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.
Los músculos intercostales, entre las costillas los usamos para inspirar y expirar aire de los pulmones simplemente expandiendo y contrayendo la caja torácica y si pusiera una correa alrededor del pecho, un cinturón de aliento, con solo mirar ese movimiento veríamos un movimiento sinusoidal apacible, conforme respiramos.