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Cold Water Exposure
Take the Plunge
Cold Water Immersion (CWI) is the seemingly masochistic act of deliberately submerging oneself in uncomfortably cold water. While this activity became popular about a decade ago among fitness nerds, it seems to have reemerged lately into the consciousness of the general health and wellness population. True, this activity may seem like a generally horrible way to spend 15 minutes of your time, CWI is an effective way to recover from exercise, elevate your mood & focus for hours, increase your metabolism and improve your general response to adversity.
There is no generally accepted protocol for CWI. Most scientific studies use prolonged exposure to water no colder that 50 degrees Fahrenheit. At these temperatures, individuals remain in the water up to 30 minutes or more. However, individuals are using water that is just above freezing. Obviously, the colder the water, the shorter the necessary exposure time, but also the greater the risk.
As a rule of thumb, you want to use a water temperature that is cold enough that you want to immediately get out, but warm enough that you can overcome that initial reaction. That said, there are plenty of published hypothermia tables that can keep you well within the margins of safety. Use of the hypothermia tables and repeated bouts of CWI will give you a good idea of what water temperature to use. If you feel a jolt of energy, an elevation of your mood, and you shiver for a bit after the plunge, you are doing it correctly.
My current protocol is 20-25 minutes of exposure to 55 degree water up to my neck. For convenience, I just fill up my tub with well-water. At this temperature I am able to remain in the water and gradually calm myself down from the initial fight or flight reflex. After a plunge, my mood is elevated, my aches and pain are reduced or eliminated, and I tend to shiver off and on for about an hour.
Recovery vs. Adaptation
How and when to use CWI in the context of exercise? Generally speaking, the use of CWI to enhance fitness seems to involve a trade off between acute muscular recovery and acute muscular adaption. That is to say, taking a cold plunge in the immediate hours after a workout is perfectly appropriate if your goal is to reduce pain/discomfort. However, if you want to maximize your body’s adaptation to exercise, CWI should be avoided for at least a 4 hours after working out. That said, CWI effects the adaptions to anaerobic exercise differently the aerobic exercise.
Anaerobic exercise involves stimulating Type II muscle fibers with resistance training. Anything from lifting weights to doing pushups can be considered anaerobic exercise. If your goal is muscle hypertrophy (getting huge), CWI in the hours immediately following a workout will attenuate your gains. How much time to wait before your ice-bath is difficult to determine as there is no standard protocol used when studying CWI. However, waiting at least 4 hours and as many as 8 hours seems to allow the body adequate time to adapt to the stress of your workout. This timeframe allows your immune system to inflame the muscle fibers, clean up the damaged cells and then adapt and rebuild those muscle fibers such that they are better equipped to deal with your next training session. This is the process of muscular adaptation and CWI immediately following a weight-lifting workout appears to interfere with this process. When you expose muscles to CWI, the muscle’s cellular metabolism slows down. In this context the immune system cannot adequately, “clean up,” the damaged muscle fibers. Furthermore, CWI appears to slow down the protein synthesis required to increase the size of muscle.
Studies looking at CWI and training for strength or speed, as opposed size, have shown mixed results. Some studies show CWI having little to no effect on strength and speed while other studies show CWI as attenuating those gains as well.
CWI has also been studied in the context of aerobic (endurance) training and appears to have no deleterious effects on performance gains. This is probably to due to two factors. One, endurance training involves type 1 muscle fibers. These are our endurance fibers and their performance is generally predicated on mitochondrial density, not muscle fiber size or contraction force. CWI does not appear to effect mitochondrial biogenesis (creation) or function. Two, CWI does not appear to have a detrimental effect on the heart or blood vessels, the primary drivers of endurance adaptation.
To reiterate, if you want to maximize muscle growth it is best to wait on CWI for at least 4 hours. If you want to run, hike, bike longer and faster, CWI can be done immediately after a workout. That’s all well and good, but how does CWI help with muscular recovery?
Because CWI dampens the body’s inflammatory response to physical stress, it reduces the muscle pain and stiffness associated with that process. Furthermore, CWI will reduce that pain associated with stress to other forms of connective tissue, such as ligaments and tendons. Furthermore, CWI immediately following a workout will reduce muscle temperature, which is the primary reason for muscle fatigue. Reducing muscle temperature and CWI’s analgesic effect will allow you to get back out there should you need or want to workout multiple days in a row.
Mood, Energy & Focus
As one can probably guess, cold water immersion activates your fight or flight reflex as a cold plunge stimulates your sympathetic nervous system. This reflex causes a release of a hormonal cocktail that is meant to get your attention focused on the task at hand and compel you to remove your body from the perceived threat of cold water. Not surprising, it appears that the colder the water, the more intense the stimulation of the sympathetic nervous system. CWI increases your heart rate, your blood pressure and the hormones norepinephrine and dopamine. A study from 2000 in which participants remained in 57 degree water for 1 hour showed an increase in dopamine and norepinephrine of 530% and 250% respectively. The dramatic increase in these hormones with a concomitant increase in heart rate and blood pressure explains why participants in CWI report a subjective increase in energy, focus and mood elevation for hours following a cold plunge.
While CWI decreases the body’s metabolism on the surface, in the skin and peripheral muscles, there appears to be a net-increase in overall body metabolism. CWI stimulates this net-increase in calories burned through muscle shivering and activation of brown fat.
When the body perceives a drop in core temperature, the hypothalamus mediates the shivering reflex, stimulating skeletal muscle to rapidly contract in small movements. These rapid movement, shivering, produce heat and burn calories raising our overall metabolism.
Additionally, cold water exposure has been shown to stimulate,“brown fat.” Humans have two types of fat, white and brown. White fat is the more familiar adipose tissue that troubles us aesthetically. The role of white fat is energy storage and it is non-metabolic in that it just hangs around waiting to get used, not generating any calorie burn by itself. Brown fat gets its color because of the density of mitochondria in this tissue. Mitochondria produce engergry for the cells in which they reside, making brown fat metabolic, or calorie burning. While we are born with a large amount of brown fat to keep us warm as infants, this tissue is gradually reduced as a an overall percentage of our total body fat. That said, repeated use of CWI or even just repeated exposure to any cold stimulus increase the production of brown fat in adults. The more brown fat we have, the more calories we burn when it is stimulated.
Shivering and brown fat stimulation can continue in the hours after the cold plunge due to a phenomenon called, “after-drop.” When we first enter cold water, the blood vessel in the body’s periphery constrict, shunting blood to our core in an attempt to stabilize our core body temperature. Once you get out of the cold water, those same peripheral blood vessels now dilate, allowing the warm blood in the core to flow to the body’s periphery. When this warm blood flows through the cold tissue in the skin and muscles, it loses its heat and flows back through the cardiovascular system, dropping our core temperature. This drop in core temperature has the effect of both producing the shivering reflex, but also stimulating the metabolic function of our brown fat.
Resilience & Grit
Resilience and grit are subjective qualities that we often identify in individuals that seem to be able to remain collected while experiencing difficult trials and tribulations. More specifically, these qualities seem to indicate that an individual is able to maintain, “top-down” control over initial bodily and emotional reflexes in favor of a relatively calm, calculated response to an external threat. This control is exhibited by our frontal lobe, the seat of executive brain function. This area of our brain can be trained to temporarily suppress our body’s initial reaction to CWI. Studies have show that repeated exposure to cold water consistently reduces not only an individual’s perception of discomfort, but also the body’s physiological response to the discomfort.
CWI seems to be growing in popularity in the general population as a potent health and wellness tool. As a physical modality, cold water exposure definitively helps with musculoskeletal recovery and increases your metabolism. Mentally, CWI helps with mood elevation and clarity. While you can spend thousands of dollars to have a chilled and filtered plunge pool, CWI can be done cheaply and simply by filling up your bathtub and jumping in. Alternatively, if you live in a colder environment, you can fill up a tub of water outside and invest in a cheap de-icer to keep the water above freezing. This last strategy is the most efficient as exposure at this temperature should be limited to no more than 5 minutes of exposure. Happy plunging!