Context: The active-knee-extension test (AKE) and the straight-leg-raise test (SLR) are widely used for flexibility assessment. A number of investigations have tested the reliability of these measures, especially the AKE. However, in most studies, the sample involved subjects with normal flexibility. In addition, few studies have determined the standard error of measurement (SEM) and minimal detectable difference (MDD), which can provide complementary and more clinically relevant information than the intraclass correlation coefficient (ICC) alone.
Objectives: This study aimed to determine the AKE and SLR intrarater (test-retest) reliability in subjects with flexibility deficits, as well as the correlation between the 2 tests.
Design: Reliability study, test-retest design.
Setting: Academic laboratory.
Subjects: 102 recreationally active participants (48 male, 54 female) with no injury to the lower limbs and with flexibility deficits in the hamstrings muscle group.
Main outcomes: Intrarater reliability was determined using the ICC, complemented by the SEM and MDD.
Measures: All participants performed, in each lower limb, 2 trials of the AKE and the SLR.
Results: The ICC values found for AKE and SLR tests were, respectively, .87-.94 and .93-.97. The values for SEM were low for both tests (2.6-2.9° for AKE, 2.2-2.6° for SLR), as well as the calculated MDD (7-8° for AKE; 6-7° for SLR). A moderate to strong, and significant, correlation between AKE and SLR was determined for the dominant limb (r = .71) and the nondominant limb (r = .67).
Conclusions: These findings suggest that both AKE and SLR have excellent intrarater reliability. The SEMs and MDDs recorded are also very encouraging for the use of these tests in subjects with flexibility deficits.
Keywords: flexibility assessment; hamstrings; intraclass correlation coefficient; standard error of measurement; minimal detectable change.