A physical therapist notes a linear increase in systolic blood pressure with exercise. What explains this change?

A linear increase in systolic blood pressure during exercise can be attributed to increased cardiac output. As physical activity begins, the body's demand for oxygen rises, necessitating an increase in blood flow to the muscles. The heart responds to this demand by pumping more blood per minute, which is referred to as cardiac output. Cardiac output is determined by the heart rate and stroke volume (the amount of blood ejected with each heartbeat). During exercise, both of these parameters typically increase, leading to heightened blood flow and, consequently, an elevation in systolic blood pressure.

While other factors like peripheral resistance also play a role in blood pressure regulation, during exercise, the primary influence on systolic blood pressure is the increase in cardiac output as the body works to meet the demands of active tissues.