Back muscles are the same as all other muscles in the body in that they require exercise to remain strong. Regular day-to-day activities such as walking and climbing stairs do not work the lower back adequately and the absence of exercise will lead to weak back muscles, according to Spine-Health.com. Doing regular strengthening exercises that target the lower back may help prevent injury and lower back pain.

Leg Raises

1. Lie flat on your back on an exercise mat with your legs straight and lifted a couple of inches off the floor. Use your abdominal (stomach) muscles and hip flexors (hip muscles) to raise your legs while keeping the knees straight to a 90-degree angle and then slowly let them back down without letting them touch the floor. This exercise will work your abdominal muscles as well as strengthen the lower back, according to MyFit.ca.
   
   Get a spotter to assist you if you want to increase the intensity. When your legs reach the highest point, a spotter standing behind you can grab your ankles and throw your feet toward the floor adding significantly to the resistance since you will be trying to slowly lower your legs. Start with one set 10 leg raises and work your way up to five sets of 10.
   

   The Swim

2. Lie flat of your stomach with your arms and legs extended away from you. Imagine you are swimming. Lift your chest and head off the mat and lift one arm and one leg (on opposite sides) at the same time and then alternate. Raise the arm and leg as high as you can and hold this position for about two seconds before alternating to the other arm and leg. Draw in your abdominal muscles while you do the exercise, inhaling to lift the limbs and exhaling to let them down, according to Pilates-Back-Joint-Exercise.com. Start with one set of 10 repetitions and work up to five sets of 10.
   

   Barbell Rows

3. If you have access to a rowing machine, this exercise is excellent for toning lower back muscles. In a seated position, grip the handles of the rower with a straight back and your legs bent slightly at the knees. Pull the weight from the handles into your body and pull your shoulder blades as far back as you can while keeping your back straight.
   
   Slowly return the handles to the forward position, feeling your lateral muscles in your back stretch as you move back to the starting position. Inhale as you pull and exhale as you release. Start with one set of 10 repetitions and increase to five sets of 10.
   

   Back Extensions

4. Lie face down on a hyperextension bench (this is the kind of bench where your torso hangs off the front) and hook your ankles under the pads for support. Place your arms across your chest and raise your body until it is perpendicular to the floor. Hold the position for a couple of seconds, and then slowly return to a relaxed position with your head hanging toward the floor. This exercise isolates the lower back muscles and can be intensified by holding weights in your hands. Start with one set of 10 repetitions and increase to five sets of 10.