Effects of hyperflexion on acute stress responses in ridden dressage horses

- We investigated effects of hyperflexion on acute stress responses in riding horses.
- Salivary cortisol, heart rate variability, behaviour and rein tension were measured.
- Horses had significantly higher cortisol concentrations directly after hyperflexion.
- More distinctive head movements were shown during hyperflexion.
- There were no significant treatment effects on heart rate variability.

The effects of hyperflexion on the welfare of dressage horses have been debated. This study aimed to investigate acute stress responses of dressage horses ridden in three different Head-and-Neck-positions (HNPs). Fifteen dressage horses were ridden by their usual rider in a standardised 10-min dressage programme in either the competition frame (CF), hyperflexion (“Low-Deep-and-Round”; LDR) or a looser frame (LF) in a balanced order on three separate test days. Heart rate (HR), heart rate variability parameters (HRV), behaviour and rein tension were recorded during the test. Salivary cortisol concentrations were measured 60 min before and 0, 5, 15 and 30 min after the test. Rein tension was significantly lower in LF and did not differ between CF and LDR; however approx. 15% of recordings in CF and LDR were above the sensor detection limit of 5 kg. The horses had significantly higher cortisol concentrations directly after LDR compared to LF. In addition, the horses showed more distinctive head movements, including head waving, during LDR. There were no significant treatment effects on HR and HRV. In conclusion, the results indicate that LDR may be more stressful to these horses during riding.