explain how, theres ALOT of evidence to prove its both productive and counter
considering the medical community has still not concluded whether it actually is a performance enhancement or not, i wonder how you have been able to conclude it isnt?
off the top of my head from the studies i can remember
it has been shown to increase insulin mimicking effects
it has been shown to be CNS stimulant and improve strength
its been shwon to constrict blood vessels making oxygen transportation harder for the body
it has been shown to increas fat burning during exercise, but decrease it post exercise
its been shown to be an appetite suppressent, however once worn off has actually been shown to promote appetite
caffiene has been shown to improve endurance in athletes
so id say concluding caffeines effects is abit difficult