Assessing agreement in lower-body joint interlimb asymmetries in isometric, dynamic, and loaded conditions

Interlimb asymmetry (ILA) for static and dynamic movements can indicate aberrant musculoskeletal and neuromuscular function. The purpose of this analysis was to measure ILA agreement in different isometric, dynamic, and loaded conditions at the ankle, knee, and hip, for single-joint and lower-body ILA; to assess the effect of a load on kinetic and kinematic ILA during jumps; and to evaluate the effect of physiological fatigue on gait ILA. Twenty-two men (30.2 ± 5.0 years, 1.8 ± 0.08 m, 85.6 ± 10.0 kg, 16.9 ± 5.4% body fat) participated in ankle, knee, hip, and lower-body assessments of relative (N·kg⁻¹) and peak isometric strength (N); dynamic peak range of motion (º) and dynamic peak forces (N) without and with load (9.7 kg); and tibial impact (g) during aerobic capacity tests (pre- and at-fatigue). Agreements between ILA (≥10% vs. <10%) were calculated using different variables and assessed across different formulae through Kappa coefficients (κ). The difference in ILA with and without load, and pre- and at-fatigue, was analyzed using paired t-tests (α = 0.05). An analysis of single-joint ILA showed good agreement between the formulae (κ range: 0.412–1.00, p values: 0.045–<0.001), but poor agreement with lower-body ILA. Load increased ILA in both countermovement and drop jumps, whereas physiological fatigue did not. This research estimated normative baseline ILAs for military personnel and showed that ILA is a task-, metric-, and joint-specific measurement.