Rectal and gastrointestinal temperature differ during passive heating and subsequent recovery

We aimed to compare rectal temperature (T_rec) and gastro-intestinal temperature (T_GI) during passive heating and subsequent recovery with and without ice slurry ingestion. Twelve males (age: 25 ± 4 years, body mass index: 25.7 ± 2.5 kg m⁻²) were immersed in hot water on two occasions (T_rec elevation:1.82 ± 0.08 °C). In the subsequent 60-min recovery in ambient conditions, participants ingested either 6.8 g kg⁻¹ of ice slurry (−0.6 °C, ICE) or control drink (37 °C, CON). During passive heating, T_rec was lower than T_GI (P < 0.001), in the recovery, T_rec was higher than T_GI (P < 0.001). During passive heating, mean bias and 95%LoA (Limits of Agreement) was −0.10(±0.25)ºC and −0.12(±0.36)ºC for CON and ICE, respectively. In the recovery, mean bias and 95%LoA was 0.30(±0.60)ºC and 0.42(±0.63)ºC for CON and ICE, respectively. T_rec and T_GI differed during both heating and recovery, and less favourable agreement between T_rec and T_GI was found in the recovery from passive heating with or without ice slurry ingestion.