Convergent Validity of the Y Balance Test and Hopping for Distance Tests

Abstract

The Y Balance TestTM (YBT) and single (SH), triple (TH), and crossover hop (COH) for distance, functional tests that reportedly require dynamic balance, are commonly used to assess lower extremity injury risk. Convergent validity is the degree to which two different instruments measure the same underlying construct. If different tests are measuring the same construct, practitioners can select one test for use instead of a battery of assessments. PURPOSE: To determine the degree of convergent validity of the YBT and 3 hopping tests to measure dynamic balance. METHODS: Cross-sectional study of 41 recreationally active adults (27 female, 14 male, age: 23.4 ± 1.8 years old, height: 172.5 ± 9.5 cm, weight: 68.5 ± 10.7 kg) who performed the YBT, SH, TH, and COH on each leg. The YBT includes 3 reach directions: anterior, posteromedial, and posterolateral. YBT composite score (CS) was calculated by summing the 3 reach distances and dividing it by 3 times the participant’s leg length. Performance asymmetry was calculated by dividing the dominant limb by the non-dominant limb distances. Pearson (continuous) and Spearman (ordinal) correlation coefficients were used to assess correlation between performance, as well as limb asymmetry on the YBT and 3 hopping tests. RESULTS: The hopping tests were strongly and significantly correlated with each other (r = 0.82-0.84; p < 0.001 for all). YBT CS was strongly and significantly correlated with individual reach distances (r = 0.72-0.90; p < 0.001 for all). No statistically significant correlation was found between YBT and any of the hopping tests nor between YBT asymmetry measures. The only statistically significant correlation between performance asymmetry was between the COH and TH (r = 0.56; p < 0.001). CONCLUSION: Performance and asymmetry of YBT and 3 hopping tests are not measuring the same underlying construct of dynamic balance. Clinicians should not substitute the YBT for hop tests, and may consider including both to measure dynamic balance.