Abstract
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 (1) do not alter the peripheral whole-body responses to exercise; (2) improve vigilance, alertness, and mood and cognitive processes during and after exercise; and (3) 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.
Highlights
The world of sport has always had a high tolerance for the use of caffeine
For a 70 kg person, this amounted to the ingestion of 700–900 mg or the equivalent of *5–7 cups of coffee, which exceeds typical caffeine use in the general population. While studies using these high doses of caffeine reported ergogenic effects in endurance-type activities, there were pronounced effects on the physiological responses to exercise, including increased heart rates, a doubling of the catecholamine levels, higher blood lactate levels, and increased blood free fatty acid (FFA) and glycerol levels in many subjects [1,2,3,4]
When the caffeine dose was reduced to a moderate level (5–6 mg/kg bm), the ergogenic effects were maintained and the physiological responses and side effects were reduced but were still present [1, 2, 5]
Summary
While studies using these high doses of caffeine reported ergogenic effects in endurance-type activities, there were pronounced effects on the physiological responses to exercise, including increased heart rates, a doubling of the catecholamine levels, higher blood lactate levels, and increased blood free fatty acid (FFA) and glycerol levels in many subjects [1,2,3,4]. The administration of a low caffeine dose (3 mg/kg bm) produced an ergogenic effect, with no changes in exercise heart rate and the levels of catecholamines, lactate, FFA, and glycerol [2]. It may have been expected that the use of higher caffeine doses would have increased but the majority of research continues to use moderate (5–6 mg/kg bm) or low (B3 mg/kg bm) doses
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