Performance and reliability of the Lower Quarter Y Balance Test in healthy adolescents from grade 6 to 11.

Background: The Lower Quarter Y Balance Test (YBT-LQ) has been widely used in the field to assess dynamic balance performance in various populations. However, no study has demonstrated test-retest reliability of the YBT-LQ in adolescents including several age cohorts, even though reliability is necessary to provide repeatable performance data.
Objective: Thus, we examined test-retest reliability of the YBT-LQ in healthy adolescents.
Methods: In a school setting, 178 secondary school students (93 female, 85 male) in sixth to eleventh grades (11-19 years) performed the YBT-LQ twice, 7 days apart. Normalized maximal reach distances (% leg length) for all three directions (i.e., anterior, posterolateral, posteromedial) and both legs and the composite score were used as outcome measures. Intraclass correlation coefficient (ICC _3,1 ) and standard error of measurement (SEM) were calculated to assess relative and absolute test-retest reliability, respectively. Practical relevance of the YBT-LQ was determined by calculating the minimal detectable change (MDC _95% ).
Results: Irrespective of grade, test-retest reliability for all distances reached was predominately "excellent" (i.e., ICC _3,1 > 0.75) and the rather small SEM values ranged from 1.77 to 5.81%. Depending on grade and reach direction, MDC values of 4.90 to 16.10% represent the minimum amount of change needed to identify clinically relevant effects in repeated measurements of the YBT-LQ performance.
Conclusions: The observed values suggest that the YBT-LQ is a reliable test and suitable to detect changes of dynamic balance performance in healthy adolescents from grade six to eleven (i.e., aged 11-19 years).
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