Why does your heart beat faster when you run?
Show answer & explanation
Answer: Muscles need more oxygen
Lungs tell heart to beat faster — Wrong. Lungs don't control heart rate. The brain's autonomic nervous system monitors oxygen and CO2 levels, then signals the heart to adjust. Lungs just exchange gases.
Muscles need more oxygen ✓ — Correct! Running muscles burn fuel and need lots of oxygen. Your heart pumps faster to deliver oxygen-rich blood to working muscles—up to 5 times faster than at rest!
Stomach digests food faster — Wrong. Digestion actually slows during exercise as blood diverts to muscles instead of the stomach.