And now the fun thing: you take an aged individual, who might have 20% or 30 % less anabolic response to protein than a young person. If you exercise them, you can bring them up to the same level as a young person.

These two factors suggest that activity might be the main determinant of anabolic resistance, and an aging individual or age within an individual is simply a proxy for activity.

So, muscle itself doesn’t seem to get that old. It actually still responds completely normal and we can normalize for age by physical activity.