During aerobic activity, heart rate generally:

• A. Decreases
• B. Increases
• C. Stays the same
• D. Fluctuates randomly

Answer: (B)

During aerobic activity the body's muscles need more oxygen and nutrients to produce energy. To meet that demand, the heart beats faster, increasing the amount of blood pumped each minute (cardiac output). This rise in heart rate helps deliver more oxygen to working muscles and remove waste products like carbon dioxide, so heart rate climbs as exercise intensity grows. It may level off at a higher steady rate during sustained effort, but it does not stay the same or decrease, and it doesn’t change randomly. Overall, heart rate increases with aerobic effort and is a useful measure of exercise intensity.