CORE™ wearable sensor: Comparison against gastrointestinal temperature during cold water ingestion and a 5 km running time-trial.

Five km running time-trials (TT) are associated with rapid and significant increases in core body temperature (T). For such races, real-time feedback from pre-exercise and exercise T may be helpful in the design of an optimal pacing strategy aimed at limiting the possibility of developing heat-related illnesses. This study compared measurements of T obtained with a wearable device, the CORE™, to those of a gastrointestinal pill (GI pill), during cold water ingestion and a 5 km running TT. Twelve participants (25 ± 4 yrs) ingested 7.5 mL/kg fat-free mass of 4 °C water over the first 5 min of a 120 min sitting period, after which they completed a 5 km running TT at 30 °C, 50% relative humidity. A T difference > ± 0.25 °C between sensors was deemed clinically unacceptable. Prior to water ingestion, the CORE-derived T was 0.49 ± 0.25 °C lower than the GI pill. The CORE was irresponsive to the 0.26 ± 0.22 °C peak decline in T captured with the GI pill 40 min following water ingestion. Prior to the TT, T was 0.30 ± 0.25 °C lower with the CORE than the GI pill. During the TT, the CORE underestimated the rate of increase in T by 0.0125 ± 0.019 °C/min compared with the GI pill, and mean absolute difference in T between sensors was of 0.47 ± 0.34 °C. In conclusion, the CORE does not capture the cooling effect of cold water ingestion and provides a clinically relevant underestimation of T during a 5 km running TT in the heat.