What is Caffeine?
Caffeine, by definition, is a drug that stimulates the central nervous system (see pre-workout ingredients), causing increased heart rate and alertness. It’s a plant product that is most commonly found in coffee beans, tea, soft drinks, cocoa and chocolate. Caffeine is also found in some prescription and non-prescription drugs, including cold, allergy and pain relievers.
Caffeine acts as a stimulant by exerting an effect on the central nervous system. The effects of caffeine on the body may begin as early as 15 minutes after ingesting and last up to six hours. It has many effects on the body’s metabolism, including stimulating the central nervous system. This can make you more alert and give you a boost of energy.
From MedlinePlus.gov, https://www.uhs.umich.edu/caffeine
Caffeine and Exercise
“Caffeine is a common substance in the diets of most athletes ([typically in various pre-workout supplements]) and it is now appearing in many new products, including energy drinks, sport gels, alcoholic beverages and diet aids.”
“It can be a powerful ergogenic aid at levels that are considerably lower than the acceptable limit of the International Olympic Committee and could be beneficial in training and in competition.”
“Caffeine does not improve maximal oxygen capacity directly, but could permit the athlete to train at a greater power output and/or to train longer. It has also been shown to increase speed and/or power output in simulated race conditions. These effects have been found in activities that last as little as 60 seconds or as long as 2 hours.”
There is less information about the effects of caffeine on strength; however, recent work suggests no effect on maximal ability, but enhanced endurance or resistance to fatigue. There is no evidence that caffeine ingestion before exercise leads to dehydration, ion imbalance, or any other adverse effects. The ingestion of caffeine as coffee appears to be ineffective compared to doping with pure caffeine. Related compounds such as theophylline are also potent ergogenic aids. Caffeine may act synergistically with other drugs including ephedrine and anti-inflammatory agents. It appears that male and female athletes have similar caffeine pharmacokinetics, i.e., for a given dose of caffeine, the time course and absolute plasma concentrations of caffeine and its metabolites are the same. In addition, exercise or dehydration does not affect caffeine pharmacokinetics. The limited information available suggests that caffeine non-users and users respond similarly and that withdrawal from caffeine may not be important. The mechanism(s) by which caffeine elicits its ergogenic effects are unknown, but the popular theory that it enhances fat oxidation and spares muscle glycogen has very little support and is an incomplete explanation at best. Caffeine may work, in part, by creating a more favourable intracellular ionic environment in active muscle. This could facilitate force production by each motor unit.
References
https://www.ncbi.nlm.nih.gov/pubmed/11583104
Dosage of Caffeine
Caffeine is a popular work-enhancing supplement that has been actively researched since the 1970s. The majority of research has examined the effects of moderate to high caffeine doses (5–13 mg/kg body mass) on exercise and sport. These caffeine doses have profound effects on the responses to exercise at the whole-body level and are associated with variable results and some undesirable side effects. Low doses of caffeine (<3 mg/kg body mass, ~200 mg) are also ergogenic in some exercise and sport situations, although this has been less well studied. Lower caffeine doses do not alter the peripheral whole-body responses to exercise; improve vigilance, alertness, and mood and cognitive processes during and after exercise; and are associated with few, if any, side effects. Therefore, the ergogenic effect of low caffeine doses appears to result from alterations in the central nervous system. However, several aspects of consuming low doses of caffeine remain unresolved and suffer from a paucity of research, including the potential effects on high-intensity sprint and burst activities. The responses to low doses of caffeine are also variable and athletes need to determine whether the ingestion of ~200 mg of caffeine before and/or during training and competitions is ergogenic on an individual basis.
“Caffeine is probably the most widely used drug. It falls in the stimulant class, and effects the central nervous system. The lethal dose of caffeine is too high to be of daily concern; the lethal dose is 170 mg/kg, or 12.5-14.6 g for an average adult male.”
“Doses of 100-200 mg result in increased alertness and wakefulness, faster and clearer flow of thought, increased focus, and better general body coordination. It also results in restlessness, a loss of fine motor control, headaches, and dizziness.”
References
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4213371/
http://svmsl.chem.cmu.edu/vmsl/Caffeine/Caffeine_effects.htm
Side Effects
While consuming moderate amounts of caffeine does not seem to have long-term detrimental effects, consuming larger amounts of caffeine (1000 mg or about ten 6-oz cups of coffee a day) on a regular basis may be linked to conception problems, increased episodes of heartburn, and changes in bowel habits.
Too much caffeine may lead to sleep deprivation and a tendency to disregard the normal warning signals that the body is tired and needs rest. Caffeine does not replenish energy or prevent emotional fatigue; food and sleep are the only remedies for these. When normal sleeping patterns are continually disrupted, mood depression may occur. Too much caffeine may also lead to anxiety-related feelings such as excessive nervousness, sweating and tremors.
People who take medications for depression, anxiety or insomnia, high blood pressure, other heart problems, chronic stomach upset or kidney disease should limit caffeine until discussing the matter with a clinician.
References
https://www.uhs.umich.edu/caffeine
From Wikipedia
“Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is the world’s most widely consumed psychoactive drug. Unlike many other psychoactive substances, it is legal and unregulated in nearly all parts of the world. There are several known mechanisms of action to explain the effects of caffeine. The most prominent is that it reversibly blocks the action of adenosine on its receptor and consequently prevents the onset of drowsiness induced by adenosine. Caffeine also stimulates certain portions of the autonomic nervous system.
Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). It is found in the seeds, nuts, or leaves of a number of plants native to South America and East Asia and confers on them several survival and reproductive benefits. The most well known source of caffeine is the coffee bean, a misnomer for the seed of Coffea plants. Beverages containing caffeine are ingested to relieve or prevent drowsiness and to improve performance. To make these drinks, caffeine is extracted by steeping the plant product in water, a process called infusion. Caffeine-containing drinks, such as coffee, tea, and cola, are very popular; in 2005, 90% of North American adults consumed caffeine daily.”
