Physiological Considerations in Open Water Swimming (Part 2)

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In our last post, we reviewed two important human reflexes that may play a role in open water swim fatalities: The cold water shock response, and the mammalian diving reflex. There are several more:

Flight or Flight Response. As an acute stress response, this is essentially a basic survival instinct: a comprehensive neurological discharge of the “sympathetic nervous system”, the control system that primes a human or an animal to fight or flee when life is on the line. The sequence is straight forward: once there is a conscious recognition of a significant threat, neural changes in the brain quickly trigger the secretion of the “stress hormones” adrenaline and noradrenaline in the adrenal medulla (an organ attached to the kidneys). Significant release of adrenaline and noradrenaline promptly prepare the body for violent muscular action: Increased blood pressure, heart rate, stroke volume, respiratory rate, tidal lung volume, muscle tone, muscle tension and blood flow to working muscles; pupils dilate to improve vision; Blood clotting function improves (to reduce potential losses); emotional reactions increase, especially anxiety or aggression; and excessive attention is given to negative stimuli, a hypersensitive tendency to overreact.

How does this reflex play into open water swimming? If you are relaxed when swimming, without fear, anxiety or expectation, then it is unlikely there will be a significant sympathetic outflow during open water swimming (using an open water siwm buoy can help relieve anxiety). However, it is hard not to get caught up in the excitement and rapid ramp-up of a race. Most competitors can almost feel the adrenaline coursing through their veins even before starting, especially if there are high expectations of performance, or the need to outperform another competitor. Conversely, some may possibly have a fear of not doing well in the face of friends and supporters. Or worse, some may have limited confidence in their ability to swim in open water, to survive the “washing machine” experience that is often at the start of mass open water swim.

Once the event starts, adrenaline causes many to go out too fast, pushing harder than their abilities allow for a sustainable swim. And if in the middle of an intense effort, you miss a breath, or get struck or run over causing anger, aggression and/or a true fear for your life, then this emotional rush will dramatically add to the adrenaline surge already evident at the beginning of the event. Blood pressure, cardiac contractility, heart rate, and respiratory rate can be stimulated to extreme levels, to a point where a latent, previously undiagnosed cardiac problem may be exposed—the heart cannot cope with the demands placed on it—cardiac ischemia (angina) and myocardial infarction (heart attack) become possible. This is not a ladder you want to keep climbing.

Staying in control is easier said than done. One way is simply to let go of any expectations of your swim, and to prioritize getting into a comfortable, sustainable rhythm. Warm up easily before you start, then find some space at the swim start. Swim your swim, with your rhythm, at your pace, as if you were alone doing it. Never push early in an endurance swim.

Autonomic Conflict. After reading the previous post about the diving reflex, which tends to slow things down, and both the cold water shock response and the fight or flight response (above), which tends to spike things up, it is pretty clear that there are hormonal and neurological forces within your body that are in conflict when swimming in cold water. When control systems are giving mixed messages to an end-organ like the heart, there are some significant implications. Recent research has demonstrated that the electrical pattern that controls the rhythm of the heart can become so distorted that the heart can no longer pump blood efficiently. Arrhythmias such as heart block, or atrial or ventricular fibrillation can occur spontaneously and quickly if these reflex inputs are allowed to flourish—and they can be lethal, even in young, healthy and capable swimmers.

Simply put, do not let these reflexes rule your swims. Warm up adequately, get gradually acclimatized to the cool water, stay within yourself, and stay true to your capabilities. And it may be better not to compete mass start swims until you have solid confidence in your swimming abilities and lots of experience in open, deep water.

Photo Credit: Dawn – Pink Chick

Physiological Considerations in Open Water Swimming (Part 1)

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A simple definition of Physiological: “the organic processes and phenomena of an organism or any of its parts or of a particular bodily process”.

With the growth and immense popularity of open water swimming and triathlon in the last 15 years, a disturbing trend has come to light which is the disproportionate number of deaths in the swim portion of triathlons. The numbers are chilling. In the period 2007-2012 there have been 52 deaths recorded by Triathlon USA, and of those, 44 were in the swim portion of the race, and all of them were in open water, and not one in a pool.

Why at the beginning of a race? No one is exhausted or dehydrated or overheated. Are there any trends to suggest an obvious explanation? Not really. These athletes were a mixture of young and old, male and female, experienced racers and rookies. These people have been in the beginning, the middle, and the end of a swim when they collapsed. The length of race did not seem to matter, whether sprint, Olympic or Ironman distance. They were in fresh and salt water. Some were even able to grasp onto a paddle board before going under, while some were never seen going under. And there are often few witnesses in the water nearby who could accurately describe what happened. The autopsies, when done, do not reliably show lungs full of water, damaged hearts, or significant trauma—since autopsies don’t show everything, they are frequently signed off as death by cardiac arrest. So can we learn anything from what is going on here?

To maximize your ability to survive open water swimming, check out the following basic physiological reflexes that may be contributing to risk of sudden death in open water swimming. They are all easy to understand.

The Cold Shock Response. No mystery here: jumping into cold water is a significant strain on your body (even when the lake is a comfortable 22°C, that is still 15°C less than your body temperature). Your heart rate and breathing rate spirals upward dramatically, as does your blood pressure (due to massive vasoconstriction in your limbs and skin), and your demand for oxygen (as your body now very dramatically needs to generate heat with shivering). In susceptible individuals, this cardiac strain can lead to angina, myocardial infarction, and potentially cardiac arrhythmias.

The solution? Don’t jump or dive into cold water. Ease into it—walk into cool water if you can. Acclimatizing slowly each time you go. And swim in cool water regularly to get comfortable with cool water swimming. Your body can adjust without a shocking response if you give it a chance to. And of course, do not combine cold water swimming with alcohol or a variety of other drugs that might distort your feeling of the cold, which in turn would distort your perceptions of heat loss, and your risk of hypothermia.

The Mammalian Diving Reflex. All mammals use a fundamental survival reflex when diving to conserve oxygen use—this allows aquatic mammals (e.g., seals, dolphins, whales, walruses) and diving birds like penguins to stay underwater for extended periods of time. This reflex is also evident in humans (especially in infants), and has clear implications when swimming in open water.

How does this work? When the face specifically is submerged and exposed to cold water, nerve receptors in the face relay this information to the brain and the vagus nerve to dramatically slow the heart rate (called bradycardia) and the urge to breathe. Blood supply to the periphery is also constricted, to further reduce oxygen demand. The degree of the effect is proportional to the coldness of the water, and it is increased further with breath-holding. Unlike the cold shock response described above, it is not triggered with the limbs or body contacting cold water.

How cold does the water have to be? Although one source suggests 16C or less, the reflex likely varies with how well you are acclimatized to cold water (one the day, and over time), as well as your overall health and fitness. Chances are if it feels cold to you, it is cold enough to elicit a diving reflex.

To lessen the effect of the diving reflex, two things are important: First, get used to swimming in cool open water, by going out into it regularly. And second, initially splashing water on the face before fully entering the water to swim is important. If the water is particularly cold (16C/61F or less), you might consider a series of short swims of only 15-30 seconds, standing with head out of the water in between, to acclimatize the face to the cold. Check your pulse in your neck before you enter the water, and after you have acclimatized to get a sense of how you are doing.

Photo Credit: Dawn – Pink Chick

The Wild Open Water Environment: Waves and Wind

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One of the first things that pool swimmers discover when transitioning to open water swimming is a difference in the water surface – it is rarely as smooth as a pool. Whether a surface ripple, a light chop, variable swells, a tide, a visible current, or true waves with whitecaps, these new variables will challenge the discipline of your pool stroke. The question arises: can you really continue to swim as if you are in a pool?

When encountering waves, you may feel you are fighting the water, prompting the consideration of trying to work with the waves. Try to swim through (or underneath) some if they are large and coming head on, and float over some others to take advantage of being at the top of a wave. And if there are waves coming from the side, you may need to become a one-sided breather, and you may need to correct your swim path regularly because you are being pushed sideways. Paradoxically, if you can relax your body while swimming in wavy conditions, you can feel what the water is doing better, which improves your navigational abilities and can even make it fun! Essentially, then, windy, wavy conditions demand adjustments – to your mental preparedness, to your willingness to adapt to changing conditions, to your stroke, to your breathing and stroke cadence, and to your sighting techniques.

First, as always, establish an easy, and complete (with complete emptying) breathing cycle that does not accumulate carbon dioxide. Staying relaxed remains more essential than ever. An open water swim buoy can help with this. If the conditions elicit fear or overwhelm your abilities, you probably shouldn’t be out there, unless you are practicing in shallow water with a group to develop your skills. If your swim stroke cadence and breathing cycle can stay easily adaptable and changeable with every wave, you can actually enjoy swimming in rough water, like surfers that have learned to adapt to every wave. Work to feel the rocking peak-and-trough pattern of the waves and adjust to it. When you are in a trough, with a new wave possibly about to swamp you, you might say to yourself, “this is not a good time to breathe”, and just glide for an extra second or two while continuing to expire before attaining the next high point, where the breathing and the sighting becomes easy. You are simply learning a new dance.

Swimming a straight line is a major challenge in open water–there are no dark lane lines on the lake bottom to guide you, and ripples in the sand may not be reliable. To swim straight, you have to look forward with your eyes out of the water. “Sighting” is simply the process of popping your head up to look forward to a landmark that you should have at least thought about before you started swimming. It can be useful to look for landmarks that are off your intended course, so that when you see them, you know to change course. Sighting is most easily done by extending the neck and head upward or by pushing down slightly with your reaching hand to allow your head to pop up just enough to see (think alligator), just before you turn to breathe. A quick glance forward once your eyes clear the surface, before turning the head to inhale. How often you sight is dictated how straight you normally swim, or by how much you may be being pushed off course by the wind, waves, or current. Sight only as much as necessary–lifting your head too high can be hard on your neck, cause the wetsuit to chafe your neck, and can cause your legs to drop, compromising the efficiency of your body position.

This sighting technique will not be very useful if you are in a trough between waves when you look for a landmark, as instead, you will just see a wall of water. Herein lies the need to feel the rocking nature of the waves, so that you can sight when at or near the crest of a wave. The bigger the waves, the more helpful it is to sight for a higher landmark, like a mountain, as opposed to a buoy, which you may not be able to see.

In less familiar circumstances such as wind and waves, staying calm and in control of your breathing, your stroke, and your ability to sight to stay on course is more important than ever. Try using a safety swim buoy so you are seen by other boaters, and stay flexible and willing to adjust to the water waves and movements. Work with the water conditions, not against them. Repeated exposure and practice in all water conditions increases comfort when challenged with common open water variables, especially wind and waves. Always bring an open water swim buoy!

Photo Credit: Elmar Eye

Swim Buddy Breathing Cadence

Breathing Cadence & Recovering Your Breathing

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In the last post, we considered the importance of complete expirations in the water and a normal breathing rhythm while swimming freestyle, to avoid the build-up of carbon dioxide (which drives the urge to breathe), shortness of breath, anxiety, and even panic when not done adequately. In this discussion, we consider the importance of rate of breathing while swimming and the use of a safety swim buoy.

Just like breathing on land, breathing while swimming should vary somewhat with exercise intensity, but the difference is that swimmer’s breathing rate is regimented and dictated by the cadence of your arm strokes. Essentially then, the only time you can breathe in is in a short window as you turn your head to one side, and leaving a disproportionally longer time to breathe out, while your face is facing down, with your head almost completely submerged in the water. It would almost seem to need the luck to be able to match your breathing rhythm to your arm stroke rhythm without either hyperventilating or not breathing enough to meet the exercise demands of swimming. Either way, you cannot sustain this breathing rate, causing you loss of control of your breathing and then your stroke pattern, and with it anxiety. How does one keep a breathing rate both under control, and yet modifiable as demands of exercise increase?

There are two answers to this seeming conundrum. First, recall that swimming is the only exercise where you have to build your stroke around your breathing (not the other way around). So one needs to get comfortable gliding with each of your strokes – holding one arm straight out in front of you, while the other rests at your side after completing a pull phase until you have adequately expired into the water and you are ready to breathe in again. Your stroke rhythm and your physical movements wait for your breathing cycle to be completed; your stroke is built around your complete breathing cycle. To get good at this, always start swimming this way, to practice establishing your breathing cadence over everything else.

The second variable to manipulate is your breathing cycle. Most swimmers are taught to breathe (and therefore swim) symmetrically, to breathe on both sides, separated by 3 alternating arm strokes. Breathe in on the left side, then, while continuously expiring, right arm, left arm, and right arm pull before turning to the right to breathe in. This is called breathing every three. However, this may be too easy or too hard, depending on how hard you are swimming, so what is the alternative? Learning how to alter cadences. Many sprinters will breathe every two arm strokes, breathing on the same side. Long distance swimmers may start breathing every four or even five arm strokes, given that they may have developed large lung capacities. And most important, experienced swimmers can change easily if they need to. They change from breathing from every 4 to every 3, and sometimes breathe every two arm strokes as they need to, whether for more air, because they missed a breath because of a wave, or because they needed to sight off to the other side at that time. An experienced swimmer can alter breathing cadence on the fly without needing to stop to regroup.

Occasionally, even good swimmers find themselves hyperventilating with a loss of control of breathing. They may have swallowed water, didn’t warm up properly, started swimming too fast, got hit by another swimmer, or underestimated the coldness of the water.  When this happens in open water, it can be initially scary, as they may not be any immediate safety platform or open water swim buoy to grab onto, which may intensify the anxiety of the moment. Here too though, there is a solution:  having a reliable recovery stroke to return to (your happy place), be it heads up breast stroke, side stroke, backstroke, simply easy treading water, or having a safety swim buoy to hold on to. All of these are, of course, much easier wearing a wetsuit, which provides warmth and floatation while you recover your breathing, and usually settles within 1-2 minutes if the head stays out of the water. To find your happy place, you need to practice it in open water (preferably using an open water swim buoy), until you can trust your ability to get to it, in case of loss of breathing control. When your respiratory rate has returned to normal, restart your swim stroke easily, gliding long enough with each breath to regain breath control.

Photo Credit: charlottehbest via Compfight cc

It’s All About Breathing

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It is now early June, and the lake temperature (incredibly) at Gyro Beach here in Kelowna this morning was a balmy 18°C today. It is warm enough to enjoy swimming in the lake–already we have fishermen, paddlers, sailors, waterskiers, power-boaters, windsurfers and swimmers vying for their piece of the water (it’s important to be seen using a safety swim buoy). However, with the enjoyment of the open water summer season now underway, we also have the return of an old nemesis: drowning, most of which are preventable. A sobering reality: Okanagan Lake remains the number one body of water for drownings in BC.  (http://www.castanet.net/news/Central-Okanagan/118722/Deadly-waters)

This column will provide some simple open water swimming tips, including recommending to buy open water swim buoy, and will be written by the members of the Across The Lake Swim Society, who has been encouraging people to safely enjoy swimming in open water well enough to, yep, swim across our fine lake.

It’s all about breathing.

Whatever you have learned about the technical aspects of your arm strokes, or your cadence, or your body position when learning endurance swimming, none of it matters anywhere near as much as breathing does, and most importantly, staying in control of your breathing. There is no other sport where you have to as much as think of breathing: Inspirations are done on demand, without any barriers, at the depth and rate you desire, consistent with the intensity of the activity that you are doing, while expirations can seemingly just passively fall out of you. Swimming though, is quite different: For most strokes, how you breathe and when you breathe appears to be dictated by your stroke; to get good at this requires you to get comfortable with inspiring only when your mouth is sufficiently out of the water, while expiring well and completely requires learning to forcibly blow air into the water, in a way that does not build up carbon dioxide and cause hyperventilation, or air hunger due to hypoxia. For most newcomers to swimming, this is the rate limiting step: Often after as little as 25 meters of swimming, inexperienced swimmers are short of breath, simply because their breathing cadence has not adequately dealt with their needs—they become too short of breath to continue, and it has nothing to do with fitness. How does that happen? An example on land may help:

Imagine walking briskly for a few hundred meters, breathing out quickly and incompletely every 3rd step, and inspiring quickly right after that—how long would it take before you got short of breath?

So the first fact you need to know: Swimming is the only sport where breathing matters — a lot. It is the only sport where you need to build your technical skills (your stroke) around your breathing, not the other way around. If you are a beginner, you may want to start even just standing in a pool, developing a breathing cadence that is manageable first—every expiration is with your face in the water, and every inspiration is where your face is out of the water. This should feel boring and repetitive before you proceed to move slowly in the water, perhaps with fins on, repeating the same thing: every expiration is in the water, every inspiration is out of the water. Start with a side stroke position, propelling yourself with your fins only, with one arm extended with your face exposed out of the water, turning your face into the water to breathe out. Try this on both sides, and when ready to try it, alternate to the other side while moving forward. Beginner swim classes for children and adults are available at most YMCA’s and local swimming centers to work through these basic principles.

The second fact you need to know: The drive to breathe is not dictated as much by lack of oxygen as it is a build-up of carbon dioxide. So it means that, as you become short of breath in most circumstances, the solution is not to gasp for more air, but in fact to more completely blow carbon dioxide out. Try hyperventilating briefly—e.g., take 5-10 full excursions of air, focusing on blowing air out completely with each breath—and then stay still, and feel what that does to your breathing rate.  You will notice that you will have little urgency to breathe. So while it would seem that swimming 25m of a pool should not cause shortness of breath after less than a minute of exercise, the reason it does so is because of the progressive carbon dioxide retention in the lungs and body, as a result of repeated, incomplete emptying of your lungs.  Learning to breathe out (and not so much in) well is the first key principle to keeping the drive to breathe under control. Developing a comfortable and flexible rhythm of inspirations and expirations while swimming is equally important.

When doing a freestyle stroke, the need to breathe out completely with every breath has to become automatic, with every stroke. For some, it can help to hum nasally and continuously as soon as your face enters the water, so as to prevent CO2 retention, to prevent water going up your nose, and so as not to breath-hold; and it helps to give one last surge of expiratory effort just before turning to breathe, again through the nose, for complete emptying. When turning the head, take a breath in with your mouth, which is much more efficient for inspiration than breathing in through your nose. Learn a pattern of prioritizing nasal breathing with expiration, and exclusively oral breathing with inspiration. As you work harder, the expiration can become a combination of both oral and nasal breathing, but it always needs to be complete. If this pattern of breathing continues to be difficult, try simple slow breast stroke, with your head mostly out of the water as you breathe in, and blowing out slowly but completely as your face dips into the water as you extend your arms forward. Practice this as a breathing drill, not a swimming drill, until you can do it all day without becoming short of breath. If practicing in the open water, we suggest an open water swim buoy so you can be seen. This safety swim buoy is towed behind you with no drag but is highly visible.

Photo Credit: KristianVJ via Compfight cc