Cortisol release, heart rate and heart rate variability, and superficial body temperature, in horses lunged either with hyperflexion of the neck or with an extended head and neck position.
Authors: Becker-Birck M, Schmidt A, Wulf M, Aurich J, von der Wense A, Möstl E, Berz R, Aurich C
Journal: Journal of animal physiology and animal nutrition
Summary
# Editorial Summary: Hyperflexion and Equine Stress Response Researchers at the University of Veterinary Medicine Vienna investigated whether forcibly flexing a horse's neck into hyperflexion—a common practice in ridden disciplines—triggers an acute stress response, using salivary cortisol, heart rate variability (HRV), and thermal imaging as markers. Sixteen horses were lunged on two consecutive days wearing side reins in either extended or hyperflexed positions, with physiological measurements taken before and after exercise. Whilst lunging itself elevated salivary cortisol concentrations roughly two-fold (0.73–0.68 ng/ml baseline to 1.38–1.41 ng/ml post-exercise, *p*<0.001) and reduced HRV parameters (SDRR and RMSSD), these stress indicators did not differ significantly between the hyperflexion and extended neck positions. One notable finding was increased thermal variation in the cranial neck region during hyperflexion, suggesting localised physiological changes. The practical implication is reassuring for moderate-speed lunging without additional pressure—neck hyperflexion alone does not appear acutely stressful—but this conclusion applies narrowly to passive positioning; when combined with active ridden interventions (transitions, collection, or corrective pressure), the thermal findings and study authors' cautionary note suggest clinicians and coaches should remain alert to cumulative stress effects that passive measurements might miss.
Read the full abstract on PubMed
Practical Takeaways
- •Hyperflexion alone during moderate-speed lunging does not appear to cause acute stress responses measurable via cortisol and heart rate variability — but rider intervention and additional training intensity may change this
- •Both head positions produced similar increases in cortisol and heart rate during lunging, suggesting the exercise itself rather than head position drives acute stress responses
- •Increased local temperature changes in hyperflexion may warrant attention to potential muscular tension or circulation effects in the neck region
Key Findings
- •Salivary cortisol increased significantly in response to lunging on both days (from ~0.70 to ~1.39 ng/ml, p<0.001) but did not differ between hyperflexion and extended neck positions
- •Heart rate variability parameters (SDRR and RMSSD) decreased during lunging on both days (p<0.001) with no significant difference between hyperflexion and extended positions
- •Superficial neck temperature showed increased difference between maximum and minimum in the cranial region during hyperflexion (p<0.01)
- •Hyperflexion of the head alone at moderate lunging speeds without whip contact did not produce acute physiological stress indicators distinct from extended neck position