Reliability and error in step parameters and balance measures across different walking styles in adults

The margin of stability (MOS) and the variability of step parameters characterize balance control capabilities during walking. MOS has been validated against clinical balance tests, but the test-retest reliability during various walking styles has not been investigated. This study aimed to examine the test-retest reliability of MOS and step parameters and the variability of those same parameters during forward, backward, and tandem walking in healthy adults.

MOS and step data, including normalized stride velocity (nSV), normalized step length (nSL), step width (SW), and relative time in double support (%DS), were obtained from fifteen participants who completed five trials each of forward, backward, and tandem walking twice, six weeks apart. The intraclass correlation coefficient (ICC) was used to assess the test-retest reliability. Additionally, standard error of measurement (SEM), and minimal detectable change at 95% confidence (MDC₉₅) were calculated for each outcome measure.

The MOS and step parameters demonstrated moderate to excellent reliability during forward (ICC range: 0.83-0.95), backward (ICC range: 0.76-0.93), and tandem walking (ICC range: 0.66-0.93). Variability of MOS and step parameters showed poor reliability for forward (ICC range: -0.29-0.12), backward (ICC range: -0.07-0.69), and tandem walking (ICC range: 0.07-0.39). SEM values for step parameters ranged from 0.02 mm to 31.05 mm across walking styles, and MDC95 values ranged from 0.05 mm to 86.06 mm.

The current study shows that the MOS is reliable across different walking styles. In contrast, variability showed poor reliability in the overground walking protocol and should be interpreted with caution.