Boost endurance levels by adding protein to a carbohydrate drink
Endurance athletes increased post-workout performance by 51% with this specific amount of protein and carbs
by Jeff S. Volek, Ph.D., R.D.
Strength and power athletes know that adequate protein is needed to gain muscle mass. Endurance athletes, on the other hand, who are not focused on building additional muscle mass, typically focus more on carbohydrate intake with little attention to protein. Carbohydrate intake can prevent blood sugar from dropping during exercise, delay fatigue and allow athletes to exercise longer. The question recently posed is whether adding protein to carbohydrate offers any additional advantage for endurance athletes than carbohydrate alone. There are many reasons a little protein could be advantageous for endurance athletes. Two recent studies tested the effects of adding protein to carbohydrate during endurance exercise.
Protein/carb beverage increases post-workout performance 51%
Researchers in the United Kingdom examined different beverages and their effects on recovery in highly trained cyclists.  The cyclists were required to ride to exhaustion on three separate occasions. Prior to each ride to exhaustion, they performed a standardized bout of exercise to deplete muscle glycogen levels. Immediately after the exercise and two hours into recovery they were given one of three beverages: a commercial carb-based drink (31g carbs), a commercial high-carb drink (73g carbs), and a beverage that contained both carbs and protein (63g carbs, 14g protein). After four hours into recovery, the subjects performed a cycle-to-exhaustion test at 70% of their maximal power output. When the cyclists consumed the beverages containing only carbs, they lasted about 22 minutes. With the carb-protein beverage, however, they lasted 32 minutes, a 51% improvement in performance.
Protein/carb post-workout beverage improves recovery
Exercise science researchers at James Madison University had trained cyclists ride to exhaustion on four separate occasions.  During each trial, the cyclists consumed either a 19g carb beverage with added 5g protein (carb-protein), a 19g carb beverage (carb), a matched 24g carb beverage with additional carbs to match the calories provided by protein (carb-carb) or a placebo (water) every 15 minutes until fatigue. Subjects cycled the longest with the carb-protein beverage (126 minutes) with the next best performance in the carb-carb trial (121 minutes) followed by the carb (118 minutes) and water (107 minutes) trials. Interestingly, the carb-protein trial also had lower levels of muscle damage markers. Consistent with less muscle damage, the carb-protein trial had increased muscle strength 24 hours after exercise compared to the other trials, indicating better recovery.
Protein helps endurance sports
Prolonged endurance exercise can result in significant protein breakdown to provide fuel for exercise. Protein may aid recovery by providing amino acid building blocks for protein synthesis that would otherwise need to be broken down from existing muscle. Thus, protein could prevent a catabolic state. Certain amino acids may also enhance exercise-related immune responses.
Regardless of the exact mechanisms, these two studies show that adding protein to carbohydrate helped endurance athletes, even when additional carbohydrate is added to match for total calories. Strength athletes are not the only ones who would benefit from adding protein to their sports beverage; endurance athletes would benefit as well.