Muscle congestion means that blood enters the muscle, and the blood flow in a certain part of the muscle accelerates and the blood volume increases. For people who exercise muscles, congestion is definitely good. Just like congestion during sexual impulse, it is of great benefit! In training, when a large amount of blood flows to the target muscle and accumulates in the muscle, the muscle will become bigger and harder. It's like blowing a balloon. The bigger it is, the harder it is!