Biomechanics of the Lower Extremity Dynamic Balance Tests: Kinematics and Electromyography Analysis of the Y-Balance Test and the Star Excursion Balance Test
Type of DegreePhD Dissertation
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Lower extremity dynamic balance is maintained through a sequence of segmental motions within a kinetic chain. Reaching dynamic balance tests measure the distance in which one can extend his/her center of gravity over the base of support in different directions, for the purpose of quantifying the limitations of postural control. Two related tests were used interchangeably to assess the dynamic control through the performance of a dynamic single-leg balance tasks; the Star Excursion Balance Test (SEBT) and the Lower Quarter Y Balance Test (LqYBT). Comprehensive analyses, including assessment of muscular activity and kinematics, were used to better identify differences between the performance of SEBT and LqYBT. Thus, the purpose of this study is to examine the differences between the SEBT and LqYBT, regarding reaching distances; hip and knee frontal and sagittal plane kinematics; muscle activation profiles of the gluteus medius, adductor magnus, hamstring, and quadriceps; and the gastrocnemius musculature of the stance leg. Also, this research examined if sex (male or female), hip, and knee passive joints range of motion affect the achieved reaching distances. Twenty-six healthy, recreationally active, participants volunteered for this study (15 females [age M = 21.7, SD = 1.4 years] and 11 males [age M = 21.7, SD = 2.28 years]). Lower extremity muscle activation was obtained during the forward reaching phase of the LqYBT, and the SEBT tested directions. The frontal and sagittal plane kinematics of the hip and knee were calculated at the maximum reach of the anterior, posteromedial, and posterolateral directions of the two balance tests. Hip and knee passive range of motion were also performed to indicate if they had an influence on the achieved reaching distances. Significant differences in reaching distances were observed in the posteromedial and the posterolateral directions between the LqYBT and the SEBT. The activation of the gluteus medius was significantly higher in female participants preforming the LqYBT compare to male participants in the anterior and posterolateral reaching directions. Female participants showed a significant increase in the activation of the adductor magnus, and the quadriceps muscles, performing the posteromedial reaching direction of the LqYBT compare to males. The performance of the LqYBT was characterized with a significantly increased hip abduction/adduction range of motion compare to the SEBT in all three reaching directions. Significant differences in hip flexion between the two balance tests were indicated for all three reaching directions. Significantly increased knee abduction/adduction range of motion were observed in the posteromedial and posterolateral reaching directions of the LqYBT compared to the SEBT. It was concluded that the two balance tests significantly differ, thus using them interchangeably in the field or transform outcomes between the two tests might not be appropriate when assessing the postural control of healthy recreationally active populations.