Effect of a Lactate-Guided Conditioning Program on Fitness Markers in the Equine Athlete

Effect of a Lactate-Guided Conditioning Program on Fitness Markers in the Equine Athlete\ud A.L. Fisher, H.M. Greene MS, R.J. Talmadge PhD, Y.S. Nout-Lomas DVM, PhD\ud \ud Hypothesis: A lactate-guided conditioning program (CP) implementing twice-weekly short-duration high-intensity exercise bouts and once-weekly low-intensity longer-duration exercise bout effectively increases fitness in horses.\ud \ud Rationale: Blood lactate concentration ([LA]) is a measure of fitness in equine athletes. Most equine CPs are based on regular bouts of similar intensity exercise. Here we explore the effect of a CP that includes two shorter higher-intensity bouts and one longer low-intensity bout/week.\ud \ud Methods: Six adult horses were subjected to a 12-week CP that consisted of twice-weekly exercise on an equine treadmill (6%-incline) for 25min at a velocity at which [LA] is 4.0mmol/L (VLA4.0) and once-weekly for 45min at a velocity at which [LA] is 2.5mmol/L (VLA2.5). VLA2.5 and VLA4.0 were determined by incremental-step standardized-exercise-test (SET) before the CP and adjusted every 3wks (total 4 SETs). SETs started at 4.0m/s and were followed by 0.5m/s increments every 5min (6%-incline). Blood was collected for [LA], creatine kinase (CK), and aspartate aminotransferase (AST) before each speed increase and at 2, 4, and 24hrs after termination of the SET, when [LA] reached ???4mmol/L. Repeated-measures ANOVA was used for analysis.\ud \ud Results: Over the course of the SETs horses showed an increase in heart rate, packed cell volume, and [LA]. In all horses VLA2.5 and VLA4.0 increased throughout the 12-week CP, consistent with improved fitness. VLA2.5 increased from 5.9??0.6 to 6.6??0.7m/s (p=0.034) and VLA4.0 from 6.4??0.6 to 7.4??0.6m/s (p=0.011). For each SET there was a trend for CK to increase 2hrs post-exercise, however, this was not significant. There was a trend for the post-warm-up CK and AST to reduce over the 12-week CP (CK: 217??23 to 141??18; AST: 216??13 to 171??11). \ud \ud Principal Conclusions: This lactate-guided CP was effective at increasing fitness in these horses. Submaximal exercise can elevate CK and AST and these changes appear to be attenuated with conditioning.President's Research, Scholarship, and Creative Activities Program Grant (YSN), Cal Poly Pomon