Sport- and Side-Specific Postural-Control Profiles in Elite Athletes: A Cross-Sectional Analysis of Centre of Pressure Path Length, ML/AP Directionality, and Frequency-Domain Descriptors

Background/Objectives: Postural control in elite athletes may reflect sport- and side-related balance demands. Conventional Centre of Pressure (CoP) path length alone offers only limited information about directional and frequency-domain sway characteristics. This cross-sectional study described CoP path length, mediolateral/anteroposterior (ML/AP) directionality, and power spectral density (PSD)-derived frequency-domain descriptors in elite athletes from sports with distinct movement demands. Methods: A total of 116 asymptomatic elite athletes from volleyball, football, short track, ice hockey, and field hockey were assessed during single-leg stance. CoP path length, the ML/AP index, and PSD outcomes were analysed. PSD was calculated in LabVIEW using a fast Fourier transform (FFT) routine from the complete 60 s trial acquired at 1 kHz after removal of the DC component. Spectra were not normalised and are reported as absolute spectral-density values in mm2/Hz. PSD outcomes were summarised in low-frequency (0.02–0.6 Hz) and higher-frequency (1–5 Hz) windows, and the PSD quotient was defined as PSD 0.02–0.6 Hz/PSD 1–5 Hz. Results: Observed sport–sex groups differed in subject-averaged CoP path length (F(5,110) = 22.26, p < 0.001, eta_p2 = 0.503), ML/AP index (F(5,110) = 4.07, p = 0.002, eta_p2 = 0.156), PSD 0.02–0.6 Hz (F(5,110) = 38.67, p < 0.001, eta_p2 = 0.637), PSD 1–5 Hz (F(5,110) = 4.83, p < 0.001, eta_p2 = 0.180), and the exploratory PSD quotient (F(5,110) = 3.33, p = 0.008, eta_p2 = 0.132). Paired-side comparisons showed greater right-side CoP path length, greater right-side PSD 0.02–0.6 Hz, and a higher right-side ML/AP index, whereas PSD 1–5 Hz and the PSD quotient did not differ significantly between sides. Conclusions: The combined analysis of CoP path length, ML/AP directionality, and PSD-derived descriptors characterised sport-, sex-, and side-specific postural-control profiles in this cohort. Mechanistic interpretations of segmental neuromuscular control remain tentative because the study was cross-sectional and did not include electromyography, kinematics, or prospective injury data.