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

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.

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

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

After swimming, rats that drank whey protein had more leucine in their blood than those drinking other proteins at 1 and 1.5 hours after eating.