Recovery heart rates as a predictor of race position in race-fit National Hunt racehorses

Prediction of race-fitness using the principles of excess post-exercise oxygen consumption is a potentially valuable applied exercise physiology tool. We hypothesised that horses with a faster heart rate recovery (HRR) after a field test would perform better in their subsequent race. Twenty mature (17 experienced, 3 unraced) National Hunt horses (15 geldings, 5 mares; 6.5±1.1 years; 489±33.5 kg), underwent 34 pre-race 3-interval field exercise tests using telemetric heart rate (HR) and global positioning satellite (GPS) monitoring on a 1,400 m track inclined 32 m. Horses were classified into 3 groups based on post-exercise HRR values obtained 1 minute after peak HR during interval 3 (>140 bpm; unfit; 120-140 bpm; fit-to-race; <120 bpm; fully fit). All horses were from the same yard, under the same management and in their final stage of training (race-ready). Horses were excluded if they were lame or clinically unwell. The outcome measure of finishing in the top third of the field was compared to classification using 2×2 tables (Statcalc, EpiInfo). Peak HR, peak speed and 1 min HRR were 213.4±5.1 bpm, 49.3±1.8 kph and 125.3±15.8 for interval 3. Horses classified as unfit (n=8) did not race. Fully fit and fit-to-race horses competed in 26 jump races (23 hurdles, 3 bumper; 3,200-5,000 m). Fully fit (n=16) horses were more likely to finish in the top 3rd of the field than fit-to-race (n=10) (odds ratio 12.0; 95% confidence interval 1.8-81.7; P=0.01). We conclude that HRR following interval exercise can be used as a predictor of race position in National Hunt racehorses and a useful guide for trainers.