You may already know that you should have a protein-rich snack after exercising, but are you actually getting the right kind to stimulate muscle growth? A new study from the University of Texas Medical Branch finds that eating a mix of protein types—whey, casein and soy—right after your workout may help you get bigger than just a single type of protein alone. That's because the combo of the three proteins seems to prolong the body’s amino acid (protein) delivery to muscles, increasing the amount of time that your pecks, lats and delts are in their "growth state." This happens because different forms of protein get absorbed by the body at different rates, researchers say. Soy is considered an “intermediate” deliverer of amino acids, whey is a “fast” protein and casein is a “slow” protein, taking a few hours to digest. The longer you can supply the muscle with amino acids, the better it is for growth and recovery, says Mark Cope, nutrition research scientist at Solae Global, the consumer goods company that founded the study. Since muscles need a full day or two to recover after strength training (not just 60 minutes), combining whey with soy and casein delivers a more balanced amino acid profile and provides a prolonged delivery of critical nutrients to the muscle. Not sure how to get this mass-maximizing combo without eating three different snacks? Look for ready-made protein smoothies, bars and products (like MHP’s Power Pak Pudding and PowerBar’s ProteinPlus Bites) that have a combination of whey and soy protein. You can also make your own post-workout protein snack by mixing milk (that's where you'll find casein), soy and whey powders, along with fruit and ice.