Support Moment Distribution While Squatting With Different Depths and Percentages One Rep Max

Squatting to different depths or with different loads changes the demands on the neuromuscular system, thus potentially altering training effects. Previous studies have used EMG to assess joint contributions with various depths or loads. Another method for assessing this is to examine how each joint contributes to the total support moment (Ms) during the squat. PURPOSE: Examine how hip, knee, and ankle contributions to Ms change with increasing squat loads and depths. METHODS: 19 females (age: 25.1 ± 5.8 year; squatting experience: 3.8 ± 2.6 years) participated in this study. Participants performed squats at above parallel (AP), parallel (P), and below parallel (BP) depths with 0%, 50%, and 85% of a measured 1 rep max. Kinematics were recorded using a 12-camera motion capture system while ground reaction forces were measured with two force plates. Joint moments at the ankle, knee, and hip were summed to calculate Ms. Differences between depths and loads in peak Ms and the percent each joint contributed to peak Ms were evaluated using a 3x3 repeated measures ANOVA. RESULTS: Peak Ms increased as load increased (0%: 2.2 ± 0.3 Nm/kg, 50%: 3.1 ± 0.2 Nm/kg, 85%:3.8 ± 0.1 Nm/ kg, p<.001), but not as depth increased (p=.149). There was a significant depth*load interaction for hip contributions to Ms (p=.013), with hip contributions increasing with heavier loads for AP and P depths, but not BP (Figure 1A). There was also a depth*load interaction for knee contributions to Ms (p=.046). However the opposite pattern was displayed. As load increased, knee contributions to Ms decreased for the AP and P depths, but not BP (Figure 1B). Ankle contributions to Ms did not change with depth (p=.483) or load (p=.581). CONCLUSION: Total demand on lower extremity joints increases with increasing load but not depth in the back squat. At AP and P depths, increasing load involves the hip musculature more and the knee musculature less. At deep depths changing load does not impact how much each joint contributes to Ms.FIGURE 1: Percent contributions to total support momment at different depths and loads for the hip (A) and knee (B).