Reliability of Biodex Balance System Measures

TLDR

The Biodex Balance System uses spring resistance levels 1–8 to vary platform stability. Twenty active adults performed 20‑second upright standing trials on the system’s freely rotating platform at spring resistance level 2, producing overall, anterior‑posterior, and medial‑lateral stability indices. Reliability of the BBS stability indices was high (R = .94–.93 across eight trials), and a protocol of two practice trials followed by two test trials yielded acceptable reliabilities (R = .90–.76), replicated in 27 athletes (R = .92–.93).

Abstract

Abstract This study examined the reliability of measures of dynamic balance obtained using the Biodex Balance System (BBS). Twenty male (n = 10) and female (n = 10) active adults engaged in weight-bearing sports volunteered for this study. Dynamic balance was assessed using measures obtained from the BBS at a spring resistance level of 2. Spring resistance levels range from 1 (least stable) to 8 (most stable). The BBS uses a circular platform that is free to move in the anterior-posterior and medial-lateral axes simultaneously, which permits three measures to be obtained: an overall stability index (OSI), an anterior-posterior stability index (APSI), and a medial-lateral stability index (MLSI). Measures were obtained from 20-sec trials during which participants were asked to maintain an upright standing position on their dominant limb on the unstable surface of the BBS. An examination of measures obtained across 8 trials indicated that the BBS produced reliable measures as indicated by R = .94 (OSI), R = .95 (APSI), and R = .93 (MLSI). Based on findings in this study, the testing protocol recommended providing 2 practice trials (Trial 1 and Trial 2) followed by 2 test trials (Trial 3 and Trial 4). Reliability estimates for Trials 3 and 4 were R = .90 (OSI), R = .86 (APSI), and R = .76 (MLSI). Replication of this protocol with a separate group of 27 collegiate athletes resulted in reliability estimates of R = .92 (OSI), R = .89 (APSI), R = .93 (MLSI).