Cardiovascular Capacity
Measurements of heart size do not appear to correlate directly with racing speed, stride length, or stride frequency. However, the ability of the body to pump blood can help identify athletic potential in an unproven horse. There is a hypothesis that measurements of a horse’s heart at rest are directly related to the same horse’s cardiac function during exercise. Therefore, attempts have been made to take resting measurements of horses using an electrocardiograph (ECG). This has led to the development of the "Heart Score" which measures the QRS interval. However, no work has correlated this to a horse's oxygen uptake (VO2Max) and it the test has not been a good predictor of future athletic ability.
On the other hand, the Pearson correlation coefficient has fund a link between oxygen uptake and echocardiographic measures. There is also evidence that maximal oxygen consumption and heart size are more important predictors of performance for horses that run longer distances because their energy consumption is mainly aerobic.
Read more about this topic: Circulatory System Of The Horse
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