Reproducibility and concurrent validity of hip joint angle test for estimating hamstring flexibility in recreationally active young men.

The purposes of this study were twofold: (a) to examine the test-retest reproducibility and concurrent validity of the horizontal hip joint angle test (H-HJA) and vertical hip joint angle test (V-HJA) for estimating hamstring flexibility measured with an inclinometer during the passive straight-leg raise test (PSLR) and (b) to determine whether the H-HJA cutoff scores may be used for V-HJA for the detection of short hamstring flexibility in active recreationally young adults. Fifty young men underwent the H-HJA, V-HJA, and PSLR on the right and left legs 3 times in a randomized order with a 4-week interval between trials under a controlled laboratory environment. Reproducibility was examined using coefficient of variation (CV) and intraclass correlation coefficient (ICC3,1) and their respective confidence limits. Regression and kappa correlation analyses were performed to examine the association of H-HJA and V-HJA with the PSLR test, and the 95% limits of agreement between H-HJA and V-HJA were calculated to check if there were differences in the raising scores. The results demonstrated acceptable reproducibility measures for the H-HJA (4.12% CV; 0.93 ICC), V-HJA (4.99% CV; 0.92 ICC), and PSLR (4.83% CV; 0.88 ICC). The H-HJA (R = 0.62) and V-HJA (R = 0.63) results were significantly associated with those of the PSLR. The 95% limits of agreement between the H-HJA and V-HJA reported systematic bias (+7.12 cm) and a wide 95% random error ( ±13.72 cm). This study concluded that the test-retest reproducibility of the H-HJA, V-HJA, and PSLR is acceptable and that the validity of H-HJA and V-HJA is moderate. Furthermore, the H-HJA cutoff scores should not be used for V-HJA for the detection of short hamstring muscles in young adults.