Stimulants and Athletic Performance (Part 1 of 2): Amphetamines and Caffeine

Abstract

In brief: Some athletes use amphetamines and caffeine to fight fatigue, but the effects of these substances on athletic performance are unclear. Both can be harmful. Amphetamines affect the central nervous system (CNS) and can cause tremulousness, anxiety, insomnia, and fever. Caffeine can increase free fatty acid utilization, mask fatigue through CNS stimulation, and increase the force of skeletal muscle contraction. The International Olympic Committee has banned the use of amphetamines altogether, and has banned caffeine when its values are greater than 15 μ g· ml⁻¹ in a urine test.