Reliability of force-platform measures of postural sway and expertise-related differences.

CONTEXT: Although reliability is a population-specific property, few studies have investigated the measurement error associated with force-platform parameters in athletic populations.

OBJECTIVE: To investigate the skill-related differences between athletes and nonathletes in reliability of center-of-pressure (COP) summary measures under eyes-open (EO) and eyes-closed (EC) conditions.

DESIGN: Test-retest reliability study.

SETTING: COP was recorded during double-leg quiet standing on a Kistler force platform before and after a fatiguing treadmill exercise, with EO and EC.

PARTICIPANTS: 31 male participants including 15 athletes practiced in karate and 16 nonathletes.

MAIN OUTCOME MEASURES: Standard deviation (SD) of amplitude, phase-plane portrait, SD of velocity, mean total velocity, and area were calculated from 30-s COP data. Intraclass correlation coefficient (ICC), standard error of measurement, and coefficient of variation (CV) were used as estimates of reliability and precision.

RESULTS: Higher ICCs were found for COP measures in the athlete (compared with the nonathlete) group, postfatigued (compared with prefatigued) condition, and EC (compared with EO) tests. CVs smaller than 15% were obtained for most of the COP measures. SD of velocity in the anteroposterior direction showed the highest reliability in most conditions.

CONCLUSIONS: Tests with EC and to a lesser extent tests performed in the athlete group and in the postfatigued condition showed better reliability.