An Open Water Swim Safety Idea





As I mentioned in my last blog post, I recently visited in Tokyo with the Japan Triathlon Union about the issue of athlete safety.  I had the chance to speak (albeit with translation!) with the race directors from many of Japan’s major triathlon races.

Dr. Masakazu Kawai, from the Yamagata prefecture, had a novel idea about swim safety to share with the group.

But first, to set the stage….

We know that being able to rescue a swimmer in distress in one of the most important aspects of an effective safety plan for a triathlon or stand-alone open water swim.  Fortunately, in most cases, the on-water lifesaving team is able to spot swimmers in distress who might be struggling to swim, or wave, or even simply yell that they need help.

For the lifeless swimmer–the victim of drowning, near drowning, or cardiac arrest–identification of the victim can be much more challenging.  And yet identification of the victim, prompt rescue from the water, and provision of CPR and use of the AED, if needed, is the chain of action that must be accomplished in just a very few minutes in order to avoid a fatality.  This chain all begins with identifying the victim.

In a crowd of swimmers, oftentimes all wearing black wetsuits, it can be hard to spot the single athlete who has gone lifeless and who is floating, but no longer swimming.  From afar, it can be difficult to tell whose arms are whose and it can be difficult to tell if a head is rotating to take a breath.

This is where Dr. Kawai’s idea might be helpful.  He suggests the use of a small, inflated, brightly-colored balloon that would be attached to each swimmer’s swim cap.  As the athlete is swimming, the balloon would bob left and right, with each turn of the head.  If an athlete goes lifeless, the balloon would simply sit still on the top of the water.  In a group of swimmers, then, there would be a very visible clue to a single lifeless swimmer–the single balloon that was no longer bobbing.  This might be visible even from a considerable distance and allow early, perhaps immediate, recognition of the lifeless swimmer.

Watch a short video clip that shows the idea and let me know what you think.  I’ll pass along any feedback to Dr. Kawai.  He’s also looking for event organizers to trial his idea.  We need simple, creative ideas like this.









Related Posts:

  1. Some Great New Videos from WTC SwimSmart Initiative
  2. Swim Safe in 2014
  3. Triathlon Safety Initiatives

Update on Swimming Induced Pulmonary Edema (SIPE)







I saw this week that there was an important new paper on swimming induced pulmonary edema (SIPE).  Richard Moon, MD, and his colleagues at Duke University published a report entitled, “Immersion Pulmonary Edema and Comorbidities:  Case Series and Updated Review” in a recent edition of the sports medicine journal, Medicine & Science in Sports & Exercise (1).

SIPE is known to occur not only in recreational or competitive swimmers, but also in divers.  In fact, the condition was first recognized because of breathing difficulties encountered by military divers.  As triathlete and swimmer readers here will know, there are many reasons why an athlete might develop shortness of breath during an open water swim.  Water conditions, water and air temperature, exertion, and anxiety all play a role.  SIPE is something different, altogether, though.  This is a condition that develops because of immersion in the water, in which fluid builds up in the lungs and makes breathing difficult.  The condition is believed to be self-limiting; if a swimmer gets out of the water, the condition will resolve.  The underlying mechanisms and risk factors are not completely understood.

I’ve written about this condition in 2 previous blog posts….SIPE and More on SIPE.  These posts might be a good starting point.

The newly published report is important because it reviews the medical literature and gathers all of the pertinent information about pre-existing medical conditions, or so-called comorbidities, in victims of SIPE.  Dr. Moon is probably the world’s foremost authority on the topic of SIPE, so this new report deserves our attention.


The Study

There are 2 parts to the study:  1) a look at the Duke University experience with recreational swimmers who’ve had a SIPE episode and 2) a review of the medical literature on SIPE cases, both in military and recreational divers and swimmers.

In the first part, the investigators collated information on 41 swimmers who, over the past several years, had been studied at Duke University after reporting a SIPE episode.  The mean age was 50.1 +/- 10.8 years (range, 25-71 years).  Complete medical history data was available for 36 of the 41 swimmers.

In the second part, the investigators collected 45 previously published articles in the medical literature that reported on 292 cases of SIPE.  There were 156 recreational swimmers or divers (89 men and 67 women), with a mean age of approximately 47.8 +/- 11.3 years.  There were also 136 military swimmers or divers (135 men and 1 woman), with a mean age of approximately 23.3 years (range, 18-47 years).

For each of these groups, the investigators gathered information about pre-existing medical conditions in order to determine potential risk factors for the development of SIPE, focusing on:  hypertension (high blood pressure), lung disease, overweight/obesity, sleep apnea, hypothyroidism, and cardiac abnormalities).


The Results

Among the Duke University group, 9 (25%) of the 36 swimmers with available health history were completely healthy.  The remaining 27 (75%) had 1 or more medical/health conditions, including:

  • overweight/obesity in 12
  • hypertension in 7
  • cardiac arrhythmias in 4
  • heart valve problem (mitral valve prolapse) in 1
  • reduced heart function in 2
  • repaired congenital heart conditions in 2
  • asthma in 3
  • COPD in 1
  • reactive airways disease in 1
  • hypothyroidism in 3
  • diabetes in 2
  • polycystic ovary syndrome in 1
  • obstructive sleep apnea in 2

Twelve subjects had more than one of these conditions.

In the literature review, all of the 136 military swimmers and divers were healthy; they had none of the pre-existing medical/health conditions that were surveyed.  In contrast, 70 (45%) of the 156 recreational swimmers or divers had one or more significant pre-existing risk factors:

  • asthma in 4
  • enlarged heart in 2
  • arrhythmias in 2
  • coronary artery disease in 3
  • diabetes in 4
  • exercise-induced cough in 1
  • Elevated serum lipids in 22
  • hypertension (high blood pressure) in 25
  • thickening of the left ventricle in 9
  • peripheral vascular disease in 1
  • sleep apnea in 6

As a side note, approximately 17% of cases in the literature review reported similar previous episodes or follow-up episodes that were suggestive of SIPE, giving an important look at the potential recurrence rate.  And in total, 6 fatal cases of SIPE were identified in the literature review.


My Thoughts

How can all of this collated information be useful to us?

First, it’s important to note that all of the military swimmers and divers included in the literature review were healthy.  We shouldn’t overlook the possibility that even completely healthy swimmers may experience SIPE.

Second, the recurrence rate of ~17% in the literature review is probably an underestimate.  No doubt, some swimmers who experienced a worrisome episode of SIPE might avoid future swimming altogether.  It’s very important to remember that this condition may recur.

Third, it’s very apparent that, among recreational swimmers who experience SIPE, the prevalence of important pre-existing medical conditions is rather high, at 75% in the Duke group and 45% in the recreational swimmers in the literature review.  I suspect that the Duke investigators were more thorough in their history-taking and the 75% is probably more reflective of the reality.

The investigators’ aim was to identify risk factors for SIPE.  Sadly, there’s obviously no single, unifying thread here.  Hypertension (high blood pressure) was the most commonly identified condition among the cases, but this accounted for only ~15% of the cases.  As I mentioned at the top, the physiologic underpinnings of SIPE are not completely understood and indeed there may be more than one responsible mechanism leading to some common final pathway by which fluid accumulates in the lungs.  All of the various cardiovascular abnormalities identified in the cases might conceivably play a role.  There’s more to learn.

It’s worth noting that the long list of medical conditions that were identified deserve careful medical attention before participating in recreational swimming events.



I’ll reprint here my best advice to athletes and event organizers regarding SIPE.  I originally included this in another blog post, but this is still my best advice!

  1. Triathletes and open water swimmers should be aware of SIPE and the possibility that this condition can be lethal.
  2. Symptoms of SIPE can manifest for the first time even in experienced swimmers.  Symptoms may develop rapidly, be unexpected, and confuse the athlete about the cause.
  3. The development of SIPE does not appear to be confined to cold water swims or only to victims who are wearing a wetsuit at the time.
  4. SIPE appears to be self-limiting–that is, the symptoms will subside if the victim stops exercising and gets out of the water.
  5. Because of #2, #3, and #4, athletes who experience breathing difficulties in the open water should treat the problem like a medical emergency and STOP swimming and SEEK immediate assistance.  Because of the challenges of rescue in the open water, your life could depend on recognizing a problem early and getting out of the water.  I would encourage affected athletes to get complete medical evaluation as soon as possible after an episode.
  6. There appear to be no effects on lung function after an episode of SIPE, but repeat episodes of SIPE may occur.
  7. Affected athletes have described a variety of strategies for preventing repeat episodes of SIPE.  From athlete accounts, no single strategy appears to be universally successful.
  8. Affected athletes should use EXTREME CAUTION in subsequent open water training and races, being hypervigilant for warning signs.
  9. Event organizers and on-water rescue personnel should be familiar with SIPE.  The safety plan should allow for athletes with breathing difficulties to be removed from the water as quickly as possible.



1.  Peacher DF, Martina S, Otteni C, et al.  Immersion pulmonary edema and comorbidities:  Case series and updated review.  Med Sci Sports Exerc 2015;47(6):1128-1134.


Related Posts:

1.  Swimming Induced Pulmonary Edema (SIPE)

2.  More on Swimming Induced Pulmonary Edema (SIPE)

Triathlon, Open Water Swimming, and the Heart: What Can We Learn From Dolphins and Seals?








A recent study about marine mammals caught my eye.  I don’t know much about non-human biology and physiology, but this study on dolphins and seals may shed some light on the problem of fatalities during open water swimming or triathlon events.

The Study

A group of investigators headed by Terrie Williams from the University of California at Santa Cruz shared their report, “Exercise at depth alters bradycardia and incidence of cardiac anomalies in deep-diving marine mammals” in the January 16th edition of Nature Communications (1).

This group of investigators has been interested in the physiology of the so-called “dive response” in marine mammals.  This is a response that is governed by the involuntary, or autonomic, nervous system, which has two antagonistic components:  the parasympathetic nervous system and the sympathetic nervous system.  As a group, the marine mammals depend on feeding by chasing pray to depths that can range up to 3,000 m.  Even at lesser depths, these mammals must maintain a breath-hold under large hydrostatic pressures while they undergo extreme exertion to catch their pray.  During a dive, breath-holding stimulates the parasympathetic nervous system to slow the heart rate (producing bradycardia).  At the same time, the exertion required to chase pray stimulates the sympathetic nervous system, producing an increase in the heart rate.  The current study offers the first detailed study of the interplay between the components of the autonomic nervous system during routine diving and feeding activity in these animals.

The investigators created an electrocardiograph-accelerometer depth monitor that was deployed on 10 Atlantic bottle-nosed dolphins and 3 Weddell seals.  This device allowed high-fidelity recording of the heart rate, ECG, water depth, and swimming stroke frequency (a measure of exertion) during dives.  For the dolphins, measurements were made for 74 dives to depths of up to 210 m.  For the seals, measurements were made for 91 dives to depths of up to 390 m.

The Results

As expected, there was a strong relationship between diving depth and heart rate for both species, with heart rates falling during descent and reaching a minimum at the lowest depth of the dive.  Superimposed on this effect was an additional effect of exertion.  For the dolphins, the maximum heart rate was 1.7 to 3.7 times greater during periods of extreme exercise compared to gliding alone.  For the seals, the maximum heart rate was 1.5 to 1.8 times greater during periods of extreme exercise compared to gliding alone.

The surprising finding was that cardiac arrhythmias occurred in more than 73% of the dives.  The investigators defined arrhythmias to include ectopic beats or significantly increased variability in the interbeat interval (IBI).  There were apparently no sustained or fatal arrhythmias., but there were discrete examples of “wandering pacemaker” and ventricular premature beats.  In the Weddell seals, there were often patterns of alternating periods of tachycardia (fast heart rate) and bradycardia (low heart rate) during periods of constant, intense exertion.

The presence of cardiac arrhythmias was strongly correlated with increased depth of dive (parasympathetic activation) and increased exertion (sympathetic activation).  As an example, cardiac arrhythmias occurred in 81% of the dolphin dives to >210 m but in only 26% of dives to <100 m.

The authors concluded that our previous understanding of the dive reflex in marine mammals was not totally correct.  Given that these animals depend on diving for their food sources, the development of cardiac arrhythmias during feeding appears to be mal-adaptive.  In fact, feeding might actually be dangerous.

My Thoughts

At first glance, the physiology of the diving response of dolphins and seals during feeding seems far afield from open water swimming and triathlon.  And moreover, we already know about the development of cardiac arrhythmias during submersion in breath-holding humans as well as other marine species.  The important observation here, though, is what I might call “irritability” or “instability” in the heart rhythm during periods of intense parasympathetic and intense sympathetic activation….and that’s the possible link to human fatalities during open water swimming or triathlon.

We know from autopsy reports of triathletes who’ve died during the swim portion of an event that there are sometimes only subtle abnormalities of the heart, and often nothing that seems explanatory.  That leaves us in a difficult position to explain such deaths.  In a previous blog post, I wrote about one very plausible hypothesis. Two UK physiologist,s X and X, proposed the concept of “autonomic conflict,” where a surge in both the parasympathetic and sympathetic stimulation of the heart might lead to a fatal arrhythmia.  I’ve been intrigued with this hypothesis because it seems to fit many of the observations made about the swim victims.  It is easy to see where exertion, cold water, anxiety, etc. might lead to strong sympathetic activation.  And it’s equally easy to see where facial wetting, water entering the mouth/hypopharynx/nasopharynx, and breath-holding, even without diving, might lead to strong parasympathetic activation.  In that instant, in an athlete with some sort of susceptible heart, a fatal arrhythmia might occur.

The new observations about the dolphins and seals seem to play into this hypothesis.


Related Posts:

1. Fatalities in Open Water Swimming:  What’s the Mechanism?

2. Triathlon Fatalities:  2013 in Review



1.  Williams TM, Fuirman LA, Kendall T, et al.  Exercise at depth alters bradycardia and incidence of cardiac anomalies in deep-diving marine mammals.  Nature Communications 2015;6:6055.




Some Great New Videos from WTC SwimSmart Initiative

Here’s a quick update from the World Triathlon Corporation (WTC) SwimSmart initiative.  They’ve put together a YouTube playlist called “SwimSmart Saturdays,” a 9-part series of short (~1-2 minute) video clips that illustrate their 9-point checklist for race day swim safety:

  1. Prepare Early
  2. Work Your Way Up
  3. Be in the Know
  4. Safety First
  5. Tried and True Gear
  6. Warm Up Right
  7. Assess the Situation
  8. Start Easy, Relax and Breathe
  9. Be Alert and Ask for Help

This is all great advice for triathletes looking to have a safe day at the race.

Related Posts:

1.  Swim safe in 2014

2.  USAT and race safety

3.  Triathlon fatalities:  2013 in review

New USA Triathlon Water Temperature Safety Recommendations


At its November meeting of the Board of Directors, USA Triathlon (USAT) adopted new Recommendations for Multi-Sport Age Group Swim Segments.  These new recommendations mark a step forward in terms of race safety.  USAT also agreed to collect data during the 2014 season from every event regarding water temperature and athlete rescues, incidents of hypothermia or heat-related illness, and other medical emergencies that occur during the swim portion.  These data will help to guide further review of the recommendations by the USAT Swim Collar Task Force and possibly set the stage for further scientific investigation about hypothermia and heat-related illness in the triathlete population specifically.

The graphic below illustrates the new recommendations:


These recommendations are targeted at race directors, local officials, and athletes.  They apply to age group events but not to professional races.  Satisfactory, or so-called neutral, water temperature ranges for races of various distances are defined as:

  • <750 meters, 55-89 F
  • 750-1500 meters, 56-87 F
  • >1500 meters, 57-86 F.

The neutral temperature ranges are shown in green in the graphic.  When the water temperature falls outside of the neutral range, the recommendations advise that the swim portion should be shortened or cancelled.   These temperature ranges are shown in yellow or red in the graphic.  Discretion is left to the race director, though, who may consider other safety-related factors such as air temperature, humidity, acclimation, regional adaptation, and wind.

There is no change to the current rules regarding measurement of the water temperature or to the use of wetsuits.  From the USAT competitive rules:

Measuring Water Temperature.  It is recommended, but not required that the water temperature for a race be finally determined by measurement made within 2 hours of the race start.  A water temperature measurement should also be taken prior to any pre-race meetings in order to forecast to the athletes as early as possible the likely water temperature on race day and the likelihood of whether wet suits will be allowed on race day.

Wet suits.  Each age group participant shall be permitted to wear a wet suit without penalty in any event sanctioned by USA Triathlon up to and including a water temperature of 78 degrees Fahrenheit.  When the water temperature is greater than 78 degrees, but less than 84 degrees Fahrenheit, age group participants may wear a wet suit at their own discretion, provided however that participants who wear a wet suit within this temperature range shall not be eligible for prizes or awards.  Age group participants shall not wear wet suits in water temperatures equal to or greater than 84 degrees Fahrenheit.

Open Water Swimming, Hypothermia, and Heat-related Illness

Open water swimming is as old as the ages.  Mass participation in open water swimming events is relatively new, though.

In today’s triathlons and open water swimming events, there is tremendous heterogeneity among the participants in terms of age, size, body fat, and swimming ability.  All of these factors affect an individual athlete’s ability to withstand prolonged exposure to cold or warm water temperatures.  The important concept is maintenance of core body temperature.  In ordinary circumstances, the human body core temperature is tightly controlled to reamin near 37 C by processes known as thermoregulation.  There is a balance between heat gained from the environment or generated by exercise….and the heat lost to the environment.

The condition of hypothermia is loosely defined as a core body temperature <35 C.  With mild hypothermia, there may be an increase in the blood glucose level and increases in both the heart rate and respiratory rate.  With a continued fall in core body temperature, shivering begins, muscle movements become labored and then difficult, and mental confusion develops.  This progression can be insidious.  Athletes should be vigilant.  With severe hypothermia, the heart rate and respiratory rates fall, there is a further decline in mental status, and individuals may die of cardiac arrest.

During cold exposure, the body can generate heat through shivering and conserve heat by vasoconstriction of the peripheral blood vessels.  For an athlete, exercise is also a mechanism to generate body heat.  Because of differences in their intrinsic physiology or differences in body fat, children and older adults will chill faster than young and middle-aged adults.  As a group, men will chill faster than women.  For an adult who is not swimming, the neutral water temperature that will allow maintenance of a stable core body temperature is approximately 32-34 C.  For adults who are swimming (at a moderate pace, for up to 60 minutes) the neutral water temperature is approximately 21-25 C (70-77 F).  For harder or shorter efforts, the neutral temperature may be substantially lower.  Swimmers will become hypothermic at a rate which is proportional to the duration of immersion and the difference between the neutral temperature and the ambient water temperature.

Once the core body temperature falls during cold water immersion, it may continue to fall even after removal from the water, in a condition known as afterdrop.  In a classic study of non-wetsuit swimmers in San Francisco Bay, 5 of 11 swimmers developed hypothermia after a swim of up to 45 minutes in 53 F water on New Year’s Day.  In 10 of the 11 swimmers, there was a significant decrease in the core body temperature after emerging from the water, over a period of of up to 30 minutes.  After a long, cold swim, athletes should exercise special caution during the 1st transition and the beginning of the bike portion.

The possibility of hypothermia during open water swimming is what prompted the use of wetsuits for triathlon events.  By adding insulation and allowing the body to conserve heat, the wetsuit effectively lowers the neutral water temperature for any given open water swim.  Each of the various governing bodies has developed policies about water temperature and the use of wetsuits.

At the other end of the temperature spectrum, hyperthermia results when the core body temperature is elevated.  In medical circles, we use the term fever to characterize a mild to moderate rise in the core temperature.  While there’s no official definition, we might choose >38 C to indicate a fever.  With hyprethermia due to heat exposure, the body’s temperature can continue to rise to >40 F and heat stroke can result.  Symptoms include an increase in the heart rate and respiratory rate, muscle weakness or cramping, and eventually a deterioration in the level of consciousness.  The human body responds to hyperthermia by sweating and by dilating the peripheral blood vessels and allowing heat to transfer more easily to the environment.  It is easier for the body to transfer heat to surrounding air than to surrounding water.

For adult men who are immersed but not swimming, the core body temperature has been shown to increase during prolonged exposure to water temperatures of 36-37 C.  For adults who are swimming at moderate intensity, the core body temperature may increase in water temperatures of 28-32 C (82-89 F).  These facts are the basis for having an upper limit of water temperature for which wetsuit use is allowed and safe.

Water Temperature Guidelines for Other Organizations

The issue of safe temperatures for open water swimming events has long been controversial.  The several governing bodies for open water swimming have each studied this issue and developed their own guidelines in recent years.

USA Swimming, the national governing body for swimming in the United States in 2011 developed a comprehensive list of safety recommendations following the death of American open water swimmer, Fran Crippen, during a race held in the United Arab Emirates in very warm water.  Included were changes to USA Swimming’s water temperature guidelines.  Citing from the USA Swimming rules for open water swimming (2013 Rulebook):

  • The water temperature shall not be less than 16 C (60.8 F).
  • For races of 5K and above, the water temperature shall note exceed 29.45 C (85 F)
  • The air temperature and water temperature when added together shall not be less than 30 C (118 F) nor greater than 63 C (177.4 F).

FINA, the international governing body for the aquatic sports (swimming, diving, synchronized swimming, water polo, and open water swimming) sets the minimum allowable water temperature for open water swimming at 16 C (60.8 F) (see FINA 2013 Open Water Swimming Rules).  In June of this year, FINA adopted a new rule governing the maximum temperature allowable for open water swimming events.  At the recommendation of its Technical Open Water Swimming Committee, FINA has now set the maximum allowable temperature at 31 C (87.8 F).  This new rule came under almost immediate criticism because it is less restrictive than the current USA Swimming limit of 85 F.

For additional context, FINA specifies the allowable water temperature for swimming pool events to be between 25 and 28 C, and recognizes that athletic performance falls off at water temperatures greater than 27 C.

The International Triathlon Union (ITU), the international governing body for the sport of triathlon, has adopted water temperature safety guidelines that also account for the race distance and the air temperature.  All swims should be cancelled for water temperatures <13 C and all long distance swims (3000m or 4000m) should be cancelled for water temperatures <14 C.  Races can be shortened depending upon the air and water temperatures (see the 2013 ITU Competition Rules).  For age group athletes, the use of a wetsuit is forbidden above 22-24 C and is mandatory below 14-16 C, depending upon the race distance.

World Triathlon Corporation (WTC), the owner of the Ironman brand events, announced their SwimSmart initiative in May of this year.  For their North American Ironman events, WTC adopted a safe temperature range of 52 to 88 F.  If the water temperature is outside that range, the swim portion of the event will be shortened or cancelled.  For all of their events, wetsuits are permitted for water temperatures up to 76.1 F (24.5 C) and prohibited for water temperatures greater than 83.8 F (28.8 C).  Athletes wearing a wetsuit when the water temperature is between those cutoff temperatures are not eligible for age group awards.

My Advice

For Athletes.  Athletes are usually aware of the rules regarding wetsuit use.  They should also be aware of the potential issues of hypothermia or heat-related illness during a race.  These new recommendations from USAT provide a framework for critical thinking about this issue.  Athletes should use sound judgment and extra caution when participating in events at the extremes of the temperature range.  At the low end, extra consideration should be given to the use of a wetsuit even if a race is short.  USAT chose not to implement a policy about mandatory wetsuit use, but they do allow race directors to enforce such a rule.  My personal view is that swimmers should use a wetsuit for any race where the water temperature is 60 F or less.  At the high end of the temperature range, athletes should pay extra attention to their hydration and make certain that their pace or effort is moderated.  In the end, only the athlete can make the decision to participate.  Water temperature is one factor that should be taken into consideration when athletes make judgments about their safety.  If you think it’s unsafe, don’t participate.

For Race Directors.  The new recommendations define a very broad neutral temperature range.  The vast majority of events will be held in venues where the water temperature will fall into this range.  When the water temperature falls outside the neutral range, though, race directors should be very cautious about deviating from the recommendations to shorten or cancel the swim portion of a race.  In cold conditions, race directors should give due consideration to requiring athletes to wear a wetsuit.  For races at either extreme of the temperature spectrum, race directors should provide athletes with information about hypothermia, heat-related illness, and advice about the use of a wetsuit.