Agreement between mean weighted skin temperature formulas during exercise.

There are many formulas to calculate mean weighted skin temperature (Tmws) with little evidence for their agreement with each other. This investigation assessed the agreement of five common Tmws formulas (≤7 sites) with a 12-site formula (Hardy-DuBois 12-site, HDB12). It was hypothesized that a formula with more measurement sites (Hardy-Dubois 7-site, HDB7) would have more agreement during steady-state exercise in moderate (20°C) and warm (30°C) conditions. Ten well-trained male participants (age: 37 ± 12 yr, height: 178 ± 7 cm, mass: 76 ± 9 kg, body fat: 8 ± 2%, V̇o2peak: 66 ± 10 mL/kg/min) cycled at 55% of peak oxygen uptake for 60 min. The Tmws were calculated for HDB12, HDB7, Palmes/Park 6-site (PP6), Teichner 6-site (TEI6), Ramanathan 4-site (RAM4), and Burton 3-site (BTN3) formulas. Good agreement was determined when the mean bias, mean absolute error (MAE), or root mean squared error (RMSE) was ≤0.5°C or the limits of agreement (LOA) were ≤1.0°C. The Tmws formulas were in better agreement with HDB12 in warm compared with moderate conditions. The best performing formulas were RAM4, BRT3, and TEI6; mean bias was low in RAM4 (moderate: 0.2°C; warm: 0.1°C) and BRT3 (moderate: 0.1°C; warm: 0.0°C) and RMSE was low in TEI6 (moderate: 0.6°C; warm: 0.4°C) compared with the others. The large deviation in torso skin temperature for HDB7 (moderate: -2.0°C; warm: -1.6°C) resulted in consistent underestimation of HDB12 (mean bias, moderate: -0.8°C; warm: -0.5°C). Due to its popularity, the four-site RAM4 is acceptable for cycling in 20°C and 30°C conditions, when a 12-site formula is not feasible.NEW & NOTEWORTHY This investigation is the first to show Tmws formula agreement during exercise in moderate (20°C) and warm (30°C) environments. This study uniquely contributes to the present knowledge by showing better agreement between all formulas and the criterion in the 30°C environment than in the 20°C environment during exercise. This study supports the prevalent use of the Ramanathan formula currently in research.