Conclusion:
Adrenaline rush, or how I call it "The Zone", is a specialized way of a human to protect itself, placing it's full potential on brief moments, or depending on how stressful an environment has become. Again, it is triggered by the Fight or Flight response, which is also triggered by stress. Although the feeling, I've felt is not the flight response type, but the fight type, and is coinciding with the boxing saying "Killer instincts". Remember, being the threat is more relaxing, than being at threat. Through experience, a constant burst of "The Zone", will develop a sense of contentment, well-being, and happiness, which is perhaps the after effect of exercise, since adrenaline is released with endorphins at the same time. It may also develop an optimistic and narcissistic approach in life, but it all depends on the person. I theorize, that primitive species of humans, are far more physically controlling, and that adrenaline rush is created, through the evolution of man, because of the inactive fighting lifestyle of man. As we get civilized, brute force is less used nowadays, so we diminish ourselves from our truest potential, but to protect our species, our body has found a way to trigger the same primitive strength, but only on few moments called "The Zone", in order to use the actual human strength, as was the case in the past.
Final Thoughts:
I sometimes say things to people like.. "If you can feel the feeling that I feel right now, or if I can share it to the world, the world would be a better place, everyone will be so contented and happy." I theorize that it may be the effect of both the adrenaline and endorphins. So if you're feeling depressed and want to feel great, then try a workout session now, because the feeling stays for long, so go use that adrenaline! I'm inspired to write this post a week ago, because of it's significance, especially today, where I started again back to my usual training regimen. Today I used 18 oz gloves (A pretty heavy glove that I wanted to replace for a lighter one) which clearly reduced my efficacy, speed, and power. The impact was reduced, but I still managed to drop the heavy bag from it's chains, nonetheless. Adrenaline must be the culprit for that sudden increase in punching power.