At any rate, the supplement is legit. Kendall points out that it helps on multiple fronts as an aid for enhancing power, building muscle, and boosting endurance. She says, "Creatine supplementation works by increasing the availability of creatine and phosphocreatine (PCr) within the muscle, helping to maintain energy during high-intensity exercise such as weightlifting, circuit workouts, and tempo runs. Increasing the availability of PCr may also help speed up recovery between sets."
Because of the length of time creatine has been on the market, there are literally hundreds of research studies published supporting its benefits and safety. Back in the day, there was some concern that supplementing with creatine screwed up your kidneys, but subsequent research has shown that's not a concern for the vast majority of healthy people.
Kendall also notes that while creatine gets most of its cred for improving muscular strength and size, it's also a powerhouse for endurance athletes, particularly during interval workouts at lactate threshold, speed work, and hill routines. "Creatine supplementation has been shown to decrease recovery time during repeated intervals, and increase power output at lactate threshold. Improvements in speed, power, and running economy during your training sessions translates to better race-day performance."