Creatine is an amino acid, which (in the form of phosphocreatine - creatine phosphate) is an important store of energy in muscle cells. Phosphocreatine is broken down to creatine and phosphate, during short bursts of intense exercise (up to half a minute). The energy released is then used to regenerate the primary source of energy, ATP (adenosine triphosphate).
As phosphocreatine becomes depleted, power decreases as ATP production is not fast enough to regenerate the demand of the exercise. Consequently it makes sense that a larger store of phosphocreatine in muscle would reduce fatigue during sprinting and short bursts of intense exercise.
Extra creatine also should aid the muscles rate of regeneration of phosphocreatine following sprints, leading to less fatigue in repetitions. Furthermore, long term creatine supplementation has shown to improve strength and lean body mass.