Hot & Bothered Triathletes: An Introduction to Heat Transfer

Conduction, Convection, Radiation, and Transpiration: An Introduction to Heat Transfer

With it becoming ever more difficult to gain performance edges in bike aerodynamics and nutritional supplements, technology is turning to a relatively unexplored realm of sports performance augmentation–the clothes on our backs. I’m going to spend the next several installments of this blog analyzing different claims about “beat the heat” garments. Before we start in earnest, it will help to go a little more in-depth about how the body deals with excess heat during competition. Some of this will be review from the book, and some of this will be new material.

ironman triathlete, triathlete, triathlons, cycling, cyclist

Substantial research on endurance sport clothing began ahead of the 2000 Summer Games in Sydney, which produced everything from body-length swimsuits to hooded track suits. Much of the research was then applied to time trial suits for professional cyclists. All of this was in the name of better aerodynamics (or hydrodynamics, in the case of the swimmers). This has some utility in long endurance events, but more concerning to long-course racers than cutting through the air is staying cool in it.

As discussed my book FASTER: Demystifying the Science of Triathlon Speed, heat dissipation is the predominant limiting factor on speed once you begin the run portion of any triathlon. That’s because your speed decreases significantly while maintaining the same level of physical exertion. Without all that airflow passing over your body, you lose a major resource for heat dissipation. And, depending on your local conditions, you could also suffer heat-induced injuries even while on the bike.

Drinking water and maintaining electrolytic balance is key to succeeding in extremely hot competitions. But beyond certain temperature, humidity, and exertion limits, there’s only so much hydration can do. Other forms of physiological damage become unavoidable as heat continues to accumulate in the body. The only remedy is to find a way to expel heat faster. Sports apparel manufacturers have taken note of this and are now pursuing methods to expedite heat transfer from the body.

Swimmers, triathlon, triathlete, swim

It’s not an easy problem to solve.

If you think the law of gravity can be a real pain while climbing up a hill, try the laws of thermodynamics on for size! They have been used to suggest everything from the cause of global warming to the theory that the entire universe will die someday. So, thermodynamics isn’t exactly the best field of research in which to find cheerful optimists.

Indeed, there are major limitations on staying cool. The body releases heat through every method of heat transfer possible, and they are still not enough to dissipate all the excess energy in hot conditions. Let’s quickly review those methods to establish a basis of comparison.

Next week, please join me back in 8th grade physics class for a refresher on how heat dissipates from the body.

If you’re interested in getting faster, you’ll be fascinated by FASTER: Demystifying the Science of Triathlon Speed. In Faster, astronautical engineer and triathlon journalist Jim Gourley explores the science of triathlon to see what truly makes you faster—and busts the myths and doublespeak that waste your money and slow down your racing. With this knowledge on your side, you can make simple changes that add up to free speed and faster racing.

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