摘要：We investigated the effects of incline on cardiopulmonary function in five trained 2-year-old Thoroughbred horses during exercise on a high-speed treadmill. The horses began exercise at 1.5 m/s for 2 min followed by 1 min step increments at 4.0, 7.0, 8.0, 9.2, and 10.4 m/s. Each horse performed the exercise test on separate days with at least 2 days interval at four different inclines (0, 3, 6 and 10%). The sequence of exercise test was randomized. The major findings were: 1) Oxygen uptake (Vo2), carbon dioxide production (Vco2), minute ventilation (VE), tidal volume (VT), heart rate (HR), cardiac output (Qt), and % O2 extraction increased linearly with speed and incline, however the regression estimates of the change in Vo2/change in speed (ΔVo2/ΔSp) increased with increasing incline. 2) VE increased linearly with speed and was a function of increased VT and respiratory frequency (f), however the linear increase in VE with incline was solely due to increased VT as f was unchanged. 3) The VE/Vo2 slope for 0% incline was greater than the slope 3%, 6%, 10% incline. 4) The increase in arterio-mixed venous oxygen content difference (Ca-vDO2) with speed and incline was mainly due to the decrease in CvO2, whereas CaO2 increased only slightly with incline and speed. 5) The increased Qt with speed and incline was due to increases in HR, as stroke volume was unchanged with speed and incline.
