Effects - a stimulant acts on the brain to stimulate the body both mentally and physically. Athletes might want to use stimulants to enhance their performance by increasing alertness and decreasing fatigue. Dangers - the misuse of stimulants can cause a rise in blood pressure and body temperature; increased and irregular heartbeat; aggressiveness and anxiety; loss of appetite; addiction. Competitors have died through misusing stimulants. Stimulant use and exercise make it difficult for the body to cool down. The heart and other organs may stop working normally. This can be fatal.