Saturday, September 08, 2012

Open water swimming: A rule of thumb for the prevention of Hypothermia and Hyperthermia!

Open water swimming needs a "rule of thumb" or a temperature benchmark that can be easily remembered.

There are so many variables to determine what are safe open water conditions. So, to avoid either hypothermia and hypothermia, swimmers and event directors may want to consider a "one size fits all" approach. Thus, I am going to suggest benchmarks that can be easily remembered and I need guidance. ANy Science guys out there would could be greatly helpful.

I checked out several kayak forums, news groups and info sites regarding hypothermia and they have a "rule of thumb" measurement to determine what makes for safe kayaking.

From the New River Campground
"... One of the biggest risks of river rafting is hypothermia. For dealing with this the golden rule of air and water temperature was developed. The rule is simple, just add the air temperature and the water temperature to get the combined temperature. If the combined water plus air temperature is less than 120, wet or dry suits are recommended. If the combined temperatures are below 100 degrees, wet or dry suits should be required. Here at New River Campground Canoeing and Kayaking we believe in following this rule, and will require you to have a wet or dry suit if you wish to go on the river when the combined temps are below 100 degrees. .." 

The "rule of thumb" above leaves the air-temp and humidity out of the equation but they seem pretty reliable as a benchmark from an anecdotal point of view.

There are benchmarks for air-temps too. For instance, today in a suburb of Los Angeles where I live the air temp today will be 93-degrees with 47% humidity. Per the chart above that is border line danger for the Heat Index tells us that it will feel like 103-degrees. Note, extreme caution per the chart above is when the Heat Index reaches 91-degrees.

When Fran Crippen died in Abu Dabai, Crippen told his coach, Richard Shoulberg, before the race that the air temp was 100-degrees and that the water temp was 87-degrees. [Link]

See the chart above, 100-degrees as an air-temp is bordering upon Extreme-Caution. Even the water temperature if converted to an air-temp with 0% humidity was nearing the Extreme Caution zone. Consequently, all the coaches on the beach and all the swimmers in the water that day had no idea what they doing to themselves. The trouble was that all of the data was available but all of the above were ignorant to the dangers.

Then, a year later a near sequel in Shanghai with near fatal consequences occurred...

From Swimming World:

FINA World Championships, Open Water: Petar Stoychev, Ana Marcela Cunha Win Controversy-Marred 25K Races 
"... This all takes place against the backdrop of the death of Fran Crippen at the UAE stop of the FINA Open Water 10K World Cup less than a year ago in October 2010. Calls for rules to enhance athlete safety were met with a slew of recommendations from two separate commissions (FINA, USA Swimming), which included a recommended maximum temperature of [88-degrees Fahrenheit.] Again, these recommendations have yet to be codified into the rule books. 
Throughout the men's race, 10 more swimmers did not finish the race including an open water veteran like Italy's Valerio Cleri. For the women, four more swimmers did not finish the course including USA's Claire Thompson. Thompson ignored USA Swimming's suggestion that the U.S. not participate in the event, and the team had to let her race due to the Amateur Sports Act. ..."

What frustrates me is that the press nor I paid attention to the air temps at Shanghai. The average temps the time of year when the race was conducted is around 95-degrees. With one fatal race behind us and a second potentially fatal one in Shanghai, it's demonstrable that a combined air-and-water-temp over 185-degrees has proven both fatal and near-fatal.

SO where do we go with this and what number as a benchmark do we come up with? Here is what I suggest by taking the New River Campground quoted above and their benchmark as a possible ratio:

New River Campground kayaking Model:
  1. Air-temp + Water-temp = 100  (Wetsuits or drysuits are mandatory)
  2. Air-temp + Water-temp = 120  (Wetsuits or drysuits recommended)

Open water swimming suggested model:
  1. Air-temp Heat Index + Water Temp = 100  (Wetsuits mandatory)
  2. Air-temp Heat Index + Water Temp = 120  (Wetsuits recommended)
  3. Air-temp Heat Index + Water Temp = 140  (Choice of swimming attire)
  4. Air-temp Heat Index + Water Temp = 170  (DO NOT RACE)

To simplify even more: 100-degree to cold to swim, 170 to hot!

1 comment:

Anonymous said...

Water provides something like 20x the cooling (or heating) that air does, and open-water swimming is a nearly full-immersion sport. Air temps have near-zero bearing. However, 87-degree water is too close to (resting) core body temps to provide sufficient cooling for heavy exercise like open-water racing. This is unlike air temps of 87, where the body can use evaporative cooling rather than simply conduction. The race guideline should be based solely on water temps, and should be low enough to avoid overheating. Kayaking guidelines use the same flawed assumption that air & water provide equal rates of cooling, and are often criticized for understating the risk of cold water.