Final answer:
During exercise, cardiac output and blood pressure increase slowly at first and reach a steady state as the body adapts to the heightened energy requirements. These changes facilitate the increased oxygen delivery needed for muscle activity.
Step-by-step explanation:
During the first few minutes of exercise, the body undergoes various physiological changes to meet the increased energy demands. One of the factors that increases slowly and eventually reaches a steady state is cardiac output (CO), which is the volume of blood the heart pumps per minute. Cardiac output is a product of heart rate (HR) and stroke volume (SV). Initially, at rest, a healthy young adult may have a CO of approximately 5 liters per minute. As exercise commences, CO starts to increase and can reach up to 20 liters per minute for nonathletes and even higher for well-trained aerobic athletes.
Corresponding with the increase in CO, blood pressure also rises from normal resting levels (typically around 120/80 mmHg) to higher levels during peak exercise. The body's requirement for oxygen increases to compensate for the ATP generated without oxygen during muscle activity. This increased demand for oxygen results in a higher breathing rate and subsequent increased delivery of oxygen to muscles. All these changes continue until a steady state is achieved, where the body's needs are met by the cardiovascular system's performance during exercise.