Oxygen deficit-oxygen debt relationships in ponies during submaximal treadmill exercise

Abstract

The O 2 deficit-O 2 debt relationship in ponies was examined at two levels of treadmill exercise. Five healthy ponies exercised for 8 min at two work rates (WR): (1) 50 m/min at 6% grade and (2) 70 m/min at 12% grade. The O 2 deficit and O 2 debt were calculated using open-circuit measurement of pulmonary gas exchange during the transition from rest to steady-state exercise and during recovery from exercise. The O 2 deficit was significantly ( P < 0.05) than the O 2 debt at each of the two work rates. The means (± SEM) for the deficit and the O 2 debt, respectively, in liters were: (1) low WR = 0.45 ± 0.12; 0.92 ± 0.13high WR = 1.03 ± 0.20; 1.62 ± 0.12. Given the observation that the O 2 deficit and the O 2 debt are generally equal in humans during exercise below the anaerobic threshold, these findings suggest a species difference in the O 2 deficit-O 2 debt relationship. It is hypothesized that the difference in O 2 deficit between man and pony is related to faster V̇ O 2 kinetics fort he on-transient of exercise in which involves a more rapid increase in cardiac output coupled with a release of splenic stored erythrocytes.