Aim: To describe the inter- and intraobserver reliability of lower extremity flexibility tests, and to explore the effect of sports activity on the results.
Methods: A total of 66 subjects consisting of 20 professional athletes, 26 active subjects performing any sporting activity and 20 control subjects were included. Various flexibility tests were performed to determine hamstring, quadriceps and hip adductor muscle flexibility by two examiners blinded to each other for interobserver reliability. Intraobserver reliability of tests were evaluated by one the examiners 1 week later. Inter- and intraobserver reliability was analyzed with intraclass correlation coefficient (ICC), coefficient of variation (CV) and critical difference (CD).
Results: ICC analysis showed that inter- and intra-observer reliability results were satisfactory for all measurements. Athletes performed the best results of inter- and intraobserver reliability for flexibility tests in means of CV and CD compared with active and control groups (P<0.05). Popliteal angle measurement was the most reliable one among hamstring flexibility tests where as the least reliable test was chair sit and reach test in all groups.
Conclusion: This is the first study evaluating extensively the reliability of flexibility tests in different intensities of sports activity. Flexibility measurements of quadriceps and hip adductor muscles can be used reliably in clinical practice as hamstring flexibility tests. The intensity of performed activity may have an effect on the reliability of flexibility tests.