Squatting works your legs and hips, but your lower back and abdominals also are heavily taxed. The act of supporting a heavy bar on your upper back takes lower back and core strength combined with good technique to avoid soreness. Modify your technique, strengthen key muscles and increase your flexibility to limit the pain you experience following squatting. Consult a health care practitioner before beginning any strength training program.
The angle of your knees and hips depends on bar placement, all of which have an effect on your lower back when squatting. The greater the degree of rotation, or forward lean, at your hip joint, the more your lower back is going to work. Low-bar squatting greatly increases both the activity and strain at your hip joints. So, by squatting with the bar higher, yet still not on your neck, you can avoid additional lower back stress. Ensure that your lower back is flat or arched, and never round your back when squatting.
As your lower back is heavily involved in squatting, regardless of bar position, your muscles must be strong to support a heavy squat. Strengthen your lower back with good mornings. Hold the bar on your back and have your feet in the same position you use to squat. Arch your back and lean forward with your knees slightly bent. Continue to lean forward until your torso is parallel to the ground or you are in danger of your back rounding, then straighten up. Perform no more than eight repetitions per set, but never go to muscular failure on this exercise.
Your core supports you when squatting and keeps you from collapsing forward. Weak abdominals can result in more lower back stress as the muscles of your back must work to compensate for this weakness. Whether your choose to perform heavy, weighted situps and crunches to strengthen your abdominals, planks and side planks to strengthen your entire core, or weighted side bends to target your obliques, perform your core exercises to failure. By working until you cannot perform another rep at that weight while still maintaining your form, you build the strength and endurance these muscles need to support your body during squats.
If your hamstrings are lacking flexibility, they will pull your tailbone under you at the bottom of your squat. This causes your lower back to round and places a good deal of stress on your lumbar vertebrae. Lengthening your hamstrings can help you keep good form throughout your squat. Start with a brisk 5 minute walk or jog. Then, lie on your back. Wrap a towel around your right leg or foot, and grasp the ends of the towel in each hand. Straighten your right leg and bring it as close to your torso as possible by pulling gently on the towel. You should feel a stretch in the back of your leg. Hold the position for about 20 seconds. Then, stretch the left leg in the same fashion. Repeat the stretch on both legs two more times.