Biomechanical effects of equine training aids: A systematic review

Abstract

Equine training aids, including auxiliary reins such as draw reins, Pessoa-type systems and side reins, are widely used during lungeing and ridden exercise to improve posture, back engagement and movement quality. Despite their extensive practical application, the biomechanical effects of these devices remain poorly defined and are often inferred from traditional training concepts rather than objective scientific evidence. This systematic review synthesised the available literature evaluating the biomechanical effects of equine training aids using objective outcome measures. Following a structured search and PRISMA-guided screening process, studies were classified into those that provided direct biomechanical evidence (kinetic, kinematic or electromyographic outcomes), indirect biomechanical proxies or nonbiomechanical contextual information. After application of strict biomechanical inclusion criteria, only a small subset of studies directly evaluated locomotor biomechanics. Most available investigations assessed indirect physiological responses, local mechanical effects or descriptive outcomes. Among biomechanically focused studies, draw reins and Pessoa-type systems were the most frequently investigated devices. The limited direct evidence indicates that training aids can modify posture, movement coordination and external load distribution during exercise. Reported changes in ground reaction forces and trunk or limb kinematics were generally modest and context-dependent. Importantly, electromyographic studies do not consistently demonstrate increased activation of key axial musculature, challenging the assumption that training aids directly enhance back muscle engagement. Overall, this review highlights an apparent mismatch between the widespread use of training aids and the limited objective biomechanical evidence supporting their purported benefits. Current data suggest that training aids primarily influence postural control rather than producing consistent biomechanical or neuromuscular improvements, underscoring the need for well-controlled studies employing standardised biomechanical methods.