Video
ABC World News Tonight with David Muir Full Broadcast - Feb. 14, 2024Metabolic enhancer for enhanced physical performance -
When we eat more than we need for daily anabolism, the excess nutrients are typically stored in our body as fat. Thermic effect of food also known as thermogenesis — your body uses energy to digest the foods and drinks you consume and also absorbs, transports and stores their nutrients.
Energy used during physical activity — this is the energy used by physical movement and it varies the most depending on how much energy you use each day. Physical activity includes planned exercise like going for a run or playing sport but also includes all incidental activity such as hanging out the washing, playing with the dog or even fidgeting!
Basal metabolic rate BMR The BMR refers to the amount of energy your body needs to maintain homeostasis. Factors that affect our BMR Your BMR is influenced by multiple factors working in combination, including: Body size — larger adult bodies have more metabolising tissue and a larger BMR.
Amount of lean muscle tissue — muscle burns kilojoules rapidly. Crash dieting, starving or fasting — eating too few kilojoules encourages the body to slow the metabolism to conserve energy.
Age — metabolism slows with age due to loss of muscle tissue, but also due to hormonal and neurological changes. Growth — infants and children have higher energy demands per unit of body weight due to the energy demands of growth and the extra energy needed to maintain their body temperature.
Gender — generally, men have faster metabolisms because they tend to be larger. Genetic predisposition — your metabolic rate may be partly decided by your genes.
Hormonal and nervous controls — BMR is controlled by the nervous and hormonal systems. Hormonal imbalances can influence how quickly or slowly the body burns kilojoules.
Environmental temperature — if temperature is very low or very high, the body has to work harder to maintain its normal body temperature, which increases the BMR. Infection or illness — BMR increases because the body has to work harder to build new tissues and to create an immune response.
Amount of physical activity — hard-working muscles need plenty of energy to burn. Regular exercise increases muscle mass and teaches the body to burn kilojoules at a faster rate, even when at rest.
Drugs — like caffeine or nicotine , can increase the BMR. Dietary deficiencies — for example, a diet low in iodine reduces thyroid function and slows the metabolism. Thermic effect of food Your BMR rises after you eat because you use energy to eat, digest and metabolise the food you have just eaten.
Hot spicy foods for example, foods containing chilli, horseradish and mustard can have a significant thermic effect. Energy used during physical activity During strenuous or vigorous physical activity, our muscles may burn through as much as 3, kJ per hour.
Metabolism and age-related weight gain Muscle tissue has a large appetite for kilojoules. Hormonal disorders of metabolism Hormones help regulate our metabolism. Thyroid disorders include: Hypothyroidism underactive thyroid — the metabolism slows because the thyroid gland does not release enough hormones.
Some of the symptoms of hypothyroidism include unusual weight gain, lethargy, depression and constipation. Hyperthyroidism overactive thyroid — the gland releases larger quantities of hormones than necessary and speeds the metabolism.
Some of the symptoms of hyperthyroidism include increased appetite, weight loss, nervousness and diarrhoea. Genetic disorders of metabolism Our genes are the blueprints for the proteins in our body, and our proteins are responsible for the digestion and metabolism of our food.
Some genetic disorders of metabolism include: Fructose intolerance — the inability to break down fructose, which is a type of sugar found in fruit, fruit juices, sugar for example, cane sugar , honey and certain vegetables. Galactosaemia — the inability to convert the carbohydrate galactose into glucose.
Galactose is not found by itself in nature. It is produced when lactose is broken down by the digestive system into glucose and galactose. Sources of lactose include milk and milk products, such as yoghurt and cheese.
Phenylketonuria PKU — the inability to convert the amino acid phenylalanine into tyrosine. High levels of phenylalanine in the blood can cause brain damage.
High-protein foods and those containing the artificial sweetener aspartame must be avoided. About Cardiovascular Research. Cardiovascular Research CVR is the international journal of the European Society of Cardiology ESC for basic and translational research across different disciplines and areas.
Our mission: To reduce the burden of cardiovascular disease. Help centre Contact us. All rights reserved. Did you know that your browser is out of date? To get the best experience using our website we recommend that you upgrade to a newer version.
Learn more. Show navigation Hide navigation. Sub menu. Benefits of exercise on metabolism: more profound than previously reported 02 Apr Topic s : Prevention. Disclosures : None. The major known effects of adenosine are to decrease the concentration of many CNS neurotransmitters, including serotonin, dopamine, acetylcholine, norepinephrine and glutamate [ , , ].
Caffeine, which has a similar molecular structure to adenosine, binds to adenosine receptors after ingestion and therefore increases the concentration of these neurotransmitters [ , ]. This results in positive effects on mood, vigilance, focus, and alertness in most, but not all, individuals [ , ].
Researchers have also characterized aspects of adenosine A 2A receptor function related to cognitive processes [ ] and motivation [ , ].
In particular, several studies have focused on the functional significance of adenosine A 2A receptors and the interactions between adenosine and dopamine receptors, in relation to aspects of behavioral activation and effort-related processes [ , , , ]. The serotonin receptor 2A 5-HT2A has also been shown to modulate dopamine release, through mechanisms involving regulation of either dopamine synthesis or dopaminergic neuron firing rate [ , ].
Alterations in 5-HTR2A receptors may therefore affect dopamine release and upregulation of dopamine receptors [ , ]. This may therefore modulate dopamine activity, which may help to elucidate some of the relationships among neurotransmitters, genetic variation and caffeine response, and the subsequent impact on exercise performance.
Muscle pain has been shown to negatively affect motor unit recruitment and skeletal muscle force generation proportional to the subjective scores for pain intensity [ , ].
In one study, progressively increased muscle pain intensity caused a gradual decrease in motor firing rates [ ]. However, this decrease was not associated with a change in motor unit membrane properties demonstrating a central inhibitory motor control mechanism with effects correlated to nociceptive activity [ ].
Other studies also indicate that muscle force inhibition by muscle pain is centrally mediated [ ]. Accordingly, caffeine-mediated CNS mechanisms, such as dopamine release [ ], are likely imputable for pain mitigation during high-intensity exercise [ , , , , , , , ].
Although there appears to be strong evidence supporting the analgesic effects of caffeine during intense exercise, others have found no effect [ , ]. The attenuation of pain during exercise as a result of caffeine supplementation may also result in a decrease in the RPE during exercise.
Two studies [ , ] have reported that improvements in performance were accompanied by a decrease in pain perception as well as a decrease in RPE under caffeine conditions, but it is unclear which factor may have contributed to the ergogenic effect.
Acute caffeine ingestion has been shown to alter RPE, where effort may be greater under caffeine conditions, yet it is not perceived as such [ 12 , , , ].
Others have not found changes in RPE with caffeine use [ ]. A more recent study by Green et al. The authors noted that individual responses to caffeine might explain their unexpected findings. In the last decade, our understanding of CNS fatigue has improved.
When caffeine and NECA were given together, the effects appeared to cancel each other out, and run time was similar to placebo. When the study was repeated with peripheral intraperitoneal body cavity injections instead of brain injections, there was no effect on run performance.
The authors concluded that caffeine increased running time by delaying fatigue through CNS effects, in part by blocking adenosine receptors [ ]. Caffeine also appears to enhance cognitive performance more in fatigued than well-rested subjects [ , , ]. This phenomenon is also apparent in exercise performance [ ] both in the field [ ] and in the lab [ 60 , 63 , ].
The placebo effect is a beneficial outcome that cannot be attributed to a treatment or intervention but is brought about by the belief that one has received a positive intervention. The nocebo effect is directly opposite to this in that a negative outcome occurs following the administration of an intervention or lack of an intervention e.
knowingly ingesting a placebo [ ]. For example, the nocebo may be a substance without medical effects, but which worsens the health status of the person taking it by the negative beliefs and expectations of the patient. An example of this was reported in a study [ ] where well-trained cyclists exhibited a linear dose—response relationship in experimental trials from baseline to a moderate 4.
Athletes improved as the perceived caffeine doses increased; however, a placebo was used in all interventions. Similarly, Saunders et al. Therefore, readers are encouraged to consider whether studies that have explored the effects of caffeine on exercise have examined and reported the efficacy of the blinding of the participants.
At the highest level of sports, competitors will be near their genetic potential, will have trained intensively, followed prudent recovery protocols, and will have exploited all strategies to improve their performance—the use of an ergogenic aid, when legal, safe and effective, is an alluring opportunity.
Accordingly, caffeine is one of the most prominent ergogenic aids and is used by athletes and active individuals in a wide variety of sports and activities involving aerobic endurance. Caffeine has been shown to benefit several endurance-type sports including cycling [ 60 , , ], running [ 91 , , ] cross-country skiing [ ] and swimming [ ].
Much of the caffeine-exercise body of literature has focused on endurance-type exercise, as this is the area in which caffeine supplementation appears to be more commonly used and likely beneficial in most, but not all, athletes [ 11 , 12 , 13 ].
For example, the caffeine concentration in over twenty thousand urine samples obtained for doping control from to was measured after official national and international competitions [ , ].
A recent 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 [ ].
Forty-six studies met the inclusion criteria and were included in the meta-analysis. Time-trial completion time showed improvements of 2. However, there was some variability in outcomes with responses to caffeine ingestion, with two studies reporting slower time-trial performance, and five studies reporting lower mean power output during the time—trial [ ].
Dozens of endurance studies are highlighted through this review is various sections, showing consistent yet wide-ranging magnitudes of benefit for endurance performance under caffeine conditions.
Strength and power development through resistance exercise is a significant component of conditioning programs for both fitness and competitive sport. In resistance exercise, strength is most commonly assessed using 1 repetition maximum 1RM [ ], or different isometric and isokinetic strength tests [ ].
Although several studies exploring the effects of caffeine on strength performance have been published since the ISSN caffeine position stand [ 40 ], some uncertainty surrounding the benefits of caffeine in activities involving muscular endurance, strength and power remains.
Caffeine was shown to be ergogenic for muscular endurance in two meta-analyses reporting effect sizes ranging from 0. However, others have shown that it enhances strength but not muscular endurance [ , ], and when studies have examined multiple strength-muscular endurance tasks, there were benefits across the board [ 67 , ], none at all [ 98 , ], or even impairments in muscular endurance with caffeine use [ , ].
Ingesting caffeine prior to a muscular endurance task is likely to delay muscular fatigue, but these effects are not consistent among all studies.
Three meta-analyses explored the acute effects of caffeine on strength, and all reported ergogenic effects [ , , ].
However, the effects in these meta-analyses were small, ranging from 0. Such small improvements in muscular strength likely have the greatest practical meaningfulness for athletes competing in strength-based sports, such as powerlifting and weightlifting athletes which already seem to be among the highest users of caffeine [ ].
Power output is also assessed during different protocols of intermittent-sprinting and repeated-sprints often with the Wingate cycling test as well as assessments during running [ ] or swimming repeated sprints [ ]. The data for repeated sprint and power performance using Wingate data has been mixed.
In an older study, 10 male team-sport athletes performed 18, 4-s sprints with 2-min active recovery [ ].
A more recent study examining the effects of acute caffeine ingestion on upper and lower body Wingate performance in 22 males did not report significant findings when measuring lower body mean and peak power using the Wingate test [ ]. An older study by Greer et al.
One meta-analysis reported that caffeine ingestion enhances mean and peak power during the Wingate test [ ], although the effect sizes of 0. In contrast, another meta-analysis that examined the effects of caffeine on muscle power as assessed with the Wingate test for three of the studies, and repeated sprints for a maximum of s for the fourth, did not report benefits from ingestion of caffeine [ ].
An average caffeine dose of 6. A study by Lee et al. This might suggest that the rest interval between sprints may modulate the ergogenic effects of caffeine. Indeed, a recent meta-analysis that focused on the effects of caffeine on repeated-sprint performance reported that total work, best sprint, and last sprint performance was not affected by caffeine ingestion [ ].
Several studies have also shown substantial variability in outcomes. Similarly, Woolf et al. Ballistic movements such as throws and jumps are characterized by high motor unit firing rates, brief contraction times, and high rates of force development [ ].
Many studies have explored the effects of caffeine on jumping performance [ , ]. The body of evidence has indicated that caffeine supplementation increases vertical jump height during single and repeated jumps; however, the magnitude of these effects is rather modest, with effect sizes ranging from 0.
Besides jumping, several studies have explored the effects of caffeine on throwing performance. Overall, the current body of evidence indicates that caffeine supplementation may be useful for acute improvements in ballistic exercise performance in the form of jumps and throws.
However, more research is needed to explore the effects of caffeine on different throwing exercise tests, as this has been investigated only in a few studies.
Generally, the primary sports-related goal of strength and power-oriented resistance training programs is to move the force-velocity curve to the right, indicating an ability of the athlete to lift greater loads at higher velocities [ ]. Several studies have explored the effects of caffeine on movement velocity and power in resistance exercise using measurement tools such as linear position transducers [ ].
These studies generally report that caffeine ingestion provides ergogenic effects of moderate to large magnitudes, with similar effects noted for both mean and peak velocity, and in upper and lower-body exercises [ 67 , , ]. Even though this area merits further research to fill gaps in the literature, the initial evidence supports caffeine as an effective ergogenic aid for enhancing velocity and power in resistance exercise.
Even though caffeine ingestion may enhance performance in the laboratory, there has been a paucity of evidence to support that these improvements transfer directly to sport-specific performance. To address this issue, several studies have also explored the effects of caffeine on sport-specific exercise tasks using sport simulation matches.
Many studies conducted among athletes competing in team and individual sports, report that caffeine may enhance performance in a variety of sport tasks. However, there are also several studies that report no effects as outlined below:. Basketball — increased jump height, but only in those with the AA version of the CYP1A2 gene [ ], increased number of free throws attempted and free throws made, increased number of total and offensive rebounds [ ], but did not improve sprint time [ ], nor dribbling speed [ ].
Volleyball — increased number of successful volleyball actions and decreased the number of imprecise actions [ , ], although caffeine did not improve physical performance in multiple sport-specific tests in professional females [ ], nor performance in volleyball competition [ ].
Football - did not improve performance for anaerobic exercise tests used at the NFL Combine [ ]. Rugby — increased the number of body impacts, running pace, and muscle power during jumping [ , ], but did not impact agility [ ]. Field hockey — increased high-intensity running and sprinting [ ], and may offset decrements in skilled performance associated with fatigue [ ].
Ice-hockey - has limited impact on sport-specific skill performance and RPE, but may enhance physicality during scrimmage [ ]. Combat sports — increased number of offensive actions and increased the number of throws [ ].
Cross-country skiing — reduced time to complete a set distance [ ] and improved time to task failure [ ]. In summary, although reviews of the literature show that caffeine ingestion is, on average , ergogenic for a wide range of sport-specific tasks, its use might not be appropriate for every athlete.
Specifically, the use of caffeine needs to be balanced with the associated side-effects and therefore experimentation is required in order to determine the individual response before assessing whether the benefits outweigh the costs for the athlete.
Athletes should gauge their physical response to caffeine during sport practice and competition in addition to monitoring mood state and potentially disrupted sleep patterns. There is a lack of research examining potential interindividual differences in strength or anaerobic power-type exercise, but this is not the case for endurance exercise.
In the myriad of studies examining caffeine on endurance performance, the benefits of caffeine do not appear to be influenced by sex, age, VO 2 max, type of sport, or the equivalent dose of caffeine [ 13 , , ]. Nevertheless, there appears to be substantial interindividual variability in response to caffeine under exercise conditions, which may be attributed to several factors outlined below.
Genetic variants affect the way we absorb, metabolize, and utilize and excrete nutrients, and gene-diet interactions that affect metabolic pathways relevant to health and performance are now widely recognized [ ].
In the field of nutrigenomics, caffeine is the most widely researched compound with several randomized controlled trials investigating the modifying effects of genetic variation on exercise performance [ 75 , , , ]. Numerous studies have investigated the effect of supplemental caffeine on exercise performance, but there is considerable inter-individual variability in the magnitude of these effects [ 11 , 13 , 44 ] or in the lack of an effect [ , ], when compared to placebo.
Due to infrequent reporting of individual data it is difficult to determine the extent to which variation in responses may be occurring. The performance of some individuals is often in stark contrast to the average findings reported, which may conclude beneficial, detrimental, or no effect of caffeine on performance.
For example, Roelands et al. These inter-individual differences appear to be partly due to variations in genes such as CYP1A2 and possibly ADORA2A , which are associated with caffeine metabolism, sensitivity and response [ ]. In the general population, individuals with the AC or CC genotype slow metabolizers have an elevated risk of myocardial infarction [ ], hypertension and elevated blood pressure [ , ], and pre-diabetes [ ], with increasing caffeinated coffee consumption, whereas those with the AA genotype show no such risk.
Additionally, regular physical activity appears to attenuate the increase in blood pressure induced by caffeine ingestion, but only in individuals with the AA genotype [ ]. In that group, a 6. Among those with the CC genotype i.
In those with the AC genotype there was no effect of either dose [ ]. The findings are consistent with a previous study [ ] that observed a caffeine-gene interaction indicating improved time trial cycling performance following caffeine consumption only in those with the AA genotype.
In contrast, previous studies either did not observe any impact of the CYP1A2 gene in caffeine-exercise studies [ , ], or reported benefits only in slow metabolizers [ 75 ].
There are several reasons that may explain discrepancies in study outcomes. The effects of genotype on performance might be the most prominent during training or competition of longer duration or an accumulation of fatigue aerobic or muscular endurance [ ], where caffeine appears to provide its greatest benefits, and where the adverse effects to slow metabolizers are more likely to manifest [ , ].
Indeed, in a study of performance in elite basketball players [ ], only in those with the AA genotype caffeine improved repeated jumps which requires maintaining velocity at take-off repeatedly as an athlete fatigues throughout a game muscular endurance - even though there was no caffeine-genotype interaction effect for this outcome.
However, caffeine similarly improved performance in those with the both AA and C-genotypes during a simulated basketball game [ ]. In a cross-over design of 30 resistance-trained men, caffeine ingestion resulted in a higher number of repetitions in repeated sets of three different exercises, and for total repetitions in all resistance exercises combined, which resulted in a greater volume of work compared to placebo conditions, but only in those with the CYP1A2 AA genotype [ ].
Although more research is warranted, there is a growing body of evidence to support the role of CYP1A2 in modifying the effects of caffeine ingestion on aerobic or muscular endurance-type exercise, which helps to determine which athletes are most likely to benefit from caffeine.
The ADORA2A gene is another genetic modifier of the effects of caffeine on performance. The adenosine A 2A receptor, encoded by the ADORA2A gene, has been shown to regulate myocardial oxygen demand and increase coronary circulation by vasodilation [ , ].
The A 2A receptor is also expressed in the brain, where it has significant roles in the regulation of glutamate and dopamine release, with associated effects on insomnia and pain [ , ].
The antagonism of adenosine receptors after caffeine ingestion is modified by the ADORA2A gene, which may allow greater improvements in dopamine transmission and lead to norepinephrine and epinephrine release due to increased neuronal firing [ ] in some genotypes versus others. Dopamine has been associated with motivation and effort in exercising individuals, and this may be the mechanism by which differences in response to caffeine are manifested [ , , ].
Currently, only one small pilot study has examined the effect of the ADORA2A gene rs on the ergogenic effects of caffeine under exercise conditions [ ]. Twelve female subjects underwent a double-blinded, crossover trial comprising two min cycling time trials following caffeine ingestion or placebo.
Caffeine benefitted all six subjects with the TT genotype, but only one of the six C allele carriers. Further studies are needed to confirm these preliminary findings and should include a large enough sample to distinguish any effects between the different C allele carriers i.
CT vs. CC genotypes and potential effects related to sex. The ADORA2A rs genotype has also been implicated, by both objective and subjective measures, in various parameters of sleep quality after caffeine ingestion in several studies [ , , , ]. Adenosine promotes sleep by binding to its receptors in the brain, mainly A 1 and A 2A receptors, and caffeine exerts an antagonist effect, blocking the receptor and reversing the effects of adenosine and promoting wakefulness [ ].
This action of caffeine may also serve athletes well under conditions of jetlag, and irregular or early training or competition schedules. Psychomotor speed relies on the ability to respond, rapidly and reliably, to randomly occurring stimuli which is a critical component of, and characteristic of, most sports [ ].
Genetic variation in ADORA2A has been shown to be a relevant determinant of psychomotor vigilance in the rested and sleep-deprived state and modulates individual responses to caffeine after sleep deprivation [ ].
Those with the CC genotype of ADORA2A rs consistently performed on a higher level on the sustained vigilant attention task than T-allele -carriers; however, this was tested in ADORA2A haplotypes that included combinations of 8 SNPs.
This work provides the basis for future genetic studies of sleep using individual ADORA2A SNPs. As mentioned, the ADORA2A genotype has also been implicated in sleep quality and increases in sleep disturbance [ ].
Increased beta activity in nonREM sleep may characterize individuals with insomnia when compared with healthy good sleepers [ ]. A functional relationship between the ADORA2A genotype and the effect of caffeine on EEG beta activity in nonREM sleep has previously been reported [ ], where the highest rise was in individuals with the CC genotype, approximately half in the CT genotype, whereas no change was present in the TT genotype.
Consistent with this observation, the same study found individuals with the CC and TC genotypes appeared to confer greater sensitivity towards caffeine-induced sleep disturbance compared to the TT genotype [ ].
This suggests that a common variant in ADORA2A contributes to subjective and objective responses to caffeine on sleep. Given that anxiety may be normalized in elite sports even at clinical levels, factors that contribute to anxiety should be mitigated whenever possible.
Anxiety may be caused by stress-related disorders burnout , poor quality sleep patterns often related to caffeine intakes and possibly as a response to caffeine ingestion due to genetic variation, even at low levels [ ]. As previously mentioned, caffeine blocks adenosine receptors, resulting in the stimulating effects of caffeine [ ].
A common variation in the ADORA2A adenosine A 2A receptor gene contributes to the differences in subjective feelings of anxiety after caffeine ingestion [ , ], especially in those who are habitually low caffeine consumers [ ].
This may be particularly relevant to athletes who possess the TT variant of rs in the ADORA2A gene. These individuals are likely to be more sensitive to the stimulating effects of caffeine and experience greater increases in feelings of anxiety after caffeine intake than do individuals with either the CT or CC variant [ , , ].
Sport psychologists commonly work with athletes to help them overcome anxiety about performance during competitions. Anxiety before or during athletic competitions can interfere not only in performance, but also in increased injury risk [ ].
Athletes who are more prone to performance anxiety may exacerbate their risk for feelings of anxiety depending on their caffeine use and which variant of the ADORA2A gene they possess. Monitoring the actions of caffeine in those individuals who are susceptible, may alleviate some of the related feelings of anxiety with caffeine use.
Given that anxiety may disrupt concentration and sleep and negatively impact social interactions, athletes with higher risks and prevalence for anxiety, may want to limit or avoid caffeine consumption if caffeine is a known trigger during times where they are feeling anxious or stressed, such as at sporting competitions or social gatherings or other work and school events.
The importance of both sleep and caffeine as an ergogenic aid to athletes highlights the importance of optimizing rest and recovery through a better understanding of which athletes may be at greater risk of adverse effects of caffeine on mood and sleep quality, possibly due to genetic variation.
This information will allow athletes and coaching staff to make informed decisions on when and if to use caffeine when proximity to sleep is a factor. These considerations will also be in conjunction with the possibility that an athlete will benefit from caffeine in endurance-based exercise as determined in part, by their CYP1A2 genotype, albeit with a clear need for future research.
The quantification of habitual caffeine intake is difficult, which is problematic for studies aiming to compare performance outcomes following caffeine ingestion in habitual versus non-habitual caffeine users.
This concern is highlighted by reports showing large variability in the caffeine content of commonly consumed beverages, e.
Self-reported intakes may therefore be unreliable. Newly discovered biomarkers of coffee consumption may be more useful for quantifying intakes in the future, but currently, these are not widely available [ ].
Different protocols for the length of the caffeine abstinence period preceding data collection is also a relevant factor in determining variability in performance outcomes.
For example, in shorter caffeine abstinence periods e. alleviating the negative symptoms of withdrawal, which in itself may improve performance [ ]. These effects may be more pronounced in those genetically predisposed to severe withdrawal effects [ ].
Although genes have been associated with habitual caffeine intake using GWAS research [ , ], it is important to highlight that these associations are not directly applicable to determining differences in performance outcomes in response to acute caffeine doses for regular or habitual caffeine users versus non-habitual users.
Furthermore, associations between genes and habitual caffeine intake do not elucidate potential mechanisms by which caffeine intake behaviors may influence subsequent performance following caffeine supplementation [ , ]. In animal model studies, regular consumption of caffeine has been associated with an upregulation of the number of adenosine receptors in the vascular and neural tissues of the brain [ ].
Although, this did not appear to modify the effects of caffeine in one study [ ], in another, chronic caffeine ingestion by mice caused a marked reduction in locomotor exploratory activity [ ].
Changes in adenosine receptor number or activity have not been studied in humans. There does not appear to be a consistent difference in the performance effects of acute caffeine ingestion between habitual and non-habitual caffeine users, and study findings remain equivocal. In one study, habitual stimulation from caffeine resulted in a general dampening of the epinephrine response to both caffeine and exercise; however, there was no evidence that this impacted exercise performance [ ].
Four weeks of caffeine ingestion resulted in increased tolerance to acute caffeine supplementation in previously low habitual caffeine consumers, with the ergogenic effect of acute caffeine supplementation no longer apparent [ ].
Caffeine ingestion improved performance as compared to placebo and control, with no influence of habitual caffeine intake. However, a limitation of this study is the short h caffeine withdrawal period in all groups which may have resulted in performance improvements due to the reversal of caffeine withdrawal effects, rather than impact of acute-on-chronic caffeine administration and the effects of habituation to caffeine on exercise performance [ , ].
In addition, habitual caffeine intake was estimated using a food frequency questionnaire, which might be a limitation given the already mentioned variation of caffeine in coffee and different supplements. There is wide variability in caffeine content of commonly consumed items, and as such, an objective measure e.
Based on these observations, the assumption that habitual and nonhabitual caffeine consumers will or will not respond differently to caffeine supplementation during exercise, requires further study.
However, caffeine appears to be most beneficial during times or in sports where there is an accumulation of fatigue, i. A recent review [ ] reported that the effect size of caffeine benefits increase with the increasing duration of the time trial event, meaning that timing caffeine intake closer to a time of greater fatigue, i.
This supports the notion that endurance athletes with longer races may benefit most from caffeine for performance enhancement since they have the greatest likelihood of being fatigued. This also supports findings in other investigations that show ingesting caffeine at various time points including late in exercise may be most beneficial [ ].
For example, an early study [ ] aimed to understand whether or not there were benefits to a common practice among endurance athletes, such as those participating in marathons and triathlons, which is to drink flat cola toward the end of an event. When researchers investigated the ingestion of a low dose of caffeine toward the end of a race e.
The study also demonstrated that the effect was due to the caffeine and not the carbohydrate, which may also aid performance as fuel stores become depleted [ ]. This may have been due to the faster absorption with caffeinated gum consumption, and due to the continued increase in plasma caffeine concentrations during the cycling time trial, when athletes may become fatigued i.
However, there was significant interindividual variability, highlighting the need for athletes to experiment with their own strategies as far as dosing and timing are concerned. The optimal timing of caffeine ingestion may depend on the source of caffeine.
As stated earlier, some of the alternate sources of caffeine such as caffeine chewing gums may absorb more quickly than caffeine ingested in caffeine-containing capsules [ 60 ]. Therefore, individuals interested in supplementing with caffeine should consider that timing of caffeine ingestion will likely be influenced by the source of caffeine.
Currently, only a few investigations [ 96 , , , , , ] have included both trained and untrained subjects in their study design. A limitation of this study is that the swimming exercise task differed between the trained and untrained participants.
Specifically, the study utilized m swimming for the trained swimmers and m for the untrained swimmers, which is a likely explanation for these findings. However, some have also postulated that this is because athletes perform more reliably on a given task than nonathletes, and increased test-retest reliability might prevent type II errors [ ].
In contrast to the above evidence regarding the importance of training status, other research has shown that training status does not moderate the ergogenic effects of caffeine on exercise performance.
One study [ ] showed similar performance improvements 1. Similarly, Astorino et al. More recently, a small study by Boyett et al. Subjects completed four experimental trials consisting of a 3-km cycling time trial performed in randomized order for each combination of time of day morning and evening and treatment.
They reported that both untrained and trained subjects improved performance with caffeine supplementation in the morning; however, only the untrained subjects improved when tested in the evening.
Although there were some limitations to this study, these observations indicate that trained athletes are more likely to experience ergogenic effects from caffeine in the morning, while untrained individuals appear to receive larger gains from caffeine in the evening than their trained counterparts.
This may further complicate the training status data with a possible temporal effect [ ]. The concentration of adenosine receptors the primary target of caffeine do appear to be higher in trained compared to untrained individuals, but this has only been reported in animal studies [ ].
Boyett et al. Although some studies comparing training status of subjects support the notion [ ] that training influences response to caffeine during exercise, most do not [ 96 , , ] and this was also the finding in a subsequent meta-analysis [ ]. It is possible that the only difference between trained and untrained individuals is that trained individuals likely have the mental discipline to exercise long or hard enough to benefit more from the caffeine stimulus, which might provide an explanation for why in some studies, trained individuals respond better to caffeine [ ].
Currently, it seems that trained and untrained individuals experience similar improvements in performance following caffeine ingestion; however, more research in this area is warranted.
The impacts of caffeine on sleep and behavior after sleep deprivation are widely reported [ ]. Sleep is recognized as an essential component of physiological and psychological recovery from, and preparation for, high-intensity training in athletes [ , ].
Chronic mild to moderate sleep deprivation in athletes, potentially attributed to caffeine intakes, may result in negative or altered impacts on glucose metabolism, neuroendocrine function, appetite, food intake and protein synthesis, as well as attention, learning and memory [ ].
Objective sleep measures using actigraphy or carried out in laboratory conditions with EEG have shown that caffeine negatively impacts several aspects of sleep quality such as: sleep latency time to fall asleep , WASO wake time after sleep onset , sleep efficiency and duration [ ].
Studies in athletes have also shown adverse effects in sleep quality and markers for exercise recovery after a variety of doses of caffeine ingestion [ , , ]. Although caffeine is associated with sleep disturbances, caffeine has also been shown to improve vigilance and reaction time and improved physical performance after sleep deprivation [ , , , , ].
This may be beneficial for athletes or those in the military who are traveling or involved in multiday operations, or sporting events and must perform at the highest level under sleep-deprived conditions [ , , , ]. Even though caffeine ingestion may hinder sleep quality, the time of day at which caffeine is ingested will likely determine the incidence of these negative effects.
For example, in one study that included a sample size of 13 participants, ingestion of caffeine in the morning hours negatively affected sleep only in one participant [ ]. Unfortunately, athletes and those in the military are unlikely to be able to make adjustments to the timing of training, competition and military exercises or the ability to be combat ready.
However, to help avoid negative effects on sleep, athletes may consider using caffeine earlier in the day whenever possible. Pronounced individual differences have also been reported where functional genetic polymorphisms have been implicated in contributing to individual sensitivity to sleep disruption [ , ] and caffeine impacts after sleep deprivation [ ] as discussed in the Interindividual variation in response to caffeine: Genetics section of this paper.
As with any supplement, caffeine ingestion is also associated with certain side-effects. Some of the most commonly reported side-effects in the literature are tachycardia and heart palpitations, anxiety [ , ], headaches, as well as insomnia and hindered sleep quality [ , ].
For example, in one study, caffeine ingestion before an evening Super Rugby game resulted in a delay in time at sleep onset and a reduction in sleep duration on the night of the game [ ]. Caffeine ingestion is also associated with increased anxiety; therefore, its ingestion before competitions in athletes may exacerbate feelings of anxiety and negatively impact overall performance see caffeine and anxiety section.
For example, athletes competing in sports that heavily rely on the skill component e. However, athletes in sports that depend more on physical capabilities, such as strength and endurance e.
These aspects are less explored in research but certainly warrant consideration in the practical context to optimize the response to caffeine supplementation. The primary determinant in the incidence and severity of side-effects associated with caffeine ingestion is the dose used.
Side-effects with caffeine seem to increase linearly with the dose ingested [ ]. Therefore, they can be minimized—but likely not fully eliminated—by using smaller doses, as such doses are also found to be ergogenic and produce substantially fewer side-effects [ ].
In summary, an individual case-by-case basis approach is warranted when it comes to caffeine supplementation, as its potential to enhance performance benefit needs to be balanced with the side-effects risk. In addition to exercise performance, caffeine has also been studied for its contribution to athletes of all types including Special Forces operators in the military who are routinely required to undergo periods of sustained cognitive function and vigilance due to their job requirements Table 1.
Hogervorst et al. They found that caffeine in a carbohydrate-containing performance bar significantly improved both endurance performance and complex cognitive ability during and after exercise [ 82 ]. Antonio et al. This matches a IOM report [ ] that the effects of caffeine supplementation include increased attention and vigilance, complex reaction time, and problem-solving and reasoning.
One confounding factor on cognitive effects of caffeine is the role of sleep. Special Forces military athletes conduct operations where sleep deprivation is common. A series of different experiments [ 42 , , , , , , , ] have examined the effects of caffeine in real-life military conditions.
In three of the studies [ , , ], soldiers performed a series of tasks such as a 4 or 6. The investigators found that vigilance was either maintained or enhanced under the caffeine conditions vs. placebo , in addition to improvements in run times and obstacle course completion [ , , ]. Similarly, Lieberman et al.
Navy Seals. The positive effects of caffeine on cognitive function were further supported by work from Kamimori et al. The caffeine intervention maintained psychomotor speed, improved event detection, increased the number of correct responses to stimuli, and increased response speed during logical reasoning tests.
Under similar conditions of sleep deprivation, Tikuisis et al. When subjects are not sleep deprived, the effects of caffeine on cognition appear to be less effective. For example, Share et al. In addition to the ability of caffeine to counteract the stress from sleep deprivation, it may also play a role in combatting other stressors.
Gillingham et al. However, these benefits were not observed during more complex operations [ ]. Crowe et al. Again, no cognitive benefit was observed. Other studies [ , , , ] support the effects of caffeine on the cognitive aspects of sport performance, even though with some mixed results [ , ].
Foskett et al. This was supported by Stuart et al. firefighting, military related tasks, wheelchair basketball [ ]. The exact mechanism of how caffeine enhances cognition in relation to exercise is not fully elucidated and appears to work through both peripheral and central neural effects [ ].
In a study by Lieberman et al. Repeated acquisition are behavioral tests in which subjects are required to learn new response sequences within each experimental session [ ]. The researchers [ 42 ] speculated that caffeine exerted its effects from an increased ability to sustain concentration, as opposed to an actual effect on working memory.
Other data [ ] were in agreement that caffeine reduced reaction times via an effect on perceptual-attentional processes not motor processes. This is in direct contrast to earlier work that cited primarily a motor effect [ ]. Another study with a sugar free energy drink showed similar improvements in reaction time in the caffeinated arm; however, they attributed it to parallel changes in cortical excitability at rest, prior, and after a non-fatiguing muscle contraction [ ].
The exact cognitive mechanism s of caffeine have yet to be elucidated. Based on some of the research cited above, it appears that caffeine is an effective ergogenic aid for individuals either involved in special force military units or who may routinely undergo stress including, but not limited to, extended periods of sleep deprivation.
Caffeine in these conditions has been shown to enhance cognitive parameters of concentration and alertness. It has been shown that caffeine may also benefit sport performance via enhanced passing accuracy and agility. However, not all of the research is in agreement. It is unlikely that caffeine would be more effective than actually sleeping, i.
Physical activity and exercise in extreme environments are of great interest as major sporting events e. Tour de France, Leadville , Badwater Ultramarathon are commonly held in extreme environmental conditions.
Events that take place in the heat or at high altitudes bring additional physiological challenges i. Nonetheless, caffeine is widely used by athletes as an ergogenic aid when exercising or performing in extreme environmental situations.
Ely et al. Although caffeine may induce mild fluid loss, the majority of research has confirmed that caffeine consumption does not significantly impair hydration status, exacerbate dehydration, or jeopardize thermoregulation i.
Several trials have observed no benefit of acute caffeine ingestion on cycling and running performance in the heat Table 2 [ , , ]. It is well established that caffeine improves performance and perceived exertion during exercise at sea level [ , , , ].
Despite positive outcomes at sea level, minimal data exist on the ergogenic effects or side effects of caffeine in conditions of hypoxia, likely due to accessibility of this environment or the prohibitive costs of artificial methods.
To date, only four investigations Table 3 have examined the effects of caffeine on exercise performance under hypoxic conditions [ , , , ]. Overall, results to date appear to support the beneficial effects of caffeine supplementation that may partly reduce the negative effects of hypoxia on the perception of effort and endurance performance [ , , , ].
Sources other than commonly consumed coffee and caffeine tablets have garnered interest, including caffeinated chewing gum, mouth rinses, aerosols, inspired powders, energy bars, energy gels and chews, among others. While the pharmacokinetics [ 18 , , , , ] and effects of caffeine on performance when consumed in a traditional manner, such as coffee [ 47 , 49 , 55 , , , , ] or as a caffeine capsule with fluid [ 55 , , , ] are well understood, curiosity in alternate forms of delivery as outlined in pharmacokinetics section have emerged due to interest in the speed of delivery [ 81 ].
A recent review by Wickham and Spriet [ 5 ] provides an overview of the literature pertaining to caffeine use in exercise, in alternate forms.
Therefore, here we only briefly summarize the current research. Several investigations have suggested that delivering caffeine in chewing gum form may speed the rate of caffeine delivery to the blood via absorption through the extremely vascular buccal cavity [ 58 , ].
Kamimori and colleagues [ 58 ] compared the rate of absorption and relative caffeine bioavailability from caffeinated chewing gum and caffeine in capsule form. The results suggest that the rate of drug absorption from the gum formulation was significantly faster.
These findings suggest that there may be an earlier onset of pharmacological effects from caffeine delivered through the gum formulation. Further, while no data exist to date, it has been suggested that increasing absorption via the buccal cavity may be preferential over oral delivery if consumed closer to or during exercise, as splanchnic blood flow is often reduced [ ], potentially slowing the rate of caffeine absorption.
To date, five studies [ 59 , 60 , 61 , 62 , 63 ] have examined the potential ergogenic impact of caffeinated chewing gum on aerobic performance, commonly administered in multiple sticks Table 4.
To note, all studies have been conducted using cycling interventions, with the majority conducted in well-trained cyclists. However, more research is needed, especially in physically active and recreationally training individuals.
Four studies [ 64 , 66 , 68 , ] have examined the effect of caffeinated chewing gum on more anaerobic type activities Table 4. Specifically, Paton et al. The reduced fatigue in the caffeine trials equated to a 5. Caffeinated gum consumption also positively influenced performance in two out of three soccer-specific Yo-Yo Intermittent Recovery Test and CMJ tests used in the assessment of performance in soccer players [ 66 ].
These results suggest that caffeine chewing gums may provide ergogenic effects across a wide range of exercise tasks. To date, only Bellar et al. Future studies may consider comparing the effects of caffeine in chewing gums to caffeine ingested in capsules. Specifically, the mouth contains bitter taste sensory receptors that are sensitive to caffeine [ ].
It has been proposed that activation of these bitter taste receptors may activate neural pathways associated with information processing and reward within the brain [ , , ]. Physiologically, caffeinated mouth rinsing may also reduce gastrointestinal distress potential that may be caused when ingesting caffeine sources [ , ].
Few investigations on aerobic [ 69 , 74 , 75 , 76 , ] and anaerobic [ 72 , 73 , 78 ] changes in performance, as well as cognitive function [ 70 , 71 ] and performance [ 77 ], following CMR have been conducted to date Table 5.
One study [ ] demonstrated ergogenic benefits of CMR on aerobic performance, reporting significant increases in distance covered during a min arm crank time trial performance.
With regard to anaerobic trials, other researchers [ 72 ] have also observed improved performance, where recreationally active males significantly improved their mean power output during repeated 6-s sprints after rinsing with a 1.
While CMR has demonstrated positive outcomes for cyclists, another study [ 78 ] in recreationally resistance-trained males did not report any significant differences in the total weight lifted by following a 1.
CMR appears to be ergogenic in cycling to include both longer, lower-intensity and shorter high-intensity protocols. The findings on the topic are equivocal likely because caffeine provided in this source does not increase caffeine plasma concentration and increases in plasma concentration are likely needed to experience an ergogenic effect of caffeine [ 69 ].
Details of these studies, as well as additional studies may be found in Table 5. The use of caffeinated nasal sprays and inspired powders are also of interest. Three mechanisms of action have been hypothesized for caffeinated nasal sprays. Firstly, the nasal mucosa is permeable, making the nasal cavity a potential route for local and systemic substance delivery; particularly for caffeine, a small molecular compound [ 11 , 12 , 30 , 31 ].
Secondly, and similar to CMR, bitter taste receptors are located in the nasal cavity. The use of a nasal spray may allow for the upregulation of brain activity associated with reward and information processing [ ]. Thirdly, but often questioned due to its unknown time-course of action, caffeine could potentially be transported directly from the nasal cavity to the CNS, specifically the cerebrospinal fluid and brain by intracellular axonal transport through two specific neural pathways, the olfactory and trigeminal [ , ].
No significant improvements were reported in either anaerobic and aerobic performance outcome measures despite the increased activity of cingulate, insular, and sensory-motor cortices [ 79 ]. Laizure et al. Both were found to have similar bioavailability and comparable plasma concentrations with no differences in heart rate or blood pressure Table 6.
While caffeinated gels are frequently consumed by runners, cyclists and triathletes, plasma caffeine concentration studies have yet to be conducted and only three experimental trials have been reported. Cooper et al. In the study by Cooper et al. In contrast, Scott et al.
utilized a shorter time period from consumption to the start of the exercise i. However, these ideas are based on results from independent studies and therefore, future studies may consider exploring the optimal timing of caffeine gel ingestion in the same group of participants.
More details on these studies may be found in Table 7. Similar to caffeinated gels, no studies measured plasma caffeine concentration following caffeinated bar consumption; however, absorption and delivery likely mimic that of coffee or caffeine anhydrous capsule consumption.
While caffeinated bars are commonly found in the market, research on caffeinated bars is scarce. To date, only one study [ 82 ] Table 7 has examined the effects of a caffeine bar on exercise performance.
Furthermore, cyclists significantly performed better on complex information processing tests following the time trial to exhaustion after caffeine bar consumption when compared to the carbohydrate only trial.
As there is not much data to draw from, future work on this source of caffeine is needed. A review by Trexler and Smith-Ryan comprehensively details research on caffeine and creatine co-ingestion [ 32 ].
With evidence to support the ergogenic benefits of both creatine and caffeine supplementation on human performance—via independent mechanisms—interest in concurrent ingestion is of great relevance for many athletes and exercising individuals [ 32 ].
While creatine and caffeine exist as independent supplements, a myriad of multi-ingredient supplements e. It has been reported that the often-positive ergogenic effect of acute caffeine ingestion prior to exercise is unaffected by creatine when a prior creatine loading protocol had been completed by participants [ , ].
However, there is some ambiguity with regard to the co-ingestion of caffeine during a creatine-loading phase e. While favorable data exist on muscular performance outcomes and adaptations in individuals utilizing multi-ingredient supplements e. Until future investigations are available, it may be prudent to consume caffeine and creatine separately, or avoid high caffeine intakes when utilizing creatine for muscular benefits [ ].
You enhance viewing 1 of your 1 enhanxer articles. For Metabolic enhancer for enhanced physical performance access Hunger control tips for better meal planning a risk-free trial. Andrew Metabolic enhancer for enhanced physical performance BSc Hons, MRSC, ACSM, is the editor of Sports Performance Bulletin and a enhancfd of the Pergormance College of Sports Medicine. Phyical is a sports enbancer writer and fr, specializing in sports nutrition and has worked in the field of fitness and sports performance for over 30 years, helping athletes to reach their true potential. He is also a contributor to our sister publication, Sports Injury Bulletin. They use the latest research to improve performance for themselves and their clients - both athletes and sports teams - with help from global specialists in the fields of sports science, sports medicine and sports psychology. They do this by reading Sports Performance Bulletin, an easy-to-digest but serious-minded journal dedicated to high performance sports. The speed of metabolism Metabplic age, activity levels, genetics and other factors. Regular meals, sleep, and physsical may all help boost metabolism. Calories provide the energy the Metabolic enhancer for enhanced physical performance Effective against drug-resistant pathogens, Metabolic enhancer for enhanced physical performance only physcal move but also to breathe, digest food, circulate blood, grow cells, repair wounds, and even to think. The rate at which the body burns calories to produce this energy is called the metabolic rate. Scientists use various formulae to measure resting metabolic rate RMRalso known as resting energy expenditure REE. RMR and REE refer to the amount of energy a body uses at rest, for example, sleeping or sitting. The rate can vary between individuals.
0 thoughts on “Metabolic enhancer for enhanced physical performance”