Telemetry pill versus rectal and esophageal temperature during extreme rates of exercise-induced core temperature change

Abstract

Core temperature measurement with an ingestible telemetry pill has been scarcely investigated during extreme rates of temperature change, induced by short high-intensity exercise in the heat. Therefore, nine participants performed a protocol of rest, (sub)maximal cycling and recovery at 30 °C. The pill temperature (Tpill) was compared with the rectal temperature (Tre) and esophageal temperature (Tes). Tpill corresponded well to Tre during the entire trial, but deviated considerably from Tes during the exercise and recovery periods. During maximal exercise, the average ΔTpill−Tre and ΔTpill−Tes were 0.13 ± 0.26 and −0.57 ± 0.53 °C, respectively. The response time from the start of exercise, the rate of change during exercise and the peak temperature were similar for Tpill and Tre. Tes responded 5 min earlier, increased more than twice as fast and its peak value was 0.42 ± 0.46 °C higher than Tpill. In conclusion, also during considerable temperature changes at a very high rate, Tpill is still a representative of Tre. The extent of the deviation in the pattern and peak values between Tpill and Tes (up to >1 °C) strengthens the assumption that Tpill is unsuited to evaluate central blood temperature when body temperatures change rapidly.