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.

Racehorses competing in short (i.e., ‘sprinters’), middle- or longer-distance (i.e., ‘stayers’) flat races are assumed to have natural variation in locomotion; sprinters having an innately shorter stride than stayers. No study has objectively tested this theory. Here, racehorses (n = 421) were categorised as sprinters, milers or stayers based on known race distance (n = 3269 races). Stride parameters (peak length and frequency) of those racehorses were collected from prior race-pace training sessions on turf (n = 2689; ‘jumpout’, n = 1013), using a locomotion monitoring device. Pedigree information for all 421 racehorses was extracted to three-generations. In training, sprinters had a shorter stride of higher frequency and covered consecutive furlongs faster than stayers (p < 0.001). Relatively short or longer stride did not predict race success, but stayers had greater race success than sprinters (p < 0.001). Peak stride length and frequency were moderately heritable (h2 = 0.15 and 0.20, respectively). In conclusion, differences in stride were apparent between sprinters and stayers (e.g., shorter stride in sprinters) during routine training, even after accounting for their pedigree. Objective data on stride characteristics could supplement other less objectively obtained parameters to benefit trainers in the appropriate selection of races for each individual racehorse.

The racing industry is supported by a predominance of female stablehands and work riders, but few become professional jockeys. Female jockeys have recently had notable race success. No study has assessed whether the sex of the rider may subtly influence racehorse physiology to affect performance. Here, using a validated exercise tracking system (the ‘Equimetre’™) that records many physiological parameters simultaneously, this study characterised racehorse cardiovascular (heart rate, heart rate recovery) and biomechanical (stride length and frequency) parameters at various exercise intensities (slow canter to hard gallop) to address the question whether any parameter varied according to sex of the rider. A total of 530 Thoroughbreds, varying in age (2–7 years old) and sex (including geldings), from one racing yard in Australia, completed a total of 3,568 exercise sessions, monitored by a single trainer, on varying track surfaces (sand, turf, or fibre). Different work riders,103 in total (male, n = 66; female, n = 37) of which n = 43 were current or past registered professional jockeys, participated in the study. Data were analysed using analysis of variation (ANOVA) or mixed-effect models, as appropriate. Sex of the rider did not influence (P > 0.05) racehorse speed nor stride length at any training intensity. Racehorse heart rate and peak heart rate increased with training intensity (P < .001), with no difference according to sex of rider (P > 0.05). Racehorse heart rate recovery was influenced by sex of the rider, but only at the extremes of the reversed, usual training intensity on each surface (e.g. heart rate after galloping on sand was significantly lower with male riders, P = 0.03). Finally, analysis of 52,464 race results indicated a similar chance of a top-three placing for male and female jockeys. In conclusion, this study, using objectively obtained data, demonstrates for the first time no overt effect of the rider’s sex on racehorse physiology in training and performance in racing. Such data could encourage greater female participation in racing and improve access of female jockeys to better quality mounts in racing events.

Studies assessing the effect of the rider’s sex on racehorse performance and physiology during training have not been reported, mostly due to the paucity of available data for female participants within the sport. Here, using a validated system (the ‘Equimetre’™) that records all parameters simultaneously, we objectively report the effect of rider’s sex on racehorse cardiovascular (heart rate, heart rate recovery) and biomechanical parameters (stride length and frequency) at various exercise intensities (slow canter to hard gallop). 530 Thoroughbreds, varying in age (2-7 years old) and sex (including geldings), from one racing yard in Australia, completed a total of 3,568 exercise sessions, monitored by a single trainer, on varying track surfaces (sand, turf, or fibre). 103 different work riders (male, n=66; female, n=37) of which n=43 were current or past registered professional jockeys, were used. Data were analysed using analysis of variation (ANOVA) or mixed-effect models, as appropriate. Sex of the rider did not influence racehorse speed (P=0.06) nor stride length (P=0.42) at any training intensity. Heart rate and peak heart rate increased with training intensity (P<.001), with no difference according to sex of rider (P=0.73). Heart rate recovery after exercise appeared influenced by rider sex, but only when the usual training intensity on each surface was reversed, suggesting an interaction between racehorse anticipation of exercise and rider sex. Male jockeys had slightly higher strike rate in races in Australia, but not the UK. This study demonstrates no overt effect of rider sex on racehorse performance and physiology.

Background Studies assessing the effect of the rider’s sex on racehorse performance and physiology during training have not been reported, mostly due to the paucity of available data for female participants within the sport. Here, using a validated system (the ‘Equimetre’™) that records all parameters simultaneously, we objectively report the effect of rider’s sex on racehorse cardiovascular (heart rate, heart rate recovery) and biomechanical parameters (stride length and frequency) at various exercise intensities (slow canter to hard gallop). Methods 530 Thoroughbreds, varying in age (2-7 years old) and sex (including geldings), from one racing yard in Australia, completed a total of 3,568 exercise sessions, monitored by a single trainer, on varying track surfaces (sand, turf, or fibre). 103 different work riders (male, n=66; female, n=37) of which n=43 were current or past registered professional jockeys, were used. Data were analysed using analysis of variation (ANOVA) or mixed-effect models, as appropriate. Results Sex of the rider did not influence racehorse speed (P=0.06) nor stride length (P=0.42) at any training intensity. Heart rate and peak heart rate increased with training intensity (P<.001), with no difference according to sex of rider (P=0.73). Heart rate recovery after exercise appeared influenced by rider sex, but only when the usual training intensity on each surface was reversed, suggesting an interaction between racehorse anticipation of exercise and rider sex. Male jockeys had slightly higher strike rate in races in Australia, but not the UK. Conclusions This study demonstrates no overt effect of rider sex on racehorse performance and physiology.