Well-trained swimmers wearing approved wetsuits maintained core temperature down to a median critical cold-water temperature of 15.0°C, below the current 16°C regulatory mandate, with no differences between genders or wetsuit types.
Key Findings
Results
The critical cold-water temperature (Tcrit) at which core temperature could no longer be maintained while wearing an approved full-length wetsuit was significantly below the current 16°C regulation.
Median Tcrit was 15.0°C [95% CI: 14.8–15.3°C]
Tcrit was significantly below the 16°C regulation (P < 0.001)
Study recruited 20 trained swimmers (12 men, 8 women)
Tcrit was identified using segmental linear regression applied to core temperature data from progressive cooling swim trials
Results
No significant difference in Tcrit was observed between male and female swimmers.
P = 0.78 for gender comparison
Men: Tcrit = 15.0°C (95% CI: 14.6–15.3°C)
Women: Tcrit = 14.91°C (95% CI: 14.6–15.4°C)
Results
No significant difference in Tcrit was observed between sleeved and sleeveless wetsuit designs.
P = 0.90 for wetsuit type comparison
Sleeved wetsuit Tcrit: 15.1 ± 0.5°C
Sleeveless wetsuit Tcrit: 15.1 ± 0.6°C
Comparison was conducted in a subset of n = 8 swimmers who completed additional swim trials with both wetsuit types
Results
Body fat percentage, metabolic heat production, and body surface area-to-mass ratio were significant predictors of Tcrit.
Multiple regression model R² = 0.41, P = 0.008
Body fat percentage β-coefficient: −0.06088, P = 0.0390
Metabolic heat production β-coefficient: −0.004416, P = 0.0079
Body surface area-to-mass ratio β-coefficient: −370.6, P = 0.0078
Methods
The experimental protocol involved progressive cooling from 16°C in a swim flume while swimming at race-representative intensity wearing approved wetsuits.
Swim trials lasted 120 minutes
Water temperature started at 16°C and decreased approximately 0.15°C every 10 minutes
Swimmers wore full-length World Aquatics-approved wetsuits
A subset of n = 8 completed an additional trial comparing sleeved versus sleeveless wetsuit designs
Conclusions
Despite empirical evidence that trained swimmers can tolerate temperatures below 16°C, the authors recommend maintaining the current 16°C mandate.
The recommendation is based on providing 'appropriate safety margins for the diverse competitive population and variable real-world conditions encountered in open water swimming competitions'
The authors note the findings 'provide objective evidence supporting current conservative regulatory approaches'
The current World Aquatics regulation requires water temperature to be at or above 16°C for wetsuit-permitted competitions
Skutnik B, Owen M, Hite M, Sweitzer L, Petersen J, Johnson B, et al.. (2026). Safe cold-water thresholds while wearing wetsuits approved for open water swimming competitions.. Journal of applied physiology (Bethesda, Md. : 1985). https://doi.org/10.1152/japplphysiol.01102.2025