The R wave is a component of the electrocardiogram (ECG or EKG), which is a test that measures the electrical activity of the heart. It represents the upward deflection seen in the QRS complex, indicating the depolarization of the ventricles. This phase is crucial for the heart's pumping action, as it signals the contraction of the heart muscle. In a typical ECG reading, the R wave follows the P wave and precedes the T wave. The height and duration of the R wave can provide important information about heart health and function, helping healthcare professionals diagnose conditions such as arrhythmias or myocardial infarctions.