During Kapāla: the inhalation is passive (a natural rebound), while the exhalation is sharp and forceful from the lower belly — one contraction per second. The skull-shining name refers to the cleansing of the frontal sinuses by the rapid air pressure changes. Śūnyaka is an empty-lung retention. Viśrāma is a quiet recovery breath before the next round. Avoid with high blood pressure, heart conditions, or pregnancy.