Impact of Treadmill Running on Circulating Cortisol Concentrations in Clinically Healthy Dogs

Basal cortisol concentration is used to screen for hypoadrenocorticism (HAD) in dogs with chronic gastrointestinal disease, but low values often lead to unnecessary ACTH stimulation tests. This study evaluated treadmill exercise as a potential alternative method for stimulating cortisol release. Nineteen healthy pet dogs (mean age: 5.2 years, median weight: 23.4 kg) were included. After a baseline blood draw (T0), dogs were acclimated to a treadmill with treats to minimize stress. They then walked and trotted for 10 min, followed by a 30 min rest before a second blood draw (T1). Pre- and post-treadmill exercise cortisol levels were compared using a randomization (permutation) test for paired data. Median pre-exercise serum cortisol was 1.36 μg/dL (IQR: 0.9-2.095), and post-exercise was 1.1 μg/dL (IQR: 0.895-1.585), with no significant difference (p = 0.0915). After exercise cortisol increased in 9 of 19 and decreased in 10 of 19 dogs. These findings suggest that treadmill exercise for 10 min does not reliably stimulate cortisol release, assessed 30 min post-exercise. Basal cortisol concentrations in this cohort of clinically healthy dogs were lower than previously described.