Dimensionality Reduction of Full-Body Strength-Power Metrics to Identify Distinct Strength Domains in Elite Rugby Union Athletes

ABSTRACT: Payne, LKD, Varley, MC, Carey, DL, Driller, MW, and James, LP. Dimensionality reduction of full-body strength-power metrics to identify distinct strength domains in elite rugby union athletes. J Strength Cond Res XX(X): 000-000, 2026-The aim of this study was to determine the extent of shared and unique information among strength tests and to evaluate whether factors identified through exploratory factor analysis reflect distinct strength domains in professional rugby union players. Twenty professional male rugby union athletes (age 24.4 ± 3.8 years; height 186.3 ± 5.2 cm; body mass 107.6 ± 10.9 kg) completed a battery of 4 upper-body and 5 lower-body isometric, dynamic, and reactive strength tests. A total of 18 metrics were entered into exploratory factor analysis to identify distinct strength domains. Exploratory factor analysis reduced the data set into 2 upper-body domains (pressing and pulling) and 4 lower-body domains (isometric, dynamic, reactive, and relative). These domains together explained 73% of the variance in the upper-body data and 79% of the variance in the lower-body data. The isometric domain was driven by early-phase force at 100 and 200 ms, while peak force contributed less strongly. The dynamic domain was defined by heavy squat velocity, which diverged inversely from countermovement jump height, reflecting load-velocity differences. The reactive domain was shaped by contact time and countermovement depth, highlighting the role of temporal mechanics. The relative domain was defined by drop jump height and countermovement jump momentum, emphasizing the influence of body mass on ballistic force expression. Eighteen test metrics were successfully reduced to 6 distinct domains of strength in professional rugby union athletes. This framework provides a concise basis for profiling upper-body and lower-body strength to reduce redundancy and retain key information needed for training and monitoring rugby athletes.