Heart Rate Variability in Post-Race Thoroughbred Racehorses.

Performance horses can require a tremendous amount of time, training, and finances to maintain optimal health and reach maximum fitness levels. Racehorses are one of the many performance horses that require such vigorous maintenance schedules to compete. Measuring heart rate variability (HRV) in these equine athletes can allow for post-training, postcompetition recovery and stress analysis. In this study, we measured HRV parameters in 13 Thoroughbred (TB) racehorses at Delta Downs Racetrack, located in Vinton, Louisiana. Data were recorded in short-term readings of 5 minutes at 0 to 1 hour post-race (depending on if they went to test-barn), 12 hours, and 24 hours post-race, in 7 TB racehorses. An additional 6 TB racehorses were recorded only at rest (no race or strenuous workouts for over a week). The R-R readings were less (P < 0.0001) at 0 to 1 hour post-race (753.6 ± 43.2) compared with 12 hours (1382.8 ± 44.5), 24 hours (1503.7 ±40.0) and rest (1370.9 ± 39.3). The heart rate (HR) was greater (P < 0.0001) at 0 to 1 hour post-race (82.8 ± 4.6) compared with 12 hours (43.9 ± 1.4), 24 hours (40.3 ± 1.4) and rest (44.0 ± 1.4). The RMSSD was less (P < 0.0001) at 0 to 1 hour post-race (16.9 ± 2.8) compared with 12 hours (31.6 ± 3.1), 24 hours (33.6 ± 1.6) and rest (33.6 ± 3.4). The SDNN was less (P < 0.0003) at 0 to 1 hours post-race (23.7 ± 2.9) compared with 12 hours (38.7 ± 2.9), 24 hours (36.8 ± 1.6) and rest (36.2 ± 2.7). The pNN50 was less (P < 0.0044) at 0 to 1 hour post-race (3.5 ± 3.2) compared with 12 hours (8.9 ± 1.8), 24 hours (11.8 ± 1.3) and rest (11.7 ± 2.9). None of the 12- and 24-hour readings were different from each other or at rest indicating these horses appeared to have recovered from their race within 12 hours. [ABSTRACT FROM AUTHOR]