Effect of a warm-up on energy supply during high intensity exercise in horses

The V overdot O-2max in racehorses is approximately double that of elite human athletes and the rate of increase in V overdot O-2 at the onset of high intensity exercise is much greater than in man, The kinetics of gas exchange are affected by a warm-up prior to exercise in humans, there being a greater aerobic contribution to high intensity exercise after warm-up, Our hypothesis was that a warm-up would increase aerobic energy delivery in racehorses during high intensity exercise, Thirteen fit Standardbred racehorses ran to fatigue at 115% of V overdot O-2max On a treadmill at 10% slope, Prior to acceleration, horses were exercised either for 5 min at 50% V overdot O-2max followed by 5 min walk, or walked for 2 min, Samples of expired gas were collected every 10 s during the run for determination of V overdot O-2 and V overdot CO2 and measurement of maximal accumulated oxygen deficit (MAOD), Blood lactate concentration was measured 5 min post exercise, We found that with a warm-up, horses had faster kinetics of gas exchange and a greater proportion of their total energy requirement was supplied by aerobic sources. The aerobic contribution to total energy requirement with and without warm-up was, respectively, 79.3 +/- 1.0% and 72.4 +/- 1.7% (P < 0.01). There was also a higher MAOD (P < 0.01) in horses that had not been given a warm-up (mean +/- s.e.m. 34.7 +/- 2.6 and 47.3 +/- 2.6 mlO(2)eq/kg bwt with and without a warm-up respectively), However, there were no significant differences in total run time or estimated total energy expenditure between the 2 protocols. We concluded that during high intensity exercise to fatigue lasting 1 to 2 min, more than 70% of energy supply is from aerobic energy sources and that this contribution is even greater when the horses have received a warm-up.