Non-Invasive Measurement of Core Body Temperature in Marathon Runners

Long-term accurate measurements of core body temperature are essential to study human thermoregu-lation in ambulatory settings and during exercise, but they are traditionally carried out using highly-invasive techniques. To enable a continuous unobtrusive moni-toring of core body temperature on ambulatory patients and exercising athletes, we have designed a wireless wearable system that measures the tympanic tempera-ture inside the ear, as well as skin and environmental temperature, and that allows remote monitoring of the collected measurements. In this paper, we describe the design and implementation of the system and show that it can be used to identify the circadian rhythms of core body temperature, as well as to detect the variation in core body temperature due to prolonged physical exertion. We further describe the lessons learnt during a pilot deployment of our telemetric system on several athletes during the 5th Lübeck Marathon, and discuss the impact of environmental parameters such as tem-perature and wind on the accuracy and meaningfulness of the measured values. 1