Effect of exercise on physiological, blood and endocrine parameters in search and rescue-trained dogs

Exercise induces a variety of physiological and laboratorial changes of different magnitude and direction, depending on the characteristics of the performed exercise (duration and intensity) and on the fitness and training level of the dog. The present research aims to describe the normal response to a session of search and rescue exercise in trained dogs in order to distinguish these changes from those derived from exhaustion or diseases. Nine healthy and trained dogs of both sexes (five females and four males), aged between 24 months and seven years (mean: 3.5 years) were studied. Exercise consisted in a normal session of searching and rescue training of 20 min of duration, carried out in an open terrain. During the exercise, heart rate (HR) was monitored continuously with a HR-meter. Furthermore, respiratory rate (RR) and rectal temperature (RT) were measured and venous blood samples were extracted at rest (R), immediately after exercise (E) and at 5, 15 and 30 min of a passive recuperation (5REC, 15REC and 30REC). The following laboratorial parameters were studied: red blood cells (RBC), hemoglobin concentration (HB), packed cell volume (PCV), RBC volumetric indices, white blood cells (WBC), creatinine (CREAT), total plasma protein (TPP), lactate (LA), glucose (GLU), triacylglycerols (TAG), creatine kinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), Na, K, Cl, cortisol (CORT) and insulin (INS). Clinical signs indicative of exhaustion or exercise intolerance were not observed in the dogs during the study. HR increased with E and remained over the reference range until 30REC. RR and RT also rose with E, with the highest RR at 5REC. RBC, HB and PCV were not affected by E, whereas WBC increased at E. TPP, GLU, AST and K were not affect by E neither by REC. E induced elevations in CK, LDH, LA and INS, reaching R values at 30REC, 30REC, 15REC and 5REC, respectively. Plasma Na decreased with E and recovered at 30REC. Plasma Cl decreased with E, without additional significant changes. Circulating CORT concentrations were reduced with E, with the highest reduction at 10REC. Modifications of RR, RT, WBC, CREAT and TAG persisted throughout the recovery period. In conclusion, significant modifications in physiological and laboratorial parameters were induced by the searching and rescue exercise, with values outside the reference range for healthy dogs. These data provide a data base for evaluating ill or injured dogs during this type of exercise. In addition, there was not evidence of dehydration, electrolyte imbalances, and stress or muscle disorders in the studied dogs.