Cardiovascular endurance is the ability of the heart, lungs and blood vessels to deliver oxygen to working muscles and tissues, as well as the ability of those muscles and tissues to utilize that oxygen over an extended period of time with moderate intensity.
Even though the symptoms of the stimulants and depressants are quite opposite, the causes of these symptoms are completely unrelated. A stimulant could cause one area of the brain to release a chemical and a depressant could affect a completely different area of the brain. They don't have to counteract each other.
