Creatine helps muscles store the type of energy they need for strength, speed and power in short bursts, called anaerobic exercise. In one study, 50 moderately trained men and women measured their maximum anaerobic running capacity on a series of treadmill tests over three days. Participants then took 5 grams of creatine four times per day or a placebo. After five days, participants repeated the three-day treadmill test. While there was no effect in women, men who took creatine increased their anaerobic running capacity by 23 percent, without significant weight gain.