An untrained 25 year-old woman is physically active. The demographic data of her weight and height is 60 kilograms and 158 centimeters, respectively. She has a resting heart rate of 80 beats/min and stroke volume of 70 ml. She usually walks to study and regularly jogging. During exercise, her heart rate slowly increases and decreases at the end of exercise. She does not complain about chest pain or any symptoms.