Dr. Robert Portman is and exercise scientist and coauthor of three books,

and has authored hundreds of articles on how nutrition can improve fitness, health and athletic performance.

Dr. Portman teaches us that there are five macro-nutrients that an endurance athlete needs to know how to use: Water, Proteins, Carbohydrates, Fats, and electrolytes. By knowing WHEN and HOW MUCH to use the macro-nutrients, we can raise our performance, avoid bonking and G.I. distress.

Once we understand how to utilize these macro-nutrients, there are micro-nutrients that can further tweak and enhance our performance.

Over the last 30 years, Dr. Portman has reshaped sports nutrition and the development of energy products with proven performance and recovery benefits, including: Endurox R4, Accelerade and now Body Glove SURGE, an energy shot for endurance athletes.

Unsure of how much hydration and nutrition to use on your next workout? Check out The Portman Calculator: easily compute your hydration and nutrition needs for a workout or race.

Here are some other interesting articles that Dr. Portman has written:

Check out our new sponsor's, "Race Course in Review" by Vasque Running Shoes

Take the Tailwind Challenge at: Tailwind Nutrition

Download a free audio book at Audible

Dr. Robert Portman: Optimizing your energy systems

Trail Runner Nation