We’ve all been told that protein and carbohydrates are a ‘must-have’ for endurance athletes after a tough workout—but why? New research explains the performance-boosting power behind your post-run shake.

In the study, men who consumed a protein-carb drink after an intense cycling workout had an increase in the production of proteins in the body responsible for building myofibrils—basic units of muscle that make your muscles contract.

However, researchers were surprised to find that the drink didn’t help the body produce proteins responsible for building mitochondria—the energy-producing powerhouses in your cells that are part of your body’s aerobic system.

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So does this mean that endurance athletes can skip post-workout protein and swig Kool-Aid instead? Just the opposite. Eating carbs with protein can increase your muscle mass and speed up recovery time, improving performance, explains lead study author Leigh Breen, Ph.D., of McMaster University. Take this study, for example: When comparing two timed rides on a stationary bike, James Madison University researchers found that cyclists who consumed a carbohydrate-protein mix after their first trial rode 13 percent longer on their second trial (compared to those who only consumed a plain carbohydrate mix).

Interested in making your own recovery blend? After a cardio workout, aim for a 2-1 (carb to protein) ratio for your recovery drink, says sports nutritionist, Nancy Clark, M.S., R.D. The carbs refuel the depleted glycogen (energy) stores in your muscles, and the protein builds and repairs the muscle fibers.

Typically experts recommend about 20 grams of protein. Try mixing together this summer smoothie recipe:

• 20 grams of vanilla whey protein
• 1 cup of blackberries (7 grams)
• 1 cup of raspberries (7 grams)
• ½ cup of blueberries (9 grams)
• ½ cup of pineapple (10 grams)
• 11 grams 2% milk or 10 grams of unsweetened soymilk