The Sneaky Cycling Hangover You Should Know About

Feeling Faint After Cycling? You May Have Post-Exercise Hypotension

If you’ve ever climbed off an indoor bicycle after an intense class and felt dizzy, woozy, or as though you might pass out, you’re no stranger to post-exercise hypotension. The condition (called PEH, for short) is just what it sounds like: A drop in arterial blood pressure that occurs after a single exercise session—whether it’s indoor cycling, running, or another intense activity—a decline that can last for hours.

It can make you feel as though your world has (literally!) been turned upside down.

This can happen to people who generally have normal blood pressure as well as those who have high blood pressure (or hypertension), though the magnitude of the drop tends to be more dramatic among those with hypertension. After exercising intensely, drops in blood pressure of 18 to 20 mm Hg for systolic blood pressure and 7 to 9 mm Hg for diastolic have been seen in those with hypertension, according to a review in the journal Hypertension; by contrast, those whose blood pressure is usually normal may experience declines of 8 to 10 mm Hg (systolic) and 3 to 5 mm Hg (diastolic). It can happen to men and women alike, and to adults of all ages, according to research in the Journal of Human Hypertension.

Many people who exercise regularly tend to have lower blood pressure and a slower heart rate than more sedentary people who aren’t as fit.

In this case, low blood pressure is a mark of cardiovascular fitness—a good thing! But some people experience a drop in blood pressure after exercising that can lead to dizziness, blurred vision, nausea, excessive thirst, and clammy skin. Some people who experience such a drop even faint after completing a hardcore workout.

Who’s Vulnerable and Why 

If you’re prone to postural hypotension (a.k.a., orthostatic hypotension), a rapid drop in blood pressure that happens when you stand up suddenly from a sitting or lying down position, you may be especially susceptible to PEH. The same is true if you’re pregnant or if you’re dehydrated.

The intensity at which you exercise also may be a factor: In a 2015 study in the journal Experimental Physiology, researchers monitored participants’ symptoms and physiological responses to cycling for one hour at 30 percent of their maximum heart rate (MHR) and 70 percent of their MHR:  When participants cycled at the higher intensity, they experienced lightheadedness and feeling faint 32 percent faster after stopping than they did after the lower intensity session.

What’s more, you may be especially susceptible to these effects at certain times of day: A 2008 study from the U.K. found that when cyclists rode at 70 percent of their maximal effort for 30 minutes at 8 a.m. and at 4 p.m., they experienced more intense post-exercise hypotensive effects in the afternoon than in the morning.


How to Avoid It

Drinking plenty of water throughout the ride can help prevent symptoms. A 2012 study from Japan had participants cycle for 60 minutes at a moderate intensity under two different conditions—while drinking plenty of water during the workout or going water-free. As they recovered after the ride, the cyclists in the water intake protocol didn’t experience the drop in blood pressure that they did when they rode under the dry conditions. You’ve heard it before: Consume plenty of H2O before, during, and after your ride to hasten recovery and help you feel good during and after your workout.

Remember, too, that preventing post-exercise hypotension is one reason why it’s important to spend a few minutes cooling down, allowing your heart rate to slow down naturally, after going hard in a cycle class. (Another is to avoid blood pooling in your legs, which can lead to a rapid drop in blood pressure, along with dizziness, fainting, muscle cramps, nausea, or other unpleasant symptoms.) When you do get off the bike, move slowly to give your body time to adjust to the change in position.

If despite taking these precautions you frequently experience intense symptoms of post-exercise hypotension or you actually faint, it’s wise to see your doctor.

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