Why Runners Get Dizzy After Racing

Returning your body to normal after a finish isn’t always simple.

Hannah asks: I ran my first half marathon last week and everything went fine until I crossed the finish line. After I stopped running, I got really lightheaded and felt like I might pass out. I sat down, and then about 15 to 20 minutes later this feeling passed. What would cause this? I never experienced this during training.

Feeling dizzy or lightheaded after exercising is not altogether uncommon.

Sudden stopping after running can cause a drop in blood pressure, which may induce dizziness, fainting, and/or nausea. That being said, it’s always best to check in with your physician and discuss these symptoms to alleviate any concerns you may have.

As you run, blood vessels dilate, muscles contract, and the heart pumps faster in order to meet the energy demand of running. In addition to providing movement, these muscle contractions also serve to pump blood back to the heart, assisting with the venous return of blood flow. This pumping cycle helps meet the increased oxygen demand running requires.

When you cross the finish line and stop, the heart loses the pumping assistance of these muscles. With blood vessels dilated and no return pumping action, blood quickly pools in your extremities, causing our blood pressure to drop.

Also, your race effort typically means a faster run pace than a training run, and this increased intensity means a higher heart rate and an increase in sweating. Race effort also may mean a lower fluid intake during the race as you speed through support stops, pushing for a PB. This minimal fluid intake combined with heavy sweating results in lower blood volume, which means lower blood pressure.

It’s best to keep moving after crossing the finish line. Keep walking if possible, and, if not, pick up your legs like you are marching or walk in place for several minutes. You can also contract your upper-body muscles by clenching your fists, or pressing the palms of your hands together.

Pick up water and sports drink in the finish chute and start drinking immediately to replace lost fluids and electrolytes. Also, wearing compression socks can assist with venous return to the heart, so you may want to consider giving them a try.

It’s always wise to include a cooldown phase after finishing any run to allow the body time to return to normal. A cooldown lets the heart rate slow down gradually, and most importantly, allows blood flow to be redistributed from an exercise state to a non-exercise state.

Going forward, if you feel dizzy after a run, lie down immediately and elevate your legs above your heart, putting your feet up on a chair or bench.

Finally, do not get in your car and drive until you are certain you are alright. Consider bringing a friend with you to your next race too, it’s always nice to have support with you and it’s a good safety measure as well!

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