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Feeling dizzy isn’t cool anymore: Why feeling faint after exercise means you’re doing it wrong

Updated: Sep 29, 2023

By Nicole DeBusk

Ever been on the peloton, out on a run, or in a hiit class and felt extremely dizzy when the workout is done? Us too. Can you remember if you slowly transitioned to less-strenuous movements before calling the workout session done? This is commonly referred to as “cooling down” after a workout and can be very important for your health.

The Back Story

For the last ten years my partner has had a device in his chest that records his heart to make sure that everything is functioning properly. The device was placed in his chest after he fainted on a run. For years his heart has shown no signs of any issues, even when his doctors have put it under conditions of stress to see if his heart has a negative response. While his medical team haven’t been able to find anything wrong with his heart, they decided to keep the device in place to make sure that they haven’t missed anything.

We recently moved, and so he found a new cardiologist near our new home. The device, which looks like an old MP3 player (millennials, you know what I mean), is now out of battery, and my partner finally wants it out of his chest. The first thing his new cardiologist asks is for him to describe exactly what was happening before he passed out. My partner explained that he had been running, stopped at a crosswalk to wait and cross, and then woke up with a bunch of people hovering over him. We watched as the doctor’s expression shifted, like everything finally made sense to him.

Here is what we learned…

When you exercise your muscles need more oxygen, therefore your heart rate will increase, pumping out more blood to deliver more oxygen to your working muscles. After the muscles have used the oxygen, the help squeeze blood back towards the heart. When you suddenly stop working out, your heart and muscles will stop working so hard. When this happens, your body has a harder time getting all of that extra blood from your lower limbs back to your heart, and afterwards, your brain. Therefore, when your blood is slower to deliver oxygen up to your brain, you may get dizzy, or even faint.

Image: Diagram of blood flow throughout body

Because my partner stopped running abruptly at a crosswalk, all of the blood bringing oxygen to his leg muscles while he ran wasn’t able to travel back up to his heart, and subsequently, his brain, quick enough.

I don’t know about you, but I was always under the impression that the “cool down” was to help your muscles not be so sore after, and because of this I thought, “eh, I’ll take the risk.”

Maybe in place joggers aren't crazy?

So, those people still jogging in place at crosswalks aren’t necessarily way too excited about exercise; they’re on to something. They are doing continuous light movement to make sure their heart and muscles are helping blood travel back up through their bodies. Pretty cool, right?

The next time you’re so tired that you want to immediately quit your workout session and call it a day, give yourself a minute or two to slow yourself out of it. If you’re old enough to know what an MP3 player is, or any of the iPod series that played music for us before the iPhone, then you are old enough to take your heart and brain health seriously.



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