Knee Angle Effect on Pressure Distribution during Weighted Squats in Female Sprinters

October 14, 2015 / By: Harris, M., Duoos, B.

Weighted squats are commonly performed to enhance performance in various sports; however, improper lifting technique may increase the probability of injury, including lower back pain.  Balance loss during lifting may cause excessive vertebral column load when using the squat technique as compared to the stoop technique. Evaluating pressure changes over the forefoot (FF), mid-foot (MF), and rear-foot (RF) while performing weighted squats (W) may reveal important pressure distribution information regarding proper lifting technique. This information can lead to recommendations which may result in decreased risk of injury.

Purpose: To determine the relationship between knee joint angles during squats with and without weight (NW) and pressure distribution in the feet.

Methods: Eleven Division III female track and field  sprinters (age:19.545 ±0.820 yrs.; ht:167.35±­3.89 cm.; wt:57.850±2.325 kg.) who actively participate in the team’s weight lifting program  performed one set of three reps of weighted squats at three different knee angles (120,90,45°) with a 45 lb. bar (NW). A second set followed with additional weight resulting in a total of 95 lbs. (W).

Results: Data collected proved that additional weight added during squats contributes to a significant increase in mean peak pressure (PP) throughout the feet, Left (L) vs. Right (Rt) insole.  At 120º PP for WLRF vs. NWLRF was significant (170.0±119.5 vs. 47.5±40.0, p=0.014).  At 120º PP for WLMF vs. NWLMF was significant (99.3±77.5 vs. 27.5±15.3, p=0.036). At 120º PP for WRtFF vs. NWRtFF (131.4±40.4 vs. 76.6±26.2, p=0.002) was significant. At 90º PP for WRtFF vs. NWRtFF (166.6±101.1 vs. 54.8±42.2, p=0.006) was significant. At 90º PP WLMF vs. NWLMF (109.3±84.8 vs. 24.5±25.5, p=0.033) was significant. At 90º PP WRtMF vs. NWRtMF (117.3±96.6 vs. 22.7±20.5, p=0.037) was significant. At 90º PP for WLFF vs. NWLFF (160.5±94.8 vs. 77.1±41.3, p=0.025) was significant. At 45º PP for WRtRF vs. NWRtRF (171.6±132.0 vs. 53.4±27.7, p=0.046) was significant.  At 45º PP for WLFF vs. NWLFF (200.2±112.5 vs. 91.7±64.0, p=0.019) was significant. At 45º WRtFF vs. NWRtFF (211.4±121.8 vs. 81.2±64.3, p=0.010) was significant.

Conclusion: Weight added during weighted squats increased mean PP in the FF at 45° and at all three knee angles (120°, 90°, 45°) NW vs. W in the left vs. right insole.