Intrasession reliability of force platform parameters in community-dwelling older adults.

OBJECTIVE To investigate the intrasession reliability of center of pressure (COP) parameters calculated from force platform measurements. DESIGN A cross-sectional study. SETTING Gait and balance laboratory. PARTICIPANTS Community-dwelling healthy older adults (N=63) above the age of 62 years (mean age, 78.74 y). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES COP was estimated from a force platform, and the following parameters were calculated: (1) the total length of the COP displacement, (2) area of sway, (3) length of the COP displacement in the sagittal plane, and (4) length of the COP displacement in the frontal plane. Intraclass correlation coefficients (ICCs) were calculated by using 3 successive trials with 4 different test conditions. The test conditions were (1) normative standing with eyes open, (2) normative standing with eyes closed, (3) narrow stance with eyes open, and (4) narrow stance with eyes closed. RESULTS The ICCs for the tests with eyes closed (.710-.946) were higher than those for tests with eyes open (.841-.945). The highest value was obtained for the vector sum of the COP during anteroposterior movement in narrow stance with eyes closed (.946). The value .710 was the lowest of all parameters and was an outlier for the narrow stance with eyes closed test, which was otherwise very reliable. CONCLUSIONS Eight of 16 calculated ICCs showed excellent reliability (>.90). They can be recommended for further use in clinical trials. Tests with closed eyes were more reliable than tests with eyes open. We recommend using eyes closed test conditions when assessing static balance control. For these tests, all the calculated ICCs were over .90, except for measurements of sway area.