When rats exercised and then ate a small amount of whey protein hydrolysate, their muscles built protein faster than when they ate regular whey protein at the same dose.

A small dose of whey protein hydrolysate made a key muscle-building signal stronger in rats than regular whey protein or no protein.

When rats ate a larger dose of regular whey protein, their blood had more leucine than when they ate the same amount of hydrolyzed whey protein an hour later.

A larger dose of regular whey protein activated a key muscle-building pathway more than hydrolyzed whey protein or no protein in rats.

Neither type of whey protein affected insulin levels in rats' blood an hour after exercise, regardless of dose.

For rats, the best time for muscle protein building after eating regular whey protein is about an hour later.