<body><h2>Caffeine</h2><p><span style=”color: black;”> </span></p><p><span style=”color: black;”> syn. 1,3,7-trimethylxanthine syn. methyltheobromine</span></p><p><span style=”color: black;”> </span></p><p><span style=”color: black;”> <div id=’imgblock’><img data-pointer=’9097’/></div></span></p><h2><span style=”color: black;”> Description: </span></h2><p> Caffeine is classified as a central nervous system (CNS) stimulant. It belongs to a broad category of physiologically active molecules called alkaloids. Caffeine is specifically a methylated alkaloid of the xanthine family, sharing structural and functional similarity to other drugs of the class including paraxanthine, theophylline, and theobromine. As with other xanthines, caffeine is known for possessing mild (as opposed to strong) stimulant properties. It is typically described as providing increased physical energy, mental alertness, and excitability, but not euphoria. Although widely identified as a drug, caffeine is naturally occurring in many plants-based foods including tea, coffee, guarana, cocoa, and cola. It is the most widely consumed of all stimulants, with estimates suggesting that nearly 90% of the adult U.S. population use caffeine on a regular basis.</p><p> </p><p><div id=’imgblock’><img data-pointer=’9098’/></div></p></p><p>Caffeine is rapidly absorbed from the digestive tract, usually reaching peak effect 15-60 minutes after administration. It has a moderate duration of activity, exhibiting a plasma elimination half-life of 2.5 to 4.5 hours. Caffeine’s primary mechanism of action involves antagonism (blocking) of adenosine A1 and A2A receptors in the brain.186 Adenosine has CNS depressing activities, slowing down the firing rate of neurons. It is known to influence the release and activity of the neurotransmitters dopamine and acetylcholine. By antagonizing adenosine, caffeine facilitates both dopaminergic and cholinergic neurotransmission. It may also influence the secondary cellular messenger cyclic adenosine monophosphate (cAMP), as well as prostaglandin biosynthesis.187 Additionally, caffeine has a mild diuretic effect, reducing the reabsorption of water by the kidneys.188 As a sports supplement, caffeine is usually taken immediately before exercise or an athletic competition, so as to provide a short-term boost in energy during the activity. Its ability to increase mental alertness makes it useful for many sports, but especially those requiring more focus. More than that, however, caffeine is known to increase motor activity. This means that it may actually enhance the control of muscle contraction. This is, of course, another key activity that might serve to improve athletic performance under some situations. Caffeine might also support bodybuilding and sports performance efforts indirectly, by allowing the individual to practice and exercise harder, with more mental and physical intensity, so that training is ultimately more productive. The individual response to caffeine may vary.</p><h2> Promoted Benefits:</h2><p> Caffeine is promoted to increase mental alertness, focus, physical energy, endurance, and overall sports performance.</p><h2> Clinical Studies:</h2><p> Caffeine has been the subject of extensive clinical study. It has been shown to improve performance in placebo-controlled studies with trained adults. Its Clinical Support Rating is 5 (5/5).</p><p> One placebo-controlled study examined the effects of varying doses of caffeine on exercise performance in a group of trained cyclists.189 The subjects took one of three doses, 1 mg/kg, 2 mg/kg, or 3 mg/kg of bodyweight per day prior to exercise. The exercise consisted of a baseline ride on a stationary cycle ergometer at 80% oxygen consumption. This was followed by a 4-min recovery break, and then a 15-min VO2peak performance trial. The performance trial was initiated 60 minutes after ingestion of caffeine or a placebo. The subjects taking the 2 mg/kg and 3 mg/kg doses of caffeine noticed a 4% and 3% improvement in performance during the trial (respectively), while the 1 mg/kg dose had no effect. The improvements varied a great deal between individuals, with some noticing very strong, and some only minor, benefits from caffeine supplementation</p><p> Another placebo-controlled study looked at the effects of caffeine in a group of medium distance runners.190 The subjects used a dosage of 3 mg/kg of bodyweight, which was taken 60 minutes prior to an 8 km race on a track. Compared to placebo, subjects taking caffeine noticed a 1.2% improvement in performance, which amounted to a 23.8s faster run time in comparison. Individual improvements ranged from 10 to 61 seconds of improvement in time. Heart rate was higher in the caffeine group, although the subjective ratings of perceived exertion (RPE) were lower. </p><p> Another placebo-controlled study examined the effects of caffeine in a group of male and female competitive swimmers.191 The subjects took a set dose of 250 mg, which on average equated to about four milligrams of caffeine per kilogram of bodyweight (4 mg/kg). It was taken 60 minutes prior to a swimming race, which consisted of two 100-meter sprints separated by 20 minutes. The subjects taking caffeine noticed enhanced swimming velocity in both races compared to those taking placebo. The caffeine also prevented a decrease in velocity between the first and second race, which was noticed in those taking placebo. </p><p> These and many other clinical studies support the use of caffeine to enhance performance in a variety of sports. These include endurance activities, sports requiring intermittent bursts of exertion such as team and racquet sports, and sports where sustained high intensity activity for up to 60 minutes is required, such as swimming, rowing, and middle to long distance running.192 Further research is needed to better understand all of the athletic activities in which caffeine may impart a clear ergogenic effect, and how to best utilize this agent when a positive effect may be noticed. </p><h2> Empirical Evidence: </h2><p> Caffeine is a widely used sports supplement. The feedback on its use has been strongly positive. A majority of users report some benefit with regard to mental and physical energy, focus, endurance, and overall performance. Given the predominance of such positive reports, caffeine has become an extremely popular agent for providing pre-exercise or pre-event energy. For a small percentage of users, however, the stimulant properties of caffeine do not equate to any noticeable change in performance. Whether this is due to individual unresponsiveness to its ergogenic effects, or specific athletic circumstances in which caffeine may impart a beneficial effect, remains unclear. Some people are also very sensitive to the effects of caffeine, and find that its side effects outweigh its benefits. Overall, caffeine has an Empirical Evidence Rating of 5 (5/5).</p><h2> Effective Dosage: </h2><p> Based on clinical studies, a dosage of 3 mg/kg (bodyweight) of caffeine taken 15-60 minutes prior to an athletic event is recommended. This equates to about 200-250 mg for a person weighing 150-185 pounds. Studies suggest this caffeine imparts its peak effect at this moderate dosage level. Higher doses are unlikely to improve performance further, and are more likely to induce side effects. Note that coffee is not considered a good source of caffeine for improving performance, as the caffeine dosage can be very inconsistent.</p><h2> Side Effects / Safety: </h2><p> A moderate intake of caffeine (400 mg per day or 6 mg/kg of bodyweight) by healthy adults is generally considered safe, and devoid of significant side effects. Higher doses may be associated with side effects including nervousness, jitters, dizziness, elevated heart rate, and impaired performance.193 </p><p> </p></body>
