This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
[{'content': 'Increase in cardiac output in exercise is due to: \nSelect and explain. \nA. Increased HR, B. Decreased HR, C. Increased TPR, D. Increased BP', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: a (Increase in HR) Ref: Ganong, 22nd ed, p. 632, 633In muscular exercise there is increase in sympathetic activity resulting in increased cardiac contractility and heart rate. Rise in heart rate is the major event that occur in normal individuals compared to increase in contractility, rememberCardiac output = HR X Stroke volumeTherefore, cardiac output increases in normal individuals at the cost of increase in heart rate.', 'role': 'assistant'}]