In a new study from Japan, 17 healthy volunteers, average age 37, took 100 mg of coenzyme Q10 (CoQ10) per day, 300 mg of CoQ10 per day or a placebo for eight days while testing physical endurance. All participants had a chance to try each of these doses—without knowing which was which—pausing for several days in between each 8-day dosage period. Participants rode a stationary bicycle with a fixed rate of resistance for four hours, then rested for four hours and also periodically tested maximum speed for 10 seconds at a time. Those who took the 300 mg dose of CoQ10 had significantly better physical performance, less fatigue and recovered more quickly from exercise than placebo. Participants did not experience significant positive effects when taking the 100 mg dose.