Creatine is a commonly used supplement that could potentially benefit short high-intensity exercise or improve response to resistance exercise training. However, the performance and metabolic response to creatine ingestion is varied. Those starting with low muscle creatine levels are more likely to but don't always have the best response. Since creatine supplementation boosts performance in some individuals and not others, this could be construed as unfair advantage. Many questions remain about the value of creatine supplementation for performance of various sports and about how much and when to use creatine - if it should be used at all. Evidence suggests that performance benefits resulting from creatine ingestion are predominantly observed during multiple tests lasting between 30 to 90 seconds. Also, when consumed in moderate doses, there seems to be no adverse effects of creatine supplementation in healthy adults.