Smartphone-based field assessment of trunk stability and its relationship with whole-body balance in older adults: cross-sectional study. (Preprint)

BACKGROUND Maintaining balance is essential for older adults to preserve independence and reduce fall risk. However, empirical evidence linking trunk stability with balance and gait is scarce, partly due to the lack of accessible field tests. Smartphone-based accelerometry field tests offer a promising approach to assess trunk stability outside the laboratory. OBJECTIVE To determine (a) the association between trunk stability and whole-body balance and gait, and (b) to extent to which trunk stability and whole-body balance field tests align with laboratory-based assessments in older adults. METHODS Fifty-seven physically active older adults performed two trunk stability (i.e., the lumbopelvic stability [field] and the unstable sitting posturographic [laboratory] tests), two whole-body balance (i.e., the tandem stance posturographic [laboratory] and the whole-body static balance [field] tests) and two gait-related tests (i.e., the straight-line gait and the modified Timed Up & Go [field] tests) two times. A Spearman correlation analysis was performed after assessing the reliability of the variables. RESULTS Significant positive low-to-high correlations were found between the lumbopelvic stability and the whole-body static balance tests (.380<r<.700, P<.013). A low positive correlation (r=.436, P<.013) was also observed between the unstable sitting posturographic test and the tandem stance posturographic test. No correlations were found between trunk stability and any gait-related test. No moderate-to-high relationships (.289<r<.487, P<.05) were found between laboratory and field tests (both for trunk stability and whole-body balance). CONCLUSIONS Better static lumbopelvic control during exercises like back bridge and bird-dog is linked to improved whole-body balance in active older adults, suggesting these positions be included in future interventions to enhance trunk stability. Accessible smartphone-based field tests for lumbopelvic stability offer a promising approach for standardized assessment of trunk stability. However, direct extrapolation from field tools to laboratory findings is unfeasible due to lack of correlation. These findings highlight the potential of smartphone-based field tests to complement clinical and research assessments of balance in older adults.