All 5 Cardio Heart Rate Zones Explained Simply

Exercise and Heart Rate Reserve-Find Your Zone!

Here's exactly what happens every time your heart beats 🫀 It starts with an electrical signal from the SA node — your heart's natural pacemaker. That signal tells your atria to contract, pushing blood down into the ventricles. Then the ventricles contract (ventricular systole): 🫀 Right ventricle → pumps deoxygenated blood to the lungs 🫀 Left ventricle → pumps oxygen-rich blood to the rest of your body After that, the heart enters diastole — a brief relaxation where the chambers refill and pre