Test–retest reliability of vertical ground reaction forces during stair climbing in the elderly population

The purpose of the study was to determine the reliability of vertical ground reaction force (VGRF) parameters during stair ascent and descent in the elderly. Forty-two elderly subjects (80.1 SD 6.4 years) were asked to perform three stair ascents and descents at their self-selected normal speed. VGRF were measured during two consecutive steps on an instrumented staircase. Force–time curves where then parameterized into force, force-time and time variables, according to a previously suggested protocol. In addition, force and force-time variables were normalized to body weight. Intraclass correlation coefficients (ICC) type (2, 1) and coefficients of variation (CV) were calculated. Force variables showed moderate to good reliability for the normalized values with ICCs ranging from 0.537 to 0.836 and CVs between 2.52% and 6.51%. Variability of Fmax1 and Fmin appeared to be higher in stair descent with CVs of >5.20% as compared to stair ascent (