John Halliwill, PhD

Do you ever get lightheaded or feel a little dizzy after hard exercise? Maybe you have felt a little bit of “tunnel vision” after a hard sprint or when you stand up in the first hour after a long training session? This is a surprisingly common occurrence in healthy people, as recently reviewed in the European Journal of Applied Physiology. Physiology can help you understand how to use the “heart in your legs” to pump away those symptoms.

You probably know that the heart is a pump and it works to keep blood moving around your body to supply your brain, your muscles and other body organs with oxygen and nutrients. When you perform exercise, such as walking, running and biking, the heart is also being helped out by another pump—the muscle pump—which is like having a second heart in your legs.

How does that work? When we exercise, with every step, stride or pedal stroke, the muscles in our legs compress the blood vessels that pass through them. This compression pumps blood from the legs, moving it back to the heart and greatly assisting the ability of the heart to move blood around your body. But when we stop moving, like at the end of exercise or while resting from a hard workout, lots of blood flows into the legs but doesn’t get the extra push from flexing muscles to move back toward the heart. This makes us susceptible to feeling lightheaded when standing up.

Be active, and be pro-active! Don’t skip the workout, but definitely remember to cool down. A cool down of easy activity keeps the muscles pumping blood back to the heart and helps maintain blood flow to your brain. After your cool down, if you happen to feel a little lightheaded, just flex your leg muscles to turn on the pump in your legs to give blood an extra boost back to the heart and to your brain.

John Halliwill, PhD is a professor of human physiology at the University of Oregon.