The use of a standardized swimming test to evaluate race performance in Thoroughbred racehorses
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Swimming has become an accepted tool in the training programme of race horses. The purpose of this study was to evaluate whether fitness indices calculated from a standardized swimming test were related to the performance of the horse on the race track. Fifty-two Thoroughbred racehorses (4.6 Â± 1.4 years, 50 geldings, 2 stallions), all participating in races at the Hong Kong Jockey Club (HKJC), were used in this study. All horses underwent a standardised swimming test (SST) consisting of swimming two laps in an oval shaped swimming pool (1 lap = Â± 60 m). During the swimming test, heart rate (HR; beats/min) and speed (V; m/s) of the horses were monitored. In addition, of these 52 horses, 22 horses were tested a second time (after 1-21 days), to evaluate the repeatability of the swimming test and from 18 of these 22 horses, plasma lactate concentrations (LA; mmol/L) were obtained directly after SST. Race performance of horses was defined as a rating score determined by the HKJC, based on the race performance. Horses were divided into ' good performers' (placed in 1 to 5 rank at competition in the period 1 month before to 1 month after SST) and ' average performers' (placed at lower rankings). Mean HR during the SST was 178 Â± 14 bpm, mean V was 1.06 Â± 0.10 m/s and mean LA after the SST was 2.3 Â± 1.5 mmol/liter. There was a significant correlation between HR and V (r=0.720, P<0.001, n=52), but HR was not repeatable between tests (r=0.259, P=0.245, n=22). No significant correlation was found between racing performance and HR, V or LA, so it seems a SST is not suitable to predict the performance of the horse on the race track. However, in some horses HR during an SST seemed to reach HRs close to the maximum HR during a race and LA reached in some horses values higher values higher than during track work at 50 km/h. Therefore, swimming might not be such Â´mildÂ´ exercise as some trainers expect.