In a collaborative research project with numerous German veterinarians and scientists (including Dr. Marion Kornberg, Veterinary Clinic for Small Animals Trier; Prof. Dr. Andrea Tipold, University of Veterinary Medicine Hannover; Dr. Adrian Sewell, Bioscentia) we characterized this disease. Exercise induced metabolic myopathy (EIMM) results in profound muscle wekaness during physical exercise (e.g. during a hunt). EIMM is caused by an enzyme defect affecting fat metabolism. We identified the causative genetic defect in the ACADVL gene, which facilitated the development of a genetic test. Genetic testing allows the unequivocal identification of carriers for this disease. EIMM is inherited as a monogenic autosomal recessive trait. It is important to know the genotype of breeding animals to avoid the unintentional mating of two carriers. If at least one of the two breeding animals in a mating is clear of the pathogenic variant, then no affected puppies will be born.