What is a myocardial stress test?

A myocardial stress test is designed to assess the heart's performance under conditions of physical stress, which is key for evaluating its function and identifying potential issues related to cardiovascular health. During the test, the heart's response to exercise or pharmacologic stimulation is monitored, typically involving the use of an electrocardiogram (ECG) to track heart rate, rhythm, and overall cardiac performance. This test helps in diagnosing conditions such as coronary artery disease or exercise-induced ischemia, as it reveals how well the heart can handle increased workloads.

While other options involve important health assessments—like measuring blood sugar levels, assessing lung capacity, or checking joint flexibility—they do not pertain specifically to the heart's function or its response to stress. Thus, the uniqueness of option B lies in its direct focus on cardiac performance, making it the correct answer.