Which of the following is a sign to limit exercise intensity regardless of calculated values?

The onset of angina is a critical sign that indicates the need to limit exercise intensity, irrespective of any calculated values. Angina refers to chest pain or discomfort that occurs when the heart muscle doesn't get enough oxygen-rich blood. During exercise, the heart demands more oxygen, and if there is a blockage or narrowing of the coronary arteries, this can result in angina. When an individual experiences this symptom, it signifies that the heart is under undue stress, and continuing exercise could lead to serious complications, such as a heart attack. Therefore, it's imperative to reduce intensity or stop exercising immediately if angina occurs, prioritizing the individual’s safety and well-being.

Plateau in heart rate, increased respiratory rate, and fatigue during warm-up may indicate variations in fitness levels or individual responses to exercise but do not have the same urgent implication for immediate intervention that the onset of angina does.