So you use the intercostal muscles, the muscles between your ribs, to bring air in and out of your lungs just by expanding and contracting your ribcage, and if I was to put a strap  around the outside of your chest called a breath belt, and just look  at that movement, you see a rather gentle sinusoidal movement, so that's breathing.
Usate i muscoli intercostali,  ossia quelli tra le vostre costole, per espirare ed inspirare espandendo e contraendo  la cassa toracica. Se legassi un laccio  attorno al vostro petto detto cintura respiratoria,  guardandone il movimento vedreste che è un po' sinusoidale.