Both barbell back squat variations are highly effective for building strength and size in the lower body muscles. In general, the low-bar squat emphasizes the posterior chain, including the hamstrings, glutes, and lower back, due to the bar position being further down on the back. This position requires a greater forward lean, which engages the hamstrings to a greater extent to help control the movement and decelerate the body during the descent phase. The high-bar squat typically places more emphasis on the quadriceps, with less activation of the hamstrings than the low bar back squat. The high-bar squat position is higher on the back, which allows for a more upright torso position and places more stress on the knee joint and quadriceps. The activation of specific muscle groups during a barbell back squat varies depending on individual biomechanics, technique, and training status.