1. In order not to injure the spine – always keep it slightly bent in the waist area. Do not relax the psoas muscles until you lower the barbell onto the stops. Rounding the back reduces the effectiveness of the exercise and increases the risk of injury.
2. Throughout the entire set, the press should be tense. This greatly simplifies keeping the torso in a stable position and eliminates its swaying. However, do not overdo it: by excessively straining the press, you will reflexively begin to round your back.
3. Squatting and straightening up, the main thing is not to tear your heels off the floor. Squatting on your toes, you lose stability and run the risk of twisting the knee joint (it will be very much pushed forward). At the bottom, the knees should not “go beyond” the toes.
4. The depth of the squat is determined solely by how much you have enough strength to withstand the natural curve of the back and not separate the heels from the floor during the squat with the barbell. If you feel your spine starting to round and your heels off the floor, don’t squat down.
5. If the gap between the feet is slightly less than or equal to the width of the shoulders, then the center of the load is brought to the quadriceps and they are involved much more than the muscles of the back of the thigh. But this position of the legs requires excellent plasticity of the hip joint and the Achilles tendon (otherwise you will not be able to lower the hips to the floor level). If your feet are more than shoulder-width apart, you can squat with enormous weight and not worry about hip flexibility. However, the main muscles involved here are the muscles of the back of the thigh, not the quadriceps.