In the first experiment, endurance kayakers were tested both with and without creatine supplementation - the results showed that after just five days of supplementation (a loading phase) their performance over 90 second intervals improved 16%, over 150 second intervals it improved 14%, and over 300 second intervals it was 7% better.
Although these aren't the sort of distances over which endurance athletes race, they are nonetheless highly significant results. These athletes dramatically improved their speed over intervals ranging from 90 seconds to 3 minutes, and it is weel established that the ability to perform fast intervals, and perform them well, is one of the bed-rocks of endurance training - improvements in workout quality generally lead to improvements in competitive performances.
On the down side, the kayakers also gained an average of 2 kilos, which would be a negative for athletes such as marathon runners - but more of that later.
In another experiment, endurance runners at Tartu University in Estonia supplemented their diets with 30 grams of creatine monohydrate per day for six consecutive days. When compared with a control group who consumed a placebo, their performance improvement over a 300-metre interval was more than twice as great for the creatine users, and more than three times as great over a 1000-metre interval.