Does leg predomination affect measuring vasti muscle onsets during single leg squatting? A reliability study.

INTRODUCTION: Although measuring vasti muscle onset may reveal whether pain relief is associated with altering this parameter during activities in subjects with patellofemoral pain syndrome (PFPS), it may be necessary to determine whether the inherent properties of the dominant leg influences the reliability of measuring VMO-VL muscle onset. The aim of the present study was to examine the effect of leg predomination on reliability testing of the VMO-VL muscle onset measurement during single leg squatting in healthy subjects.

METHODS: The onset of VMO and VL muscles of ten healthy subjects with a right dominant leg was assessed during single leg squatting. Data was collected from the muscle bellies of the VMO and VL. This procedure was performed on the both legs, during three separate single leg squats from a neutral position to a depth of approximately 30° of knee flexion. Subjects were then asked to repeat the test procedure after a minimum of a week's interval. The full wave rectified onsets of VMO and VL were then calculated.

RESULTS: There was no significant difference between the VMO-VL onset mean values of paired test of right and left knees. The ICC (intra class correlation coefficient) values during within and between sessions tests showed the poor reliability of these measurements on both knees.

CONCLUSION: The low intratester reliability of within and between sessions measurement of VMO-VL onset on the both dominant and non-dominant legs revealed that repeatability of these measurements have little accepted reliability, however similar values of these measurements indicated that leg predomination does not affect the measurements during single leg squatting.