Core-temperature sensor ingestion timing and measurement variability

Abstract

Context: Telemetric core-temperature monitoring is becoming more widely used as a noninvasive means of monitoring core temperature during athletic events.

Objective: To determine the effects of sensor ingestion timing on serial measures of core temperature during continuous exercise.

Design: Crossover study.

Setting: Outdoor dirt track at an average ambient temperature of 4.4°C ± 4.1°C and relative humidity of 74.1% ± 11.0%.

Patients or other participants: Seven healthy, active participants (3 men, 4 women; age = 27.0 ± 7.5 years, height = 172.9 ± 6.8 cm, body mass = 67.5 ± 6.1 kg, percentage body fat = 12.7% ± 6.9%, peak oxygen uptake [Vo(2peak)] = 54.4 ± 6.9 mL•kg⁻¹•min⁻¹) completed the study.

Intervention(s): Participants completed a 45-minute exercise trial at approximately 70% Vo(2peak). They consumed core-temperature sensors at 24 hours (P1) and 40 minutes (P2) before exercise.

Main outcome measure(s): Core temperature was recorded continuously (1-minute intervals) using a wireless data logger worn by the participants. All data were analyzed using a 2-way repeated-measures analysis of variance (trial × time), Pearson product moment correlation, and Bland-Altman plot.

Results: Fifteen comparisons were made between P1 and P2. The main effect of time indicated an increase in core temperature compared with the initial temperature. However, we did not find a main effect for trial or a trial × time interaction, indicating no differences in core temperature between the sensors (P1 = 38.3°C ± 0.2°C, P2 = 38.3°C ± 0.4°C).

Conclusions: We found no differences in the temperature recordings between the 2 sensors. These results suggest that assumed sensor location (upper or lower gastrointestinal tract) does not appreciably alter the transmission of reliable and repeatable measures of core temperature during continuous running in the cold.

Figure 1

The experimental protocol was performed 3 times by each participant.

Figure 2

Core-temperature changes during exercise. We found no differences between the sensor ingested 24 hours (P1) and the sensor ingested 40 minutes (P2) before exercise (mean ± standard error of the mean). ^a Indicates that each 5-minute interval was elevated compared with the initial temperature (main effect for time) (P < .05).

Figure 3

Pearson product moment correlation with the line of identity between the sensor ingested 24 hours (P1) and the sensor ingested 40 minutes (P2) before exercise. Each data point represents a 5-minute average ± standard error of the mean.

Figure 4

Bland-Altman plot of core-temperature readings during 45 minutes of continuous exercise. The solid line represents the mean average difference (0.047°C), and the dashed lines are 2 SDs from the mean.