Barbell squats in CrossFit athletes: the effects of load and footwear type on trunk flexion and lower limb joints torques at the peak of total support torque

We examined the effects of barbell load and footwear type on hip, knee, and ankle joint torques during barbell squats in CrossFit athletes. Sixteen participants performed squats at 50%, 70%, and 90% of their 3-repetition maximum, wearing either weightlifting shoes or conventional footwear. Kinematic and kinetic data were captured using a three-dimensional analysis system, enabling the calculation of joint torques and trunk flexion angles at the instant of peak total support torque. Peak total support torque increased with load in both footwear conditions, with no interactions between footwear type and load observed for peak total support torque or individual joint contributions. Regardless of load, weightlifting shoes resulted in a lower hip torque contribution (p = 0.017) and a higher knee torque contribution (p = 0.024) compared to conventional shoes. As load increased, knee torque contribution decreased (p < 0.001), while ankle torque contribution increased (p = 0.025), accompanied by, on average, small increases in trunk flexion angle. Peak total support torque and peak trunk flexion did not coincide, potentially explaining the modest effects of load and footwear type observed. Analysis throughout the entire squat cycle is needed to fully understand joint contributions, aiding in optimizing squat techniques and footwear choices.