GLOSSARY

Caffeine Half-Life Reference Table

Low caffeine doses can be effective; the athlete must consider prior exposure, sleep, medicines and individual sensitivity.

Caffeine Half-Life describes the time for caffeine concentration to decline by half under defined conditions, with substantial individual variation.

Caffeine antagonizes adenosine receptors and can improve selected endurance, alertness and high-intensity outcomes. Response varies with dose, task and individual sensitivity. More caffeine is not necessarily more effective, and side effects can outweigh a modest performance benefit. Count caffeine from coffee, gels, drinks, tablets and combinations together. Sleep disruption, anxiety, gastrointestinal symptoms and cardiovascular complaints deserve attention. Pure concentrated caffeine powders pose a particular dosing hazard; a product's stimulant effect is not proof of adequate or safe fueling.

Caffeine delivery and clearance vary with formulation, food, metabolism, medication and individual physiology. Chewing gum and swallowed products can have different absorption patterns, while the amount in coffee can vary. CYP1A2 contributes importantly to metabolism, producing metabolites including paraxanthine. Habitual intake and withdrawal can influence study interpretation, but complete abstinence is not a universal requirement for benefit. A single genotype does not reliably determine every performance response. Consider both the intended session and the possibility of residual effects on later sleep.

For example, add the caffeine from coffee, a gel and a pre-workout product before evaluating the day's exposure. An athlete may feel more alert yet sleep poorly afterward. Judge the strategy by the intended performance task and subsequent recovery, and avoid treating the strongest sensation or largest dose as the best outcome.