Predicting Military Working Dog Core Temperature During Exertional Heat Strain: Validation of a Canine Thermal Model

Military working dogs (MWDs) operate under a wide range of conditions, including hot environments. Predicting how long a MWD can safely work without overheating is important for both health and performance. A Canine Thermal Model (CTM) was developed to predict core temperature (Tc) of MWDs. The CTM calculates heat storage from the balance of heat production from metabolism and heat exchange with the environment. Inputs to the CTM are: meteorological conditions (ambient temperature, relative humidity, solar radiation and wind speed), physical characteristics of the dog (mass, length), and metabolic activity (MET level, estimated from accelerometer data). The CTM was validated against Tc measured in 23 MWDs during training sessions (11.6 +/- 5.0 min (mean +/- standard deviation), range 4-26 min) in October (24 degrees C, 52% RH), March (14 degrees C, 74% RH), or August (28 degrees C, 64% RH), and 24 kennel MWDs during a standard exercise walk (11.4 +/- 3.3 min, range 5.6-18 min) in July (26 degrees C, 77% RH). The CTM was considered acceptable if predicted Tc was within +/- 0.5 degrees C of measured Tc at the end of exercise. Compared to Tc at the end of training sessions (39.8 +/- 0.6 degrees C, range 38.4-41.1 degrees C) and exercise walks (40.0 +/- 0.7 degrees C, range 38.9-41.4 degrees C), the CTM-predicted Tc was within +/- 0.5 degrees C for 71 of 84 cases (85%) and 19 of 24 cases (79%), respectively. The mean difference between CTM-predicted and measured final Tc during training was -0.04 +/- 0.43 degrees C, with 80 of 84 cases (95%) within the range of +/- 2 SD (Bland Altman comparison). During exercise walks the mean difference was -0.15 degrees C +/- 0.57, with 23 of 24 cases (96%) within +/- 2 SD. These results support the use of the CTM to predict Tc of MWDs for the types of physical activities described above.