RELIABILITY AND STABILITY OF THE Y BALANCE TEST IN HEALTHY EARLY ADOLESCENT FEMALE ATHLETES

Abstract

BACKGROUND/PURPOSE: Adolescent females are at an increased risk of lower extremity injuries and may be partially explained by the interaction of peak rates of skeletal growth, an immature neuromuscular system, and deficits in muscle strength and recruitment patterns. Reliable tests of dynamic stability can help identify athletes with balance deficits and assess changes in limb function after injury. Sophisticated measures of dynamic postural control, such as stabilometry, are able to detect subtle deficits in young athletes, but are expensive and may not be readily available in a clinical setting. The Y Balance Test (YBT) is a low-cost, clinical measure of dynamic postural control that mimics the demands of sports requiring unilateral balance. It requires the athlete to dynamically balance on each leg while performing a maximal reach with the other limb in three different directions: anterior (ANT), posteromedial (PM), and posterolateral (PL). The athlete is required to maintain unilateral balance during the test as maximal reach distance is measured to the nearest 0.5 cm. Though the YBT has been predicative of injury in the adult population, studies are lacking regarding the utility in adolescents. The purpose of this study was to estimate the inter- and intra- rater reliability and stability of the YBT in early adolescent females over a one-month period. METHODS: Twenty-five female athletes (mean age 12.7 ± 0.6 years) participated. Subjects were tested at their respective practice facilities and participated in various sporting activities (Figure 1). Two novice raters with minimal training in YBT administration were randomly selected from a pool of five. The raters simultaneously assessed each subject’s YBT performance and were blinded to each other’s results. A second testing session was performed approximately one month later (n=21, mean 32.3± 9.6 days) by the same two raters, blinded to previous measurements (Figure 2). The time interval was chosen to mimic a typical duration between reassessments in standard clinical care. Maximum reach distances and composite (COMP) scores were collected on both limbs and normalized to leg length (Figure 3). Intraclass correlation coefficients (ICC) were calculated for between rater (ICC 2,1) and between session (ICC 3,1) agreement. Measurement error and minimal detectable change (MDC) values were calculated for clinical interpretation. RESULTS: There was a significant increase in height (p=0.016) and weight (p=0.003) from day 1 to day 2 of testing. Interrater reliability was excellent for all corrected reach directions and COMP scores of the right limb (ICC 0.973- 0.998) and left limb (ICC 0.960-0.999) except for the day 1 left ANT reach which was good (ICC 0.811) (Figure 4). Intrarater (test-retest) reliability were moderate to excellent for the right limb (ICC 0.681- 0.908) and moderate to good for left limb (ICC 0.714 - 0.811). Standard error of measurement (SEM) percentages were all less than 2% of all respective mean reach distances. MDC values for the right and left limbs ranged between 2.02-3.62% and 2.77-3.63%, respectively (Figure 5). CONCLUSIONS/SIGNIFICANCE: The early adolescent female is a unique population, where dynamic balance deficits are escalated by the interaction of an immature neuromuscular system, peak maturational growth rates, and emergence of sex specific differences. The incidence of ACL injuries is greatest during the high school years and recommendations support the implementation of targeted neuromuscular interventions prior to the time of this peak injury risk. The YBT is a reliable and stable tool to assess dynamic balance in early adolescent females and may be utilized by clinicians, physical education teachers, and coaches to help identify high risk individuals, mitigate the risk of injury, and determine functional improvements. The time span between testing sessions in the current study was longer than previous work in attempt to improve external validity by mimicking a typical time interval between outcome measure reassessments performed in a clinical setting. Between session reliability measures were lower than previous studies in adults and highlights the unique performance variation with dynamic balance tasks in the female preadolescent population. This is exemplified by the anthropometric changes that occurred over just a one month interval. This study supports the reliability and stability of the YBT in healthy early adolescent females and can be administered by those with minimal YBT training. Though the YBT has been shown to be predicative of injury in adults and is often included in return to sport functional test batteries after injury, future studies are needed to further understand its utility in this high-risk early adolescent female population. [Figure: see text]