A Heart Rate Based Algorithm to Estimate Core Temperature Responses in Elite Athletes Exercising in the Heat

Area of Science:

• Sports Medicine
• Exercise Physiology
• Environmental Health

Background:

• Non-invasive monitoring of core body temperature (Tc) is crucial for optimizing athletic performance and preventing heat illness.
• The Estimated Core Temperature (ECTemp™) algorithm predicts Tc using heart rate (HR) data.
• Validating non-invasive methods like ECTemp™ in elite athletes exercising in heat is essential.

Purpose of the Study:

• To assess the accuracy and validity of the ECTemp™ algorithm for estimating core body temperature (Tc) in elite athletes during heat exertion.
• To determine the reliability of ECTemp™ in real-world exercise conditions within hot and humid environments.

Main Methods:

• 101 elite athletes underwent exercise testing in simulated hot and humid conditions (31.6°C, 74% RH).
• Core temperature (Tc) was measured using ingestible telemetric capsules.
• Heart rate (HR) was continuously monitored to calculate estimated core temperature (Tc-est) via the ECTemp™ algorithm.

Main Results:

• A total of 5,025 data points were collected, showing a small but significant bias (0.15 ± 0.29°C) between Tc-est and Tc.
• The algorithm demonstrated fair to excellent sensitivity and specificity for Tc-est thresholds between 37.75°C and 38.75°C.
• Sensitivity decreased significantly (0-50%) for Tc-est thresholds above 39.0°C, indicating a high rate of false negatives.

Conclusions:

• ECTemp™ provides a useful, non-invasive estimate of thermal strain in the lower to moderate core temperature ranges during heat exercise.
• The algorithm can inform athletes and coaches during heat acclimation protocols.
• ECTemp™ is not recommended as a sole tool for identifying athletes at risk of heat illness due to its limitations at high core temperatures.