REVIEW

The ingestible telemetric body core temperature sensor: a review of validity and exercise applications

Christopher Byrne¹, Chin Leong Lim²

¹ School of Sport and Health Sciences, University of Exeter, Exeter, UK
² Defence Medical and Environmental Research Institute, DSO National Laboratories, Singapore, Republic of Singapore

Correspondence to:
Dr C Byrne
School of Sport and Health Sciences, St Luke’s Campus, University of Exeter, Exeter EX1 2LU, UK; c.byrne{at}exeter.ac.uk

An ingestible telemetric temperature sensor for measuring body core temperature (T_c) was first described 45 years ago, although the method has only recently gained widespread use for exercise applications. This review aims to (1) use Bland and Altman’s limits of agreement (LoA) method as a basis for quantitatively reviewing the agreement between intestinal sensor temperature (T_intestinal), oesophageal temperature (T_oesophageal) and rectal temperature (T_rectal) across numerous previously published validation studies; (2) review factors that may affect agreement; and (3) review the application of this technology in field-based exercise studies. The agreement between T_intestinal and T_oesophageal is suggested to meet our delimitation for an acceptable level of agreement (ie, systematic bias <0.1°C and 95% LoA within ±0.4°C). The agreement between T_intestinal and T_rectal shows a significant systematic bias >0.1°C, although the 95% LoA is acceptable. T_intestinal responds less rapidly than T_oesophageal at the start or cessation of exercise or to a change in exercise intensity, but more rapidly than T_rectal. When using this technology, care should be taken to ensure adequate control over sensor calibration and data correction, timing of ingestion and electromagnetic interference. The ingestible sensor has been applied successfully in numerous sport and occupational applications such as the continuous measurement of T_c in deep sea saturation divers, distance runners and soldiers undertaking sustained military training exercises. It is concluded that the ingestible telemetric temperature sensor represents a valid index of T_c and shows excellent utility for ambulatory field-based applications.

Abbreviations: LoA, limits of agreement; RMSD, root mean-squared deviation

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