Comparison of a Body Temperature Wearable Device With Gastrointestinal Thermometry During a Warm-Weather Road Race

Kaufman, CE, Szymanski, MR, Brewer, GJ, Stearns, RL, Casa, DJ, and Huggins, RA. Comparison of a body temperature wearable device with gastrointestinal thermometry during a warm-weather road race. J Strength Cond Res 39(11): e1287-e1294, 2025-To compare estimated measures of a wearable body temperature device with gastrointestinal temperature during and at the finish of a road race. Fourteen recreational runners ([ n = 9 men, n = 5 women] [mean ± SD ] age: 48 ± 14 years, V̇O 2 peak: 47.66 ± 8.21 ml·kg -1 ·min -1 ) were recruited. The wearable body temperature device and gastrointestinal temperature were measured and compared throughout the duration of the race and at race finish ( p < 0.05). During race: Poor agreement and a high, positive relationship (Lin's Concordance Correlation Coefficient [CCC] = 0.70, 95% Limits of Agreement [LOA] ± 0.94° C, r = 0.78) were noted between the wearable body temperature device and gastrointestinal temperature. No interaction was exhibited between time and device ( p = 0.087). At race finish: Poor agreement and a low, positive relationship (CCC = 0.30, 95% LOA±1.20° C, r = 0.43) were noted between the wearable body temperature device and gastrointestinal temperature. During continuous exercise in a warm weather race, the wearable body temperature device was within the acceptable limits (±0.27° C) compared with gastrointestinal temperature. The wearable body temperature device reported the widest LOA in the race finish analyses. Typical error of estimate suggests that the mean bias values may be attributed to error. Further validation is crucial in higher internal body temperatures (>39.5° C) in varying populations, environments, and intensities both pre- and postexercise Currently, this device is not acceptable for medical use or clinical diagnosis of exertional heat stroke. Medical personnel (e.g., athletic trainers, team physicians) and additional personnel (e.g., coaches, military officers, safety managers) can benefit from valid, continuous, real-time internal body temperature monitoring in the heat.