Simple SummaryMonty Roberts is a famous horse trainer, commonly referred to as a ‘horse whisperer’, who shares his training methods all over the world, including through large public audience events. These events have the potential to compromise the horse’s welfare since the horses have usually been transported to the event on the day and stabled in an unfamiliar environment before being used in demonstrations watched by hundreds of people. This paper describes the opportunistic collection and analysis of heart rate (HR; beat-to-beat intervals) and heart rate variability (HRV) of horses being trained during Monty Roberts’ public demonstrations within the United Kingdom. HR and HRV measured during the demonstrations were lower (indicative of an increase in heart rate as measured in beats-per-minute) than recordings within the stable and consistent with low-moderate exercise intensities used during training. The HR and HRV during a specific training method known as “Join-up®” were comparable to other methods of training used by Monty Roberts during public demonstrations. In conclusion, training of horses during public demonstrations is a low-moderate physiological, rather than psychological stressor for horses, with the stress response comparable or less than those previously reported in the literature for horses being trained outside of public audience events. Furthermore, we found no evidence that Join-up® alters HR and HRV in a way to suggest that this training method negatively affects the psychological welfare of horses.AbstractEffective training of horses relies on the trainer’s awareness of learning theory and equine ethology, and should be undertaken with skill and time. Some trainers, such as Monty Roberts, share their methods through the medium of public demonstrations. This paper describes the opportunistic analysis of beat-to-beat (RR) intervals and heart rate variability (HRV) of ten horses being used in Monty Roberts’ public demonstrations within the United Kingdom. RR and HRV was measured in the stable before training and during training. The HRV variables standard deviation of the RR interval (SDRR), root mean square of successive RR differences (RMSSD), geometric means standard deviation 1 (SD1) and 2 (SD2), along with the low and high frequency ratio (LF/HF ratio) were calculated. The minimum, average and maximum RR intervals were significantly lower in training (indicative of an increase in heart rate as measured in beats-per-minute) than in the stable (p = 0.0006; p = 0.01; p = 0.03). SDRR, RMSSD, SD1, SD2 and the LF/HF ratio were all significantly lower in training than in the stable (p = 0.001; p = 0.049; p = 0.049; p = 0.001; p = 0.01). When comparing the HR and HRV of horses during Join-up® to overall training, there were no significant differences in any variable with the exception of maximum RR which was significantly lower (p = 0.007) during Join-up®, indicative of short increases in physical exertion (canter) associated with this training exercise. In conclusion, training of horses durin...