Final answer:
The standard limb leads on an ECG are created by placing four electrodes on the limbs to measure the heart's electrical activity from various angles in the frontal plane.
Step-by-step explanation:
The standard limb (hexaxial) leads in an electrocardiogram (ECG) are created by the usage of electrodes placed on the limbs. In a 12-lead ECG, there are six electrodes placed on the chest and four electrodes placed on the limbs. These limb leads are responsible for measuring the heart's electrical activity from different angles, which are essentially view points that correspond to the frontal plane of the body. The leads record the difference in electrical potential between the electrodes. The placement of these leads adheres to a specific pattern that allows for standard interpretation of the ECG. Three of these limb leads are bipolar (leads I, II, and III), measuring the potential difference between two electrodes, while the remaining three are unipolar (aVR, aVL, and aVF), focusing on the potential at one electrode relative to a reference.