As warm blooded animals, human beings have a remarkable capacity to perform in a wide variety of environmental conditions. Thanks to precisely controlled temperature regulation, we are able to dissipate heat when the conditions are warm and conserve it when it is cold. Still, as so many of us are painfully aware, there are limits to how effectively these systems can function, and there is variability between individuals which results in some being better able to handle certain environments than others.
In warm conditions, when performing physical activity, our muscles can produce enormous amounts of heat that can result in the body overheating and lead to significant damage to vital organs. In very cold environments, the same heat produced by our muscles is conserved within our core in order to ensure we don’t get too cold and don’t again sustain injury to vital organs.
It is interesting and likely a reflection of the evolutionary pressures placed on our species that we are better equipped to handle extreme cold temperatures than extreme hot ones.
Barbara Hernandez is a world champion ice swimmer. She lives in Chile, where she spends much of the year training in the glacial lake in Portillo. In the depths of winter she travels to places like Russia, Finland, and other countries where ice swimming has become a fairly popular sport (as these things go). I asked Hernandez how she prepares for competitions that are often held in water that is only a couple of degrees above freezing. “There is both physical and mental preparation. The idea is to gradually expose yourself to lower and lower temperatures. With acclimatization and training in the pool at normal temperatures it is possible to go faster and stronger in the ice swimming,” she said.
Hernandez is quite accomplished in her sport. She was the first woman to swim a mile in water at 4 degrees Celsius (39F) at 2800 meters of altitude. She swam 1-kilometer at 0 degrees C (32F) in Siberia and crossed the 9K Beagle Channel in almost two hours in water that was 7 degrees C (45F). And this is in addition to the numerous medals she has won at the World Ice Swimming championships over the years. I asked her if she and other ice swimmers are simply immune to developing hypothermia and she told me, “The truth is that ice swimmers always have hypothermia, the difference is that we learn to recognize the different degrees of hypothermia so that we recognize when we are in danger and need to stop. We also train our tolerance to pain and we work hard on recovery at the end of our swim.”
New research has shown that cold tolerance is definitely something that’s variable between individuals. It’s not just a matter of being tougher, but rather one of nerve sensations varying between individuals. While some research suggests—unlike heat adaptation—you can’t train yourself with cold exposure, Hernandez thinks that anyone can become a fan of cold water or even ice water swimming if they are motivated enough. “The important thing is to start. It’s a beautiful way to challenge ourselves physically and mentally and to get in touch with the here and now. Ice swimmers all share a love for nature and the benefits of ice water, it helps us with blood circulation, improves our immune system, and is even used as an antidepressant treatment.”
While most people do not aspire to endure the kinds of conditions that Hernandez subjects herself to, many triathletes do take on the challenge of competing in extreme temperatures. Whether hot and humid weather, or a less severe environment, temperature variations can be a significant impediment to athletic performance.
At temperatures higher than around 100 degrees F (38C), the body becomes less efficient while performing. When exposed to heat, various physiologic adaptations occur to improve cooling to prevent this temperature from being exceeded. Blood volume expands, sweating is increased often with a change in salt concentration within the sweat, and cardiac output is increased. But there is evidence to suggest that athletes who are well-adapted to heat or who can control their body temperature best in hot environments will have the best chances of success when competing.
Heat adaptation has been pretty well studied and has been shown to improve performance in measurable ways, albeit with inconsistent amounts of benefit. Athletes who have the ability to train in a hot environment prior to a race are best suited to perform well in a hotter race—but even those coming from colder climates can do things to adapt their bodies in advance of competitions.
Arriving at a destination a week in advance of an event and training while there is a time tested and proven means of heat acclimatization. Those who are unable to do this, can use sauna protocols as a means to prepare for their hotter destination. There is also some research to suggest that these heat acclimation protocols can even bear fruit for events in cooler climates, but the evidence for this is somewhat inconsistent.
Some professional cycling teams have taken things a step further, using portable temperature monitoring devices to capture body temperature data in real time and guide athletes on how to hydrate and measure out their efforts. For example, if the temperature is reading too high, an athlete would be advised to not make any big surges. These core temperature sensors are becoming the “hot” new thing in athlete data and wearables.
However, there are a few issues with this strategy, not the least of which is the unproven validity of the sensors being used. It is a novel concept and one that could have application for athletes who have to contend with hot and humid races like Kona—though whether an athlete will be willing to respond to a temperature alert by slowing down if they are in contention remains to be seen.
Still, as the climate continues to warm and more of us face hot conditions rather than those Hernandez subjects herself to, we can only benefit from paying more attention to our core temperature and, when possible, taking steps to keep it in the range where our performance will be most efficient.
Train hard, train healthy.
The MedTent will answer your science and medical triathlon-related questions. It’s written by Jeff Sankoff, an ER physician, triathlete, and coach who runs TriDoc coaching and hosts the TriDoc podcast.