Benefits of Post-Exercise Cool Down

It may be familiar to you that after exercise, especially aerobic exercise; it is recommended to slow to an easy pace. This slowing down is called the “cool down” phase of exercise, and while recommended; it is likely that many forgo it entirely. This concept not only applied post exercise, but also applies when stationary (ever seen people jumping around at a stop light?) between exercise bouts. You may not be aware, but this phase of exercise is around for several reasons, and these reasons will be outlined for you here.

What is a cool down?
A “cool down” is simply a period immediately after you have decided to finish exercise in which you slowly put the brakes on your intensity of exercise (in the case of running, simply slowing to a jog, then a walk) until moving at a comfortable, no strain pace [1]. One way to describe it is the way a plane comes in for landing; flying to the destination, it flies at a quick pace, but as it attempts to stop, it does not just drop straight out of sky. The plane will reduce speed gracefully until it lands gracefully.
 

Why is this important?
This is the meat of the subject, so let’s dive in. There are several reasons why a cool down is recommended, some quite serious and others less so.

Prevent Myocardial Infarction

This is the most serious of the reasons, but luckily, this is the least likely to happen. However, for those who have a history of cardiovascular disease, it would be prudent to mention it. Myocardial infarction (heart attack) occurs when the heart does not receive enough oxygen [2]. Taking this definition, I will now tell you a story before moving on.

I was in my exercise prescription class when my professor mentioned a man by the name of Jim Fixx. Jim was an influential figure in the 1970s and early 1980s that got the nation excited about aerobic exercise by going from a completely sedentary lifestyle to being an extremely active runner and a lifestyle advocate. He ran, a lot. On one of his runs, however, he died [3]. The ultimate reason for his death was severe blockage of several of his arteries close to the heart. However, the question remained about why Jim would die on a run, specifically? Is running bad for the heart? Unlikely.

With a bit of investigating, it was deemed that Jim had a predisposition to heart disease and that his running had actually prolonged his life [4]. Yet, even so, he had died running; he had died doing the activity claimed to be good for the heart. Well, this is the reason why the cool down period of exercise can be a life saver:

If a person has something (atherosclerosis, for example) blocking any of the large veins and arteries to and from the heart, this can lead to a heart attack. However, it is possible for us to be unaware (in a non-clinical setting) of blockage if the heart is still receiving sufficient blood to maintain normal physiological function. This means, that if the demand on the body does not increase (as with exercise, where demand dramatically increases), then it is possible for the heart to still function adequately and keep us alive. However, once demand increases (for example, in exercise), a partially blocked heart could suffer from insufficient blood entering and exiting. In this case, the heart will work harder to push blood faster (increase in heart rate) and more forcefully (increase in stroke volume) to accommodate the need. Even in such an instance, you could not notice the heart having issues, especially if a person is inexperienced. In Jim’s case, his heart was able to handle exercise before finally giving out, but there is still a third instance in which myocardial infarction could occur; this is a possible reason for Jim’s death during exercise as opposed to before exercise (Instance 1) or at the beginning of exercise (Instance 2).

 

Have you ever noticed people “running in place” during exercise outside? They look silly, don’t they? Well, if they are aware of it or not, they are doing themselves a service beyond “keeping warm”. Let’s get a bit more detail.

The body’s vascular system is made up of many different pieces, but two talked about to quite some extent, the veins and arteries, are actually different in more than just their opposite function. True, the veins tend to carry deoxygenated blood to the heart, and the arteries tend to carry oxygenated blood away from the heart. However, not only that, arteries are built to have muscles around their typically larger inside to help squeeze blood to the far reaches of the body. Veins do not have that benefit. Veins tend to be smaller in size and also have less lining muscle to help pump deoxygenated blood back to the heart. That being the case, movement leads to a stimulation of surrounding muscles, and said stimulation of muscles leads to contraction of muscles, and this contraction helps squeeze blood through the veins.


So, you have all the information you need to think of scenario 3 – the likely reason Mr. Fixx had a myocardial infarction, and the reason why a cool down is so important in regards to prevention.

Give up?


Okay, Jim did not have enough blockage of the heart to experience a myocardial infarction at rest (Instance 1), and also did not have enough blockage of the heart to cause the same scenario in the face of added demand through beginning exercise that day (Instance 2). However, if he were to exercise for a time, get his heart rate rising, his stroke volume maxed out, and then stop abruptly – for example, at a stop light waiting for the light to give him the right of way – his body would be in a state of need as his heart is pounding at an elevated pace, yet his veins are no longer being supplemented by muscular stimulation from movement.

When he stops his exercise, even for a minute and stands immobile, his body is no longer reaping the benefit of his leg muscles squeezing the blood back up to his heart (this is called “pooling” of the blood due to gravity playing a force on movement), so the heart, already taxed due to decreased blood flow entering and escaping the partially blocked veins and arteries, is forced to increase its effort to pump harder as to supply the body with enough blood. It is in this instance that the heart is taxed to a maximum, and even at maximum, it is insufficient to meet demand and a myocardial infarction occurs.

A long explanation (I left out a lot, even), but a necessary one to get an accurate grasp how all these mechanisms work together and how something as innocent as becoming immobile immediately post exercise can turn fatal. So, taking these same ideas, a “cool down” period ensures that the body keeps moving, as well as allows for a smooth transition from high demand, to medium demand, to near resting state. You take control of the transition, essentially, by decreasing intensity gradually.


  How likely is death of this nature to occur?

This is extremely unlikely. If you have a healthy heart, the chances are extremely low. However, if you suffer from previous cardiac events, have had bypass surgery, or have general cardiovascular disease, then, although the chances are still quite low, it would be wise to use this method to prevent issues.

Obviously, all risk is relative to intensity and fitness level, but risk within moderate exercise (40-60% VO2max) in those with proven cardiovascular disease is 1 myocardial infarction per 294,000 hours of exercise, and 1 death in 784,000 hours of exercise [5]. Translation: tiny.


Stretching

While the first reason for an adequate “cool down” was a hefty one, a serious one, and a rare one, this one applies to all. Far more light hearted, the bottom line is stretching is easier when your body does not require you to be gasping for air (often, a sharp, somewhat abrupt motion – not ideal for delicate stretching). Granted, a person could easily stretch a while later, but the benefits of having warm muscle bellies offers greater pliability [6]. So, a cool down, allowing your physiology to ease into a near resting state while still keeping blood circulating would be the most beneficial in terms of effectiveness and prevention of injury.

Prevent Blood Pooling

I touched on this in the first reason for an adequate cool down, but even in those with a healthy cardiovascular system, it is beneficial to cool down as to decrease the potential for light headedness, or in the worst case scenario, syncope (passing out) [7]. This is because as less of the leg muscles are used, muscle is not, even with a healthy heart, as easily pushed back up to the torso, so blood has a tendency to pool/stay in the legs and feet, hence the lack of blood in the superior regions of the body (such as the head) and cause for dizziness. Also, due to a lack of blood, the body vasoconstricts vessels so remaining blood that is not being pooled inferiorly is pulled inwards to vital organs [9]. This being the case, hands can get shaky, lose color, and feel tingly for a temporary amount of time [8].

How long should the cool down be?
A cool down length is generally relative. A few minutes is likely enough time for one’s body to calibrate and relax. About the same amount of time it took to warm up is likely enough for a cool down [10]. Granted, if your intensity was near maximal, a one minute cool down is likely too short. The opposite is likely unnecessary (light activity, ten minute cool down).

SUMMARY

After all that, the take away is cool downs can be useful, and in certain circumstances necessary. A cool down is especially necessary for those with varying degrees of cardiovascular disease or family history of cardiovascular disease. It helps prevent sudden cardiac arrest, myocardial infarction, aids in reducing dizziness, syncope, cold hands, as well as making stretching a better, more productive experience.

Writer: Nicolas Verhoeven

                                                                                                  Citations

[1] Cooldown | Define Cooldown at Dictionary.com. (n.d.). Retrieved from http://dictionary.reference.com/browse/cooldown

[2] Heart Attack - National Library of Medicine - PubMed Health. (n.d.). Retrieved from http://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0021982/

[3] JAMES F. FIXX DIES JOGGING - AUTHOR ON RUNNING WAS 52 - NYTimes.com. (n.d.). Retrieved from http://www.nytimes.com/1984/07/22/obituaries/james-f-fixx-dies-jogging-author-on-running-was-52.html

[4] THE DOCTOR'S WORLD - JAMES FIXX - THE ENIGMA OF HEART DISEASE - NYTimes.com. (n.d.). Retrieved from http://www.nytimes.com/1984/07/24/science/the-doctor-s-world-james-fixx-the-enigma-of-heart-disease.html?pagewanted=all

[5] ACSM | Articles. (n.d.). Retrieved from https://www.acsm.org/public-information/articles/2012/01/19/exercising-with-coronary-heart-disease

[6] STRETCHING AND FLEXIBILITY - How to Stretch. (n.d.). Retrieved from http://web.mit.edu/tkd/stretch/stretching_5.html

[7] Keeping Up With Cooling Down. (n.d.). Retrieved from http://certification.acsm.org/blog/2013/april/keeping-up-with-cooling-down

[8] ] Kingma, B. R. (2010). Cold-induced vasoconstriction at forearm and hand skin sites: the effect of age. European Journal of Applied Physiology, 109(5), 915-921. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892071/

[9] Rowlands, D. G. (2015). Sympathetic Vasoconstrictive Responses during Exercise- or Drug-Induced Vasodilatation. American Heart Association. Retrieved from http://circres.ahajournals.org/content/23/1/45.full.pdf

[10] Warm Up, Cool Down. (n.d.). Retrieved from http://www.heart.org/HEARTORG/GettingHealthy/PhysicalActivity/FitnessBasics/Warm-Up-Cool-Down_UCM_430168_Article.jsp

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