MAXIMAL ACCUMULATED OXYGEN DEFICIT IN THOROUGHBRED HORSES

Thoroughbred horses have a high aerobic capacity, approximately twice that of elite human athletes. Whereas the aerobic capacity of horses c an be accurately measured, there have been no measurements of anaerobi c capacity. The aim of this study was to determine whether maximal acc umulated O-2 deficit (MAOD) could be measured in horses and used as an estimate of anaerobic capacity, as in human athletes. Six fit Thoroug hbred horses were used with the exercise protocol utilizing a treadmil l set at a 10% incline. O-2 uptake V-o2 was measured via an open-flow system for seven submaximal speeds (3-9 m/s), and maximal V-o2 (135 +/ - 3 ml . kg(-1). min(-1)) was determined. The horses performed three t ests at 105 and 125% and six tests at 115% of maximal Got. The MAOD te st was performed with the treadmill accelerated rapidly from 1.5 m/s ( mean acceleration time 8 s) to the calculated speed (11-14 m/s). V-o2 was measured every 10 or 15 s, and the test ended when the horse no lo nger kept pace with the treadmill. The mean run times were 165, 98, an d 57 s for intensities of 105, 115, and 125% maximal V-o2. The mc an M AOD values were 31 +/- 2, 30 +/- 1, and 32 +/- 2 (SE) ml O-2 eq/kg for the three intensities (P > 0.05). The proportion of energy derived fr om aerobic and anaerobic sources was calculated from the difference be tween calculated O-2 demand and the V-o2 curve. There was no correlati on between MAOD and maximal Got. Calculations revealed that anaerobic energy sources may supply <30% of the total energy in Thoroughbred and Standardbred races, and we conclude that the aerobic component of ene rgy supply during racing may be greater than previously thought. The s imilar MAOD results for the three intensities indicate that MAOD can b e repeatably measured in horses.