New open-water swimming research published in the International Journal of Exercise Science explores how full-sleeve wetsuits impact core body temperature during warm-water triathlons. Conducted by researchers at the University of Nevada, Las Vegas, the study monitored triathletes completing open-water swims in temperatures ranging from 27.9°C to 28.3°C to evaluate whether wetsuit insulation increases heat stress risks.
Evaluating Wetsuit Thermal Responses in Warm Water
Triathlon mortality data indicates that approximately 67% of race fatalities occur during the swimming leg, with cardiac arrest as the primary cause, according to historical research cited by Harris and colleagues. While exact triggers remain under investigation, researchers have long hypothesized that hyperthermia brought on by wetsuit use in warm water could contribute to cardiovascular strain. Unlike land exercise where sweat evaporation cools the body, aquatic thermoregulation depends entirely on convection and conduction with the surrounding water.
To investigate these thermal effects, researchers Katsiaryna Afanasyeva, Alina P. Swafford, James W. Navalta, Graham R. McGinnis, and John A. Mercer evaluated four participants with an average age of 49.5 years. The subjects completed two separate 700-meter open-water swims at self-selected submaximal paces. In the first trial, participants wore a full-sleeve wetsuit. In the second trial, they swam without a wetsuit.
Core Temperature Patterns and Polynomial Analysis
During the trials, core body temperature was tracked continuously using ingestible temperature pills programmed with a 15-second sampling rate. Researchers analyzed the resulting core temperature versus time datasets by fitting them with 1st, 2nd, and 3rd order polynomials, evaluating goodness-of-fit through the sum of squared residuals.
The study found that all participants showed improved curve-fitting using at least a 2nd order polynomial when wearing a wetsuit, indicating an individualized nonlinear rate of core temperature change. However, two participants showed no polynomial fit improvement during the non-wetsuit condition. Crucially, the data revealed no risk of hyperthermia for participants in either condition during the warm-water tests.
Swim Performance and Governing Body Regulations
Performance metrics from the study showed that swim times were significantly faster when participants wore the full-sleeve wetsuit, averaging 742.5 seconds compared to 907.5 seconds without a wetsuit. This performance advantage highlights why athletes frequently opt for wetsuits when permitted.
Current sports regulations enforce strict temperature thresholds for wetsuit usage to balance thermal safety with performance equity. World Triathlon rules prohibit wetsuits for swim distances of 1,501 meters or longer when water temperatures exceed 24.6°C for athletes seeking awards. For shorter distances of 1,500 meters or less, the cutoff threshold drops to 22°C. Meanwhile, USA Triathlon permits wetsuits in water temperatures between 25.6°C and 28.8°C, though participating athletes forfeit eligibility for age-group awards and ranking points.
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