Effects of warm-up intensity on oxygen transport during supramaximal exercise in horses

Objective - To determine whether warm-up exercise at different intensities alters kinetics and total contribution of aerobic power to total metabolic power in subsequent supramaximal exercise in horses. Animals - 11 horses. Procedures - Horses ran at a sprint until fatigued at 115% of maximal oxygen consumption rate (•Vo_2max), beginning at 10 minutes following each of 3 warm-up protocols: no warm-up (NoWU), 1 minute at 70% •Vo_2max (moderate-intensity warm-up [MoWU]), or 1 minute at 115% •Vo_2max (high-intensity warm-up [HiWU]). Cardiopulmonary and blood gas variables were measured during exercise. Results - The •Vo₂ was significantly higher in HiWU and MoWU than in NoWU throughout the sprint exercise period. Blood lactate accumulation rate in the first 60 seconds was significantly lower in MoWU and HiWU than in NoWU. Specific cardiac output after 60 seconds of sprint exercise was not significantly different among the 3 protocols; however, the arterial mixed-venous oxygen concentration difference was significantly higher in HiWU than in NoWU primarily because of decreased mixed-venous saturation and tension. Run time to fatigue following MoWU was significantly greater than that with NoWU, and there was no difference in time to fatigue between MoWU and HiWU. Conclusions and Clinical Relevance - HiWU and MoWU increased peak values for •Vo₂ and decreased blood lactate accumulation rate during the first minute of intense exercise, suggesting a greater use of aerobic than net anaerobic power during this period.