Heart Rate, Speed and Lactate During the Cross-Country Phase of an Advanced and CCI*** Three-Day Event

Performance in three-day event horses is influenced by the horse’s innate ability combined with its level of fitness. Heart rate (HR) and blood lactate have been routinely measured in laboratory settings to evaluate fitness and/or ability in horses. To investigate whether these measurements are useful in assessing performance during competition, 11 horses competing at the advanced and CIC*** levels at an American horse trial were studied. Each horse’s HR and speed were measured during the cross-country phase of the competition using the KER ClockItTM Sport smartphone application along with a Bluetooth compatible heart rate monitor. Plasma lactate was measured 5 min after the conclusion of cross-country. V200 was estimated from each horse’s average HR and speed during cross-country using a HR-speed relationship that was determined in a series of separate standarized exercise tests. These measurements were evaluated relative to the horse’s final finish position at the competiton. HR averaged 199.4 ± 6.9 bpm (range 192-207 bpm) and speed averaged 536.0 ± 14.4 m/min (range 514-564 m/min) during cross-country. Plasma lactate averaged 9.9 ± 4.0 mmol/l (range 4.8-17.8 mmol/l). Lactate was positively correlated with heart rate during XC (R2=.82). Lactate was less strongly correlated with speed (R2 = .40). HR was poorly correlated with speed (R2=.14). Top finishers had lowest HR and lowest plasma lactates. Top-finishing horses had higher V200. An interesting finding was that horses with higher V200 (>550 m/min) during cross-country had lower (better) dressage scores. Since a high V200 is indicative of a fitter horse, this may seem counterintuitive in the eventing community where conventional wisdom says that fitter horses do less well in dressage. This study suggests just the opposite; the same qualities that allow horses to run around cross-country at near optimal speeds with low HRs and lactates contribute to better dressage performances. Results suggest that measuring heart rate, speed and lactate during cross-country may provide useful insights into an event horse’s fitness and/or ability.