I learned something interesting during this past holiday while watching the kids play in the pool. We have always known that spending time in the pool relaxes them, especially when their anxiety is very high. In fact, getting into the pool just before a total meltdown can sometimes stop the meltdown from happening.
So, as I sat there, I started looking for reasons why they have this response to the pool and came across something called the mammalian dive reflex.
This reflex is triggered when a mammal’s face comes in contact with or is submerged in cool water. When this occurs, information that the face has encountered water is transmitted to the brain, resulting in the immediate closure of the airway as well as a number of physiological changes to optimize the body’s conservation of oxygen.
The first change is a reduction of the heart rate by approximately 10-25% occurs immediately upon facial contact with water (even simply splashing the face with water will achieve this effect). The slowing of the heart rate reduces the rate of oxygen entering the bloodstream allowing the body to conserve oxygen and for vital organs to more efficiently use it.
Then the blood vessels contract to reduce blood flow and capillaries in the extremities (fingers, toes, hands, feet, arms, and then legs) begin to constrict which restricts blood flow to those areas. Blood is thus directed towards the vital organs, which include the heart, lungs, and brain – all of which are fueled by significantly higher amounts of oxygen than other peripheral organs.
As you go deeper in the water, the lungs and the air contained inside of them will compress, resulting in a higher percentage of blood volume in this area due to a combination of the dive reflex and the smaller lung volume. Blood, which is similar in many forms to ocean water will not be able to be compressed due to its liquid/fluid nature and will retain its volume regardless of the depth that a diver may reach, leading to a higher concentration of blood in the lungs.
So, how does that prevent meltdowns?
Anxiety activates the sympathetic nervous system. But there is a co-equal branch called the parasympathetic nervous system, or what is often referred to as the “rest and digest,” “feed and breed,” or “tend and befriend” system, because it dampens sympathetic responses and keeps the body in a restorative and resting state. In 2015, scientists found that the dive reflex occurs from signals sent by the trigeminal nerves in the face. When cold water hits the face — and it must get just below the eyes and above the cheekbones — a message is sent to the vagus nerve. The vagus nerve, which controls the parasympathetic nervous system, connects the base of the brain to the rest of the body and regulates the heart rate and breathing, among other essential functions. The result is that the parasympathetic nervous system is activated, and the sympathetic nervous system is deactivated.
Activating the diver’s reflex gives us a real-time, sure-fire way to reset an overactive (or hyper-aroused) nervous system — and the good news is that you don’t have to take up free-diving. The next time you feel especially anxious or stressed, try one of these techniques:
- Fill a large bowl with icy water and, while holding your breath, plunge your face in for 30 seconds. (If you are uncomfortable holding your breath that long, either physically or mentally, try one of the alternatives below.)
- Try finishing your next shower with 30 seconds of cold water. If that seems too jarring, you can ease yourself into it by submerging only your face in cold water.
- Place ice cubes in a Ziploc bag and press it against your face while holding your breath for a count of 6 to 8 seconds (Make sure the bag covers your eyes and the space above your cheekbones). Repeat if necessary. A bag of frozen vegetables will also do the trick.
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