Energysource 41 is an all in one sports drink for use both during and after exercise it contains 4 parts carbohydrate to 1 part whey protein isolate and key electrolytes 41 is the pros choice for hard training and multi day endurance events use 41 when you anticipate a big step up in training intensity or volume such as a training camp the ingredients in 41 help sustain performance during extended exercise and help maintain hydration by enhancing the absorption of water whey isolate