Measuring the Rider–Horse Dyad Across Olympic Equestrian Disciplines: A Scoping Review of Methodological Gaps and Priorities for Show Jumping

(1) Background: Rider–horse coordination underpins equestrian performance; yet, its definition, quantitative indicators, and measurement methods remain inconsistent across Olympic disciplines. This scoping review mapped the constructs, metrics, and measurement approaches in dressage, show jumping, eventing, and transferable equestrian contexts, with show jumping as the principal application context. (2) Methods: Following PRISMA-ScR guidance and a Population–Concept–Context framework, Web of Science Core Collection, Scopus, and PubMed were searched from database inception to 10 September 2026. Evidence was charted by discipline, measurement domain, measurement configuration, and synchronisation status. (3) Results: A total of 121 evidence sources were included. Among 108 empirical or methodological studies, 47 were kinematic/biomechanical, 23 performance/statistical, 15 behavioural/welfare-related, 13 kinetic/pressure/interface, and 10 neuromuscular/physiological. Only 12 used synchronised rider–horse time-series or event-based measurements, and none of the show-jumping studies met the strict synchronisation criterion. Coordination was commonly inferred from single-partner signals, interface measures, or aggregate performance outcomes. (4) Conclusions: The key limitation is not sensor availability, but the lack of validated dyadic methods. Future show-jumping studies should use common time bases, predefined biomechanical events, paired variables, and prospective validation, while integrating behavioural and clinical evidence when interpreting welfare-related outcomes.