It's Europe's first state-of-the-art carbohydrate-protein energy and hydration drink - for use DURING exercise. It contains 4 Parts carbohydrate to 1 Part whey protein, hence the name. Research shows that this critical ratio, when used during exercise, provides athletes with more energy than carbohydrate alone. Based on the Award Winning complex carbohydrate found in standard EnergySource, 4:1 is easy on the stomach, hypotonic and refreshing. Performance proven in the toughest races. Most endurance athletes should be aware the primary cause of fatigue is the depletion of muscle and liver glycogen (carbohydrate) and that ingesting carbohydrates during exercise will delay the onset of this fatigue. However many athletes remain unaware that EnergySource 4:1 containing 4 parts Carbohydrate and 1 part Protein can extend the time to fatigue up to an incredible 29% when compared to a carbohydrate only drink and 57% when compared with water. Here's why. Consuming carbohydrates during exercise delays the onset of fatigue by fuelling your muscles via blood glucose and therefore sparing muscle and liver glycogen (carbohydrate stored in your muscles and liver). The amount of carbohydrate (energy) that is delivered to the working muscles is determined by the amount of insulin released by the Pancreas in response to the rise in your blood sugar caused by the ingested carbs. Ingested Protein also causes insulin to be released, and, with the right carbs and protein, in the right ratio (4 Carbs to 1 Protein) the gastric emptying speed is not slowed and there is a larger insulin response resulting in more carbohydrate (energy) being 'driven' into the working muscles during exercise. The more carbs i.e. energy, going into the working muscles the more endurance you will have.