Wireless measurement of rectal temperature during exercise may circumvent some limitations associated with the use of a conventional wired probe. We determined, for the first time, whether temperatures provided in vivo by wireless ingestible thermometric telemetric pills and a rectal probe compare favorably under conditions producing slow and rapid increases and decreases in rectal temperature. While wearing a rectal probe linked to a wireless ingestible thermometric telemetric pill, 13 participants completed the following phases: 1)30 min sitting; 2)45 min passive heat exposure (40–42 °C); 3)45 min sitting while ingesting 7.5 g of ice slurry · kg body mass−1; 4)running exercise (38 °C)at 68% V˙O2max until a 39.5 °C increase in rectal probe temperature and; 5)cold-water (10 °C)immersion until a 1.5 °C decrease in rectal probe temperature. Acceptable differences between devices were taken as ≤ 0.3 °C. Mean differences within phases were all < 0.3 °C, whereas 95% limits of agreement ranged from ±0.2 °C to ±0.4 °C, coefficient of variations from ±0.3% to ±0.6% and typical error of measurements from ±0.1 °C to ±0.2°. Of the 14881 rectal temperature values measured over the experiment with the wireless ingestible thermometric telemetric pills and rectal probe, 91% of the differences between devices were found to be ≤ 0.3 °C. Results suggest that rectal temperatures provided by a wireless ingestible thermometric telemetric pill used as a suppository agree with those of a conventional wired probe. Hence, rectal temperature can reliably be measured using a wireless ingestible thermometric telemetric pill as a suppository.
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