Exploration of Inertial Sensor-Derived Kinematic Predictors for Dynamic Balance Assessment in the Active Adult

The modified Star Excursion Balance Test (mSEBT) is a clinical tool for dynamic balance assessment. While researchers have examined individual joint kinematic predictors of dynamic balance performance, limited data exist on body and joint sway during the test execution. Further investigation of kinematic predictors' influence on dynamic balance is needed to improve assessment methodologies. This study aimed to examine the relationship between the center of mass and lower limb kinematics as predictors of mSEBT performance.

Twenty-seven participants with no history of lower limb joint instability were recruited for this study. The inertial sensors were positioned on the non-dominant leg: trunk, thigh, shank, and foot. The participants completed the mSEBT barefoot following standardized practice trials with three test trials per direction. The reach distance and lower limb kinematic data were recorded. Spearman rank's correlation and stepwise multiple regression analyses identified key predictors of dynamic balance performance.

Ankle dorsiflexion was a strong predictor of normalized reach distance in the anterior direction (r² = 0.34, p < 0.001). Body center of mass displacement was the strongest predictor of posteromedial and posterolateral reach (r² = 0.55, p < 0.001; r² = 0.57, p = < 0.001, respectively). The combined influence of the body center of mass and hip flexion accounted for 65% of the variance in the posterior reach assessments.

This study highlights the key biomechanical factors that influence dynamic balance, focusing on the interaction between joint mobility and segmental control. Ankle dorsiflexion is critical for anterior balance, whereas hip flexion and body center of mass displacement are essential for posterior balance.