Due to what does the volume of muscles increase during sports, physical labor?

During sports, you can see that the muscles have increased in volume. After a while, we will notice that they have returned to their previous form. This happens after each prolonged load, for example, when lifting a barbell or dumbbell. Muscle volume increases due to blood flow, as cells need sufficient oxygen. But playing sports increases muscles for a long time. Muscle fibers are torn and regenerated in greater quantities. This is how muscle growth occurs in athletes.