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Validity, Reliability, and Inertia of Four Different Temperature Capsule Systems


Medicine & Science in Sports & Exercise: January 2018 - Volume 50 - Issue 1 - p 169–175
doi: 10.1249/MSS.0000000000001403
Applied Sciences

Purpose Telemetric temperature capsule systems are wireless, relatively noninvasive, and easily applicable in field conditions and have therefore great advantages for monitoring core body temperature. However, the accuracy and responsiveness of available capsule systems have not been compared previously. Therefore, the aim of this study was to examine the validity, reliability, and inertia characteristics of four ingestible temperature capsule systems (i.e., CorTemp, e-Celsius, myTemp, and VitalSense).

Methods Ten temperature capsules were examined for each system in a temperature-controlled water bath during three trials. The water bath temperature gradually increased from 33°C to 44°C in trials 1 and 2 to assess the validity and reliability, and from 36°C to 42°C in trial 3 to assess the inertia characteristics of the temperature capsules.

Results A systematic difference between capsule and water bath temperature was found for CorTemp (0.077°C ± 0.040°C), e-Celsius (−0.081°C ± 0.055°C), myTemp (−0.003°C ± 0.006°C), and VitalSense (−0.017°C ± 0.023°C; P < 0.010), with the lowest bias for the myTemp system (P < 0.001). A systematic difference was found between trial 1 and trial 2 for CorTemp (0.017°C ± 0.083°C; P = 0.030) and e-Celsius (−0.007°C ± 0.033°C; P = 0.019), whereas temperature values of myTemp (0.001°C ± 0.008°C) and VitalSense (0.002°C ± 0.014°C) did not differ (P > 0.05). Comparable inertia characteristics were found for CorTemp (25 ± 4 s), e-Celsius (21 ± 13 s), and myTemp (19 ± 2 s), whereas the VitalSense system responded more slowly (39 ± 6 s) to changes in water bath temperature (P < 0.001).

Conclusions Although differences in temperature and inertia were observed between capsule systems, an excellent validity, test–retest reliability, and inertia was found for each system between 36°C and 44°C after removal of outliers.

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1Department of Physiology, Radboud Institute for Health Sciences, Radboud University Medical Center, Nijmegen, THE NETHERLANDS; 2Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, THE NETHERLANDS; 3TNO, CBRN Protection/Training and Performance Innovations, Rijswijk, THE NETHERLANDS; and 4Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UNITED KINGDOM

Address for correspondence: Thijs M. H. Eijsvogels, Ph.D., Department of Physiology (392), Radboud University Medical Center, PO Box 9101, 6500 HB Nijmegen, the Netherlands; E-mail:

Submitted for publication May 2017.

Accepted for publication August 2017.

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© 2018 American College of Sports Medicine