual caffeine intake also may play a role in between-individual response variation. 7. Caffeine has been shown to be ergogenic for cognitive function, including attention and vigilance, in most individuals. 8. Caffeine may improve cognitive and physical performance in some individuals under conditions of sleep deprivation. 9. The use of caffeine in conjunction with endurance exercise in the heat and at altitude is well supported when dosages range from 3 to 6 mg/kg and 4–6 mg/kg, respectively. 10. Alternative sources of caffeine such as caffeinated chewing gum, mouth rinses, energy gels and chews have been shown to improve performance, primarily in aerobic exercise. 11. Energy drinks and pre-workout supplements containing caffeine have been demonstrated to enhance both anaerobic and aerobic performance.
... One of the most widely consumed bioactive compounds naturally present in foods and beverages and that has analgesic potential is caffeine (1,3,7-trimethylxanthine) (10). Many studies have demonstrated that the ingestion of caffeine reduces both muscle pain (11)(12)(13)(14) and perceived exertion (14,15) during physical exercise in healthy individuals. These findings suggest that the ingestion of caffeine before a bout of exercise might be a promising candidate to alleviate the exacerbated sensations of pain and exertion during exercise in FM patients. ...
... One of the most widely consumed bioactive compounds naturally present in foods and beverages and that has analgesic potential is caffeine (1,3,7-trimethylxanthine) (10). Many studies have demonstrated that the ingestion of caffeine reduces both muscle pain (11)(12)(13)(14) and perceived exertion (14,15) during physical exercise in healthy individuals. These findings suggest that the ingestion of caffeine before a bout of exercise might be a promising candidate to alleviate the exacerbated sensations of pain and exertion during exercise in FM patients. ...
... It should be pointed out that isometric handgrip tasks are of limited functional relevance and not commonly used as part of an exercise training program to treat FM patients (9). Moreover, studies that observed an effect of caffeine ingestion on perceived muscle pain and perceived exertion during exercise in healthy individuals used higher doses of caffeine (i.e., ≥ 5 mg of caffeine per kg of body mass) (11)(12)(13)(14)(15)) and a whole-body exercise model (e.g., cycling) that involves the recruitment of large muscle groups. Thus, whether caffeine reduces muscle pain and effort sensations during a whole-body exercise in FM patients is still unknown. ...
Article
Objective Exacerbated perceived exertion and muscle pain responses during exercise might limit physical activity practice in fibromyalgia patients. Thus, nutritional strategies that can reduce perceived exertion and muscle pain during exercise in fibromyalgia patients would be useful. The purpose of this study was to investigate the effects of acute caffeine intake on the perceptions of exertion and muscle pain during a moderate intensity exercise in women with fibromyalgia.Method: Using a randomized, double-blinded, placebo-controlled and crossover experimental design, eleven sedentary women diagnosed with fibromyalgia (age: 44.6 ± 10.5 years; body mass index: 28.5 ± 4.5 kg.m⁻²) ingested a capsule containing either caffeine (5 mg per kg of body mass) or cellulose (placebo), 60 minutes before performing a 30-minute constant-load cycling exercise, with work rate fixed at 50% of their individual peak workload attained in an incremental exercise test. Ratings of perceived leg muscle pain and perceived exertion were assessed every 5 minutes of exercise.Results: The perceived leg muscle pain was similar (F(1,10) = 1.18, p = 0.30, ŋ² = 0.11) between caffeine (2.1 ± 1.2 arbitrary units) and placebo conditions (2.2 ± 0.9 arbitrary units). The perceived exertion, however, was on average 8 ± 6% lower (F(1,10) = 12.13; p = 0.006; ŋ² = 0.55) during exercise in the caffeine condition (12.4 ± 1.3 arbitrary units) than in the placebo condition (13.1 ± 1.1 arbitrary units).Conclusions: These findings indicate that acute caffeine intake could be an attractive strategy to attenuate the exacerbated perceived exertion of fibromyalgia patients during moderate intensity exercise.
... 19 Previous research has suggested that the lower-body and upper-body musculature exhibit divergent responses to caffeine ingestion with the effects being more pronounced in the lower-body musculature. 20,21 In support of this idea, Warren et al 19 reported that caffeine has a greater ergogenic effect on the knee extensor muscles compared with the smaller muscle groups such as the elbow flexors. During maximal voluntary contractions, knee extensor activation level is generally 85% to 95%. ...
... In one study, at baseline, the percentage of motor unit recruitment of the knee extensors and elbow flexors during maximal contractionsas assessed using the interpolated-twitch electrical stimulationwas at 83% and 97%, respectively. 20 Due to the lower muscle activation level at baseline, after the ingestion of caffeine, performance was only improved for the lower body but not for the upper body. 20 These results might explain why we did not observe significant improvements in upper-body muscle endurance. ...
... 20 Due to the lower muscle activation level at baseline, after the ingestion of caffeine, performance was only improved for the lower body but not for the upper body. 20 These results might explain why we did not observe significant improvements in upper-body muscle endurance. In addition, these results might explain why we did not find significant increases in upper-body strength following caffeine ingestion when compared with the placebo control conditions. ...
Purpose: To explore the effects of three doses of caffeine on muscle strength and muscle endurance. Methods: Twenty-eight resistance-trained men completed the testing sessions under five conditions: no-placebo control, placebo-control, and with caffeine doses of 2, 4, and 6 mg.kg−1. Muscle strength was assessed using the one-repetition maximum (1RM) test; muscle endurance was assessed by having the participants perform a maximal number of repetitions with 60% 1RM. Results: In comparisons with both control conditions, only a caffeine dose of 2 mg.kg−1 enhanced lower-body strength (d=0.13–0.15). In comparisons with the no-placebo control condition, caffeine doses of 4 mg.kg−1 and 6 mg.kg−1 enhanced upper-body strength (d=0.07–0.09) with a significant linear trend for the effectiveness of different doses of caffeine (p=0.020). Compared to both control conditions, all three caffeine doses enhanced lower-body muscle endurance (d=0.46–0.68). For upper-body muscle endurance, we did not find significant effects of caffeine. Conclusions: We found a linear trend between the dose of caffeine and its effects on upper-body strength. This study found no clear association between the dose of caffeine and the magnitude of its ergogenic effects on lower-body strength and muscle endurance. From a practical standpoint, the magnitude of caffeine’s effects on strength is of questionable relevance. A low dose of caffeine (2 mg.kg−1)—for an 80kg individual, this dose of caffeine contained in one to two cups of coffee—may produce substantial improvements in lower-body muscle endurance with the magnitude of the effect being similar to that attained using higher doses of caffeine.
... A meta-analysis by Warren In subgroup meta-analyses, an ergogenic effect of caffeine was found for lower-body but not upper-body muscular strength. These differential effects of caffeine are suggested to be due to the size of the activated muscle [16,32,33]. It seems likely that the caffeine-induced increase in muscular strength is due to increased motor unit recruitment and not motor synchronization, as the latter may not be affected by caffeine ingestion and is also more related to the rate of force development [34,35]. ...
... It seems likely that the caffeine-induced increase in muscular strength is due to increased motor unit recruitment and not motor synchronization, as the latter may not be affected by caffeine ingestion and is also more related to the rate of force development [34,35]. In this context, it is proposed that caffeine may elicit an ergogenic effect and increase motor unit recruitment in larger (e.g., knee extensors) but not smaller muscle groups (e.g., elbow extensors and forearm flexors) [16,32,33]. Black et al. [33] reported that the percentage of motor unit recruitment of the knee extensors and elbow flexors during maximal contractions before caffeine ingestion was 83% and 97%, respectively. ...
... In this context, it is proposed that caffeine may elicit an ergogenic effect and increase motor unit recruitment in larger (e.g., knee extensors) but not smaller muscle groups (e.g., elbow extensors and forearm flexors) [16,32,33]. Black et al. [33] reported that the percentage of motor unit recruitment of the knee extensors and elbow flexors during maximal contractions before caffeine ingestion was 83% and 97%, respectively. Following caffeine ingestion, muscular strength increased only in the knee extensors, possibly because of the lower muscle activation level at baseline (i.e., before caffeine ingestion). ...
Article
Objectives: Caffeine ingestion has well-established ergogenic effects for resistance exercise performance. However, the concept of a minimum effective caffeine dose has not yet been thoroughly examined in the literature. Therefore, this review aimed to explore the minimum ergogenic dose of caffeine on resistance exercise outcomes, such as muscular strength, endurance, and velocity, using a meta-analytic approach. Methods: The search for eligible studies was performed through six databases. The methodological quality of the included studies was assessed using the PEDro checklist. A random-effects meta-analysis was performed for data analysis. Twelve studies that provided caffeine supplementation in doses from 0.9 to 2 mg/kg were included. The studies were classified as being of good or excellent methodological quality. Results: The results revealed an ergogenic effect of caffeine for muscular strength (Cohen d: 0.17; 95% confidence interval [CI], 0.03-0.31; P = 0.02), muscular endurance (Cohen d: 0.21; 95% CI, 0.07-0.35; P = 0.003), and mean velocity (Cohen d: 0.56; 95% CI, 0.12-1.01; P = 0.01). Conclusions: This review demonstrated an ergogenic effect of very low doses of caffeine on resistance exercise performance. The magnitude of these effects was similar to that previously reported with higher caffeine doses. These findings highlight that the minimal ergogenic doses of caffeine are even lower than previously suggested. Such doses of caffeine can be consumed through a regular diet, because for most individuals, a dose of approximately 1 to 2 mg/kg is equivalent to a dose of caffeine in one to two cups of coffee.
... Many studies also found that the MVC is not significantly altered by caffeine (Sébastien et al., 2011;Kalmar and, Cafarelli, 1999), and our meta-analysis observed the same result. The reasons of this result are probably due to high interindividual changes (Sébastien et al., 2011), or due to a larger than expected day-to-day variation in MVC or fatigue from a previous testing day (Black et al., 2015). Therefore, the MVC can be used as an indicator of overall fatigue, but it cannot be used as a characteristic indicator of the effects of caffeine on neuromuscular fatigue. ...
... And for the cardiorespiratory fitness classification, HR was higher with caffeine than with placebo (Apostolidis et al., 2020). HR did not differ between the caffeine and placebo conditions for either leg cycling or arm crank cycling, and caffeine induced reductions in muscle pain and in the absence of changes in HR during submaximal exercise (Black et al., 2015). However, a significant main effect for time was found for HR during leg cycling, with HR increasing progressively over time compared to the first minute of the time trial (Black et al., 2015). ...
... HR did not differ between the caffeine and placebo conditions for either leg cycling or arm crank cycling, and caffeine induced reductions in muscle pain and in the absence of changes in HR during submaximal exercise (Black et al., 2015). However, a significant main effect for time was found for HR during leg cycling, with HR increasing progressively over time compared to the first minute of the time trial (Black et al., 2015). This is because caffeine directly reduces parasympathetic nervous system activity, so caffeine ingestion during exercises HR response (Sondermeijer et al., 2002), but in higher intensity exercise, this difference tends to disappear because the sympathetic nervous system affects the automaticity of the sinoatrial node and has a major influence on HR control (Sonntag et al., 2012). ...
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Background: Caffeine is often used as a stimulant during fatigue, but the standard of characteristic physiological indicators of the effect of caffeine on neuromuscular fatigue has not been unified. The purpose of this systematic review and meta-analysis is to summarize current experimental findings on the effects of caffeine on physiological indexes before and after neuromuscular fatigue, identify some characteristic neuromuscular physiological indexes to assess the potential effects of caffeine. Methods: The Preferred Reporting Items for Systematic Reviews and Meta-analyses are followed. We systematically searched PubMed, Google academic, and Web of Science for randomized controlled trials. We searched for studies on caffeine's (i) effects on neuromuscular fatigue and (ii) the influence of physiological indexes changes. Meta-analysis was performed for standardized mean differences (SMD) between caffeine and placebo trials in individual studies. Results: The meta-analysis indicated that caffeine significantly improves voluntary activation (VA) (SMD = 1.46;95%CI:0.13, 2.79; p < .00001), PTw (SMD = 1.11, 95%CI: -1.61, 3.84; p < .00001), and M-wave (SMD = 1.10, 95%CI: -0.21, 2.41; p < .00001), and a significant difference (p = .003) on measures of Peak Power (PP), and insignificant difference on measures of heart rate (HR) (I2 = 0.0, p = .84) and Maximal oxygen uptake (VO2 ) (I2 = 0.0, p = .76). Conclusion: The analysis showed that caffeine intake had a relatively large effect on VA, potentiated twitch (PTw), M-wave, which can be used as characteristic indexes of caffeine's impact on neuromuscular fatigue. This conclusion tends to indicate the effects of caffeine on neuromuscular fatigue during endurance running or jumping or muscle bending and stretching. The caffeine intake had a big effect on the electromyogram (EMG) and peak power (PP), and its effect role needs to be further verified, this conclusion tends to indicate the effect of caffeine on neuromuscular fatigue during jumping or elbow bending moment movements. HR, VO2 , maximal voluntary contraction (MVC) cannot be used as the characteristic indexes of caffeine on neuromuscular fatigue. This conclusion tends to indicate the effect of caffeine on neuromuscular fatigue during endurance exercise. However, the results of meta-analysis are based on limited evidence and research scale, as well as individual differences of participants and different physical tasks, so it is necessary to interpret the results of meta-analysis cautiously. Therefore, future research needs to explore other physiological indicators and their indicative effects in order to determine effective and accurate characteristic indicators of caffeine on neuromuscular fatigue.
... Surprisingly, even with these multiple effects of caffeine on central and peripheral sites, only a few studies have investigated the consequence of caffeine ingestion on neuromuscular fatigue during a high-intensity wholebody exercise (6)(7)(8). Neuromuscular fatigue can be defined as a transitory exercise-induced reduction of the muscle ability to generate power (9), which can be related to failure of the central nervous system to voluntarily activate the muscle (central fatigue) and/or processes distal to or at the neuromuscular junction (peripheral fatigue) leading to an attenuated response of the active muscle to a given neural input (for a review see Weavil and Amann (10)). One study reported that caffeine increased total work in a 10-min cycling time trial (TT), but exercise-induced reduction in evoked quadriceps twitch force (a marker of peripheral fatigue) and voluntary activation (a marker of central fatigue) were similar in magnitude under both caffeine and placebo conditions (6). ...
... Neuromuscular fatigue can be defined as a transitory exercise-induced reduction of the muscle ability to generate power (9), which can be related to failure of the central nervous system to voluntarily activate the muscle (central fatigue) and/or processes distal to or at the neuromuscular junction (peripheral fatigue) leading to an attenuated response of the active muscle to a given neural input (for a review see Weavil and Amann (10)). One study reported that caffeine increased total work in a 10-min cycling time trial (TT), but exercise-induced reduction in evoked quadriceps twitch force (a marker of peripheral fatigue) and voluntary activation (a marker of central fatigue) were similar in magnitude under both caffeine and placebo conditions (6). It is important to highlight that post-exercise neuromuscular fatigue measurements in the mentioned study were assessed 20 min after exercise cessation, when central and peripheral fatigue might have been largely recovered (11). ...
... The present study indicated that, for detecting caffeine-induced improvements in endurance performance, the sensitivity of a closed- Caffeine ingestion improved performance during the 4,000-m cycling TT (B1.8%), similar to what has been previously reported for TT of similar distance and duration (6,29). Caffeine also increased time to task failure during a constant-load trial (B35%), a result that also corroborates previous findings (15,30). ...
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We examined whether endurance performance and neuromuscular fatigue would be affected by caffeine ingestion during closed- and open-loop exercises. Nine cyclists performed a closed-loop (4,000-m cycling time trial) and an open-loop exercise (work rate fixed at mean power of the closed-loop trial) 60 min after ingesting caffeine (CAF, 5 mg/kg) or placebo (PLA, cellulose). Central and peripheral fatigue was quantified via pre- to post-exercise decrease in quadriceps voluntary activation and potentiated twitch force, respectively. Test sensitivity for detecting caffeine-induced improvements in exercise performance was calculated as the mean change in time divided by the error of measurement. Caffeine ingestion reduced the time of the closed-loop trial (PLA: 375.1±14.5 s vs CAF: 368.2±14.9 s, P=0.024) and increased exercise tolerance during the open-loop trial (PLA: 418.2±99.5 s vs CAF: 552.5±106.5 s, P=0.001), with similar calculated sensitivity indices (1.5, 90%CI: 0.7-2.9 vs 2.8, 90%CI: 1.9-5.1). The reduction in voluntary activation was more pronounced (P=0.019) in open- (-6.8±8.3%) than in closed-loop exercises (-1.9±4.4%), but there was no difference between open- and closed-loop exercises for the potentiated twitch force reduction (-25.6±12.8 vs -26.6±12.0%, P>0.05). Caffeine had no effect on central and peripheral fatigue development in either mode of exercise. In conclusion, caffeine improved endurance performance in both modes of exercise without influence on post-exercise central and peripheral fatigue, with the open-loop exercise imposing a greater challenge to central fatigue tolerance.
... An interpolated-twitch electrical stimulation protocol was employed to assess maximal voluntary isometric contraction (MVIC) , the percentage of motor unit activation (%ACT) and voluntary torque (VT) during MVIC (Black et al., 2015). Additionally, peak twitch torque (TT) in the relaxed muscle, the time to peak tension, and half relaxation time were also assessed on all 7 visits to the laboratory. ...
... Peak TT was determined as the average of the two post-MVIC stimulations and was used in subsequent analyses. %ACT was calculated as 100% Â (1 À ITT/TT) (Black et al., 2015). MVIC was determined as the peak torque during the 3 s MVIC. ...
... The primary mechanisms by which caffeine increases muscular strength, muscular endurance, and power performance are potentially related to its ability to augment muscle fiber conduction velocity and motor unit recruitment [177]. It might be that increasing the dose of caffeine also increases these properties in a linear dose-response fashion, potentially explaining the findings of Astorino et al. [172] and Pallarés et al. [173]. ...
... For instance, Trevino et al. [180] compared the effects of 5 and 10 mg/kg of caffeine on isometric strength. Their results indicated that neither of the doses were effective for acute increases in strength; however, they tested the strength of the elbow flexors, and previous research has demonstrated that caffeine is not always ergogenic for this muscle group [177]. ...
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Caffeine is a widely utilized performance-enhancing supplement used by athletes and non-athletes alike. In recent years, a number of meta-analyses have demonstrated that caffeine’s ergogenic effects on exercise performance are well-established and well-replicated, appearing consistent across a broad range of exercise modalities. As such, it is clear that caffeine is an ergogenic aid—but can we further explore the context of this ergogenic aid in order to better inform practice? We propose that future research should aim to better understand the nuances of caffeine use within sport and exercise. Here, we propose a number of areas for exploration within future caffeine research. These include an understanding of the effects of training status, habitual caffeine use, time of day, age, and sex on caffeine ergogenicity, as well as further insight into the modifying effects of genotype. We also propose that a better understanding of the wider, non-direct effects of caffeine on exercise, such as how it modifies sleep, anxiety, and post-exercise recovery, will ensure athletes can maximize the performance benefits of caffeine supplementation during both training and competition. Whilst not exhaustive, we hope that the questions provided within this manuscript will prompt researchers to explore areas with the potential to have a large impact on caffeine use in the future.
... It has been suggested by Warren et al. (2010) that smaller muscles, such as muscles of the upper arm, have a limited ability for increased motor unit recruitment with caffeine ingestion. Differences in the effects of caffeine on upper and lower body were also noted in a recent study by Black, Waddell, and Gonglach (2015). These authors (Black et al., 2015) reported increases (+6.3%) in maximal voluntary strength in the lower (i.e. ...
... Differences in the effects of caffeine on upper and lower body were also noted in a recent study by Black, Waddell, and Gonglach (2015). These authors (Black et al., 2015) reported increases (+6.3%) in maximal voluntary strength in the lower (i.e. knee extensors), but not the upper body (i.e. ...
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The goal of this randomized, double-blind, cross-over study was to assess the acute effects of caffeine ingestion on muscular strength and power, muscular endurance, rate of perceived exertion (RPE), and pain perception (PP) in resistance-trained men. Seventeen volunteers (mean ± SD: age = 26 ± 6 years, stature = 182 ± 9 cm, body mass = 84 ± 9 kg, resistance training experience = 7 ± 3 years) consumed placebo or 6 mg kg −1 of anhydrous caffeine 1 h before testing. Muscular power was assessed with seated medicine ball throw and vertical jump exercises, muscular strength with one-repetition maximum (1RM) barbell back squat and bench press exercises, and muscular endurance with repetitions of back squat and bench press exercises (load corresponding to 60% of 1RM) to momentary muscular failure. RPE and PP were assessed immediately after the completion of the back squat and bench press exercises. Compared to placebo, caffeine intake enhanced 1RM back squat performance (+2.8%; effect size [ES] = 0.19; p = .016), which was accompanied by a reduced RPE (+7%; ES = 0.53; p = .037), and seated medicine ball throw performance (+4.3%, ES = 0.32; p = .009). Improvements in 1RM bench press were not noted although there were significant (p = .029) decreases in PP related to this exercise when participants ingested caffeine. The results point to an acute benefit of caffeine intake in enhancing lower-body strength, likely due to a decrease in RPE; upper-, but not lower-body power; and no effects on muscular endurance, in resistance-trained men. Individuals competing in events in which strength and power are important performance-related factors may consider taking 6 mg kg −1 of caffeine pre-training/competition for performance enhancement.
... An interpolated-twitch electrical stimulation protocol was employed to assess maximal voluntary isometric contraction (MVIC) , the percentage of motor unit activation (%ACT) and voluntary torque (VT) during MVIC (Black et al., 2015). Additionally, peak twitch torque (TT) in the relaxed muscle, the time to peak tension, and half relaxation time were also assessed on all 7 visits to the laboratory. ...
... Peak TT was determined as the average of the two post-MVIC stimulations and was used in subsequent analyses. %ACT was calculated as 100% Â (1 À ITT/TT) (Black et al., 2015). MVIC was determined as the peak torque during the 3 s MVIC. ...
... The mean caffeine dose administered was 4.9 ± 1.3 mg/kg, with 19 studies (30 trials) using 6 mg/kg [37, 39-42, 44, 46, 55-58, 64, 66, 69, 70, 74-76, 78], nine studies (26 trials) using 5 mg/kg [38,43,49,54,62,63,67,68,73,81], four studies (five trials) using 4 mg/kg [41,53,60,71], nine studies (15 trials) used 3 mg/g [48, 50-52, 57, 59, 61, 65, 72, 77, 80], one study each used 4.5 mg [45], 200 mg [31], 250 mg [79], and 9 mg/kg [38]. ...
... 38, 39, 41-49, 51-56, 60, 62, 63, 66, 68, 71], 13 used time to complete a set amount of work[37, 40, 50, 57-59, 61, 64, 65, 67, 69, 70, 74], and nine studies used amount of work done in a set amount of time[72,73,[75][76][77][78][79][80]. Forty-four trials administered caffeine 60 min prior to exercise, with the remainder of studies ...
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Background: Caffeine is a widely used ergogenic aid with most research suggesting it confers the greatest effects during endurance activities. Despite the growing body of literature around the use of caffeine as an ergogenic aid, there are few recent meta-analyses that quantitatively assess the effect of caffeine on endurance exercise. Objectives: To summarise studies that have investigated the ergogenic effects of caffeine on endurance time-trial performance and to quantitatively analyse the results of these studies to gain a better understanding of the magnitude of the ergogenic effect of caffeine on endurance time-trial performance. Methods: A systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance. Results: Forty-six studies met the inclusion criteria and were included in the meta-analysis. Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3-6 mg/kg) as well as an overall improvement following caffeine compared to placebo in mean power output (3.03 ± 3.07%; effect size = 0.23 ± 0.15) and time-trial completion time (2.22 ± 2.59%; effect size = 0.41 ± 0.2). However, differences in responses to caffeine ingestion have been shown, with two studies reporting slower time-trial performance, while five studies reported lower mean power output during the time-trial. Conclusion: Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.
... Importantly, the meta-analysis by Grgic (2018) noted that none of their included studies assessed the effectiveness of blinding and no studies examined the effect of caffeine ingestion on upper body WANT performance (Grgic, 2018). Despite previous work demonstrating caffeine induced increases in upper body strength (Black, Waddell, & Gonglach, 2015), there is evidence to suggest that the effects of caffeine may not be uniform across the upper and lower body (Grigic & Mikulic, 2017;Tallis & Yavuz, 2018). It is also not necessarily appropriate to compare upper body maximal voluntary contraction data to more dynamic modes of anaerobic exercise (Black et al., 2015). ...
... Despite previous work demonstrating caffeine induced increases in upper body strength (Black, Waddell, & Gonglach, 2015), there is evidence to suggest that the effects of caffeine may not be uniform across the upper and lower body (Grigic & Mikulic, 2017;Tallis & Yavuz, 2018). It is also not necessarily appropriate to compare upper body maximal voluntary contraction data to more dynamic modes of anaerobic exercise (Black et al., 2015). It has been suggested that in smaller muscle masses, such as muscles of the upper arm, there may be a limited ability for increased motor unit recruitment associated with caffeine ingestion (Warren, Park, Maresca, McKibans, & Millard-Stafford, 2010). ...
Article
The current study examined the effect of acute caffeine ingestion on mean and peak power production during upper body Wingate test (WANT) performance, rating of perceived exertion, readiness to invest effort and cognitive performance. Using a double-blind design, 12 males undertook upper body WANTs, following ingestion of caffeine (5 mg*kg⁻¹) or placebo. Pre-substance ingestion, 60 mins post substance ingestion and post exercise participants completed measures of readiness to invest physical and mental effort and cognitive performance. Peak power was significantly higher (P = .026), fatigue index greater (P = .02) and rating of perceived exertion lower (P = .025) in the presence of caffeine. Readiness to invest physical effort was also higher (P = .016) in the caffeine condition irrespective of time point (pre, 60 mins post ingestion and post exercise). Response accuracy for incongruent trials on the Flanker task was superior in the presence of caffeine (P = .006). There was a significant substance × time interaction for response speed in both congruent and incongruent conditions (both P = .001) whereby response speeds were faster at 60 mins post ingestion and post exercise in the caffeine condition, compared to placebo. This is the first study to examine the effects of caffeine ingestion on this modality of exercise and suggests that caffeine ingestion significantly enhances peak power, readiness to invest physical effort, and cognitive performance during WANT performance.
... It is unclear why the strength increases identified in males do not translate to females for the lower body and it was postulated [19] that lower body maximal strength improvements with caffeine may be due to the mechanism of caffeine stimulating the CNS. Indeed, investigations [29,30] have observed muscular activation lower with the knee extensor compared to other muscle groups, reporting 85-95% for knee extensor activation compared to 90-99% for other muscle groups. Therefore, caffeine may be ineffective with muscle groups able to activate to near maximal levels, whereas caffeine can support knee extensors to achieve greater activation via CNS stimulation increasing muscle unit recruitment. ...
... As caffeine has been shown to enhance motor unit recruitment, it may be expected that caffeine ingestion would improve performance in larger muscles of the lower body, compared to smaller muscles of the upper body as previ- ously stated [19]. There is further support from Black and colleagues [30] that the ergogenic responses are likely to be due to increased motor unit recruitment as they cast doubt on caffeine's ability to reduce pain and perception at higher intensities despite improved performance. They conclude that the enhanced strength and increased muscle activation could represent the most plausible mechanism in which caffeine exerts it ergogenic effect during resistance exercise. ...
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Caffeine supplementation has shown to be an effective ergogenic aid enhancing athletic performance, although limited research within female populations exists. Therefore, the aim of the investigation was to assess the effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females. In a double-blind, randomised, counterbalanced design, fourteen strength-trained females using hormonal contraception consumed either 3 or 6 mg·kg−1 BM of caffeine or placebo (PLA). Following supplementation, participants performed a one-repetition maximum (1RM) leg press and repetitions to failure (RF) at 60% of their 1RM. During the RF test, rating of perceived exertion (RPE) was recorded every five repetitions and total volume (TV) lifted was calculated. Repeated measures ANOVA revealed that RF (p = 0.010) and TV (p = 0.012) attained significance, with pairwise comparisons indicating a significant difference between 3 mg·kg−1 BM and placebo for RF (p = 0.014), with an effect size of 0.56, and for 6 mg·kg−1 BM (p = 0.036) compared to the placebo, with an effect size of 0.65. No further significance was observed for 1RM or for RPE, and no difference was observed between caffeine trials. Although no impact on lower body muscular strength was observed, doses of 3 and 6 mg·kg−1 BM of caffeine improved lower body muscular endurance in resistance-trained females, which may have a practical application for enhancing resistance training stimuli and improving competitive performance.
... Caffeine can improve performance (Black et al., 2015;Siegel-Tike et al., 2015) acting through an enhance in central nervous system and in fat oxidation rate (Paton et al., 2015;Thomas et al., 2016). There are many studies suggesting that caffeine improves power and endurance compared to placebo or other supplements (Ganio et al., 2009;Nikolopoulos et al., 2011;Spence et al., 2013;Hodgson et al.,2013;Miller et al., 2014;Glaister et al., 2015). ...
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Aims: To record the prevalence and the type of supplement use among cyclists and to estimate the effect of caffeine, carbohydrates, energy drinks and meddiet score on 200m and 4km cycling time-trial performances in a Greek sample. Methods: Fifty male cycling athletes aged 32 ± 20 years participated in a randomized, double-blind study. The subjects were submitted to anthropometric measurements and body composition was assessed with bioelectrical impedance. All participants completed the meddiet Score questionnaire and a validated questionnaire about their ergogenic aids' preference. The athletes performed two cycling trials (200m and 4km) and their records were taken down and were evaluated according to their consumption of caffeine, carbohydrates and energy drinks and their meddiet score. For the statistical analysis SPSS, v20 was used. Results: Greek cyclists had a mean BMI value of 23.65 ± 2.74 and a mean body fat percentage of 15.82 ± 8.33. Endurance and speed performances were improved with caffeine consumption when compared to no consumption (7.42 ± 3.92 min vs 12.5 ± 3.16 min, p < 0.001 and 20.75 ± 15.69 sec vs 34.07 ± 16.25 sec, p < 0.05, respectively), as well as with energy drinks' consumption (8.77 ± 4.15 min vs 13.25 ± 2.47 min, p < 0.001 and 20.35 ± 14.08 sec vs 39.14±14.38 sec, p
... Many athletes believe that pre-workout supplementation improves concentration, decreases reaction time, increases power and endurance, and reduces fatigue [4,5]. The most popular pre-workout supplement is caffeine (CAF), which enhances performance through peripheral and central mechanisms [6][7][8][9]. The effects of CAF ingestion on aerobic performance are well documented [10], and previous studies also focused on the impact of CAF consumption on anaerobic performance [11,12]. ...
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Pre-exercise caffeine and guarana-based multi-ingredient supplement (MS) consumption may be more effective for physical performance improvement than caffeine and guarana alone due to the synergistic effect of biologically active ingredients in multi-ingredient supplements. This study aimed to examine the acute effect of MS on the reactive agility and jump performance in recreational handball male players. A randomized, double-blind, crossover study involved twenty four male handball players (body mass 74.6 � 8.8 kg; body height 179 � 7 cm; age 23.8 � 1.4 years).Participants were tested under three conditions: placebo, caffeine + guarana (CAF + GUA), or MS ingestion 45 min before exercise tests. Participants performed a reactive agility test (Y-shaped test) and countermovement jump (CMJ). None of the supplements improved countermovement jump height (p = 0.06). The time needed to complete the agility test was significantly (p = 0.02) shorter in the MS condition than in the placebo. The differences in agility between PL vs. CAF + GUA and MS vs. CAF + GUA conditions were not statistically significant (p = 0.88 and p = 0.07, respectively). The results of this study indicate that the caffeine-based multi-ingredient performance was effective in improvement in reactive agility but not in jump height in recreational handball male players. A similar effect was not observed with CAF + GUA ingestion alone.
... It is possible that the hypoalgesic effects of CAF may not be experienced past a certain level of intensity (24). Maximal or near-maximal intensity exercise may be too great for CAF to effectively reduce pain and effort perception (9,24). As a result, maximal-effort tests, such as the WAnT, may surpass this intensity threshold failing to enhance performance. ...
Article
Anderson, DE, LeGrand, SE, and McCart, RD. Effect of caffeine on sprint cycling in experienced cyclists. J Strength Cond Res XX(X): 000-000, 2018-Research regarding the ergogenic effects of caffeine (CAF) in anaerobic activity remains inconclusive. However, some researchers have found significant improvements in anaerobic performance when testing specifically trained athletes. A double-blind, placebo-controlled, counterbalanced, cross-over design was implemented to assess the impact of CAF on a 30-second Wingate Anaerobic Test (WAnT) in experienced cyclists. Nine experienced cyclists volunteered to participate in this study (men, n = 7 and women, n = 2). The subjects completed 2 separate experimental trials consisting of a 30-second WAnT at a resistance of 9% body mass. In a random order, 1 hour before each WAnT, subjects ingested either a CAF (∼280 mg) or placebo (PLAC) coffee. For each trial, heart rate (HR) and blood lactate (BL) values were recorded at rest, pre-WAnT, post-WAnT, and 5 minutes post-WAnT. After each trial, the subjects recorded their perception of which treatment they received. Heart rate and BL responses were not significantly different between the CAF and PLAC conditions. The ingestion of CAF did not significantly improve peak anaerobic power, mean anaerobic power, nor fatigue index. In at least 1 of the 2 trials, 44% of the subjects incorrectly guessed which substance they had ingested. The findings of this study do not show a significant correlation between CAF ingestion and improved anaerobic performance in experienced cyclists. However, performance enhancements may depend on varying individual responses to CAF. Athletes who are positive CAF responders may consider using coffee before competition to improve anaerobic performance.
... Of the different protocols used to measure time trial performance 23 studies used time to complete a set distance [38, 40-48, 50-58, 62, 63, 66, 70], 13 used time to complete a set amount of work [37, 39, 49, 59-61, 64, 65, 67-69, 71, 76], and 9 studies used amount of work done in a set amount of time [72][73][74][75][77][78][79][80] [38]. ...
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IntroductionCaffeine is a widely used ergogenic aid with most research suggesting it confers the greatest effects during endurance activities. Despite the growing body of literature around the use of caffeine as an ergogenic aid, there are few recent meta-analyses which quantitatively assess the effect of caffeine on endurance exercise. Objectives To summarise studies which have investigated the ergogenic effects of caffeine on endurance time-trial performance and to quantitatively analyse the results of these studies to gain a better understanding of the magnitude of caffeine’s ergogenic effect on endurance time-trial performance. MethodsA systematic review was carried out on randomised placebo-controlled studies investigating the effects of caffeine on endurance performance and a meta-analysis was conducted to determine the ergogenic effect of caffeine on endurance time-trial performance. Results44 studies met the inclusion criteria and were included in the meta-analysis. Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3–6 mg·kg−1) as well as an overall improvement following caffeine compared to placebo in mean power output (2.92 ± 2.18%; Effect Size = 0.22 ± 0.15) and time-trial completion time (2.26 ± 2.60%; Effect Size = 0.28 ± 0.12). However, differences in responses to caffeine ingestion have been shown, with two studies reporting slower time-trial performance while five studies reported lower mean power output during the time-trial. Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.
... 13 Our results appear to confirm such an effect. The work by Black et al. 43 provided some further support for these results. The authors used the interpolated-twitch electrical stimulation protocol and examined the percentage of motor-unit recruitment of the knee extensors and the elbow flexors during a strength assessment. ...
Article
Objectives The aims of this paper are threefold: (1) to summarize the research examining the effects of caffeine on isokinetic strength, (2) pool the effects using a meta-analysis, and (3) to explore if there is a muscle group or a velocity specific response to caffeine ingestion. Design Meta-analysis. Methods PubMed/MEDLINE, Scopus, and SPORTDiscus were searched using relevant terms. The PEDro checklist was used for the assessment of study quality. A random-effects meta-analysis of standardized mean differences (SMDs) was done. Results Ten studies of good and excellent methodological quality were included. The SMD for the effects of caffeine on strength was 0.16 (95% CI = 0.06, 0.26; p = 0.003; +5.3%). The subgroup analysis for knee extensor isokinetic strength showed a significant difference (p = 0.004) between the caffeine and placebo conditions with SMD value of 0.19 (95% CI = 0.06, 0.32; +6.1%). The subgroup analysis for the effects of caffeine on isokinetic strength of other, smaller muscle groups indicated no significant difference (p = 0.092) between the caffeine and placebo conditions. The subgroup analysis for knee extensor isokinetic strength at angular velocities of 60°·s−1 and 180°·s−1 showed a significant difference between the caffeine and placebo conditions with SMD value of 0.21 (95% CI = 0.07, 0.36; p = 0.004; +6.0%) and 0.23 (95% CI = 0.07, 0.38; p = 0.005; +5.5%), respectively. No significant effect (p = 0.193) was found at an angular velocity of 30°·s−1. Conclusions This meta-analysis demonstrates that acute caffeine ingestion caffeine may significantly increase isokinetic strength. Additionally, this meta-analysis reports that the effects of caffeine on isokinetic muscular strength are predominantly manifested in knee extensor muscles and at greater angular velocities.
... Caffeine ingestion has been reported to increase cortical and spinal neuron excitability [53], which might increase muscle activation through an increase in motor unit recruitment. Indeed, Black et al. [54] demonstrated that caffeine ingestion enhances MVC and motor unit recruitment in the knee extensors but not in the elbow flexors, supporting the hypothesis by Warren et al. [49]. ...
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This paper aims to critically evaluate and thoroughly discuss the evidence on the topic of caffeine supplementation when performing resistance exercise, as well as provide practical guidelines for the ingestion of caffeine prior to resistance exercise. Based on the current evidence, it seems that caffeine increases both maximal strength and muscular endurance. Furthermore, power appears to be enhanced with caffeine supplementation, although this effect might, to a certain extent, be caffeine dose- and external load-dependent. A reduction in rating of perceived exertion (RPE) might contribute to the performance-enhancing effects of caffeine supplementation as some studies have observed decreases in RPE coupled with increases in performance following caffeine ingestion. However, the same does not seem to be the case for pain perception as there is evidence showing acute increases in resistance exercise performance without any significant effects of caffeine ingestion on pain perception. Some studies have reported that caffeine ingestion did not affect exercise-induced muscle damage, but that it might reduce perceived resistance exercise-induced delayed-onset muscle soreness; however, this needs to be explored further. There is some evidence that caffeine ingestion, compared with a placebo, may lead to greater increases in the production of testosterone and cortisol following resistance exercise. However, given that the acute changes in hormone levels seem to be weakly correlated with hallmark adaptations to resistance exercise, such as hypertrophy and increased muscular strength, these findings are likely of questionable practical significance. Although not without contrasting findings, the available evidence suggests that caffeine ingestion can lead to acute increases in blood pressure (primarily systolic), and thus caution is needed regarding caffeine supplementation among individuals with high blood pressure. In the vast majority of studies, caffeine was administered in capsule or powder forms, and therefore the effects of alternative forms of caffeine, such as chewing gums or mouth rinses, on resistance exercise performance remain unclear. The emerging evidence suggests that coffee might be at least equally ergogenic as caffeine alone when the caffeine dose is matched. Doses in the range of 3–9 mg·kg⁻¹ seem to be adequate for eliciting an ergogenic effect when administered 60 min pre-exercise. In general, caffeine seems to be safe when taken in the recommended doses. However, at doses as high as 9 mg·kg⁻¹ or higher, side effects such as insomnia might be more pronounced. It remains unclear whether habituation reduces the ergogenic benefits of caffeine on resistance exercise as no evidence exists for this type of exercise. Caution is needed when extrapolating these conclusions to females as the vast majority of studies involved only male participants.
... They found that caffeine significantly increased explosive voluntary strength of the plantar flexors. In another interesting study, Black et al. (4) found that caffeine ingestion improved time-trial performance during leg cycling with an increase MVC and motorunit recruitment in knee extensors. The different caffeine dosages and protocols used make some comparisons difficult, and it can be a possible cause for the contradictory results. ...
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Dittrich, N, Serpa, MC, Lemos, EC, De Lucas, RD, and Guglielmo, LGA. Effects of caffeine chewing gum on exercise tolerance and neuromuscular responses in well-trained runners. J Strength Cond Res XX(X): 000-000, 2019-This study aimed to investigate the effects of caffeinated chewing gum on endurance exercise, neuromuscular properties, and rate of perceived exertion on exercise tolerance. Twelve trained male runners (31.3 ± 6.4 years; 70.5 ± 6.6 kg; 175.2 ± 6.2 cm; 9.4 ± 2.7% body fat; and V[Combining Dot Above]O2max = 62.0 ± 4.2 ml·kg·min) took part of the study. The athletes performed an intermittent treadmill test to determine maximal aerobic speed and delta 50% (Δ50%) intensity. In the following visits, they performed 2 randomized time to exhaustion tests (15.4 ± 0.7 km·h) after the ingestion of 300 mg of caffeine in a double-blind, crossover, randomized design. Maximal voluntary contraction of the knee extensor associated to surface electromyographic recording and the twitch interpolation technique were assessed before and immediately after the tests to quantify neuromuscular fatigue of the knee extensor muscles. Caffeine significantly improved exercise tolerance by 18% (p < 0.01). Neuromuscular responses decreased similarly after time to exhaustion in both exercise conditions; however, athletes were able to run a longer distance in the caffeine condition. The performance improvement induced by caffeine seems to have a neuromuscular contribution because athletes were able to run a longer distance with the same neuromuscular impairment.
... 70 As exercise intensity increases above the lactate threshold, the rate of hepatic glucose release (through glycogenolysis and gluconeogenesis) exceeds that of peripheral glucose uptake, resulting in an increase in [BGl]. 70,71 Although the increase in [BGl] is transient when exercise is prolonged, 70 it is important, at this stage, to recognize that participants tend to increase power output at the end of time trials as the finishing point approaches, [16][17][18]31,32,42,45,47,48 FIG. 4. The relationship between exercise duration and the effect of caffeine on respiratory exchange ratio, relative to placebo, during closed-loop time trial ( ‡5 minutes) performance. Each circle represents an individual study, and the size of each circle is proportional to the weighting of each study in the analysis. ...
... Most research, have investigated the effect of low or moderate doses of caffeine consumption on performance, perceptual responses and Neuromuscular factors prior to endurance exercise [7][8][9]13,14]. Nevertheless, there are a few studies that considered the effect of high doses of caffeine on endurance exercise [15,16]. ...
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Background : There are few studies that consider the effect of high doses of caffeine on aerobic power (VO2max). Also, to date, no study examined the effect of coffee intake on dragon boat paddler specifically on women. The purpose of this study was to investigate the effect of espresso coffee on improvement of aerobic power of dragon boat paddler. Material : Twenty women athletes of Guilan dragon bout team members of Malavan club of port city of Anzali (mean ±SD age, 23.60± 3.49 years; BMI,23.77±1.88kg/m2; body fat, 30.32±4.65%) were recruited to this study, after they completed a primary test without consuming any coffee, they consumed 6mg/kg of coffee (espresso or decaffeinated) and following that they completed two experimental trials. A randomized, double-blind, repeated-measures, design was employed whereby paddlers complete a 2000m paddling dragon boat ergo-meter. Results : Coffee could improve VO2max (Without coffee =74.40± QUOTE 4.99, Espresso coffee =90.10± QUOTE 6.19, Decaffeinated coffee =91.00± QUOTE 5.67, P≤ QUOTE 0.05). VO2max amount after exercise were significantly higher for both espresso coffee and decaffeinated coffee, when compared with without coffee condition. No significant differences were observed between espresso coffee and decaffeinated coffee (P≤ QUOTE 0.05). Conclusion : The present study shows that both high doses of caffeine (espresso coffee) and decaffeinated coffee can enhance VO2max during aerobic exercise including 2000m dragon boat paddling. It seems that some compounds except caffeine in decaffeinated coffee can act improve VO2max. Further studies needed for considering the effect of high doses of coffee on endurance exercises. Also in other age ranges of women athletes and other sport athletes.
... Caffeine ingestion may also enhance motor unit recruitment, thus leading to more forceful muscle contractions. 30,31 These mechanisms might explain why the pooled SMD increased when the study that provided caffeine in the mouth rinsing form was excluded. 22 After excluding the study that utilized Due to a small number of included studies, previous meta-analyses did not examine if the effects of caffeine differ between level 1 and level 2 versions of the Yo-Yo test. ...
Article
OBJECTIVES: To conduct a systematic review and a meta-analysis of studies exploring the effects of caffeine and/or sodium bicarbonate on performance in the Yo-Yo test. DESIGN: Systematic review/meta-analysis. METHODS: A total of six databases were searched, and random-effects meta-analyses were performed examining the isolated effects of caffeine and sodium bicarbonate on performance in the Yo-Yo test. RESULTS: After reviewing 988 search records, 15 studies were included. For the effects of caffeine on performance in the Yo-Yo test, the meta-analysis indicated a significant favoring of caffeine as compared with the placebo conditions (p = 0.022; standardized mean difference [SMD] = 0.17; 95% CI: 0.08, 0.32; +7.5%). Subgroup analyses indicated that the effects of caffeine were significant for the level 2 version of the Yo-Yo test, but not level 1. Four out of the five studies that explored the effects of sodium bicarbonate used the level 2 version of the Yo-Yo test. The pooled SMD favored the sodium bicarbonate condition as compared with the placebo/control conditions (p = 0.007; SMD: 0.36; 95% CI: 0.10, 0.63; +16.0%). CONCLUSIONS: This review demonstrates that isolated ingestion of caffeine and sodium bicarbonate enhances performance in the Yo-Yo test. Given these ergogenic effects, the intake of caffeine and sodium bicarbonate before the Yo-Yo test needs to be standardized (i.e., either restricted or used in the same way before each testing session). Furthermore, the results suggest that individuals competing in sports involving intermittent exercise may consider supplementing with caffeine or sodium bicarbonate for acute improvements in performance.
... (47) i Black i sar. (48). U testu sa triatloncima, i to 14 muških i 12 ženskih, primenjivan je kofein u dozi od 3 mg/kg. ...
... Effects of caffeine on the muscle itself are unlikely, because a number of studies were unable to demonstrate a significant effect of the drug on electrically evoked contractile properties (Black, Waddell, & Gonglach, 2015;Del Coso, Estevez, & Mora-Rodriguez, 2008;Eaton et al., 2016;Hespel, Op 't Eijnde, & Van Leemputte, 2002;Kalmar & Cafarelli, 1999, 2004Kalmar, Del Balso, & Cafarelli, 2006;Neyroud et al., 2019;Plaskett & Cafarelli, 2001;Smirmaul, de Moraes, Angius, & Marcora, 2016). However, to date five studies have shown a caffeine-induced effect on contractile properties (Bazzucchi, Felici, Montini, Figura, & Sacchetti, 2011;Bowtell et al., 2018;Cureton et al., 2007;Meyers & Cafarelli, 2005;Tarnopolsky & Cupido, 2000); therefore, this hypothesis should not be dismissed. ...
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New findings: What is the central question of the study? What are the effects of caffeine on neuromuscular function in a non-fatigued state and during fatiguing exercise? What is the main finding and its importance? In a non-fatigued state caffeine decreased the duration of the silent period evoked by TMS. A caffeine-induced reduction of inhibitory mechanisms in the central nervous system prior to exercise was associated with an increased performance. Individuals who benefit from caffeine ingestion may experience lower perception of effort during exercise and an accelerated recovery of M-wave amplitude post fatigue. This study elucidates caffeine's mechanisms of action and demonstrates that inter-individual variability of its effects on neuromuscular function is a fruitful area for further work. Abstract: Purpose Caffeine enhances exercise performance but its mechanisms of action remain unclear. This study investigated its effects on neuromuscular function in a non-fatigued state and during fatiguing exercise. Methods Eighteen males participated in this randomised, double-blind, placebo-controlled crossover trial. Baseline measures included plantarflexion force, drop jump, squat jump, voluntary activation of triceps surae muscle, soleus muscle contractile properties, M-wave, alpha-motoneuron excitability (H-reflex), corticospinal excitability, short-interval intracortical inhibition (SICI), intracortical facilitation (ICF), silent period evoked by transcranial magnetic stimulation (SP) and plasma potassium and caffeine concentration. Immediately after baseline testing, participants ingested caffeine (6 mg kg-1 ) or placebo. After a 1-h rest, baseline measures were repeated, followed by a fatiguing stretch-shortening cycle exercise (sets of 40 bilateral rebound jumps on a sledge apparatus) until task failure. Neuromuscular testing was carried out throughout and after the fatigue protocol. Results Caffeine enhanced drop jump height (4.2%) and decreased SP (12.6%) in a non-fatigued state. A caffeine-related decrease in SP and SICI prior to the fatiguing activity was associated with an increased time to task failure. The participants who benefited from an improved performance on the caffeine day, reported a significantly lower sense of effort during exercise and had an accelerated post-exercise recovery of M-wave amplitude. Conclusion Caffeine modulates inhibitory mechanisms of the central nervous system, recovery of M-wave amplitude and perception of effort. This study lays the groundwork for future examinations of differences of caffeine-induced neuromuscular changes between those who are deemed to benefit from caffeine ingestion and those who are not. This article is protected by copyright. All rights reserved.
... In addition to central nervous system effects of caffeine, changes in motor-unit recruitment (Black, Waddell, & Gonglach, 2015), enhanced calcium handling (Allen & Westerblad, 1995), adenosine receptor antagonism (Davis et al., 2003), and a reduced perception of effort (Bowtell et al., 2018) have been demonstrated. Doherty and Smith (2005) published a meta-analysis that clearly showed that in comparison to the placebo, caffeine could reduce RPE by~6% during exercise. ...
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Mouth rinsing has been proposed as a strategy to minimize performance decrements during Ramadan. We investigated the effect of 4 weeks of Ramadan on kicking performance in 27 Taekwondo athletes performing weekly Taekwondo Anaerobic Intermittent Kick Tests (TAIKT). The effects of a placebo, 6.4% glucose and 6-mg/kg caffeine mouth rinses on TAIKT performance and perceived exertion were investigated before, during weekly training sessions, and after Ramadan in a counterbalanced, crossover design. Ramadan had a significant negative impact on the percentage of successful kicks in Week 1 of Ramadan (pre: 76.7±0.4%, Week 1: 69.9±3.2%). The percentage of successful kicks was significantly greater in the caffeine mouth rinse condition compared to the glucose and placebo conditions during the first 3 weeks of Ramadan (caffeine: 38.3±6.8%, glucose: 36.4±6.9%, placebo: 36.0±6.5%). Caffeine decreased perceived exertion during Ramadan (0.74-1.15 AU, p>0.05). Our results showed that Ramadan had a significant negative effect on repeated high-intensity kicking efforts that should be considered when training and competing. Additionally, there were significant positive effects of a caffeine mouth rinse in a sport-specific test. These data suggest that athletes can consider mouth rinsing as a strategy to enhance performance when undertaking training or competition during a period of privation.
... Table 3. Neuromuscular function before (baseline) and after a 4-km cycling time trial after CAF and PLA ingestion in high-and lowperforming groups. between placebo and caffeine in peripheral fatigue after a 10-min TT in recreationally active participants (Black et al. 2015). Neuromuscular assessment in that study was performed only 20 min after exercise, probably enough time to promote recovery, suggesting that any difference between caffeine and placebo at the end of the exercise might have been missed. ...
Article
The influence of cyclists’ performance levels on caffeine-induced increases in neuromuscular fatigue after a 4-km cycling time trial (TT) was investigated. Nineteen cyclists performed a 4-km cycling TT 1 h after ingesting caffeine (5 mg·kg ⁻¹ ) or placebo (cellulose). Changes from baseline to after exercise in voluntary activation (VA) and potentiated 1 Hz force twitch (Q tw,pot ) were used as markers of central and peripheral fatigue, respectively. Participants were classified as “high performing” (HP, n = 8) or “low performing” (LP, n = 8) in accordance with their performance in a placebo trial. Compared with placebo, caffeine increased the power, anaerobic mechanical power, and anaerobic work, reducing the time to complete the trial in both groups (p < 0.05). There was a group versus supplement and a group versus supplement versus trial interaction for Q tw,pot , in which the postexercise reduction was greater after caffeine compared with placebo in the LP group (Q tw,pot = −34% ± 17% vs. −21% ± 11%, p = 0.02) but not in the HP group (Q tw,pot = −22% ± 8% vs. −23% ± 10%, p = 0.64). There was no effect of caffeine on VA, but there was a group versus trial interaction with lower postexercise values in the LP group than in the HP group (p = 0.03). Caffeine-induced improvement in 4-km cycling TT performance seems to come at the expense of greater locomotor muscle fatigue in LP but not in HP cyclists. Novelty Caffeine improves exercise performance at the expense of a greater end-exercise peripheral fatigue in low-performing athletes. Caffeine-induced improvement in exercise performance does not affect end-exercise peripheral fatigue in high-performing athletes. High-performing athletes seem to have augmented tolerance to central fatigue during a high-intensity time trial.
... These effects occurred in settings where neither glycogen metabolism is the primary determinant of muscular performance, nor is glycogen depletion a cause of fatigue. Improved neuromuscular performance could be attributed to improved strength and motor-unit recruitment rate [16] and/or to increased voluntary activation [2]. Others, however, have not observed any ergogenic effect of caffeine on lower body maximal strength or endurance [14,17,18] or on upper-body maximal muscle strength, power or endurance [3]. ...
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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.
... Only three studies have investigated the effects of caffeine doses <6 mg·kg −1 on strength performance in females. 16,25,26 Goldstein et al 27 and others 4 have specifically proposed that future research should examine the ergogenic effects of lower doses of caffeine. Several studies have reported severe side effects such as "intense emotional responses," tremor, heart palpitations, and tachycardia when supplementing with relatively high doses of caffeine (6-11 mg·kg −1 ). ...
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The effects of 4 mg·kg‐1caffeine ingestion on strength and power were investigated for the first time, in resistance‐trained females during the early follicular phase utilizing a randomized, double‐blind, placebo‐controlled, crossover design. Fifteen females (29.8±4.0 years, 63.8±5.5 kg [mean±SD]) ingested caffeine or placebo 60 minutes before completing a test battery separated by 72 hours. One‐repetition maximum (1RM), repetitions to failure (RTF) at 60% of 1RM, were assessed in the squat and bench press. Maximal voluntary contraction torque (MVC) and rate of force development (RFD) were measured during isometric knee‐extensions, while utilizing interpolated twitch technique to measure voluntary muscle activation. Maximal power and jump height were assessed during countermovement jumps (CMJ). Caffeine metabolites were measured in plasma. Adverse effects were registered after each trial. Caffeine significantly improved squat (4.5±1.9%, effect size [ES]: 0.25) and bench press 1RM (3.3±1.4%, ES: 0.20), and squat (15.9±17.9%, ES: 0.31) and bench press RTF (9.8±13.6%, ES: 0.31), compared to placebo. MVC torque (4.6±7.3%, ES: 0.26), CMJ height (7.6±4.0%, ES: 0.50) and power (3.8±2.2%, ES: 0.24) were also significantly increased with caffeine. There were no differences in RFD or muscle activation. Plasma [caffeine] was significantly increased throughout the protocol and mild side‐effects of caffeine were experienced by only 3 participants. This study demonstrated that 4 mg·kg‐1 caffeine ingestion enhanced maximal strength, power and muscular endurance in resistance‐trained and caffeine‐habituated females during the early follicular phase, with few adverse effects. Female strength and power athletes may consider using this dose pre‐competition and ‐training as an effective ergogenic aid.
... Caffeine (1,3,7-trimethylxanthine) is largely used to improve performance in a broad range of exercise tasks (for review, see Grgic et al. 2019). Notably, the ergogenic effects of caffeine are extended to high-intensity whole-body exercises (for review, see Southward et al. 2018), including time-totask failure tests (Silveira et al. 2018) and time trials (Black et al. 2015). During high-intensity whole-body exercises, the pulmonary system is highly demanded and may be a limiting factor (Amann 2012;Dempsey and Wagner 1999). ...
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Purpose The current study investigated the effect of caffeine on the breathing pattern during a high-intensity whole-body exercise. Methods Using a randomized, crossover, counterbalanced, and double-blind design, twelve healthy men ingested either 5 mg.kg⁻¹ of caffeine or cellulose (placebo) one hour before performing a high-intensity whole-body exercise (i.e., work rate corresponding to 80% of the difference between the gas exchange threshold and maximal oxygen uptake) until the limit of tolerance. Ventilatory and metabolic responses were recorded throughout the trial and at task failure. Results Caffeine ingestion increased time to task failure in relation to the placebo (368.1 ± 49.6 s vs. 328.5 ± 56.6 s, p = 0.005). Caffeine also increased tidal volume and inspiratory time throughout the exercise (p < 0.05). Compared to task failure with placebo, task failure with caffeine intake was marked by higher (p < 0.05) minute ventilation (134.8 ± 16.4 vs. 147.6 ± 18.2 L.min⁻¹), the ventilatory equivalent of oxygen consumption (37.8 ± 4.2 vs. 41.7 ± 5.5 units), and respiratory exchange ratio (1.12 ± 0.10 vs. 1.19 ± 0.11 units). Conclusion In conclusion, ingestion of caffeine alters the breathing pattern by increasing tidal volume and lengthening the inspiratory phase of the respiratory cycle. These findings suggest that caffeine affects the ventilatory system, which may account, in part, for its ergogenic effects during high-intensity whole-body exercises.
... Caffeine was able to improve the muscle power of an athlete and slow the decline in power output by allowing athletes to exert more force while perceiving the same levels of exertion and be more tolerant of discomfort from exercise. Caffeine's adenosine receptor antagonism in the CNS can improve individual tolerance towards low and moderate intensity exercise by inducing hypoalgesia (Black et al. 2015). At higher intensities the caffeine-induced hypoalgesia was ineffective at opposing the excessive nociceptive activation. ...
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Hypothesis:The intake of caffeine can increase physical performance during athletic activity Methods:A search for primary sources was done using PubMed with MeSH terms. The search was limited to randomized controlled trials that were published between 2015 and 2020. After application of inclusion and exclusion criteria, seven articles were selected for this literature review. Results:Of the seven randomized controlled trials selected, six demonstrated caffeine ingestion led to a statistically significant increase in physical performance. One of the randomized controlled trials found no statistically significant relationship between caffeine and run timings. The level set for statistical significance for this literature review was set to p < 0.05.Conclusion: With regards to the results of the selected studies, caffeine was shown to have ergogenic activity and was able to increase physical performance during exercise and sporting competition through multiple mechanisms. Further research should be done with greater sample sizes to determine the effect of rate of metabolism on caffeine activity and to compare caffeine responders and non-responders.
... Caffeine appears to use its effects in various parts of the body, but the most solid evidence suggests that the main target is in the CNS, which is now considered the primary mechanism by which caffeine alters mental and physical performance (20). It is believed that caffeine exerts its effects on the CNS through antagonism of adenosine receptors and leads to increases in neurotransmitter release, motor unit firing rates, and pain suppression (21)(22)(23). Adenosine is involved in numerous physiological processes and plays a very important role as a homeostatic regulator and neuromodulator in the nervous system. The main known effects of adenosine are; It is to reduce the concentration of many neurotransmitters in the CNS, including serotonin, dopamine, acetylcholine, norepinephrine, and glutamate. ...
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Caffeine is an ergogenic supplement that has been attracting attention in the sports community for many years. It has been proven in many studies that coffee consumption has a positive effect on exercise performance. This study was conducted to (I) examine the effects of caffeine on exercise performance and different performance areas, (II) to provide comprehensive recommendations on the use of caffeine in sports and exercise, and (III) to identify existing gaps in the literature and to make key recommendations for future research. This current review article provides an analytical view of studies involving the use of caffeine for the physical, physiological, and cognitive performance of individuals, and discusses factors that may affect the ergogenic effects of caffeine on the different proposed activities. Within the scope of this review, previously published studies were searched using comprehensive keywords related to "caffeine" through "ELSEVIER Science Direct (SciVerse), Taylor & Francis, EBSCOhost-Academic Search Complete, PubMed and SpringerLink, Google Scholar" databases until January 2021. As a result, it has been reported that caffeine increases endurance performance by 2-4% and improves short-term and intense intensity exercise performance in highly trained individuals. The improving effect of caffeine on cognitive performance supports the use of caffeine as an ergogenic supplement. Caffeine has been shown to increase sympathetic nervous system activity and release fatty acids from adipose and / or intramuscular stores. This mechanism, which occurs indirectly through increased adrenaline levels, has the potential to increase the availability of fatty acids for oxidation and the resting metabolic rate. At the same time, it has been observed that caffeine does not cause dehydration and is a reliable ergogenic supplement in this respect. The ergogenic effect of caffeine should be clarified by focusing on questions such as at what time of the day caffeine consumption affects caffeine ergogenicity, the effect of age on caffeine ergogenicity, caffeine intake according to athlete's training level, and the importance of genotype in terms of caffeine consumption.
... Strength loss has been suggested to be the one of the most valid and reliable indirect Exercise-Induced Hypoalgesia and Muscle Damage methods to assess EIMD [36]. In order to do this, MVC of the right knee extensors was determined prior to the exercise protocol on test day 3 and was reassessed prior to exercise on test day 5. MVC was determined as described previously [37] using a modified knee extension/leg curl machine (model GLCE-365; Body Solid, Forest Park, IL) with a force transducer (model SBO-750; Transducer Technologies Temecula, CA) fixed to the lever arm parallel to the line of pull allowing for assessment of isometric torque with the knee held at an angle of 60 below horizontal when the participant's right ankle was secured to the lever arm. The transducer was connected to a data acquisition system (model AHP 214; iWorx Systems Incorporated, Dover, NH) and torque data were sampled at 5 kHz and analyzed using a custom written program (Waddell, 2012) using MatLab software (Mathworks, Natick, MA). ...
Article
Objective: Exercise-induced muscle damage (EIMD) and the associated delayed-onset muscle soreness (DOMS) are a model for studying clinical pain; thus, our purpose was to examine the effects of isometric exercise on pressure pain threshold (PPT) in the presence and absence of DOMS. Methods: Data were collected on 23 males (22.8 ± 2.5 yrs). PPT was assessed in the right (exercising) and left (resting) quadriceps prior to, every 30 seconds during, and 2 and 15 minutes following an isometric contraction of the right quadriceps at 25% of maximal voluntary contraction (MVC) held until fatigue. Unilateral eccentric exercise was performed to induce DOMS in the exercising leg and testing was repeated 48 hours later. Results: DOMS increased (P < 0.001) and resting PPT decreased (P = 0.03) following EIMD. PPTs were elevated during exercise in the exercising (P ≤ 0.002) and resting (P ≤ 0.002) quadriceps but did not differ between the control and EIMD conditions in either leg (P ≤ 0.61). PPT remained elevated 2 and 15 minutes postexercise (P < 0.05) in the exercised quadriceps in both conditions, but values returned to baseline at 2 (P = 0.91) and 15 minutes (P = 0.28) postisometric exercise in the resting quadriceps. Conclusions: Unlike clinical pain, DOMS had no effect on the PPT response during exercise in either the exercising or resting quadriceps. The fact that exercise altered PPT in both quadriceps during exercise suggests a generalized pain inhibitory mechanism was activated. However, the restriction of postexercise effects to the exercised limb suggests localized inhibitory mechanism(s) were activated after exercise.
... Due to factors such as muscle size, muscle activation, and motor unit recruitment, it has been previously suggested that caffeine's ergogenic effect on muscular strength may be greater in the lower-body vs. upper-body [36][37][38][39][40]. However, we found an ergogenic effect of caffeine on upper-body 1RM strength, whereas no significant difference between caffeine and placebo was observed for the lower-body 1RM test. ...
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This meta-analysis aimed to explore the effects of caffeine ingestion on muscular endurance and muscular strength in women. Five databases were searched to find relevant studies. A random-effects meta-analysis of standardized mean differences (SMD) was performed for data analysis. Subgroup meta-analyses explored the effects of caffeine on upper-body and lower-body muscular endurance and muscular strength. Eight crossover placebo-controlled studies were included in the review. In the main meta-analysis that considered data from all included studies, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.25; p = 0.027) and muscular strength (SMD = 0.18; p < 0.001). In a subgroup analysis that considered only upper-body exercises, there was a significant ergogenic effect of caffeine on muscular endurance (SMD = 0.20; p = 0.007) and muscular strength (SMD = 0.17; p < 0.001). In a subgroup analysis that considered only lower-body exercises, there was no significant difference between caffeine and placebo for muscular endurance (SMD = 0.43; p = 0.092) or muscular strength (SMD = 0.16; p = 0.109). The main finding of this meta-analysis is that caffeine ingestion has a significant ergogenic effect on muscular endurance and muscular strength in women. The effects reported in this analysis are similar to those previously observed in men and suggest that women may use caffeine supplementation as an ergogenic aid for muscular performance. Future research is needed to explore the effects of caffeine on lower-body muscular endurance and muscular strength in this population.
... As traditionally accepted, there is, however, no doubt that caffeine also acts directly on the CNS to ultimately influence efferent pathways [77][78][79][80][81]. A study quantifying the in vivo occupancy of the human cerebral A 1 adenosine receptors by caffeine, using 18F-CPFPX and PET techniques, showed that a plasma caffeine concentration of~70 µM blocked 50% of the cerebral A 1 receptors [82]. ...
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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.
... Secondarily, we assessed peak muscle strength at three separate angular velocities prior to the time trials. Caffeine has been shown to increase peak strength [6,7,12,13,27] and there is some evidence that strength may contribute to the ergogenic properties of caffeine for cycling performance [28]. Therefore, we measured peak strength in an attempt to provide some physiological insight into the time trial outcomes. ...
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This project was designed to assess the effects of time of day and training status on the benefits of caffeine supplementation for cycling performance. Twenty male subjects (Age, 25 years; Peak oxygen consumption, 57 mL·kg⁻¹·min⁻¹) were divided into tertiles based on training levels, with top and bottom tertiles designated as ‘trained’ (n = 7) and ‘untrained’ (n = 7). Subjects completed two familiarization trials and four experimental trials consisting of a computer-simulated 3-km cycling time trial (TT). The trials were performed in randomized order for each combination of time of day (morning and evening) and treatment (6mg/kg of caffeine or placebo). Magnitude-based inferences were used to evaluate all treatment effects. For all subjects, caffeine enhanced TT performance in the morning (2.3% ± 1.7%, ‘very likely’) and evening (1.4% ± 1.1%, ‘likely’). Both untrained and trained subjects improved performance with caffeine supplementation in the morning (5.5% ± 4.3%, ‘likely’; 1.0% ± 1.7%, ‘likely’, respectively), but only untrained subjects rode faster in the evening (2.9% ± 2.6%, ‘likely’). Altogether, our observations indicate that trained athletes are more likely to derive ergogenic effects from caffeine in the morning than the evening. Further, untrained individuals appear to receive larger gains from caffeine in the evening than their trained counterparts.
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Purpose: to determine characteristics of correlation of girl students’ and school girls’ subjective and physiological parameters of reaction to physical load. Material: in the research sportswomen of two age groups participated: adult qualified girl students-basketball players (n=40, age 20-22years) and junior basketball players (n=35, age12-13years). Registration of heart beats rate was fulfilled with «Polar RS300X». Simultaneously, we registered subjective feeling of loaf value (heaviness) by Borg’s method. Results: it was found that in conditions of natural training and competition functioning, with equal heart beats rate values school girls feel tension of fulfilled work subjectively easier. It can be explained by higher maximal values of school girls’ heat beats rate, comparing with girls students. Equal values of heart beats rate reflect different changes in girl students’ and school girls’ organisms. That is why they can not serve reliably informative indicator of load. Conclusions: we determined characteristics of perceived tension under load of game character. It can be connected with emotional tension, which is characteristic for basketball.
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Despite the growing quantity of literature exploring the effect of caffeine on muscular strength, there is a dearth of data that directly explores differences in erogenicity between upper and lower body musculature and the dose response effect. The present study sought to investigate the effects of low and moderate dose caffeine on the maximal voluntary strength of the elbow flexors and knee extensors. Ten non-specifically strength trained, recreationally active participants (21 ± 0.3 yrs) completed the study. Using a randomised, counterbalanced and double blind approach, isokinetic concentric and eccentric strength was measured at 60 and 180 deg/s following administration of a placebo, 3 mg・kg-1 body mass caffeine and 6 mg・kg-1 body mass caffeine. There was no effect of caffeine on the maximal voluntary concentric and eccentric strength of the elbow flexors, or the eccentric strength of the knee extensors. Both 3 and 6 mg・kg-1 body mass caffeine caused a significant increase in peak concentric force of the knee extensors at 180 deg/s. No difference was apparent between the two concentrations. Only 6 mg・kg-1 body mass caused an increase in peak concentric force during repeated contractions. The results infer that the effective caffeine concentration to evoke improved muscle performance may be related to muscle mass and contraction type. The present work indicates that relatively low dose caffeine treatment may be effective for improving lower body muscular strength, but may have little benefit for the strength of major muscular groups of the upper body.
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Carbohydrate (CHO) rinsing has been shown to attenuate the decline of maximal voluntary contractions (MVC) following fatiguing exercise-perhaps via a central mechanism. This study sought to determine the effect of a CHO rinse on MVC, voluntary activation, and contractile properties following fatiguing exercise. Thirteen adults participated in a double-blind, cross-over study. MVC of the dominant knee extensors was assessed and voluntary activation (%VA) was determined using twitch-interpolation. Participants then held 50% of MVC until volitional fatigue followed by a 20s rinse with a solution of 8% maltodextrin (CHO) or placebo (PLA). MVC and %VA were reassessed immediately and 5-minutes following exercise. MVC did not differ between the CHO and PLA conditions initially (230±90 vs. 232±90 Nm; p=0.69). MVC declined following exercise (p≤0.01), but no differences were found between the CHO and PLA conditions (p≥0.59). %VA did not differ between conditions (91.9±2.9% vs. 91.5±3.8%; p≥0.11) nor did it change following exercise(p=0.57). Twitch torque (TT), rate of torque development, and rate of torque relaxation were reduced following exercise (p<0.05), but were unaffected by CHO rinsing (p>0.05). Unlike a previous study, a CHO rinse did not preserve MVC following fatiguing exercise. This was likely due to a lack of central fatigue induced by the exercise protocol (as %VA was unaffected) as the CHO rinse is thought to work via a central mechanism.
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Caffeine (CAF) has been extensively studied for its ergogenic and analgesic effects during exercise. However, the majority of these studies have been conducted in male populations. This study investigated the effects of acute CAF chewing gum on self-selected exercise intensity during a rating of perceived exertion (RPE) production trial in active females (n = 16, 21.0 ± 2.8 y). Data were also analyzed based on habitual CAF consumption level. Participants completed a V̇O2peak trial, followed by a familiarization and two randomized, triple-blinded experimental RPE production trials on an arm ergometer [clamped resistance, blinded to self-selected cadence (CAD)] with either CAF gum (300 mg; 4.8 ± 0.7 mg/kg-1 body mass) or placebo (PLA), at a prescribed RPE of 4 and 7 (10 min each). Self-selected CAD did not statistically differ (p > 0.05) between CAF or PLA for an RPE4 (37.7 ± 1.6 vs. 37.6 ± 1.6 rev·min-1) or RPE7 (42.9 ± 1.6 vs. 41.2 ± 1.7 rev·min-1), respectively. There were no statistical differences between treatment groups for any other variables, except restlessness rating which was significantly higher (3.5 vs. 2.2; p = 0.03, d = 0.64) for the CAF group compared to PLA. Secondary analysis revealed no statistical differences for any variables between habitual consumers of low (23 ± 20 mg/day) or mod/high (195 ± 93 mg/day) CAF. Our data support previous studies examining CAF in women across different testing modalities and suggest that regardless of habitual CAF consumption, females might require higher doses of CAF to replicate subjective and physiological responses commonly observed using similar RPE production protocols in male participants. These findings support the need for additional investigations into female physiological and perceptual responses following CAF ingestion.
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Objective The objective of this scoping review was to examine the research question: In the adults with or without cardiometabolic risk, what is the availability of literature examining interventions to improve or maintain nutrition and physical activity related outcomes? Sub-topics included 1) behavior counseling or coaching from a dietitian/nutritionist or exercise practitioner; 2) mobile applications to improve nutrition and physical activity; and 3) nutritional ergogenic aids. Design This study is a scoping review. A literature search of the Medline Complete; CINAHL Complete; Cochrane Database of Systematic Reviews and other databases was conducted to identify articles published in the English language from January 2005 until May 2020. Data was synthesized using bubble charts and heat maps. Setting Out-patient, community and workplace. Participants Adults with or without cardiometabolic risk factors living in economically developed countries. Results Searches resulted in 19,474 unique articles and 170 articles were included in this scoping review, including one guideline, 30 systematic reviews, 134 RCTs and five non-randomized trials. Mobile applications (n=37) as well as ergogenic aids (n=87) have been addressed in several recent studies, including systematic reviews. While primary research has examined the effect of individual-level nutrition and physical activity counseling or coaching from a dietitian/nutritionist and/or exercise practitioner (n=48), interventions provided by these practitioners have not been recently synthesized in systematic reviews. Conclusion Systematic reviews of behavior counseling or coaching provided by a dietitian/nutritionist and/or exercise practitioner are needed and can inform practice for practitioners working with individuals who are healthy or have cardiometabolic risk.
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Caffeine is one of the most famous and widely used ergogenic drugs, especially by athletes to improve sports performance. Caffeine is known to enhance muscle contraction by facilitating Ca ²⁺ release from the sarcoplasmic reticulum. While the effect of caffeine on the cross-bridge dynamics has also investigated, the results is controversial. Therefore, the purpose of this study was to examine the influence of caffeine on cross-bridge dynamics using skinned fiber preparations from rabbit soleus (N = 19 in total). We performed isometric contractions at an average sarcomere length of 2.4 μm; thereafter, skinned fibers were shortened by 20% of the fiber length at a velocity of 0.1 mm/s (slow shortening) or 0.5 mm/s (fast shortening). The contractions were performed under both normal and caffeine-containing activating solution conditions to compare the isometric, slow concentric, and fast concentric forces between conditions. The isometric force did not differ between normal and caffeine-containing activating solution conditions. Similarly, the concentric forces obtained during the slow and fast shortening trials did not differ between conditions. We also measured the stiffness and the rate of force redevelopment (kTR) during the isometric contraction phase and found that these values were not different between normal and caffeine conditions. Based on these results, we conclude that the influence of caffeine on cross-bridge dynamics is negligible, and the ergogenic effect of caffeine, from the view of muscle contractility, is by facilitating Ca ²⁺ release, as suggested in previous studies, and not by modulating the cross-bridge dynamics.
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Caffeine is a common substance in the diets of most athletes and it is now appearing in many new products, including energy drinks, sport gels, alcoholic beverages and diet aids. It can be a powerful ergogenic aid at levels that are considerably lower than the acceptable limit of the International Olympic Committee and could be beneficial in training and in competition. Caffeine does not improve maximal oxygen capacity directly, but could permit the athlete to train at a greater power output and/or to train longer. It has also ben shown to increase speed and/or power output in simulated race conditions. These effects have been found in activities that last as little as 60 seconds or as long as 2 hours. There is less information about the effects of caffeine on strength; however, recent work suggests no effect on maximal ability, but enhanced endurance or resistance to fatigue. There is no evidence that caffeine ingestion before exercise leads to dehydration, ion imbalance, or any other adverse effects. The ingestion of caffeine as coffee appears to be ineffective compared to doping with pure caffeine. Related compounds such as theophylline are also potent ergogenic aids. Caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents. It appears that male and female athletes have similar caffeine pharmacokinetics, i.e., for a given dose of caffeine, the time course and absolute plasma concentrations of caffeine and its metabolites are the same. In addition, exercise or dehydration does not affect caffeine pharmacokinetics. The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important. The mechanism(s) by which caffeine elicits its ergogenic effects are unknown, but the popular theory that it enhances fat oxidation and spares muscle glycogen has very little support and is an incomplete explanation at best. Caffeine may work, in part, by creating a more favourable intracellular ionic environment in active muscle. This could facilitate force production by each motor unit.
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The effect caffeine elicits on endurance performance is well founded. However, comparatively less research has been conducted on the ergogenic potential of anaerobic performance. Some studies showing no effect of caffeine on performance used untrained subjects and designs often not conducive to observing an ergogenic effect. Recent studies incorporating trained subjects and paradigms specific to intermittent sports activity support the notion that caffeine is ergogenic to an extent with anaerobic exercise. Caffeine seems highly ergogenic for speed endurance exercise ranging in duration from 60 to 180 seconds. However, other traditional models examining power output (i.e. 30-second Wingate test) have shown minimal effect of caffeine on performance. Conversely, studies employing sport-specific methodologies (i.e. hockey, rugby, soccer) with shorter duration (i.e. 4–6 seconds) show caffeine to be ergogenic during high-intensity intermittent exercise. Recent studies show caffeine affects isometric maximal force and offers introductory evidence for enhanced muscle endurance for lower body musculature. However, isokinetic peak torque, one-repetition maximum and muscular endurance for upper body musculature are less clear. Since relatively few studies exist with resistance training, a definite conclusion cannot be reached on the extent caffeine affects performance. It was previously thought that caffeine mechanisms were associated with adrenaline (epinephrine)-induced enhanced free-fatty acid oxidation and consequent glycogen sparing, which is the leading hypothesis for the ergogenic effect. It would seem unlikely that the proposed theory would result in improved anaerobic performance, since exercise is dominated by oxygen-independent metabolic pathways. Other mechanisms for caffeine have been suggested, such as enhanced calcium mobilization and phosphodiesterase inhibition. However, a normal physiological dose of caffeine in vivo does not indicate this mechanism plays a large role. Additionally, enhanced Na+/K+ pump activity has been proposed to potentially enhance excitation contraction coupling with caffeine. A more favourable hypothesis seems to be that caffeine stimulates the CNS. Caffeine acts antagonistically on adenosine receptors, thereby inhibiting the negative effects adenosine induces on neurotransmission, arousal and pain perception. The hypoalgesic effects of caffeine have resulted in dampened pain perception and blunted perceived exertion during exercise. This could potentially have favourable effects on negating decreased firing rates of motor units and possibly produce a more sustainable and forceful muscle contraction. The exact mechanisms behind caffeine’s action remain to be elucidated.
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Caffeine has been shown to reduce leg-muscle pain during submaximal cycle ergometry, as well as in response to eccentric exercise. However, less is known about its analgesic properties during non-steady-state, high-intensity exercise. The primary aim of this study was to examine the effect of 2 doses of caffeine on leg pain and rating of perceived exertion (RPE) during repeated bouts of high-intensity exercise. Fifteen active men (age 26.4 ± 3.9 yr) completed 2 bouts of 40 repetitions of "all-out" knee extension and flexion of the dominant leg at a contraction velocity equal to 180°/s. Before each trial, subjects abstained from caffeine intake and intense exercise for 48 hr. Over 3 days separated by 48 hr, subjects ingested 1 of 3 treatments (5 mg/kg or 2 mg/kg of anhydrous caffeine or placebo) in a randomized, single-blind, counterbalanced, crossover design. Leg-muscle pain and RPE were assessed during and after exercise using established categorical scales. Across all treatments, pain perception was significantly increased (p < .05) during exercise, as well as from Bout 1 to 2, yet there was no effect (p > .05) of caffeine on pain perception or RPE. Various measures of muscle function were improved (p < .05) with a 5-mg/kg caffeine dose vs. the other treatments. In the 5-mg/kg trial, it is plausible that subjects were able to perform better with similar levels of pain perception and exertion.
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Our objective was to perform a systematic review and meta-analysis of the research literature assessing the effect of caffeine ingestion on maximal voluntary contraction (MVC) strength and muscular endurance. Thirty-four relevant studies between 1939 and 2008 were included in the meta-analyses of caffeine's effects on MVC strength (n = 27 studies) and muscular endurance (n = 23 studies). Effect sizes (ES) were calculated as the standardized mean difference and meta-analyses were completed using a random-effects model. Overall, caffeine ingestion was found to result in a small beneficial effect on MVC strength (overall ES = 0.19, P = 0.0003). However, caffeine appears to improve MVC strength primarily in the knee extensors (i.e., by approximately 7%, ES = 0.37) and not in other muscle groups such as the forearm or the knee flexors. In an attempt to offer a physiological mechanism behind caffeine's ability to improve MVC strength, a meta-analysis was run on ES from nine studies that measured percent muscle activation during MVC in trials comparing caffeine versus placebo; the overall ES (0.67) was highly significant (P = 0.00008) and of moderate to large size, thus implicating an effect of caffeine on the CNS. Caffeine ingestion was also found to exert a small beneficial effect on muscular endurance (overall ES = 0.28, P = 0.00005). However, it appears caffeine improves muscular endurance only when it is assessed using open (i.e., by approximately 18%, ES = 0.37) and not fixed end point tests. Overall, caffeine ingestion improves MVC strength and muscular endurance. The effect on strength appears exclusively in the knee extensors, and the effect on muscular endurance appears only detectable with open end point tests.
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The effect caffeine elicits on endurance performance is well founded. However, comparatively less research has been conducted on the ergogenic potential of anaerobic performance. Some studies showing no effect of caffeine on performance used untrained subjects and designs often not conducive to observing an ergogenic effect. Recent studies incorporating trained subjects and paradigms specific to intermittent sports activity support the notion that caffeine is ergogenic to an extent with anaerobic exercise. Caffeine seems highly ergogenic for speed endurance exercise ranging in duration from 60 to 180 seconds. However, other traditional models examining power output (i.e. 30-second Wingate test) have shown minimal effect of caffeine on performance. Conversely, studies employing sport-specific methodologies (i.e. hockey, rugby, soccer) with shorter duration (i.e. 4-6 seconds) show caffeine to be ergogenic during high-intensity intermittent exercise. Recent studies show caffeine affects isometric maximal force and offers introductory evidence for enhanced muscle endurance for lower body musculature. However, isokinetic peak torque, one-repetition maximum and muscular endurance for upper body musculature are less clear. Since relatively few studies exist with resistance training, a definite conclusion cannot be reached on the extent caffeine affects performance. It was previously thought that caffeine mechanisms were associated with adrenaline (epinephrine)-induced enhanced free-fatty acid oxidation and consequent glycogen sparing, which is the leading hypothesis for the ergogenic effect. It would seem unlikely that the proposed theory would result in improved anaerobic performance, since exercise is dominated by oxygen-independent metabolic pathways. Other mechanisms for caffeine have been suggested, such as enhanced calcium mobilization and phosphodiesterase inhibition. However, a normal physiological dose of caffeine in vivo does not indicate this mechanism plays a large role. Additionally, enhanced Na+/K+ pump activity has been proposed to potentially enhance excitation contraction coupling with caffeine. A more favourable hypothesis seems to be that caffeine stimulates the CNS. Caffeine acts antagonistically on adenosine receptors, thereby inhibiting the negative effects adenosine induces on neurotransmission, arousal and pain perception. The hypoalgesic effects of caffeine have resulted in dampened pain perception and blunted perceived exertion during exercise. This could potentially have favourable effects on negating decreased firing rates of motor units and possibly produce a more sustainable and forceful muscle contraction. The exact mechanisms behind caffeine's action remain to be elucidated.
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This experiment examined the effect of a moderate dose of caffeine on quadriceps muscle pain during a bout of high-intensity cycling in low- versus high-caffeine-consuming males. College-age men who were low (< or =100 mg/day; n = 12) or high (> or =400 mg/day; n = 13) habitual caffeine consumers ingested caffeine (5 mg/kg body weight) or a placebo in a counterbalanced order and 1 hr later completed 30 min of cycle ergometry at 75-77% of peak oxygen consumption. Perceptions of quadriceps muscle pain, as well as oxygen consumption, heart rate, and work rate, were recorded during both bouts of exercise. Caffeine ingestion resulted in a statistically significant and moderate reduction in quadriceps muscle-pain-intensity ratings during the 30-min bout of high-intensity cycle ergometry compared with placebo ingestion in both low (d = -0.42) and high (d = -0.55) caffeine consumers. The results suggest that caffeine ingestion is associated with a moderate hypoalgesic effect during high-intensity cycling in college-age men who are low or high habitual caffeine consumers, but future work should consider better defining and differentiating pain and effort when examining the effects of caffeine during acute exercise.
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Athletes are among the groups of people who are interested in the effects of caffeine on endurance and exercise capacity. Although many studies have investigated the effect of caffeine ingestion on exercise, not all are suited to draw conclusions regarding caffeine and sports performance. Characteristics of studies that can better explore the issues of athletes include the use of well-trained subjects, conditions that reflect actual practices in sport, and exercise protocols that simulate real-life events. There is a scarcity of field-based studies and investigations involving elite performers. Researchers are encouraged to use statistical analyses that consider the magnitude of changes, and to establish whether these are meaningful to the outcome of sport. The available literature that follows such guidelines suggests that performance benefits can be seen with moderate amounts (~3 mg.kg-1 body mass) of caffeine. Furthermore, these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events (e.g., team and racquet sports), and sports involving sustained high-intensity activity lasting from 1-60 min (e.g., swimming, rowing, and middle and distance running races). The direct effects on single events involving strength and power, such as lifts, throws, and sprints, are unclear. Further studies are needed to better elucidate the range of protocols (timing and amount of doses) that produce benefits and the range of sports to which these may apply. Individual responses, the politics of sport, and the effects of caffeine on other goals, such as sleep, hydration, and refuelling, also need to be considered.
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Endurance athletes often ingest caffeine because of its reported ergogenic properties. Although there are a vast number of studies quantifying caffeine's effects, many research studies measure endurance performance using a time-to-exhaustion test (subjects exercise at a fixed intensity to volitional exhaustion). Time-to-exhaustion as a performance measure is not ideal because of the high degree of measurement variability between and within subjects. Also, we are unaware of any endurance sports in which individuals win by going a longer distance or for a longer amount of time than their competitors. Measuring performance with a time-trial test (set distance or time with best effort) has high reproducibility and is more applicable to sport. Therefore, the purpose of this review was to critically and objectively evaluate studies that have examined the effect of caffeine on time-trial endurance (>5 minutes) performance. A literature search revealed 21 studies with a total of 33 identifiable caffeine treatments that measured endurance performance with a time-trial component. Each study was objectively analyzed with the Physiotherapy Evidence Database (PEDro) scale. The mean PEDro rating was 9.3 out of 10, indicating a high quality of research in this topic area. The mean improvement in performance with caffeine ingestion was 3.2 +/- 4.3%; however, this improvement was highly variable between studies (-0.3 to 17.3%). The high degree of variability may be dependent on a number of factors including ingestion timing, ingestion mode/vehicle, and subject habituation. Further research should seek to identify individual factors that mediate the large range of improvements observed with caffeine ingestion. In conclusion, caffeine ingestion can be an effective ergogenic aid for endurance athletes when taken before and/or during exercise in moderate quantities (3-6 mg.kg body mass). Abstaining from caffeine at least 7 days before use will give the greatest chance of optimizing the ergogenic effect.
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This study compared independent effects of caffeine and aspirin on muscular endurance (repetitions), heart rate (HR), perceived exertion (RPE), and perceived pain index (PPI) during light resistance training bouts performed to volitional failure. It was hypothesized that the hypoalgesic properties of these ergogenic aids would decrease pain perception and potentially result in enhanced performance. College-aged men (n = 15) participated in a within-subjects, double-blind study with three independent, counterbalanced sessions wherein aspirin (10 mg x kg(-1)), caffeine (6 mg x kg(-1)), or matched placebo were ingested 1 hour before exercise, and RPE, HR, PPI, and repetitions (per set and total per exercise) were recorded at 100% of individual, predetermined, 12-repetition maximum for leg extensions (LE) and seated arm curls (AC). Repeated-measures analyses of variance were used for between-trial comparisons. Caffeine resulted in significantly greater (p < 0.05) HR (LE and AC), total repetitions (LE), and repetitions in set 1 (LE and AC) compared with aspirin and placebo. Aspirin resulted in significantly higher PPI in set 1 (LE). In LE, 47% of participants' performance exceeded the predetermined effect size (>or= 5 repetitions) for total repetitions, with 53% exceeding the effect size (>or= 2 repetitions) for repetitions in set 1 with caffeine (vs. placebo). In AC, 53% (total repetitions) and 47% (set 1 repetitions) of participants exceeded effect sizes with caffeine (vs. placebo), with only 13% experiencing decrements in performance (total repetitions). Aspirin also produced a higher PPI and RPE overall and in set 1 (vs. placebo). This study demonstrates that caffeine significantly enhanced resistance training performance in LE and AC, whereas aspirin did not. Athletes may improve their resistance training performance by acute ingestion of caffeine. As with most ergogenic aids, our analyses indicate that individual responses vary greatly.
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Nine trained cyclists were studied to determine the effects of caffeine (CAF), and glucose polymer (GP) feedings on work production (kpm) during two hr of isokinetic cycling exercise (80 rpm). Ingestion of 250 mg of CAF 60 min prior to the ride was followed by ingestion of an additional 250 mg fed at 15 min intervals over the first 90 min of the exercise. This treatment significantly increased work production by 7.4% and Vo2 by 7.3% as compared to control (C) while the subjects' perception of exertion remained unchanged. Ingestion of approximately 90 g of GP during the first 90 min (12.8 g/15 min) of the exercise had no effect on total work production or Vo2. It was, however, effective in reducing the rate of fatigue over the last 30 min of cycling. Although GP maintained blood glucose and insulin levels (P less than or equal to 0.05) above those of the C and CAF trials, total CHO utilization did not differ between treatments. During the last 70 min of the CAF trial, however, fat oxidation was elevated 31% and appeared to provide the substrate needed for the increased work production during this period of exercise. These data, therefore, demonstrate an enhanced rate of lipid catabolism and work production following the ingestion of caffeine.
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Using a motorized treadmill the study investigated the effects of the ingestion of 3 g of caffeinated coffee on: the time taken to run 1500 m; the selected speed with which athletes completed a 1-min 'finishing burst' at the end of a high-intensity run; and respiratory factors, perceived exertion and blood lactate levels during a high intensity 1500-m run. In all testing protocols decaffeinated coffee (3 g) was used as a placebo and a double-blind experimental design was used throughout. The participants in the study were middle distance athletes of club, county and national standard. The results showed that ingestion of caffeinated coffee: decreases the time taken to run 1500 m (P less than 0.005); increases the speed of the 'finishing burst' (P less than 0.005); and increases VO2 during the high-intensity 1500-m run (P less than 0.025). The study concluded that under these laboratory conditions, the ingestion of caffeinated coffee could enhance the performance of sustained high-intensity exercise.
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This study examined the exercise responses of well-trained endurance athletes to various doses of caffeine to evaluate the impact of the drug on exercise metabolism and endurance capacity. Subjects (n = 8) withdrew from all dietary sources of caffeine for 48 h before each of four tests. One hour before exercise they ingested capsules of placebo or caffeine (3, 6, or 9 mg/kg), rested quietly, and then ran at 85% of maximal O2 consumption to voluntary exhaustion. Blood samples for methylxanthine, catecholamine, glucose, lactate, free fatty acid, and glycerol analyses were taken every 15 min. Plasma caffeine concentration increased with each dose (P < 0.05). Its major metabolite, paraxanthine, did not increase between the 6 and 9 mg/kg doses, suggesting that hepatic caffeine metabolism was saturated. Endurance was enhanced with both 3 and 6 mg/kg of caffeine (increases of 22 +/- 9 and 22 +/- 7%, respectively; both P < 0.05) over the placebo time of 49.4 +/- 4.2 min, whereas there was no significant effect with 9 mg/kg of caffeine. In contrast, plasma epinephrine was not increased with 3 mg/kg of caffeine but was greater with the higher doses (P < 0.05). Similarly only the highest dose of caffeine resulted in increases in glycerol and free fatty acids (P < 0.05). Thus the highest dose had the greatest effect on epinephrine and blood-borne metabolites yet had the least effect on performance. The lowest dose had little or no effect on epinephrine and metabolites but did have an ergogenic effect. These results are not compatible with the traditional theory that caffeine mediates its ergogenic effect via enhanced catecholamines.
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Normally, caffeine ingestion results in a wide spectrum of neural and hormonal responses, making it difficult to evaluate which are critical regulatory factors. We examined the responses to caffeine (6 mg/kg) ingestion in a group of spinal cord-injured subjects [7 tetraplegic (C5-7) and 2 paraplegic (T4) subjects] at rest and during functional electrical stimulation of their paralyzed limbs to the point of fatigue. Plasma insulin did not change, caffeine had no effect on plasma epinephrine, and there was a slight increase (P < 0. 05) in norepinephrine after 15 min of exercise. Nevertheless, serum free fatty acids were increased (P < 0.05) after caffeine ingestion after 60 min of rest and throughout the first 15 min of exercise, but the respiratory exchange ratio was not affected. The exercise time was increased (P < 0.05) by 6% or 1.26 +/- 0.57 min. These data suggest that caffeine had direct effects on both the adipose tissue and the active muscle. It is proposed that the ergogenic action of caffeine is occurring, at least in part, by a direct action of the drug on muscle.
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The mechanism of action underlying the ergogenic effect of caffeine is still unclear. Caffeine increases the force of muscular contraction during low-frequency stimulation by potentiating calcium release from the sarcoplasmic reticulum. Studies have also suggested an enhancement of lipid oxidation and glycogen sparing as potential mechanisms. Given that several studies have found an ergogenic effect of caffeine with no apparent metabolic effects, it is likely that a direct effect upon muscle is important. Twelve healthy male subjects were classified as habitual (n = 6) or nonhabitual (n = 6) caffeine consumers based on a 4-day diet record analysis, with a mean caffeine consumption of 771 and 14 mg/day for each group, respectively. Subjects were randomly allocated to receive caffeine (6 mg/kg) and placebo (citrate) in a double-blind, cross-over fashion approximately 100 min before a 2-min tetanic stimulation of the common peroneal nerve in a custom-made dynamometer (2 trials each of 20 and 40 Hz). Tetanic torque was measured every 30 s during and at 1, 5, and 15 min after the stimulation protocol. Maximal voluntary contraction strength and peak twitch torque were measured before and after the stimulation protocol. Caffeine potentiated the force of contraction during the final minute of the 20-Hz stimulation (P<0.05) with no effect of habituation. There was no effect of caffeine on 40-Hz stimulation strength nor was there an effect on maximal voluntary contraction or peak twitch torque. These data support the hypothesis that some of the ergogenic effect of caffeine in endurance exercise performance occurs directly at the skeletal muscle level.
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Caffeine is a common substance in the diets of most athletes and it is now appearing in many new products, including energy drinks, sport gels, alcoholic beverages and diet aids. It can be a powerful ergogenic aid at levels that are considerably lower than the acceptable limit of the International Olympic Committee and could be beneficial in training and in competition. Caffeine does not improve maximal oxygen capacity directly, but could permit the athlete to train at a greater power output and/or to train longer. It has also been shown to increase speed and/or power output in simulated race conditions. These effects have been found in activities that last as little as 60 seconds or as long as 2 hours. There is less information about the effects of caffeine on strength; however, recent work suggests no effect on maximal ability, but enhanced endurance or resistance to fatigue. There is no evidence that caffeine ingestion before exercise leads to dehydration, ion imbalance, or any other adverse effects. The ingestion of caffeine as coffee appears to be ineffective compared to doping with pure caffeine. Related compounds such as theophylline are also potent ergogenic aids. Caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents. It appears that male and female athletes have similar caffeine pharmacokinetics, i.e., for a given dose of caffeine, the time course and absolute plasma concentrations of caffeine and its metabolites are the same. In addition, exercise or dehydration does not affect caffeine pharmacokinetics. The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important. The mechanism(s) by which caffeine elicits its ergogenic effects are unknown, but the popular theory that it enhances fat oxidation and spares muscle glycogen has very little support and is an incomplete explanation at best. Caffeine may work, in part, by creating a more favourable intracellular ionic environment in active muscle. This could facilitate force production by each motor unit.
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Caffeine, an adenosine A1, A2A, and A2B receptor antagonist, is frequently used as an adjuvant analgesic in combination with nonsteroidal anti-inflammatory drugs or opioids. In this study, we have examined the effects of novel specific adenosine receptor antagonists in an acute animal model of nociception. Several A2B-selective compounds showed antinociceptive effects in the hot-plate test. In contrast, A1- and A2A-selective compounds did not alter pain thresholds, and an A3 adenosine receptor antagonist produced thermal hyperalgesia. Evaluation of psychostimulant effects of these compounds in the open field showed only small effects of some antagonists at high doses. Coadministration of low, subeffective doses of A2B-selective antagonists with a low dose of morphine enhanced the efficacy of morphine. Our results indicate that analgesic effects of caffeine are mediated, at least in part, by A2B adenosine receptors.
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The twitch interpolation technique is commonly employed to assess the completeness of skeletal muscle activation during voluntary contractions. Early applications of twitch interpolation suggested that healthy human subjects could fully activate most of the skeletal muscles to which the technique had been applied. More recently, however, highly sensitive twitch interpolation has revealed that even healthy adults routinely fail to fully activate a number of skeletal muscles despite apparently maximal effort. Unfortunately, some disagreement exists as to how the results of twitch interpolation should be employed to quantify voluntary activation. The negative linear relationship between evoked twitch force and voluntary force that has been observed by some researchers implies that voluntary activation can be quantified by scaling a single interpolated twitch to a control twitch evoked in relaxed muscle. Observations of non-linear evoked-voluntary force relationships have lead to the suggestion that the single interpolated twitch ratio can not accurately estimate voluntary activation. Instead, it has been proposed that muscle activation is better determined by extrapolating the relationship between evoked and voluntary force to provide an estimate of true maximum force. However, criticism of the single interpolated twitch ratio typically fails to take into account the reasons for the non-linearity of the evoked-voluntary force relationship. When these reasons are examined, it appears that most are even more challenging to the validity of extrapolation than they are to the linear equation. Furthermore, several factors that contribute to the observed non-linearity can be minimised or even eliminated with appropriate experimental technique. The detection of small activation deficits requires high resolution measurement of force and careful consideration of numerous experimental details such as the site of stimulation, stimulation intensity and the number of interpolated stimuli. Sensitive twitch interpolation techniques have revealed small to moderate deficits in voluntary activation during brief maximal efforts and progressively increasing activation deficits (central fatigue) during exhausting exercise. A small number of recent studies suggest that resistance training may result in improved voluntary activation of the quadriceps femoris and ankle plantarflexor muscles but not the biceps brachii. A significantly larger body of evidence indicates that voluntary activation declines as a consequence of bed-rest, joint injury and joint degeneration. Twitch interpolation has also been employed to study the mechanisms by which caffeine and pseudoephedrine enhance exercise performance.
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Caffeine ingestion by human athletes has been found to improve endurance performance primarily acting via the central nervous system as an adenosine receptor antagonist. However, a few studies have implied that the resultant micromolar levels of caffeine in blood plasma (70 microM maximum for humans) may directly affect skeletal muscle causing enhanced force production. In the present study, the effects of 70 microM caffeine on force and power output in isolated mouse extensor digitorum longus muscle were investigated in vitro at 35 degrees C. Muscle preparations were subjected to cyclical sinusoidal length changes with electrical stimulation conditions optimised to produce maximal work. 70 microM caffeine caused a small but significant increase (2-3%) in peak force and net work produced during work loops (where net work represents the work input required to lengthen the muscle subtracted from the work produced during shortening). However, these micromolar caffeine levels did not affect the overall pattern of fatigue or the pattern of recovery from fatigue. Our results suggest that the plasma concentrations found when caffeine is used to enhance athletic performance in human athletes might directly enhance force and power during brief but not prolonged activities. These findings potentially confirm previous in vivo studies, using humans, which implied caffeine ingestion may cause acute improvements in muscle force and power output but would not enhance endurance.
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This chapter discusses the psychobiology of muscle pain during and following exercise. The chapter includes a general discussion of peripheral nociceptive inputs from noxious biochemicals and mechanical pressure as well as a discussion of central nociceptive processing in spinal and supraspinal areas. Descending modulation of pain via endogenous opioids is also discussed. Particular attention is paid to likely mechanisms of muscle pain during exercise and delayed-onset soreness following exercise. A second section of the chapter covers commonly used methods for assessing muscle pain, such as questionnaires and measures of pain threshold, pain tolerance, and pain intensity. The final section discusses individual attributes and treatment modalities that may affect pain perception. Included are specific discussions on the repeated-bout effect, differences in pain perceptions between men and women, analgesia after exercise, and pharmacological and other commonly employed treatments for pain, such as massage, ice, and heat.
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Objectives: This study examined the effects of exercise-induced muscle damage (EIMD) on the physiological and perceptual responses to 30 minutes of submaximal cycling at 60% of oxygen consumption (VO2 peak). Methods: Ten participants completed two 30-minute bouts of cycling, one before and one 48 hours after performance of strenuous (24 contractions with 120% of concentric 1-repeition maximum) eccentric exercise. Results: Eccentric exercise resulted in a significant delayed-onset muscle pain (1.6±1.6 mm to 44.8±20 mm on a 100-mm visual analog scale; P<0.001) and a 15% (P<0.001) reduction in maximal strength 48 hours after exercise. Ratings of quadriceps muscle pain (1.99±0.42 vs. 3.30±0.56; P=0.003) and perceived exertion (RPE; 13.0±0.30 vs. 13.8±0.61; P=0.02) were elevated during cycling after EIMD at identical work rates. No changes were observed in VO2 (29.6±4.6 vs. 30.2±4.4 mL/kg/min; P=0.41), heart rate (154±15 vs. 155±9 beats/min; P=0.58), and ventilation (57.2±12.1 vs. 59.8±12.7 L/min; P=0.13) during exercise after EIMD. The mean change in RPE was significantly correlated (r=0.56; P<0.01) with the change in muscle pain during cycling and delayed-onset pain during resistance exercise (r=0.86; P<0.01), but did not correlate with changes in VO2, heart rate, ventilation, and maximal strength. Discussion: These findings indicate the elevations in RPE after EIMD are likely a consequence of the EIMD with the most likely explanation being an increase in localized pain before and during cycling exercise.