helps physical and mental performance
The key component in Xplode shots is caffeine, although other compounds such as taurine, arginine AKG, N-acetyl tyrosine, and vitamin B6 are also evident. There is research evidence concerning the efficacy of these ingredients on physical and mental performance, and as such they will be briefly explored in the rest of this article.
Caffeine is probably the most common drug ingested, with coffee being the main source. It is a mild stimulant that occurs naturally in a number of plant species. Significant amounts of caffeine can be found in coffee, tea, chocolate and soft drinks such as Red Bull and Coca-Cola, although it also occurs in other products such as prescription medications, diuretics, and pain relievers. Because caffeine is a drug and yet is part of a normal diet, the IOC had placed a limit on the amount that could be consumed before exceeding ‘doping’ limits. However since January 2004 caffeine was removed from the banned list, although the IOC are monitoring the situation. Probably the reason for lifting the ban was the fact that the ergogenic effects of caffeine occur when ingested in doses of 5-6mg/kg body mass; an amount which results in urine values of caffeine lower than the previous IOC limit. There has been a wealth of information on studies reporting the positive effects of caffeine ingestion both for endurance and high intensity exercise. The ability of caffeine to stimulate the central nervous system (CNS) is another important feature of its ingestion. The effect of caffeine on the cerebral cortex results in a clearer thought process, a reduced rating of perceived exertion (RPE), and an attenuation of fatigue. The net effect is an enhanced ability to concentrate, thereby aiding athletes competing in sports where quick thinking and rapid reactions are necessary. Since caffeine stimulates the release of fatty acids from adipose tissue, there is a potential to promote ‘fat burning’. This article provides an overview of some of the reported effects of caffeine on performance and fat oxidation.
Mechanism of action
Caffeine may act in a number of different ways depending on whether the activity is intense or prolonged. With regard to intense exercise bouts, caffeine has been shown to stimulate the release of calcium ions and so enhance muscle force. With regard to prolonged exercise, caffeine is known to stimulate the release of fatty acids from adipose tissue so that muscles are capable of using them for energy at an earlier time than would be normally expected. This results in sparing the limited stores of muscle glycogen and so fatigue is offset. Furthermore, it is well established that caffeine stimulates the CNS and enables subjects to perceive the exercise as being easier and maintains arousal and mental alertness – this is mediated via the fact that caffeine inhibits adenosine uptake by cells and thereby induces a state of alertness rather than lethargy. Whatever the mechanism for enhancement of performance, it is clear that caffeine is a positive ergogenic aid for performance.
Timing and dose
Most studies which have reported the positive effects of caffeine ingestion have given a dose of at least 5-6 mg per kg body weight (5-6mg/kg) an hour before exercise. For a 70 kg person this amounts to a dose of 350-420 mg. Caffeine is rapidly absorbed by the intestine, and peak concentrations in blood are seen at approximately 60 minutes after ingestion (See Figure 1). Evidence from many laboratory-based studies has shown no advantages of taking doses greater than 6 mg/kg body weight. More is not better in this regard. On the other hand there is some evidence that doses from 2-4mg per kg body weight can also prove beneficial.
Figure 1. Blood caffeine concentrations 60 minutes after ingestion of varying doses of caffeine and throughout subsequent exercise (after Passman et al., 1995).
Form of caffeine
Table 1 shows that caffeine is present in various drinks and foods. Drinking 3 paper cups (approximately 150 ml each) of dripped coffee will ensure nearly 350 mg of caffeine is ingested. This is equivalent to 5 mg/kg body weight for a 70 kg person. Caffeine is also present in significant amounts in various analgesics such as exedrin and anacin, and of course, caffeine can be purchased in chemists as ‘ProPlus’ tablets (50 mg per tablet).
Pure caffeine is the form normally ingested in successful trials as opposed to trials with decaffeinated v caffeinated coffee. Generally, coffee has been equated with caffeine, although in some recent studies this has proved contentious. For example (Figure 2) a dose of 4.5 mg/kg body weight of caffeine was administered either as caffeine in a capsule or in coffee. Only the pure form of caffeine produced a positive effect by enhancing time to exhaustion (41 minutes vs 32 minutes) at 85% VO2max. There were no differences between the coffee and the placebo treatments or indeed the decaffeinated coffee with added caffeine. For some reason coffee does not produce the same ergogenic effect as pure caffeine. Drinking coffee is less effective from an exercise performance or capacity point of view than ingesting pure caffeine. On the other hand drinking Red Bull or Coca Cola or eating some dark chocolate can result in positive ergogenic effects.
Figure 2. Effect of caffeine or coffee on time to fatigue at 85% VO2max when provided as decaffeinated coffee (DC), decaffeinated coffee with added caffeine (DC+C), regular coffee (RC), placebo (Pl), and caffeine (CAF).
Caffeine and endurance exercise
A trawl of over 40 published studies using caffeine capsules and endurance exercise over the last 25 years has demonstrated the positive effects on both time to fatigue and in time trials. Improvements with caffeine have varied between 2 and 44%, with an average of 20% being achieved – as a rule of thumb the longer the event the greater the % improvement. The overall conclusion is that caffeine ingestion promotes prolonged activities when using either recreational or competitive athletes.
The proposed mechanism by which caffeine is purported to positively affect prolonged activity is via stimulating the adrenal gland to secrete adrenalin (epinephrine to those in N. America), which in turn targets adipose tissue to release fatty acids into the blood. The resulting increase in fatty acids can be taken up by muscle and used as a source of energy during the exercise bout and so preserve the limited muscle glycogen stores (Figure 3).
Figure 3. Theoretical model proposed to show how caffeine may positively affect prolonged performance (after Costill et al., 1978).
For example, in a study we undertook in the 1990’s we provided 6mg/kg body mass of caffeine to university football players who then underwent a simulated football match lasting 90 minutes using the Loughborough Intermittent Shuttle test (Figure 4). The average sprint times in each Block of activity was significantly faster following caffeine ingestion from Blocks 3-5 i.e. end of 1st half and into the 2nd half. Furthermore, the time to fatigue after Block 5 (i.e. after 75 minutes) was significantly longer following caffeine ingestion.
Figure 4. Effects of caffeine ingestion on average Sprint Time in a Block and on Time to Exhaustion. (Unpublished data from MacLaren)
In a study on cycling to fatigue at 70% VO2max, the efficacy of caffeine ingestion can clearly be recognised (Figure 5). In fact this study illustrates another finding in that doses above 5-6mg/kg body mass of caffeine are NOT more effective.
Figure 5. Effects of caffeine dose on Time to Exhaustion during cycling exercise. All caffeine trials enhanced the time significantly although there were no differences between caffeine trials. (Passman et al., 1995).
Numerous studies on prolonged exercise activities have used carbohydrate co-ingested with caffeine. In all cases the results have proved positive. To illustrate with one example, eight rugby union players underwent a rugby orientated shuttle running protocol involving four 21-minute blocks of activity having ingested either a placebo, a carbohydrate, or a carbohydrate + caffeine (Roberts et al., 2010). The 15-m sprint times were faster in the carb+caf trials; the motor skills were performed more quickly with carb+ caf; and the RPE was lower in the carb+caf.
Caffeine and high intensity exercise
Although fewer studies have been undertaken in this field, a few recent studies have demonstrated the beneficial effects of caffeine on high intensity exercise. Such activities have invariably resulted in fatigue between 1 and 7 minutes and include cycling, treadmill sprinting, and 2km rowing. Events in which fatigue is reached in less than 1 minute are equivocal, although repeated bouts of sprinting are likely to benefit.
Figure 5 highlights two key findings regularly shown in research on caffeine and performance – i.e. caffeine significantly improves prolonged exercise and also that doses greater than 5-6mg/kg body mass are NOT more useful. In this investigation the participants rowed 2-km after placebo or caffeine (6 or 9mg/kg) or placebo ingestion. The caffeine dose of 6mg/kg produced the fastest times followed by the 9mg/kg dose – both were superior to the placebo.
Figure 5. Positive effects of caffeine ingestion on 2-km rowing performance (after Bruce et al., 2000)
In another study using treadmill running at 120 %VO2max, participants ingested 5mg/kg caffeine or placebo 60 minutes prior to the run. Figure 6 shows that of the 9 participants, eight ran for longer (participant 7 was better on the placebo) and the average improvement in time to exhaustion was 208.2-s compared with 181-s after placebo – a 27-s enhancement.
Figure 6. Differences in time to exhaustion after caffeine ingestion when compared with placebo – values above the line show improvements in TTe whilst below the line show a detriment in performance.
Finally, in a study which used cycling as the mode of exercise, participants had to undertake four 2-min bouts of cyling at a power output corresponding to their maximal aerobic capacity followed by an all-out 1-min power sprint. Figure 7 demonstrates that caffeine ingestion resulted in a significantly higher power output (794 watts) for the power sprint compared to placebo (750 watts).
Figure 7. Power output during 4 bouts of cycling at maximal aerobic capacity followed by an all-out power sprint for 1-min (after Doherty et al., 200).
The findings clearly show that caffeine can have a significant effect on high intensity bouts of activity. However if this is the case then the proposed mechanism of stimulating fatty acid release and use is unlikely to be important here. The proposed mechanism for caffeine enhancing high intensity performance can be seen in Figure 8. Two key factors may be involved – (a) caffeine stimulates greater release of Calcium (Ca2+) ions from the sarcoplasmic reticulum and so leads to greater generation of force by the muscle, and (b) caffeine affects the brain to increase alertness, enhance motor recruitment of muscle fibres, and also to reduce the perception of effort (i.e. RPE is reduced).
Figure 8. Proposed mechanisms for the positive effects of caffeine on high intensity exercise.
Caffeine and fat oxidation
As previously mentioned ingestion of caffeine results in a significant elevation of blood fatty acid levels, and this occurs within 60 minutes after ingestion (Figure 9). The reason for this has also been presented i.e. caffeine stimulation of adrenalin release and the effect of adrenalin in stimulating adipose tissue lipolysis to release fatty acids normally bound as triglycerides within the cells (see Figure 3).
Figure 9. Fatty acid concentrations following caffeine and placebo ingestions at rest and during exercise (after Giles & MacLaren, 1984).
It is possible that this elevation of fatty acids from adipose tissue results in greater oxidation of fats during subsequent exercise. In our study (Giles & MacLaren , 1984) we observed such by measuring the respiratory exchange ratio (RER) during exercise. The RER reflects the amount of fat and/or carbohydrate oxidised – values close to 0.7 reflect greater fat oxidation and those close to 1.0 reflect carbohydrate oxidation. Figure 10 shows that following caffeine ingestion the RER is significantly lower at the start of exercise and throughout exercise when compared with placebo. So it appears that caffeine may boost fat oxidation (fat burning) when ingested before an exercise bout. Two sentences of caution however – (a) do not take caffeine with any carbohydrate since the carbohydrate negates the efficacy of caffeine, and (b) sedentary individuals are unlikely to benefit from the fat burning effect of caffeine whereas trained persons are likely to do so (sedentary persons will stimulate the release of fatty acids from fat cells somewhat but are not capable of oxidising the fatty acids sufficiently).
Figure 10. RER during 120-min of running at 65% VO2max after caffeine or placebo ingestion (after Giles and MacLaren, 1984).
Caffeine and mental function
The ergogenic effect of caffeine can also be mediated by its effect on the central nervous system (CNS). Adenosine is a potent adenosine antagonist (See Figure 11), and is a CNS stimulant which can easily cross the blood brain barrier (Davis et al., 2003). Caffeine has been shown to counteract the inhibitory effects of adenosine neuroexcitability, neurotransmitter release, arousal, and spontaneous activity. In fact, the role of caffeine as an adenosine inhibitor is the main reason for its efficacy as a CNS stimulant (Spriet, 2014). Figure 11 illustrates that caffeine competes with adenosine for the same binding site on the cell membrane and so reduces the uptake of adenosine into the cell. Remember that adenosine once inside a cell (such as a brain cell) causes an inhibition of cellular processes linked with stimulation and thereby results in ‘our little mouse’ feeling lethargic. When caffeine is present, there is a greater chance that it attaches to the adenosine receptor (so blocking adenosine from attaching) and results in increased alertness/activation.
Figure 11. Schema illustrating the effect of caffeine on adenosine uptake by a cell.
One of the ways mental processes can be assessed during exercise is by using the Borg scale of rating of perceived exertion (RPE). Almost without exception, all studies in which RPE has been assessed when comparing caffeine with a placebo demonstrate an attenuated response (Doherty & Smith, 2005). Just to illustrate the point Figure 12, taken from a study by Giles & MacLaren (1984), shows consistently lower RPE scores for trained runners who ran on a treadmill at 65%VO2max for 2-h when given 5mg/kg body mass of caffeine 1-h before exercise. These findings are not unusual when comparing caffeine with a placebo. In other words, caffeine ingestion invariably results in the exercise/work seeming easier compared with placebo.
Figure 12. Rating of Perceived Exertion (RPE) during a 2-h run on a treadmill when given caffeine or placebo (after Giles & MacLaren, 1984).
Caffeine is a diuretic and as such may lead to increases in urine production, which could have a negative effect on performance due to dehydration. However, most studies have found no effect of caffeine ingestion on either urine volume or plasma volume. This is quite possibly due to the impact of exercise on urine production overriding the stimulus of caffeine. Another consideration is that caffeine is a mental stimulant and so when taken at night will lead to insomnia and a disturbed sleep. This is not advisable if a match is played on the following day.
Caffeine is classified as a drug, yet it is a normal part of many individuals dietary intake. The ergogenic properties of caffeine are best realised when ingesting the pure form in a capsule or in drinks such as Xplode or Red Bull rather than as coffee. As such, improvements in endurance and high intensity performance can be realised by ingesting a dose of 5 or 6 mg/kg body weight (with a fluid intake of about 500 ml) 60 minutes before the activity. The diuretic effects of caffeine are not realised in exercise, although possible gastrointestinal problems may occur in some individuals. Caffeine may also be employed to aid ‘fat burning’ in trained individuals.
Caffeine has been shown to be an unquestionable useful ergogenic aid for performance ranging from high intensity bouts to prolonged activities – and not just physically but also mental performance too. Figure 13 provides an overall synopsis for the likely modes of action of caffeine on performance.
Figure 13. Likely mechanisms of action of caffeine on performance.
- Caffeine is unquestionably a potent ergogenic aid for high intensity and prolonged exercise bouts
- Caffeine stimulates mental performance too – in particular alertness, promoting improved reaction time, and attenuating RPE.
- The dose of caffeine needs to be 2-6mg/kg body mass for efficacy.
- Caffeine should be taken between 30-60 minutes before exercise
- The effect of caffeine lasts for many hours after ingestion.
- Caffeine can be taken co-ingested with carbohydrate for beneficial effects on prolonged exercise activities.
- Caffeine can be used to ‘fat burn’ when ingested in the absence of carbohydrate using trained (not sedentary) persons.
Xplode shots contain 250mg caffeine which is enough for most individuals since the dose will fall into the 2-6mg/kg range.
Xplode shots should be taken 30-45 minutes before the activity bout. If taken prior to a match, the period just before warm-up is ideal.
For better efficacy, athletes should not take any caffeine-containing foods in the 24-h before Xplode shot ingestion (i.e. no coffee, chocolate, green tea etc). This means the body will be more sensitive to the caffeine.
Xplode shots can be used first thing in the morning before a good ‘fat burning’ training session – but NO carbs please (at least not until after the training bout).
Bruce, CR., et al. (2000). Enhancement of 2000-m rowing performance after caffeine ingestion. Medicine and Science in Sports and Exercise, 32: 1958-1963.
Costill, DL., et al. (1978). Effects of caffeine on metabolism and exercise performance. Medicine and Science in Sports, 10: 155-158.
Davis, JM., et al. (2003). Central nervous system effects of caffeine and adenosine on fatigue. American Journal of Physiology, 284: R399-404.
Doherty, M., et al. (2004). Caffeine lowers perceptual response and and increases power output during high-intensity cycling. Journal of Sports Science, 22: 637-643.
Doherty, M & Smith, P. (2005). Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Scandinavian Journal of Medicine and Science in Sport, 15: 69-78.
Giles, D & MacLaren, D. (1984). Effects of caffeine and glucose ingestion on metabolic and respiratory functions during prolonged exercise. Journal of Sports Sciences, 2: 35-46.
Goldstein, ER., et al. (2010). International Society of Nutrition Position Stand: caffeine and performance. Journal of the International Society of Sports Nutrition, 7: 5-20.
Passman, WK., et al (1995). The effect of different dosages of caffeine on enduranc performance time. Internationl journal of Sports Medicine, 16: 225-230.
Roberts, SP., et al. (2010). Effectsof carbohydrate and caffeine ingestion on performance during a rugby simulation protocol. Journal of Sports Science, 28: 833-842.
Spriet, LL. (2014). Exercise and sport performance with low doses of caffeine. Sports Medicine, 44: S175-184.