Wetsuit Technology and Heat Transfer: How Wetsuits Keep Triathletes Warm

For triathletes, the swim leg of the race can often be the most daunting. Open-water swims are often cold and unpredictable, requiring athletes to have the right gear to keep them warm and comfortable. By now, you have probably seen or heard that one essential piece of gear for open-water swims is a wetsuit. Wetsuits not only help keep you warm, but they can also improve buoyancy and reduce drag, making it easier to swim faster and more efficiently. Why does this happen, and how does it work?

Heat is a form of kinetic energy, and heat transfer is the processing of moving this thermal energy from one object to another. In other words, your molecules are literally moving faster than the cold water surrounding them. Thermal energy will move from warmer surfaces to the cooler surfaces.

Wetsuits work by trapping a thin layer of water between the skin and the suit, which is then warmed by body heat. This layer of water serves as an insulating barrier, helping to keep you warm in cold water. To improve the effectiveness of this insulating layer, wetsuits are made with materials that have high heat-transfer properties.

Most wetsuits today are made from neoprene (aka polychloroprene), a synthetic rubber discovered back in the 1930s. Neoprene is a poor conductor of heat, which means it does not transfer heat away from the body as quickly as other materials. This helps to keep the insulating layer of water around the body warmer for longer periods of time.

Specially, most top-end triathlon wetsuits use Yamamoto neoprene. Neoprene is a polymer that can be created with either limestone or petroleum. Yamamoto’s limestone neoprene has 30% more air content than its petroleum-based counterpart. Air is also a poor conductor of heat. For reference water conducts heat approximately 20x as well as air. Less heat transfer out of the wetsuit into the cooler water means warmer triathlete inside the wetsuit.

In addition to neoprene, wetsuits may also be lined with materials such as titanium or silver that reflect body heat back towards the body, further increasing the effectiveness of the insulating layer of water.

The thickness of the wetsuit also plays a role in heat transfer. Thicker wetsuits provide more insulation, but they also make it more difficult for the body to move freely. Current wetsuit technology skirts this problem by having different panels with different thickness and materials. This allows the suit to be thinner and more flexible about important areas such as the shoulders, while having other areas such as torso and legs well insulated. Higher end wetsuits have more panels but are consequently much more expensive.

Heat transfer is the scientific principle that keeps you warm in a wetsuit but does not explain buoyancy and reduced drag. More to come on that in a future post!