Endurance races are one of the biggest metabolic demands that the sport horse is subjected. Frequently they show alterations causing big impacts in the animal homeostasis, having impact in the sanguine biochemistry as consequence of the sustained imbalance of the internal medium. There are little data available trying to explain enzyme kinetics during and after endurance races. This study tries to analyze the increases in the plasma concentration of several muscular enzymes in horses during a prolonged effort and its recovery. 8 horses (7-12 years) that concluded an 83km endurance race (4 stages: 23, 21, 21and 19km) were used. Jugular blood samples were taken the previous day (PRE), immediately after each veterinary examination (VG1, VG2, VG3 and VGF), and at 30, 60, 240 and 360 minutes after finishing the race (POS30, POS60, POS240, and POS360), for the determination of CK, AST, and LDH. CK (compared with CKPRE) showed significant increases from VG3 (498±195U/l); the highest value was observed at VGF (693±241U/l), and the first significant reduction of this value was POS240 (339±171U/l). AST increases hadn't significant differences. The highest value was at POS30. LDH showed significant increases only at VGF (701±296U/l), where the highest value was registered, and the first significant reduction was observed in POS360 (429±191U/l). Muscular enzymes rise after an endurance race, questioning its clinical utility. Nevertheless the kinetic during the recovery is different from that observed in muscular pathologies.