3.8.4 Standardised exercise tests
Standardised treadmill exercise tests which allow graded exercise have been developed as a method of investigating exercise physiology and causes of poor athletic performance in racehorses. The level of fitness is often more predictable and uniform in these animals than in pleasure horses. The heart rate (and often ECG) can be monitored during the exercise while the speed and incline of the treadmill are altered in a series of steps. Signs of decreased exercise tolerance which may be shown on these tests are a high maximal heart rate, a short time taken to reach maximal heart rate, a low maximal oxygen uptake and a prorecovery time with slow return of heart rate to normal. However, some of these findings can result from musculo-skeletal problems, upper airway obstruction or lung disease; they are not specific for cardiac dysfunction. Therefore, although standardised exercise tests can be helpful in establishing that a problem is present, they are less useful for identifying the specific cause of poor performance.