During inhalation, the diaphragm contracts , flattens, and moves downward, which increases the volume of your chest cavity and creates a slight vacuum that pulls air into your lungs.

Quick Scoop

  • The diaphragm is a dome-shaped muscle under your lungs that’s the main muscle for breathing in.
  • When you inhale, it contracts and moves down, changing from a dome to a flatter shape.
  • This downward movement makes your chest cavity larger and lowers the pressure inside it.
  • Because outside air is now at higher pressure, it rushes into your lungs to equalize the pressure difference.
  • At the same time, abdominal organs are gently pushed down and out as the diaphragm descends.

What happens step by step

  1. Diaphragm receives a signal from the brain to contract (start of inhalation).
  1. It contracts and pulls its central tendon downward, flattening its dome shape.
  1. The vertical size (height) of the thoracic cavity increases.
  1. Thoracic volume goes up, and intrathoracic (intrapulmonary) pressure drops slightly below atmospheric pressure.
  1. Air flows into the lungs until the pressures inside and outside are nearly equal again.

Quick forum-style explanation

Imagine the diaphragm like a flexible floor under your lungs.
When you breathe in, that “floor” pulls down like an elevator going to a lower level, making more room upstairs (your chest).
More room means lower pressure, so air basically rushes in to fill the space and inflate your lungs.

Why it matters right now

Modern research still describes the diaphragm as the major “inspiratory pump” that must not fail, because every breath you take depends on this downward contraction creating negative pressure in the chest. In everyday terms, each quiet breath you take right now is your diaphragm repeating this same motion over and over, usually without you noticing.

TL;DR: During inhalation the diaphragm contracts, flattens, and moves downward, increasing chest volume, lowering pressure, and pulling air into the lungs while gently pushing abdominal contents down.

Information gathered from public forums or data available on the internet and portrayed here.