Final answer:
An electrocardiogram (ECG) assesses the heart's conduction system during exercise by recording the electrical activity of the heart and tracking changes in the cardiac cycle.
Step-by-step explanation:
The tool that assesses the heart's conduction system during exercise, increasing the demand for oxygen, is the electrocardiogram (ECG). An ECG records the electrical activity of the heart and can identify how the heart responds to the stress of exercise. During a stress test, the ECG tracks changes in the cardiac cycle, including the depolarization and repolarization of atrial and ventricular chambers of the heart, as represented by the P waves, QRS complex, and T waves on the ECG. The test evaluates how the heart's conduction system, comprising the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers, manages the increased workload imposed by exercise.