The pelvic tilt works to strengthen the muscles of your lower back and also improves your hips' flexibility. This exercise begins with you lying on your back with your knees bent and your feet flat on the floor about as far apart as your hips. At this point the small of your back will be off the floor. Tighten your back and abdominal muscles so that the small of your back is pressing into the floor (causing your pelvis to tip forward). Hold for 12 seconds and then relax. To relieve back spasms, do this exercise five times.
Leg raises are a great exercise for relieving back spasms because they can help strengthen and loosen up the muscles of the back without putting too much strain on them. First lie on your stomach. Then tighten the muscles in one of your legs to raise it from the floor, keeping the leg straight as you raise it---you should also feel the muscles in your back tense as they help support the muscles of your leg. Keep the leg straight and up in the air for 10 seconds, and then slowly lower it back to the floor. Repeat with the other leg. Alternate between legs until you have raised each leg five times.
Knee raises are another exercise that is good for lower back spasms as they will help stretch and loosen the muscles of the back. Much like the pelvic tilt, begin this exercise lying on your back. Extend both legs out on the floor in front of you. Next, slowly bring your left knee as close to your chest as you can, using your arms to gently pull it toward your torso if you need to. Hold this pose for 15 seconds, making sure that you can feel your lower back muscles stretch. Slowly bring your left leg down to the floor and do the exercise using your right knee. Do this 10 times with both legs.