Background: Horses participating in eventing competitions experience significant challenges that lead to a high risk of severe injuries and metabolic disorders. Objectives: To investigate horses’ stress responses though heart rate (HR) and heart rate variability (HRV) in three exercise tests and their recovery periods while participating in the Fédération Équestre Internationale World Eventing Challenge. Study design: Case-control study. Methods: HR and HRV were monitored in 10 horses during the competition. However, data were collected from nine horses, as one was eliminated from the competition. Results: Beat-to-beat (RR) interval decreased during dressage (D), jumping (J) and cross-country (CC) tests, lasting 60 min after cross-country (60-CC) (D: 594.6 ± 40.2 ms, J: 420.6 ± 94.5 ms, CC: 358.0 ± 66.9 ms and 60-CC: 1424.2 ± 98.3 ms vs control: 1742.0 ± 202.3 ms, p < 0.05–0.001). HR increased during the exercise tests, extending to 60-CC (D: 101.4 ± 7.0 beats/min, J: 148.2 ± 30.5 beats/min, CC: 172.0 ± 27.0 beats/min and 60-CC: 42.2 ± 3.0 beats/min vs control: 34.8 ± 3.7 beats/min, p < 0.05–0.001). Various HRV metrics were lower during J than D, including standard deviation of normal-to-normal RR interval (D: 25.4 ± 9.1 ms vs J: 9.8 ± 6.2 ms, p < 0.01), total power band (D: 512.4 ± 261 ms 2 vs J: 126.8 ± 180.4 ms 2, p < 0.05) and standard deviation 2 (D: 35.0 ± 12.5 ms vs J: 13.4 ± 8.9 ms, p < 0.01). Changes in the indexes of the parasympathetic and sympathetic nervous systems corresponded with modifications in the RR interval and HR, respectively. Main limitations: Information on the training activity of horses and riders was unavailable. Conclusions: The more pronounced stress during J and CC tests highlights the need for greater attention during these phases for horses participating in one-day eventing events.

Background: Lunging is a training method that is performed in a round pen or on a lunge line. However, there is no consensus on applying lunging techniques for physical fitness training. Objectives: To investigate the effort intensity, autonomic responses, and method agreement in applying different lunging protocols to untrained horses. Study design: A non-randomised control trial. Methods: Sixteen untrained horses (aged 13.6 ± 6.3 years and weighing 358 ± 47.4 kg) were studied. Each horse was lunged with a similar programme on a lunge line and, subsequently, in a round pen at a two-day interval. The heart rate variability (HRV) and effort intensity, indicated as a percentage of maximum heart rate (%HRmax), were determined pre-lunging, during lunging at distinct gaits, and at 30-minute intervals for 120 minutes post-lunging. The correlation and method agreement between the two lunging methods were analysed with Pearson’s correlation coefficient and Bland–Altman plots, respectively. Results: The horses ran faster and covered longer distances during exercise on a lunge line than in a round pen. The effort intensity during cantering reached moderate levels (75.1 ± 2.4% HRmax) with occasional high-intensity levels (88.1 ± 1.3% HRmax) via both lunging methods. The HRV reached a minimum during cantering and returned to the baseline 120 minutes post-lunging. The HRV parameters (SDNN, RMSSD, LF, HF, SD1, and SD2) were strongly correlated ( rp ≥ 0.97 and p < 0.001 for all) with a large correlation effect size (R 2 > 0.85) and excellent agreement (average differences were within mean ± 1.96 SD) between the two lunging methods. Main limitations: The running speed and distance reported during lunging may not be entirely accurate due to the manual calculation required. Conclusions: Lunging can provoke optimal physiological responses in horses. The two tested lunging methods may be applied interchangeably for physical fitness training.