Modelling the oxygen cost of transport in competitions over ground of variable slope.

This study provides an objective method for estimating the oxygen consumption of horses while running on variable slopes so that realistic comparisons may be made of the locomotory transport cost involved in 3-day events, particularly the Speed and Endurance Test, at sites of differing terrain. A knowledge of the work profile over a particular course would enable competitors to plan speed and interval times appropriately along its length. We have developed a semi-empirical, but mechanistically based, model to calculate the oxygen cost of transport [COTpath in ml O2/kg/m path] for running on the flat, up or down a slope of given gradient (from -0.3 to +0.3). The model is then used to calculate the overall effort of running on a number of 3-day event courses of differing standard; the model does not assess the energetic cost of jumping. The cost of transport over the range of gradient of -0.3 to +0.3 was modelled using the following equations: On the flat or uphill: COTpath = 0.123 + 1.561(gradient); Downhill: COTpath = 0.123 + 1.591(gradient) + 9.762(gradient)2 + 14.0(gradient)3.