Abstract
<jats:p>Background: Endurance performance depends on progressive conditioning, controlled metabolic adaptation, and close veterinary supervision. This study documents the physiological and metabolic changes in two Arabian geldings during a 12-week structured conditioning program designed on Long Slow Distance (LSD) principles. Both horses underwent a four-phase training protocol including walking, trotting, cantering, and tapering, with continuous heart-rate and lactate monitoring. Data were recorded weekly for resting heart rate (HRrest), post-exercise heart rate (HR10), lactate concentration, and recovery time. Feeding emphasized slow-release energy substrates (fibre and oil) and electrolyte supplementation. Both horses demonstrated significant cardiovascular and metabolic adaptation. In Horse A, HRrest decreased from 44 to 36 bpm, HR10 from 108 to 68 bpm, and blood lactate from 7.1 to 2.9 mmol/L. Horse B showed a decline from 48 to 38 bpm (HRrest) and from 115 to 72 bpm (HR10), with lactate falling from 7.8 to 3.2 mmol/L. Recovery time improved from >20 min to 8 min. Progressive conditioning improved aerobic fitness, reduced lactic acidosis, and enhanced recovery efficiency. The veterinary role remains essential in designing individualized programs and ensuring physiological adaptation without metabolic or orthopedic compromise.</jats:p>