Why equestrians use auxiliary reins on horses, their biomechanical perceptions, and barriers to human behaviour change

Auxiliary reins (AR) such as draw- or side reins are commonly employed by equestrians but may cause equine welfare concerns. This study investigated behavioural factors underpinning AR usage and whether equestrians understand their biomechanical function. A mixed methods survey of 14–24 questions was circulated online via equestrian magazines and social media, collecting demographics, biomechanical knowledge, and behavioural factors relating to the use of AR. There were 570 responses from equestrians worldwide, with 344 (60.4 %) indicating that they had or would use AR. Univariable comparative statistics were performed between AR users and non-users. Participation in equestrian competition was significantly associated with the use of AR (X²(1, n = 570)= 20.42, p < 0.001). Equestrians who presently used or would use AR (n = 273) tended to have lower biomechanical knowledge scores than those who no longer used AR (n = 71), (W=11213, p = 0.029). Open text responses were analysed using thematic analysis, drawing on the Behaviour Change Wheel as a deductive framework. Most changes in a horse’s way of going in response to AR as reported by equestrians were not supported by scientific evidence. Social influence from those within an equestrian’s immediate environment and lack of physical riding or training skills were found to be primary drivers to start using AR. Once human behaviours were established, perceived horse characteristics and lack of rider ability were the most prominent barriers to reduced AR usage. Future research should focus on how to enhance rider knowledge and skill level, while creating a social environment that does not tolerate the inappropriate use of AR.