Effects of warm-up intensity on kinetics of oxygen consumption and carbon dioxide production during high-intensity exercise in horses

Objective-To compare effects of low and high intensity warm-up exercise on oxygen consumption ((V)over dot O-2) and carbon dioxide production ((V)over dot CO2) in horses. Animals-6 moderately conditioned adult Standardbreds. Procedures-Horses ran for 2 minutes at 115% of maximum oxygen consumption ( (V)over dot O(2)max), 5 minutes after each of the following periods: no war m-up (NoWU); 10 minutes at 50% of (V)over dot O(2)max (LoWU), or 7 minutes at 50% (V)over dot O(2)max followed by 45-second intervals at 80, 90, and 1 00% (V)over dot O(2)max (HIWU). Oxygen consumption and (V)over dot CO2 were measured during exercise, and kinetics of (V)over dot O-2 and (V)over dot CO2 were calculated. Accumulated O-2 deficit was also calculated. Results-For both warm-up trials, the time constant for the rapid exponentia l increase in (V)over dot O-2 was 30% lower than for NoWU. Similarly, the r ate of increase in (V)over dot CO2 was 23% faster in LoWU and HiWU than in NoWU. Peak values for (V)over dot O-2 achieved during the highspeed test we re not significantly different among trials (LoWU, 150.2 +/- 3.2 ml/kg/min; HiWU, 151.2 +/- 4.2 ml/kg/min; NoWU, 145.1 +/- 4.1 ml/kg/min), However, ac cumulated O-2 deficit (ml of O-2 equivalents/kg) was significantly lower du ring LoWU (65.3 +/- 5.1) and HiWU (63.4 +/- 3.9) than during NoWU (82.1 +/- 7.3). Conclusions and Clinical Relevance-Both the low-and high-intensity warm-up, completed 5 minutes before the start of high-intensity exercise, accelerat ed the kinetics of (V)over dot O-2 and (V)over dot CO2 and decreased accumu lated O-2 deficit during 2 minutes of intense exertion in horses that were moderately conditioned.