Adaptations of Racing Thoroughbreds to a Hypoxic Chamber: A Pilot Study

Abstract

Hypoxic exposure results in physiological adaptions and enhanced human athletic performance. However, few reports exist regarding responses of horses to similar conditions. The goals of this preliminary work were to evaluate whether horses could be acclimated to a hypoxic chamber (HC) and to monitor their performance. Trial 1: Two 4-yr-old Thoroughbreds were used to establish protocols for adaptation to the HC. Horses were stalled in the HC for 8 to 10 h/d while O2 concentrations were decreased over 2 wk until 13.5% O2 was achieved. On d 37, horses were removed from the HC and shipped to a track for 7 d before reentering the HC for the remainder of the 2-month study. Resting hemoglobin (Hb) was measured on d 0, 37, and 61 and ranged from 14.8 to 15.2 g/dL. Trial 2: Two 2-yr-old Thoroughbreds were maintained in the HC at 13.5% O2 for 8 to 8.5 h/d for 21 d, shipped to a track for 5 d, and then placed back in the HC 8.5 h daily for the remainder of the 31-d trial. Horses were conditioned on the treadmill or track 6 d/wk. Horses underwent a standardized exercise test (SET) prior to being initially placed in the HC. The SET was repeated on d 10 and 31. Peak heart rate (HR) reached during exercise, and HR at 3 and 5 min post-exercise were recorded. Hemoglobin was measured immediately upon cessation of exercise. There was no difference in HR at 3 min (P=0.18), and 5 min post-exercise (P=0.64). Hb was greater on d 31 compared to d 0 (P