LOWER QUARTER- AND UPPER QUARTER Y BALANCE TESTS AS PREDICTORS OF RUNNING-RELATED INJURIES IN HIGH SCHOOL CROSS-COUNTRY RUNNERS

Background: While cross-country running is a popular interscholastic sport, it also has a high incidence of running-related injuries (RRIs). Recent literature suggests that functional tests may identify athletes at increased risk of injury. The Y-Balance Test (YBT) is an objective measure used to assess functional muscle strength, balance, and expose asymmetries between tested limbs. Purpose/Hypothesis: The purpose of this study was to determine if the YBT could predict RRI in high school cross-country runners. It was hypothesized that an asymmetric right (R)/left (L) YBT reach distance for the lower or upper extremities would be associated with an increased risk of RRI. Study Design: Prospective observational cohort Methods: One hundred forty-eight athletes (80 girls, 68 boys) who competed in interscholastic cross-country in Southern California during the 2015 season participated in the study. Prior to the cross-country season, the runners completed Lower-Quarter YBT (LQ : YBT) and Upper-Quarter YBT (UQ-YBT) testing to assess lower and upper extremity asymmetry, respectively. The runners were prospectively monitored for RRI occurrence throughout the season using the Daily Injury Report form. Results: Forty-nine runners (33.1%) incurred a RRI during the 2015 season, with the lower leg (shin/calf) and knee the most common RRI sites. Girls had a higher RRI occurrence (38.8%) than boys (26.5%) (p = 0.12). Boys had greater raw scores for LQ-YBT R and L anterior (ANT), posteromedial (PM), posterolateral (PM) and composite reach distances than girls (p <= 0.05). With the exception of normalized superolateral reach distance, boys had significantly greater scores for raw and normalized R and L UQ-YBT reach distances and raw composite scores than girls (p <= 0.05). After adjusting for prior RRI, while boy runners with a LQ : YBT PM reach difference >= 4.0 cm were five times more likely to incur a RRI (Adjusted odds ratio [AOR] =5.05, 95% CI: 1.3-19.8; p=0.02), girl runners with a UQ-YBT inferolateral (IL) reach difference >= 4.0 cm were 75% less likely to incur a RRI (AOR= 0.25, 95% CI: 0.1-0.7; p=0.005). By lower extremity body region, boy runners with a UQ-YBT superolateral (SL) reach difference >= 4.0 cm were seven times more likely to incur a hip/thigh/knee RRI [AOR] = 7.20, 95% CI: 1.1-45.6; p =0.002). Conclusion: Greater lower extremity (PM) or upper extremity (SL) reach distance asymmetry, as measured by the LQ-YBT or UQ-YBT, respectively, were associated with RRI in boy high school cross-country runners.