The effect of the squat exercise on anterior-posterior knee translation in professional football players.

Although the squat exercise is considered essential for optimal athletic performance, controversy exists regarding the effect on knee stability. The purpose of this prospective study was to determine the effect of squat exercises on in vivo knee joint stability of professional football players. Thirty-two subjects with normal knees participated in a 21-week off-season training program. Subjects performed power squat exercises with barbell loads of 130% to 200% body weight twice weekly. Both knees of each subject were tested by a single examiner with a knee ligament arthrometer before the training program and at 12 and 21 weeks. Passive displacements were recorded at 67, 89, and 133 N with the knee at 30 degrees and 90 degrees of flexion. Active testing was performed with the knee in the same positions. Student's paired t-tests were used to compare pre- and postexercise measures. For all subjects, no significant differences were found between pre- and postexercise results for active and passive tests. Of the 2440 measurements taken, only 8 demonstrated increased excursions greater than 2 mm. This study demonstrates no significant increases in anterior-posterior tibiofemoral translation in athletes using the squat exercise as part of their off-season training program.