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Most past studies have examined the ergogenic effects of cocaine on animals, but the bulk of the data is easily extrapolated
to humans. While coke unquestionably stimulates certain regions of the brain, its effects on energy and strength are mostly
negative. Most of cocaine's effects are mediated by an increase in brain chemicals called neurotransmitters, which transmit
nerve signals in the brain. Normally; these chemicals rapidly break down, but cocaine prevents their re-uptake, thus extending
The two primary brain neurotransmitters affected by coke are dopamine and norepinephrine. These chemicals are also mood-elevating substances, accounting for the obvious effects of cocaine. But you pay a price for this increased stimulation, as the chemicals rapidly deplete under cocaine's influence. This leads to depression, which in turn often leads to another round of cocaine use to alleviate the rampant depression. Before you know it, you're engaged in a deadly dance with the "white lad."
Cocaine also takes a toll on other substances in the body related to energy production during exercise. For example, the drug causes an increased catecholainine response, which produces an increased release of epinephrine and norepinephrine: Both of these substances increase muscle and liver-glycogen breakdown, while increasing heart rate and blood pressure.
The rapid breakdown of glycogen leads to a buildup of lactic acid, which inhibits muscle enzymes required for energy production. Thus, you become tired faster under the influence of cocaine. The drug also fosters vasoconstriction, or tightening of small blood vessels, which inhibits oxygen delivery to muscle tissue. This leads to still more lactic-acid buildup.
Can you become conditioned to the effects of cocaine, as is the case with some other drugs, including amphetamines? A recent study published in Medicine and Science in Sports and Exercise (27:65-72, 1995) looked at the effects of cocaine on exercise in rats that were conditioned to using the drug. Cocaine still stimulated increased glycogen breakdown and lactic-acid buildup in muscle, but the rise in catecholamines was even higher than it was in non-conditioned animals.
This poses extreme danger, since catecholamines are elevated during exercise under normal circumstances. The increased release of these chemicals by cocaine can accelerate heart rate and further raise blood pressure that has already been increased by the exercise-induced catecholamine release. The risk of blood clotting also rises, and if a clot forms and lodges in a coronary artery already occluded by fat, a heart attack may result. If it happens in the brain, you've got a potential stroke.
On the plus side, cocaine does decrease one's appetite. The bad news, however, is that the effect is transitory and rapidly dissipates with continued drug use.
Finally, cocaine has a mysterious, unexplained effect on blood glucose. While increased catecholamine release usually increases blood glucose through glycogen breakdown, cocaine somehow depresses blood glucose. How it does this is anyone's guess.