If young men who don't usually work out drink a special protein-and-sugar shake about an hour after lifting weights, their muscles build protein much faster—nearly triple the rate—compared to just working out without the shake.

If young men who don’t usually lift weights drink a special protein-and-sugar shake one hour after working out, their muscles build protein much faster—nearly triple the rate—than if they just worked out alone, probably because the shake turns on key muscle-building signals in their cells.

When you lift weights and then eat a protein-rich meal with some carbs, your muscles build more protein than if you just did the exercise or just ate the meal alone — it’s like the two work better together.

For older guys who lift weights, having a protein shake with 3 grams of leucine right after workouts and before bed doesn’t help build more muscle or strength than just having a placebo drink with the same calories.

If you're a young man who lifts weights regularly, eating 1.8 grams of protein per kilogram of your body weight every day is enough to build as much muscle as you can from training—adding extra leucine powder won't help you get any bigger or stronger.

Eating protein after working out doesn't change most amino acid levels in your muscles - only the branched-chain amino acids like leucine increase with bigger protein meals.