Here are nine back-strengthening exercises you can do at home -- stretching and flexion exercises to increase flexibility, and extension exercises to strengthen the muscles needed to counteract the force of gravity.

Most back pain is due to muscle weakness. Therefore, increased strength is the answer to almost every back problem. If you develop a back problem, chances are good that you will wind up on a regimen of daily stretching and strengthening exercises to recondition your back.

A back-strengthening program needs to work on both the muscles that pull the back forward and down (flexion exercises) and the muscles that lift your trunk into an upright position (extension exercises). You need strong, flexible muscles around the lower back and abdomen to stabilize your spine and protect it from injury. You can do all of these exercises at home.

Stretching and Flexion Exercises -- To strengthen an acutely injured back, start with stretching and flexion exercises. These exercises increase flexibility and strength in the hip and lower back and in the abdominal and buttock muscles.

• Knee Pull (Without/With Head Curl). Lie on your back with knees bent and feet flat on the floor. Bring one knee up toward your chest and clasp the knee with both hands. Hold for 10–15 seconds. Return the leg to the starting position and repeat with the other leg.
Start with three repetitions and then increase gradually by one every other day until you reach 12 repetitions. Once you can do that easily, add in a head curl. While you are holding your knee for 10–15 seconds, gently curl your head up slightly, then return to the starting position. Gradually work your way up to 12 repetitions.
• Hurdler Stretch. While standing, place a chair or bench about three feet in front of you. Put the heel of one foot on the seat of the chair or the bench. Now bend forward at the waist and move your forehead toward your knee. Hold for 10–15 seconds. Return to the starting position and repeat with the other leg. Start with three repetitions and then increase gradually by one every other day until you reach 12 repetitions.
• Modified Toe-touch. While standing with your feet hip-width apart, bend forward, bringing the top of your head toward the floor, and look backward between your knees. Go as far as you can and then grasp behind your knees and try to go a little farther. Hold for 10–15 seconds. Start with three repetitions and then increase gradually by one every other day until you reach 12 repetitions.
• Modified Toe-touch With Rotation. Stand with your feet hip-width apart and bend at the waist with your forehead in the direction of your right knee. Hold for 10–15 seconds. Stand up straight again and then lower your forehead toward your left knee. Hold for 10–15 seconds. Start with three repetitions and then increase gradually by one every other day until you reach 12 repetitions.
• Pelvic Tilt. Lie on your back with knees bent and feet flat on the floor. Relax your back muscles, tighten your abdominal and buttock muscles, and press your back flat against the floor. This will tilt your pelvis forward. Once you have a totally flat back, hold the position for 10–15 seconds. Start with three repetitions and then increase gradually by one every other day until you reach 12 repetitions.
• Abdominal Curl. Lie on your back with knees bent, feet flat on the floor, and your hands clasped lightly behind your head. Without pulling with your hands, slowly curl your shoulder blades up off the floor, leaving your back on the floor. Hold for five seconds and slowly lower your head and shoulders. Start with five repetitions, increasing the number by five as the curls get easier.

Extension Exercises -- As you become more comfortable and your back muscles begin to lengthen and strengthen, you can start extension exercises. Gravity naturally pulls the back forward and down. These exercises strengthen the muscles needed to counteract the force of gravity.

• Standing Back Extension. Stand up straight with your feet hip-width apart and arms at your sides. Slowly lean your upper body back from the waist. Try to look at the ceiling. Hold for 10 seconds, then relax and straighten up. Do five repetitions and gradually add stretches two at a time as this exercise becomes easier.
• Hip Extension. Lie on your back on a table with one leg hanging over the side. Gently lower the leg from the hip toward the floor. When you feel the stretch in your hip, hold for 10 seconds. If possible, have a partner gently push on your knee to increase the stretch. Return your leg to table height. Do five repetitions and repeat with the other leg. Add stretches two at a time as this exercise becomes easier.

• Reverse Sit-up. This involves working with a partner, who will have to hold down your legs. Lie on your stomach with only your legs and pelvis on a table. Keep your upper body horizontal in the air and let your hands hang down as you look at the floor. Have your partner hold your ankles while you bend down at the waist until the top of your head is pointing to the floor. Then slowly lift your upper body until it is horizontal again. Do five repetitions and add two at a time as this exercise becomes easier.