To strengthen your back -- the most commonly injured part of the body -- it's important to condition both the muscles in it and the ones that support it, notably the abs.
Here are four moves to boost back fitness:
For the bird dog, start on your hands and knees. Tighten your abs and simultaneously lift your right arm and your left leg until they're in line with your back. Keep them straight as you hold for 15 seconds, then gently return to the start position. Do 10 reps, then switch sides and repeat.
The plank works your back, abs and glutes. Lying on your stomach, bend your elbows to support your upper body on your forearms. Tighten your abs and glutes and turn your toes under, then lift your body off the ground. Keeping your back straight, hold for a count of 10. Slowly return to the start position, rest 30 seconds, and repeat.
Side planks are a great variation. Lie on your left side, with your left elbow bent, forearm on the floor for support. Tighten your abs and glutes and lift hips off the ground, so that your body forms a 45-degree angle with the floor. Keep your back straight and avoid scrunching your shoulders as you hold for a count of 10. Work up to a total of 10 reps, then switch sides and repeat.
To finish, sit up straight on a stool and bring your shoulder blades together. Hold for five seconds, relax and repeat five to 10 times.
Do this series every other day to start. As you become stronger, aim for two sets of 10 reps on four or five days each week and ultimately two or three sets every day.
The American Academy of Orthopaedic Surgeons has more information and a downloadable spine-strengthening guide for back conditioning with these and other exercises.