Which statement describes the effect of aerobic exercise on the body?

• A. It reduces blood flow
• B. It weakens the heart
• C. It has no effect on the cardiovascular system
• D. It helps the heart deliver oxygen to muscles

Answer: (D)

Aerobic exercise makes the cardiovascular system more efficient at moving blood and oxygen to working muscles. With regular aerobic activity, the heart pumps more blood with each beat (increased stroke volume), so it delivers more oxygen and nutrients to muscles during activity. Over time, blood vessels adapt by improving circulation to those muscles, and muscles become better at using the oxygen they receive (higher VO2 max). This combination is why the statement that aerobic exercise helps the heart deliver oxygen to muscles is the best description of its effect.

Other ideas to note: blood flow to working muscles increases, not decreases; the heart generally becomes stronger and more capable, not weaker; and aerobic exercise clearly affects the cardiovascular system rather than having no effect.