To calculate leverage on the lower leg during a squat, one must consider the effective lever arm of the quadriceps, which varies with knee flexion angles and is approximately 5 cm. The external torque can be determined using ground reaction forces or knee position, although some prefer to focus on force distribution through trigonometry. There are concerns about the realism of the movement model being applied, as it may not accurately reflect practical scenarios. The discussion highlights the complexity of biomechanics in squatting and the challenges in understanding the forces involved. Overall, calculating these dynamics requires a careful analysis of various factors influencing the squat.