How obstacle approach shapes rider biomechanics: Changes in kinematics, rein tension and stirrup forces during canter.

Abstract

Show jumping performance depends on the rider's ability to regulate the horse-rider system while maintaining postural stability under dynamic constraints. Although rider biomechanics has been investigated in various equestrian contexts, integrated analyses combining 3D kinematics with rein and stirrup kinetics during jump-approach remain limited. This study aimed to analyse how approaching an obstacle changes a rider's control strategies by comparing sitting canter, two-point canter in straight line without obstacle and jump-approach canter (defined here as the five strides before obstacle) in 16 intermediate show jumpers performing over a vertical obstacle (110 cm) on both left and right canter leads. Full body kinematics and bilateral rein tensions and stirrup forces were recorded simultaneously. Compared with sitting canter, jump-approach canter was associated with significantly reduced head and lumbar sagittal range of motion, with riders adopting a more erect trunk position, supporting the hypothesis that riders enhance postural stabilization when preparing for obstacles. Stirrup forces were highest in two-point seat canter and exhibited significant lead-dependent asymmetry, with greater outside stirrup loading during straight-line conditions that diminished during approach. Rein tension increased during approach but remained bilaterally symmetrical across all conditions. These findings reveal a functional dissociation between upper-limb communication (symmetrical rein control) and lower-limb stabilization (asymmetrical stirrup loading), suggesting that riders decouple balance regulation from guiding aids to optimize horse-rider coordination during show jumping approach phases.