Squatting Exercise. The EMG activity of the VMO, VL, and ADD musculature
was recorded while subjects performed 10 consecutive squats. Subjects performed
the repeated squatting motions against gravity from full extension to 90° of knee
flexion. The squatting exercises were performed by having the subject place his/her
back against a physioball (diameter = 55 cm diameter) on the wall in an attempt
to eliminate friction between the subject and the wall and to control upper body
positioning. The feet were placed hip-width apart (distance measured from ASIS
to ASIS) in neutral tibial rotation (tibial tuberosity facing anteriorly) to standardize
subjects foot positioning. Subjects were instructed to keep the arms in 90° of
shoulder fl exion, elbows extended, and maintain the torso in an upright position
while performing the squat exercises (Figure 1).