Kinematics of the double-leg-lowering test for abdominal muscle strength

Prospective descriptive study. To investigate the kinematics of the double-leg-lowering (DLL) test of abdominal muscle strength. Adequate strength of the abdominal muscles is necessary for many household, occupational, and sports activities. Therapists, therefore, need valid measures of abdominal muscle strength. A convenience sample of 17 subjects (7 women, 10 men) was tested. Using reflective spheres to identify specific body segments, subjects were videotaped while performing DLL under 2 conditions: attempting (controlled) prevention of anterior pelvic tilting versus not attempting (uncontrolled) prevention of anterior pelvic tilting. Videotape was analyzed using the PEAK 5 2-dimensional system. The pelvis tilted anteriorly by the time the extremities were lowered a mean 3.6 degrees, regardless of condition. No significant difference in anterior pelvic tilting was associated with the 2 DLL conditions (F = 2.95, P = 0.105) but pelvic tilting did increase significantly as the lower extremities were lowered from vertical (F = 98.41, P < 0.001). There appears to be a natural tendency for the pelvis to tilt anteriorly from very early in the DLL maneuver. As healthy young subjects do not appear able to prevent the tilting, the scoring system associated with the DLL test should be questioned.