Recent work by the ACSM, on well-trained athletes reported that mg caffeine per kg kilogram of body weight one-hour prior to exercise increased running and cycling endurance in the laboratory. Caffeine may also help assist in enhancing recovery after exercise.

According to the American Physiological Society, four hours post-exercise, muscle glycogen increased 66 percent by ingesting a carbohydrate drink containing caffeine as compared to the carbohydrate-only drink.

The carbohydrate and caffeine drink post-exercise also resulted in higher blood glucose and plasma insulin. Each individual can respond differently to caffeine. It can have many side effects such as poor sleep quality, gastrointestinal distress, fatigue, headaches, muscle cramping, dehydration and anxiety.

Caffeine can also have a diuretic effect by increasing blood flow to the kidneys and inhibiting the re-absorption of sodium and water. Based on information provided by the IOC International Olympic Committee , athletes are allowed up to 12 ug micorgrams caffeine per milliliter urine before it is considered illegal 15 ug as per the NCAA.

In summary, caffeine may help assist in performance and recovery. Thus, clearance from the bloodstream is analogous to the rate at which caffeine is absorbed and metabolized.

Multiple mechanisms have been proposed to explain the effects of caffeine supplementation on sport performance. However, several extensive reviews have stated that the most significant mechanism is that caffeine acts to compete with adenosine at its receptor sites [ 5 , 13 , 14 ].

In fact, in an exhaustive review of caffeine and sport performance, it was stated that "because caffeine crosses the membranes of nerve and muscle cells, its effects may be more neural than muscular. Even if caffeine's main effect is muscular, it may have more powerful effects at steps other than metabolism in the process of exciting and contracting the muscle [ 15 ]".

Clearly, one of caffeine's primary sites of action is the central nervous system CNS. Moreover, theophylline and paraxanthine can also contribute to the pharmacological effect on the CNS through specific signaling pathways [ 5 ].

However, as noted above, rarely is there a single mechanism that fully explains the physiological effects of any one nutritional supplement. Because caffeine easily crosses the blood brain barrier as well as cellular membranes of all tissues in the body [ 15 ], it is exceedingly difficult to determine in which system in particular i.

nervous or skeletal muscle caffeine has the greatest effect [ 15 ]. In addition to its impact on the CNS, caffeine can affect substrate utilization during exercise. In particular, research findings suggest that during exercise caffeine acts to decrease reliance on glycogen utilization and increase dependence on free fatty acid mobilization [ 16 — 19 ].

Additionally, Spriet et al. Consequently, performance was significantly improved and results of this study [ 18 ] suggested an enhanced reliance on both intra- and extramuscular fat oxidation.

Another possible mechanism through which caffeine may improve endurance performance is by increasing the secretion of β-endorphins. Laurent et al. It has been established that plasma endorphin concentrations are enhanced during exercise and their analgesic properties may lead to a decrease in pain perception [ 21 ].

Caffeine consumption also promotes a significant thermogenic response. In fact, caffeine consumption at a dose of mg resulted in a significant thermogenic effect despite the fact that subjects in that particular investigation had a habitual caffeine intake of mg per day [ 24 ].

The increase in energy expenditure subsequent to caffeine ingestion had not returned to baseline 3 hours post-consumption. Overall, the findings of research studies involving caffeine supplementation and physical performance indicate a combined effect on both the central and peripheral systems.

Therefore, it is possible that caffeine acts on the central nervous system as an adenosine antagonist, but may also have an effect on substrate metabolism and neuromuscular function. Research in all areas of caffeine supplementation continues to emerge and it is necessary to understand that as a supplement, caffeine has wide ranging physiological effects on the body that may or may not result in an enhancement in performance.

Caffeine supplementation can improve sport performance but this is dependent upon various factors including, but not limited to, the condition of the athlete, exercise i.

mode, intensity, duration and dose of caffeine. Caffeine has been shown to enhance several different modes of exercise performance including endurance [ 8 , 16 , 25 — 28 ], high-intensity team sport activity [ 29 — 34 ], and strength-power performance [ 30 , 35 ].

Additionally, the use of caffeine has also been studied for its contribution to special force operations, which routinely require military personnel to undergo periods of sustained vigilance and wakefulness. In a series of investigations, McLellan et al. In the McLellan et al.

investigations [ 36 — 38 ], soldiers performed a series of tasks over several days, where opportunities for sleep were exceedingly diminished. Experimental challenges included a 4 or 6. During periods of sustained wakefulness, subjects were provided caffeine in the range of mg, and in the form of chewing gum.

The caffeine supplement was consumed in this manner as it has been shown to be more readily absorbed, than if it was provided within a pill based on the proximity to the buccal tissue [ 39 ].

In all three studies [ 36 — 38 ], vigilance was either maintained or enhanced for caffeine conditions in comparison to placebo. Additionally, physical performance measures such as run times and completion of an obstacle course were also improved by the effects of caffeine consumption [ 36 , 38 ].

Lieberman et al. Navy Seals [ 40 ]. However, in this investigation [ 40 ] the participants were randomly assigned varying doses of caffeine in capsule form delivering either , , or mg. In a manner similar to previous investigations, participants received either the caffeine or placebo treatment and one hour post consumption performed a battery of assessments related to vigilance, reaction time, working memory, and motor learning and memory.

In addition, the participants were evaluated at eight hours post consumption to assess duration of treatment effect in parallel to the half-life of caffeine, in a manner similar to a study conducted by Bell et al. As to be expected, caffeine had the most significant effect on tasks related to alertness [ 40 ].

However, results were also significant for assessments related to vigilance and choice reaction time for those participants who received the caffeine treatment. Of particular importance are the post-hoc results for the and mg doses.

Specifically, there was no statistical advantage for consuming , as opposed to mg [ 40 ]. Meanwhile, a mg dose did result in significant improvements in performance, as compared to mg. In fact, it was evident from post-hoc results that mg was at no point statistically different or more advantageous for performance than a placebo.

These studies [ 36 — 38 , 40 ] demonstrate the effects of caffeine on vigilance and reaction time in a sleep deprived state, in a distinct and highly trained population.

These findings suggest that the general population may benefit from similar effects of caffeine, but at moderate dosages in somewhat similar conditions where sleep is limited. An additional outcome of the Lieberman et al.

These results are in agreement with Bell et al. Taken together, results of these studies [ 40 , 41 ] provide some indication, as well as application for the general consumer and athlete.

Specifically, while caffeine is said to have a half-life of 2. Finally, it was suggested by Lieberman and colleagues [ 40 ] that the performance-enhancing effects of caffeine supplementation on motor learning and short-term memory may be related to an increased ability to sustain concentration, as opposed to an actual effect on working memory.

In fact, it was suggested that because caffeine has the ability to act as an antagonist to adenosine, alterations in arousal would explain the compound's discriminatory effect on behaviors relating vigilance, fatigue and alertness [ 40 ].

Recently, it was also suggested that caffeine can positively affect both cognitive and endurance performance [ 25 ].

On three separate days, subjects consumed a commercially available performance bar that contained either Results from a repeated series of cognitive function tests favored the caffeine treatment in that subjects performed significantly faster during both the Stroop and Rapid Visual Information Processing Task following min of submaximal cycling as well as after a ride to exhaustion.

In addition, participant time increased for the ride to exhaustion on the caffeine treatment, as compared to both the non-caffeinated bar and flavored water [ 25 ]. Overall, the literature examining the effects of caffeine on anaerobic exercise is equivocal, with some studies reporting a benefit [ 29 — 32 , 43 , 44 ] and others suggesting that caffeine provides no significant advantage [ 45 , 46 ].

As with all sports nutrition research, results can vary depending on the protocol used, and in particular, the training status of the athlete as well as intensity and duration of exercise.

For example, Crowe et al. Cognitive testing consisted of simple visual reaction time and number recall tests. Participants performed two second maximal cycle tests interspersed by three min of passive rest. The results were in contrast to other studies that investigated cognitive parameters and the use of caffeine [ 25 , 36 — 38 , 40 ] in that caffeine had no significant impact on reaction time or number recall, and there was no additional benefit for measurements of power.

In fact, in this study [ 47 ], the caffeine treatment resulted in significantly slower times to reach peak power in the second bout of maximal cycling. 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 endurance athletes both physically and cognitively. However, the research is conflicting when extrapolating the benefits of caffeine to cognition and shorter bouts of high-intensity exercise.

A discussion will follow examining the effects of caffeine and high-intensity exercise in trained and non-trained individuals, which may partially explain a difference in the literature as it pertains to short-term high-intensity exercise.

An extensive body of research has provided compelling evidence to support the theory that caffeine's primary ergogenic mode of action is on the CNS. However, caffeine may also be ergogenic in nature by enhancing lipolysis and decreasing reliance on glycogen utilization. In , Ivy et al.

Trained cyclists were subjected to two hours of isokinetic cycling and received three treatments on separate occasions: caffeine, glucose polymer, and placebo.

Caffeine was consumed in an absolute dose of mg, mg one hour prior to cycling and the remainder in divided doses beginning 15 min prior to onset of exercise. Results indicated a significant advantage in work produced following caffeine consumption. Specifically, work produced was 7.

Midway into two hours of cycling, fat oxidation was significantly increased above that of the control and glucose trials. Fat oxidation was maintained during the last hour of exercise and it was suggested this substrate utilization was in part responsible for the increased work production.

Results of the Ivy et al. However, Ivy et al. Specifically, when subjects consumed caffeine, they began the exercise bout at a higher intensity, but perceived this effort to be no different than when they ingested the placebo and glucose conditions. Furthermore, Ivy et al.

In a study performed by Jackman et al. In total, subjects performed approximately min of high intensity work 2-min bouts of cycling interspersed with 6 min of rest and a final ride to voluntary exhaustion.

Results indicated an increase in plasma epinephrine for the caffeine treatment, which is consistent with other caffeine supplementation studies [ 8 , 29 , 46 , 51 , 52 ]. Even though epinephrine promotes glycogenolysis, the data from this study demonstrated an increase in both muscle lactate and plasma epinephrine without a subsequent affect on net muscle glycogenolysis following the first two bouts of controlled maximal cycling.

Epinephrine can up-regulate lipolysis in adipocytes as well as glycogenolysis in muscle and liver; therefore, a direct relationship between increases in the hormone and enhanced substrate catabolism is somewhat ambiguous. Greer et al. Whereas adenosine can act to inhibit lipolysis in vivo [ 54 ], theophylline consumption at 4.

Indeed, it is possible that both theophylline and caffeine act to regulate substrate metabolism via mechanisms other than those that are catecholamine-induced [ 53 ]. Hulston and Jeukendrup [ 55 ] published data that indicated caffeine at 5. Therefore, the results of some research studies lend substantiation to the premise that caffeine may act to increase performance by altering substrate utilization [ 16 , 18 ], while results of additional investigations serve to suggest other mechanisms of action [ 50 , 56 , 57 ].

Carbohydrate consumption during exercise can decrease the body's dependence on endogenous carbohydrate stores and lead to enhanced endurance performance [ 58 , 59 ]. Therefore, it is beneficial to determine an optimal method of enhancing rates of exogenous carbohydrate delivery and oxidation.

Exogenous carbohydrate delivery is determined by various factors including, but not limited to, the rate of gastric emptying and intestinal absorption [ 58 ]. However, it has been suggested that during exercise intestinal absorption seems to have the greatest influence on the rate of exogenous carbohydrate oxidation [ 58 , 60 ].

In Sasaki et al. In addition, Jacobson et al. However, Yeo et al. It was suggested by these authors [ 63 ] and others [ 64 ] that this was the result of enhanced intestinal glucose absorption. Finally, Hulston et al. However, it was also reported that caffeine consumption had no affect on exogenous carbohydrate oxidation [ 55 ].

In addition, Kovacs et al. In contrast, Desbrow and colleagues [ 65 ] found a low dose of caffeine 1. Strategies that may enhance exogenous carbohydrate absorption and oxidation during exercise are clearly defined in the literature [ 58 — 60 ].

The combined effect of caffeine and exogenous carbohydrate intake during endurance exercise is less understood.

Therefore, future research should continue to investigate this potential ergogenic effect, as well as any corresponding physiological mechanisms. Recently, the combination of caffeine and carbohydrate has been examined as a potential means to enhance recovery by increasing the rate of glycogen synthesis post exercise.

In , Battram et al. It was postulated that the fractions respond differently to the recovery phase of exercise and thus glycogen resynthesis. Following exercise and throughout the 5-hr recovery period subjects consumed in total g of exogenous carbohydrate. Muscle biopsies and blood samples revealed caffeine ingestion did not obstruct proglycogen or macroglycogen resynthesis following exhaustive, glycogen depleting exercise [ 66 ].

It is imperative to recognize that each person may respond differently to supplements and compounds containing caffeine. An individual at rest, and even sedentary in nature, is likely to have a different response compared to a trained, conditioned athlete, or physically active person.

According to the data presented by Battram et al. In a more recent study, Pedersen et al. The data presented in these studies [ 66 , 67 ] indicate that caffeine is not detrimental to glycogen repletion, and in combination with exogenous carbohydrate may actually act to enhance synthesis in the recovery phase of exercise.

From a practical standpoint, however, it should be considered that most athletes or recreationally trained individuals would choose to supplement with caffeine prior to competition for the purpose of enhancing performance.

Moreover, clearance of caffeine in the bloodstream occurs between 3 and 6 hours, and may extend beyond that time point depending on the individual. Therefore, caffeine consumption pre- and post-exercise would have to be precisely timed so as not to interrupt sleep patterns of the athlete, which in itself could negatively affect overall recovery.

Various methods of caffeine supplementation have been explored and results have provided considerable insight into appropriate form and dosage of the compound. One of the most acknowledged studies, published by Graham et al.

Caffeine in capsule form significantly increased work capacity allowing them to run an additional km [ 26 ], as compared to the four other treatments.

It was also proposed by Graham and colleagues [ 26 ] that perhaps other indistinguishable compounds within coffee rendered caffeine less effective than when consumed in anhydrous form. This suggestion was supported by de Paulis et al. In turn, these derivatives may have the potential for altering the affects of caffeine as an adenosine antagonist, possibly reducing the drug's ability to diminish the inhibitory action of adenosine [ 68 ].

As such, McLellan and Bell [ 27 ] examined whether a morning cup of coffee just prior to anhydrous caffeine supplementation would have any negative impact on the compound's ergogenic effect. Subjects were physically active and considered to be moderate-to-high daily consumers of caffeine.

Subjects consumed one cup of coffee with a caffeine dosage that was approximately 1. The results indicated caffeine supplementation significantly increased exercise time to exhaustion regardless of whether caffeine in anhydrous form was consumed after a cup of regular or decaffeinated coffee [ 27 ].

While caffeine supplemented from a cup of coffee might be less effective than when consumed in anhydrous form, coffee consumption prior to anhydrous supplementation does not interfere with the ergogenic effect provided from low to moderate dosages. Wiles et al.

This form and dose was used to mimic the real life habits of an athlete prior to competition. Subjects performed a m treadmill time trial. Ten subjects with a VO 2max of In addition, six subjects also completed a third protocol to investigate the effect of caffeinated coffee on sustained high-intensity exercise.

Results indicated a 4. For the "final burst" simulation, all 10 subjects achieved significantly faster run speeds following ingestion of caffeinated coffee. Finally, during the sustained high-intensity effort, eight of ten subjects had increased VO 2 values [ 69 ].

In a more recent publication, Demura et al. Subjects consumed either caffeinated or decaffeinated coffee 60 min prior to exercise. The only significant finding was a decreased RPE for the caffeinated coffee as compared to the decaffeinated treatment [ 70 ].

Coffee contains multiple biologically active compounds; however, it is unknown if these compounds are of benefit to human performance [ 71 ]. However, it is apparent that consuming an anhydrous form of caffeine, as compared to coffee, prior to athletic competition would be more advantageous for enhancing sport performance.

Nevertheless, the form of supplementation is not the only factor to consider as appropriate dosage is also a necessary variable. Pasman and colleagues [ 28 ] examined the effect of varying quantities of caffeine on endurance performance.

Results were conclusive in that all three caffeine treatments significantly increased endurance performance as compared to placebo. Moreover, there was no statistical difference between caffeine trials. Navy SEAL training study published by Lieberman et al [ 40 ].

Results from that paper indicated no statistical advantage for consuming an absolute dose of mg, as opposed to mg. However, the mg dose did result in significant improvements in performance, as compared to mg, and mg was at no point statistically different or more advantageous for performance than placebo [ 40 ].

In response to why a low and moderate dose of caffeine significantly enhanced performance, as compared to a high dose, Graham and Spriet [ 8 ] suggested that, "On the basis of subjective reports of some subjects it would appear that at that high dose the caffeine may have stimulated the central nervous system to the point at which the usually positive ergogenic responses were overridden".

This is a very pertinent issue in that with all sports nutrition great individuality exists between athletes, such as level of training, habituation to caffeine, and mode of exercise. Therefore, these variables should be considered when incorporating caffeine supplementation into an athlete's training program.

Results were comparable in a separate Spriet et al. publication [ 18 ]. Once again, following caffeine supplementation times to exhaustion were significantly increased. Results indicated subjects were able to cycle for 96 min during the caffeine trial, as compared to 75 min for placebo [ 18 ].

Recently McNaughton et al. This investigation is unique to the research because, while continuous, the protocol also included a number of hill simulations to best represent the maximal work undertaken by a cyclist during daily training.

The caffeine condition resulted in the cyclists riding significantly further during the hour-long time trial, as compared to placebo and control. The use of caffeine in anhydrous form, as compared to a cup of caffeinated coffee, seems to be of greater benefit for the purpose of enhancing endurance performance.

It is evident that caffeine supplementation provides an ergogenic response for sustained aerobic efforts in moderate-to-highly trained endurance athletes. The research is more varied, however, when pertaining to bursts of high-intensity maximal efforts. Collomp et al. Compared to a placebo, caffeine did not result in any significant increase in performance for peak power or total work performed [ 46 ].

As previously stated, Crowe et al. Finally, Lorino et al. Results were conclusive in that non-trained males did not significantly perform better for either the pro-agility run or s Wingate test [ 73 ].

In contrast, a study published by Woolf et al. It is exceedingly apparent that caffeine is not effective for non-trained individuals participating in high-intensity exercise. This may be due to the high variability in performance that is typical for untrained subjects.

Results, however, are strikingly different for highly-trained athletes consuming moderate doses of caffeine. Swimmers participated in two maximal m freestyle swims; significant increases in swim velocity were only recorded for the trained swimmers. Results indicated a significant improvement in swim times for those subjects who consumed caffeine, as compared to placebo.

Moreover, time was measured at m splits, which resulted in significantly faster times for each of the three splits for the caffeine condition [ 74 ].

As suggested by Collomp et al. Participants in a study published by Woolf et al. A recent study published by Glaister et al.

Subjects were defined as physically active trained men and performed 12 × 30 m sprints at 35 s intervals. Results indicated a significant improvement in sprint time for the first three sprints, with a consequential increase in fatigue for the caffeine condition [ 31 ].

The authors suggested that the increase in fatigue was due to the enhanced ergogenic response of the caffeine in the beginning stages of the protocol and, therefore, was not meant to be interpreted as a potential negative response to the supplement [ 31 ].

Bruce et al. Results of the study revealed an increase in performance for both time trial completion and average power output for caffeine, as compared to placebo mg glucose. Time trial completion improved by 1. Anderson and colleagues [ 75 ] tested these same doses of caffeine in competitively trained oarswomen, who also performed a 2,m row.

Team sport performance, such as soccer or field hockey, involves a period of prolonged duration with intermittent bouts of high-intensity playing time.

As such, Stuart et al. Subjects participated in circuits that were designed to simulate the actions of a rugby player, which included sprinting and ball passing, and each activity took an average seconds to complete.

In total, the circuits were designed to represent the time it takes to complete two halves of a game, with a 10 min rest period. An improvement in ball passing accuracy is applicable to a real-life setting as it is necessary to pass the ball both rapidly and accurately under high-pressure conditions [ 33 ].

This study [ 33 ] was the first to show an improvement in a team sport skill-related task as it relates to caffeine supplementation. Results of this study [ 33 ] also indicated that for the caffeine condition subjects were able to maintain sprint times at the end of the circuit, relative to the beginning of the protocol.

Schneiker et al. Ten male recreationally competitive team sport athletes took part in an intermittent-sprint test lasting approximately 80 minutes in duration. Specifically, total sprint work was 8. The training and conditioning of these athletes may result in specific physiologic adaptations which, in combination with caffeine supplementation, may lead to performance enhancement, or the variability in performance of untrained subjects may mask the effect of the caffeine.

In the area of caffeine supplementation, strength research is still emerging and results of published studies are varied. The protocol consisted of a leg press, chest press, and Wingate.

The leg and chest press consisted of repetitions to failure i. Results indicated a significant increase in performance for the chest press and peak power on the Wingate, but no statistically significant advantage was reported for the leg press, average power, minimum power, or percent decrement [ 30 ].

Beck et al. For many people, a caffeinated drink is the only way to get the day started on the right footing. Image credit: Maria Orlova via Pexels copyright free. That said, caffeine does have its pitfalls.

Getting the application wrong, especially the dose, may cause adverse effects like jitteriness, headaches, stomach issues and regular trips to the bathroom. In relation to performance, it may also exacerbate the effects of adrenaline, raise heart rate and compound pre-race nerves.

In an extreme case of when caffeine use goes wrong , researchers at the University of Northumbria made an embarrassing error when they delivered 30 grams of caffeine to participants instead of 0.

The purpose of the study was to examine the effects of a moderate caffeine dose upon exercise performance but ended with two students being hospitalised.

When looking to maximise the benefits of using caffeine as part of your sporting performance, the source , amount and how you use caffeine will depend on your body size, level of conditioning, personal preference, and general goals.

We all respond differently to ingesting caffeine and it might not be for everyone. Before moving on, it's worth answering the question: Should you be using caffeine as part of your fueling strategy?

One high-profile athlete who avoids caffeine completely is middle-distance runner and double Team GB Olympian, Eilish McColgan :. I actually don't use caffeine at all in training because I've had some heart problems in the past. I was hospitalised for atrial fibrillation in and have had heart palpitations since I was a kid.

Because of this, I've never had a coffee in my life! Image credit: Aphiwat Chuangchoem via Pexels copyright free. With a half-life of around 5 hours depending on individual variations in metabolism , high concentrations of caffeine can stay in the system for several hours.

When taken during the hour before exercise, the ergogenic effect can comfortably last the duration of a 5K, 10K, or even a marathon for some individuals. For a longer race, regular low doses of caffeine throughout can be just as beneficial as a single larger dose pre-event.

I've been a big fan of caffeine since starting to race IRONMAN distances back in