Comparison of an In-Helmet Temperature Monitor System to Rectal Temperature During Exercise

Abstract

Body temperature monitoring is crucial in helping to decrease the amount and severity of heat illnesses; however, a practical method of monitoring temperature is lacking. In response to the lack of a practical method of monitoring the temperature of athletes, Hothead Technologies developed a device (HOT), which continuously monitors an athlete's fluctuations in body temperature. HOT measures forehead temperature inside helmets. The purpose of this study was to compare HOT against rectal temperature (Trec). Male volunteers (n = 29, age = 23.5 ± 4.5 years, weight = 83.8 ± 10.4 kg, height = 180.1 ± 5.8 cm, body fat = 12.3 ± 4.5%) exercised on a treadmill at an intensity of 60-75% heart rate reserve (HRR) (wet bulb globe temperature [WBGT] = 28.7° C) until Trec reached 38.7° C. The correlation between Trec and HOT was 0.801 (R = 0.64, standard error of the estimate (SEE) = 0.25, p = 0.00). One reason for this relatively high correlation is the microclimate that HOT is monitoring. HOT is not affected by the external climate greatly because of its location in the helmet. Therefore, factors such as evaporation do not alter HOT temperature to a great degree. HOT was compared with Trec in a controlled setting, and the exercise used in this study was moderate aerobic exercise, very unlike that used in football. In a controlled laboratory setting, the relationship between HOT and Trec showed favorable correlations. However, in applied settings, helmets are repeatedly removed and replaced forcing HOT to equilibrate to forehead temperature every time the helmet is replaced. Therefore, future studies are needed to mimic how HOT will be used in field situations.

Temperature Measurement Inside Protective Headgear: Comparison With Core Temperatures and Indicators of Physiological Strain During Exercise in a Hot Environment

“…Wickwire et al (15) , using the same device tested in the present study, concluded that an in-helmet measurement system provided a reasonable representation of T c , especially at higher temperatures. Gunga et al (17) also found similar results with a device placed inside a firefighter's helmet.…”

“…A likely reason for the differences in the conclusions of the aforementioned studies is the presence of the insulation effect created by placing the sensor inside a helmet, thus creating a heated microenvironment; a condition identified by Wickwire et al (15) The hardhat cavity temperatures observed in the current study at the end of exercise indicate that the environment inside the hardhat reaches temperatures that are relatively high; in fact, greater than Tsk. The insulation effect is accentuated when the sensor is held against the skin by the supporting band of the hardhat, as was the case in the present study.…”

“…The curvilinear relationships between T ih and the conventional measures are in line with the ANOVA findings since it also suggests that the relationship improves with elevated temperature. The data of Wickwire et al (15) also showed this tendency.…”

“…Skin thermistors were placed on the chest, and on (15) . An additional sensor was attached to the interior of the hardhat in the airspace created by the hardhat mounting system at the highest point in the cavity of the hardhat (T cav ).…”

“…Wickwire et al (15) found a high correlation (r = 0.801) between T re and an intra-helmet device produced by Hot Head Technologies TM . Gunga et al (16) compared T re and a double sensor placed inside a fire fighter's helmet in three environmental temperatures.…”