Time-to-contact demonstrates modulation of postural control during a dynamic lower extremity task

摘要

Postural control deficits are associated with increased risk of loss of balance and potential injury. To assess balance deficits and estimate injury risk, there is a need to evaluate postural control during dynamic activities. Analysis during dynamic activities could assess if an individual's ability to control their posture is a fixed condition or if it is dependent on the demands of a task. The purpose of this study was to evaluate changes in postural control during a dynamic lower extremity task using time-to-contact (TtC) analysis. 3D motion capture with a force plate was used to evaluate 46 healthy recreational athletes performing an anterior reach with the right foot while standing on their left leg. TtC was calculated for nine valid trials. For each trial, the time from the toe leaving the force plate to the toe touching the floor at the maximum reach distance was divided into five epochs of equal duration. TtC was averaged over each epoch. Differences in TtC were evaluated with an unbalanced mixed effects ANOVA and post hoc Tukey's HSD comparisons. Epoch was a significant main effect (p < 0.001), with both Epoch 4 and Epoch 5 having significantly greater TtC from all other epochs ( p= 0.05). Increasing TtC in later epochs suggests a higher demand for postural control when the task becomes more challenging. As an individual's reaching foot extends further from the body, postural control is adjusted to match the changing demands of the dynamic task.