Does Restricting Anterior Movement of the Knees During a Barbell Back Squat Alter Lower Extremity Biomechanics?

Abstract

INTRODUCTION: The strength implications of the barbell back squat make it ideal for use in training programs, rehabilitation, and competition. Even though the back squat is an integral part of these programs, there are also concerns about injury risk due to improper biomechanics. Restricted squats (knees kept behind the toes) are noted to reduce joint loading at the knees but may not take into account added potential risks for the entire lower extremity. Unrestricted squats are more representative of natural movement patterns but may increase joint loading especially at the knees. Research has explored the biomechanics of back squats in elite, male populations, but has yet to investigate how back squat biomechanics differ between restricted and non-restricted squats in a female, recreationally-active population. PURPOSE: Therefore, the purpose is to determine how restricting the anterior movement of the knees during barbell back squats affects joint mechanics of the lower extremities in female recreational weightlifters. METHODS: 16 healthy, female, recreationally-active, weightlifters (mean  SD, age= 25.6 4.2 yrs; height= 170.4  8.3cm; weight= 63.8 8.3 kg) participated in this study. Biomechanical analysis of joint angles and moments were performed using a 3-D motion capture system and standard procedures (Motion Analysis Corporation, Santa Rosa, Ca). Participants performed 5 squats for each of the three squat conditions; natural (NS), knee over toe (KOT), and restricted (RS). The middle 3 squats were used for data processing. A repeated measures ANOVA was used to compare sagittal plane joint angles, lower extremity joint moments, net support moments, and the relative contribution of the individual joint moment to the net support moment, expressed as a percentage. An adjusted alpha value of α