In the summer of 2013 Sergei Boutenko put 10 endurance athletes (five ultra-runners and five Cross Fitters) on green smoothies and followed them around with his camera to find out the answer to this question. Starting out as healthy athletes (or so they thought!), 10 individuals embark on a six-week experiment of continuing their typical training and racing regimen, but with one major difference: they are drinking a quart of green smoothies every day.