While it is not often claimed that spirulina affects exercise performance, a team of Greek researchers went ahead and investigated the effects of spirulina on running performance. Nine moderately trained male subjects received either supplemental spirulina or placebo daily for four weeks. Before and after this intervention, all of the subjects ran on a treadmill at 70-75 percent VO2max for two hours and then at 95 percent VO2max to failure. The whole experiment was then repeated with subject who received spirulina the first time receiving placebo the second time and vice versa.
On average, subjects were able to run more than 30 percent longer after spirulina supplementation (about two minutes and 40 seconds with spirulina versus 2:03 without). Researchers also found that spirulina supplementation increased fat oxidation and reduced carbohydrate oxidation during the two-hour run and reduced oxidative stress and increased antioxidant activity after exercise.
It is possible that spirulina supplementation enhanced performance in the high-intensity portion of the workout by reducing carbohydrate use and thus leaving more carbohydrate available. But spirulina’s antioxidant affects may also have played a role in boosting endurance at 95 percent VO2max, as free radical build-up in the muscles during exercise is an underappreciated cause of fatigue.
The study was published in Medicine & Science in Sports & Exercise.