Which of the following is a short-term effect of aerobic exercise?

The increase in breathing rate is indeed a short-term effect of aerobic exercise. When engaging in aerobic activities such as running, cycling, or swimming, the body requires more oxygen to meet the increased energy demands. As a result, the respiratory system responds by enhancing the rate and depth of breathing. This increased breathing rate allows for greater oxygen intake and carbon dioxide expulsion, supporting the heightened metabolic activity occurring during exercise.

In contrast, a decrease in blood pressure is typically a long-term adaptation to regular aerobic exercise rather than an immediate short-term effect. A decrease in heart rate is also not characteristic of aerobic exercise; in fact, during the activity itself, heart rate generally increases to supply more blood (and therefore oxygen) to the working muscles. Finally, stroke volume— the amount of blood pumped out of the heart with each beat— usually increases during aerobic exercise to improve efficiency in delivering oxygen throughout the body, rather than decreasing.