What Happens to Your Heart During an Exercise Cooldown and Why It Matters

exercise cooldown

Warming up before a workout and a cool down afterward is something almost every fitness trainer recommends, but not everyone does it!   It’s tempting to skip on one or both, especially if you’re short on time. Of the two, the cooldown is the one most people cut short or eliminate entirely. You’ve probably done this a few times yourself. You’re in a hurry and you jump off the exercise mat and head off to do the next task on your to-do list. Sound familiar?  One reason you shouldn’t skip the cooldown is because of the impact cooling down has on your cardiovascular system.  Why is a cooldown so important for your heart?

Putting Resting Heart Rate in Context

A normal resting heartbeat for an adult is 60 to 90 beats-per-minute and varies with age and which end you fall on depends on your age and how fit you are. A resting heart rate of 100 beats-per-minute might be normal for a young adult but abnormal for an elderly individual. Resting heart rate tends to slow somewhat with age. But, in the absence of underlying heart problems, a slower resting heart rate is more favorable from a health standpoint. That’s because a heart that beats fewer times per minute is more efficient and is associated with better cardiovascular health.

Regular cardiovascular exercise makes the heart more efficient and capable of doing its job. A heart with more efficiency doesn’t have to beat as many times per minute to get the job done. Some endurance athletes and physically active guys and gals have a resting heart rate in the ’50s or lower.

In fact, your resting heart rate may say something about the health of your heart and your likelihood of dying prematurely. One study found that mortality due to cardiovascular disease and from all causes rises 8% with every 10 beat per minute increase in resting heart rate. It showed the greatest increase in mortality at a heart rate of 90 beats-per-minute and above. Fortunately, you can slow your resting heart rate with regular cardiovascular exercise. If your pulse rate is above 90 at rest, talk to your physician. An overactive thyroid gland or anemia can cause a rapid heart rate.

What Happens to Your Heart When You Exercise?

During exercise, your heart rate rises significantly to meet the additional demands that exercise places on your body. Your muscles need more oxygen and ATP to fuel exercise. Your heart has to speed up and work harder to deliver that oxygen. In fact, blood flow to your working muscles increases by 3 to 4 times during exercise. In response to the increased demands, the sympathetic or fight-or-flight component of your nervous system tells your heart rate to speed up.

Once you stop exercising, your heart rate drops as the demand for increased oxygen slowly starts to fall. If you did high-intensity exercise, like a HIIT routine, the demands on your heart will stay a little higher even during recovery as you build up more waste products, such as carbon dioxide and lactic acid, during intense exercise. Your heart has to work harder to remove this waste and bring the pH of your blood back to normal. Once you stop exercising, the parasympathetic, or rest-and-relax, component of your nervous system takes over. Your heart rate starts to slow, and your breathing slows.

During exercise, the arteries in your extremities open wider to let more blood flow reach the working muscles. If you stop exercising suddenly, all of the extra blood that was being pumped to your muscles can pool in your lower extremities as the pumping action of your muscles that keeps the blood flowing has stopped. With so much blood pooling in your legs, there’s less to reach your brain and you might feel lightheaded or faint, especially if you jump up off or mat or move too quickly.

Sudden changes in activity are never good after a workout. That’s why a cooldown is so important. During a cooldown, you do low intensity, dynamic movements that keep the blood moving through your body so there’s less pooling of blood in your legs and risk of feeling lightheaded or fainting. Being fit actually increases the risk of blood pooling in the legs. When you’re fitter, your heart rate slows faster, and this worsens blood pooling in the extremities. Usually, 5 to 10 minutes of light activity is sufficient for a cooldown but it’s important not to skip it. Some cardiologists believe that cooling down slowly lowers the risk of cardiovascular events in people with heart disease. It’s not clear whether this applies to people without cardiovascular disease too.

What a Cooldown Doesn’t Do

Are there other benefits to a cooldown? Unfortunately, there’s no strong evidence that a cooldown reduces delayed onset muscle soreness. (DOMS), the stiffness and achy muscles you get after a workout your muscles aren’t accustomed to. In fact, a 2019 study found that a warm-up is more effective than a cooldown for reducing DOMS. It’s also not clear whether a cooldown lowers the risk of injury. In support of cooldowns lowering injury risk, a study of physical education students found that cooling down after a workout modestly lowers the risk of ankle injuries.  So, it may not greatly reduce your risk of injury and it probably won’t make you feel less sore after a workout, but your heart appreciates that cooldown!

The Bottom Line

Don’t skimp on the cooldown. The harder you worked, the more you need to cool down. An active cooldown that gradually decreases in intensity keeps your muscles pumping blood out of your extremities and back to other parts of your body that need it, like your brain. This reduces the chance that you’ll feel dizzy, lightheaded or even faint after a workout. Also, make sure you’re drinking enough fluid. Dehydration increases the odds that you’ll feel lightheaded and will slow your recovery.



NYTimes.com. “Is the Exercise Cool-Down Really Necessary?”
Eur Heart J. 2006;27(20):2387-2393.
Sports Med. 2018; 48(7): 1575–1595.
Journal of Human Kinetics 35(1):59-68 · December 2012.
Goossens, L., Verrelst, R., Cardon, G., and De Clercq, D. (2014), Sports injuries in physical education teacher education students. Scand J Med Sci Sports, 24: 683–691. doi:10.1111/sms.12054.


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