AbstractBackgroundHolter electrocardiographic monitoring is a cornerstone of diagnostic testing for arrhythmogenic cardiomyopathy (ACM) in Boxer dogs, but physical activity during monitoring is not controlled. In humans, exercise testing (ExT) can identify latent tachyarrhythmias associated with cardiomyopathy, and exercise increases serum cardiac troponin‐I concentrations ([hs‐cTnI]). These effects have not yet been investigated in Boxer dogs.Hypothesis/ObjectivesSubjecting Boxer dogs to brief, moderate‐intensity ExT can identify changes in Holter recordings and [hs‐cTnI] compared to baseline results.AnimalsThirty overtly healthy, client‐owned Boxer dogs.MethodsProspective interventional study. Dogs underwent baseline diagnostic testing including 24‐hour Holter monitoring and [hs‐cTnI], followed by brief ExT (accompanied, brisk stair‐climbing and ‐descending for <5 minutes).ResultsEleven dogs (37%) had >100 premature ventricular complexes (PVCs)/24 hours at baseline (3), ExT (3), or both (5). After ExT, these dogs had more PVCs/24 hours and greater increases in [hs‐cTnI] compared to those with ≤100 PVCs/24 hours. Dogs with the striatin mutation had more PVCs/24 hours and a greater increase in [hs‐cTnI] after ExT than did dogs without the striatin mutation.Conclusions and Clinical ImportanceExercise testing may improve the binary classification of Boxer dogs with or without ACM by increasing the number of PVCs and [hs‐cTnI] in affected dogs to a greater degree than in unaffected dogs. This effect also is associated with presence or absence of the striatin mutation. Exercise should be a controlled variable when screening Boxer dogs for ACM.