Why does cardiac muscle never become tired?

This is an incorrect statement. Cardiac muscle can indeed become tired or, more precisely, fatigued and fail, just like any other type of muscle. While the heart is known for its continuous and tireless activity throughout the human's life, it is not immune to fatigue.

Cardiac fatigue can occur in several situations:

1. Ischemia: When there is a reduced blood supply to the heart muscle, such as in cases of coronary artery disease or heart attacks, the heart may experience fatigue. This is because the muscle cells do not receive enough oxygen and nutrients to sustain continuous activity.

2. Arrhythmias: Irregular heart rhythms, such as atrial fibrillation or ventricular tachycardia, can also lead to cardiac fatigue. These arrhythmias disrupt the normal coordinated contraction and relaxation of the heart, making it less efficient and prone to fatigue.

3. Overexertion: Excessive and prolonged physical exertion, especially in untrained individuals, can strain the heart muscle and cause fatigue. Marathon runners, for example, may experience transient cardiac fatigue after a race.

4. Certain Medications: Some medications, including certain chemotherapy drugs or high doses of caffeine, can affect the heart's function and contribute to fatigue.

5. Heart Failure: Advanced stages of heart failure can result in cardiac fatigue as the heart becomes progressively weaker and unable to meet the body's demands.

It is crucial to recognize and address the underlying factors contributing to cardiac fatigue to maintain heart health and prevent serious complications. Regular check-ups, a healthy lifestyle, and managing underlying medical conditions can help reduce the risk of cardiac fatigue and ensure the longevity of the heart's remarkable performance.