Functional foot symmetry and its relation to lower extremity physical performance in older adults: The Framingham Foot Study

Abstract

Background While many studies use gait symmetry as a marker of healthy gait, the evidence that gait symmetry exists is limited. Because gait symmetry is thought to arise through laterality (i.e., limb preference) and affects gait retraining efforts, it is important to understand if symmetry exists during gait in older adults. Therefore, the purpose of this study was to evaluate foot and gait symmetry in the population-based Framingham Foot Study as well as to determine the effects of vertical force symmetry on physical performance measures. Methods Members of the Framingham Foot Study were included in this analysis (N=1333). Foot function and force data were collected using the Tekscan Matscan during self-selected gait, with symmetry evaluated using the symmetry index. The short physical performance battery (SPPB) measures of balance, chair stands and gait speed assessed lower extremity physical function. Participants were evaluated using quartiles of gait speed and foot symmetry to determine the effects of symmetry on lower extremity physical function. Results Individuals with faster gait speed displayed greater foot function asymmetry; individuals with −3.0% to −9.5% asymmetry in foot function performed better on the short physical performance battery (SPPB). Further, with aging, the degree of asymmetry was reduced. Conclusions While this research suggests that a moderate degree of foot asymmetry is associated with better lower extremity function, the causes of vertical force asymmetry are unknown. Future studies should evaluate the causes of foot asymmetry and should track the changes in symmetry that occur with aging.

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“…However, random error would only serve to obscure weaker relations in these data rather than create false positive associations [33]. Moreover, the large study sample greatly mitigates this issue, as it is more than sufficiently powered even with a single scan [34]. …”

Associations of Foot Posture and Function to Lower Extremity Pain: Results From a Population‐Based Foot Study

“…Further, although other studies have suggested that multiple trials may be required for a reliable measure using the Tekscan Matscan (), given the large participant numbers only 1 scan per foot was collected. However, in prior work on the Framingham Foot Study, it was noted that with a reliability of 0.50 (Metscan reliability measures noted as >0.70) (), a sample size of <300 participants was needed to appropriately power the study (). Therefore, due to the higher sample size of our study, we are confident that the findings noted are not an artifact of the single scan of each foot and that the study was adequately powered given the single assessment of foot posture and foot function.…”