Cardiovascular and locomotory parameters during training in Thoroughbred racehorses: a multi-national study

Abstract

Studies assessing concurrent speed, cardiovascular physiology and biomechanical parameters in racehorses during training have been rarely reported, mostly due to a lack of available comprehensive technology. Here, using a validated device (the ‘Equimetre’™) that records all parameters simultaneously, we report the effect of increased training speed and thus intensity, from slow canter to hard gallop, on racehorse heart rate, heart rate recovery and on biomechanical parameters, such as stride length and frequency. We also demonstrate the effects of varying track surface, horse age and sex. Cohorts comprised a total of 509 Thoroughbred racehorses in-training in either Australia or France, completing a total of 1,124 and 6,016 training sessions, respectively. Horses varied by age (2-9 years old) and sex (including geldings) and were trained by either a single trainer (Australia) or two trainers (France); both using multiple training centres that varied by track surface (sand, turf or fibre). Data were analysed using Analysis of Variation (ANOVA) or linear mixed-effect models as appropriate. Racehorses increased speed predominantly by an increment in stride length, then frequency, both of which varied according to track surface (shorter stride on sand; P<0.001). Cardiovascular parameters (peak, and recovery of, heart rate) increased with training intensity, but not linearly (Ptrend<0.001). Older horses recorded lower heart rate at 15 mins after training (P=0.002), often due to lower achieved peak heart rate at most training intensities (P<0.001 for the cohort in Australia). In conclusion, this immersive field study demonstrates the value of technology for recording physiological and biomechanical parameters of racehorses-in-training. The data could inform trainers, jockeys and owners on aspects of individual racehorse health, welfare and suitability for certain races.

Locomotory Profiles in Thoroughbreds: Peak Stride Length and Frequency in Training and Association with Race Outcomes

“…Within each category, racehorses participated in a similar number of races: (pure sprinter, 4 [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ] races); sprinter-miler, 7 [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ] races; miler, 6 [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ] races; sprinter-miler-stayer, 8 [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ] races; stayer, 7 [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ,…”

“…A tracking device (‘Equimetre™’, Arioneo, Ltd. Paris, France) was fitted to the girth prior to training by persons accustomed to using the device, as previously described [ 14 ]. The device recorded locomotory parameters (peak stride length and frequency) alongside speed (by GNSS) and cardiovascular parameters (peak HR), as previously described in detail [ 3 ]. The trainer determined the nature of each individual training session, directing the work-rider as appropriate.…”

“…In flat racing, Thoroughbreds compete in various types of races usually categorised as short (<1500 m), middle (1600–2500 m) or long (>2500 m) distance. Racehorses are usually considered to be naturally predisposed to one type of race distance, due to various physiological and morphological characteristics such as size, musculature [ 1 ], and stride [ 2 , 3 ]. Genetics is also important [ 4 ], although the precise contribution of genetics versus environmental variables which classify successful sprinters or stayers are relatively undefined.…”

“…It is axiomatic that in order to win any competition based on speed, the fastest individual will get to the finish line first. Racehorses increase speed firstly by increasing stride frequency (SF) up to a pace consistent with gallop (45+ kph) and then by increasing stride length (SL; 45–65+ kph) [ 3 , 10 ]. Therefore, in sprint races of shorter distance, the racehorse that is able to rapidly increase, or maintain a higher stride frequency, is more likely to achieve a higher speed and good performance.…”

“…For decades, breeders and trainers have attempted to relate the physiological characteristics of racehorses during their training to their race-day performance [ 12 ]. Objective measurements of locomotory parameters have only recently become available for racehorse trainers, allowing them to potentially ascertain whether a young racehorse has a greater aptitude for sprinting or longer-distance races [ 3 , 13 ]. However, to date, no study has related race performance over multiple seasons with information on locomotory profile in training–do racehorses that have only raced in sprint races demonstrate an innately shorter stride early on in training?…”