Final answer:
Systolic blood pressure increases during moderate-intensity exercise to meet the body's increased oxygen demands, which is a safe and beneficial change for the circulatory system.
Step-by-step explanation:
During moderate-intensity exercise, systolic blood pressure increases. This pressure rise occurs due to the heart pumping harder to meet the body's increased demand for oxygen-rich blood. As exercise intensity ramps up, the heart's stroke volume and cardiac output increase, which in turn raises systolic pressure. However, this pressure increase is generally safe and may even improve circulatory system tone. In contrast, diastolic pressure, which is an indicator of fluid balance, typically changes less and can indicate problems if it's too high or too low. It's important to remember that a healthy range for systolic blood pressure is generally between 100 to 120 mm Hg when at rest.