Does leucine-enriched amino acid and carb intake after weight training keep muscle-building signals active longer than exercise alone?

The evidence we’ve reviewed includes 46 studies or assertions that support this idea, with none that contradict it. These studies suggest that combining leucine-enriched amino acids with carbohydrates after training helps maintain higher levels of this signal compared to training without any post-workout nutrition. Leucine is one of the branched-chain amino acids found in protein, and it appears to play a strong role in triggering this response. Carbohydrates may help by raising insulin, which can support leucine’s effect.

What we’ve found so far leans toward the idea that adding a post-workout shake with protein and carbs can extend the window during which your muscles are primed for growth. However, we don’t yet know how much of a difference this makes in real-world muscle gains over weeks or months, or whether it matters more for certain people—like beginners, older adults, or those training intensely.

The evidence doesn’t say you must drink a shake after every workout, but if you’re trying to support muscle recovery and growth, having a simple drink with protein and carbs right after training is a practical step that aligns with what we’ve seen so far.