You have two subject's who have both undertaken an exercise training program. One subject brings you her training log and you notice that her blood pressure is constantly increasing (both systolically and diastolically) during exercise, while the second subject shows a moderate increase in systolic blood pressure and little or no change in diastolic blood pressure during exercise. Assuming both subjects are healthy with no cardiac or circulatory problems, explain to me why both subjects are experiencing normal responses to exercise.