Stuttering is not a lack of air. Under nervous stress or in a significant situation, the nervous system switches into a protective mode and seems to lock up. At that moment, it is not breathing that is blocked, but the coordination between breathing, the vocal folds, and articulation. There is air in the lungs, but the signal to start speech is temporarily inhibited. That is why it subjectively feels like there is no air to speak or the air will not go through, although in reality the problem is not the amount of air, but the fact that the automatic speech program cannot start. This is not a matter of conscious control or weak willpower, but a reflexive reaction of the nervous system.