We need fuel.
For walking the dog.
For yelling at the neighbors when they tell you to clean up after the dog.
For bench pressing 300 hundred pounds 300 times.
Our fuel is (deep breath) Adenosine Triphosphate (ATP)
I could bore you to tears with the bio-chemistry of it all; all you need to realize is that we use three mechanisms to produce ATP.
The best is 'Creatine Kinase' - notice the word Creatine in there?
This bad-boy is responsible for every gut-check bicep curl we do.
Every rep costs ATP, which converts to Adenosine Diphosphate (ADP - acronyms are fun!!) as you lower yourself into the squat - and ADP is useless.
If you are full of Creatine, it lends the missing letters of the alphabet to ADP, turning your D back into T (by lending a phosphate) and letting you finish the rep.
Food sources like meats and fish, are full of the stuff, although a great deal is lost in the cooking process.
And since most of us only store 60 -80% of our potential Creatine levels, supplementation is an effective boost.
How much hasn't been locked down yet; some bodybuilders supplement with pre-workout meals, and post workout shakes.
( Unless) Creatine is the Enemy.
Since its rise to dominance in the supplement wars, Creatine has had a fair share of detractors. Much of the bad press stems from the product's alleged side-effects.
As the theory goes, Billy Bodybuilder, arms full of Creatine, can contract (squeeze) so hard at the top of a preacher curl, that both muscle cells and connective tissues explode under the strain of his mighty flex.
Creatine, by improving the explosive energy output of Billy's guns, overwhelms the actual existing mechanical strength of the muscle itself; the result is ripping and tearing and sobbing.
Lots of sobbing.
Now there are no studies proving this - and it stands to reason that Billy might be pushing harder, due to the perceived 'boost' he feels the supplement has given him - but it is worth noting, nonetheless.
Most problems stemming from supplementation are strictly dosage related.
Stomach cramping and diarrhea at the gym aren't fun; to avoid them, follow the instruction label on the bottle - always.
If there is a 'loading phrase' (where you've taken a ton, in comparison to the regular 'maintenance phase') be sure to scale back when instructed to do so.
Many a gym-hero has adopted the 'more-is-more' mentality, and taken the max dosage, for the maximum duration; this in turn could cause maximum strain on the kidneys... and the toilet seat.