Can Leg Curls Affect Your Low Back?

The hamstrings are often neglected in favor of exercises that target the quadriceps. This can result in a muscle imbalance between the hamstrings and quadriceps, contributing to knee instability and risk of injury. The leg curl exercise is an important component of a lower leg routine as they strengthen the hamstrings. If performed correctly, leg curls do not affect the low back, but if performed incorrectly, leg curls can cause low back pain and possibly injury.

Muscles Worked

If you perform the leg curl exercise with proper exercise form, it does not involve the muscles of the low back. The hamstrings are the main movers. The gastrocnemius, the largest calf muscle, and several small muscles in the thigh, including the sartorius, gracilis and popliteus, are secondary movers. The rectus femoris, a large muscle in the front of the thigh, and the anterior tibialis, the muscle along the front of the lower leg, are stabilizers during the leg curl exercise.

Leg Curl Technique

You can perform the leg curl in a standing, seated or lying position. If done improperly or with too much weight, any version of the leg curl exercise can cause low back pain, but lying leg curls are the most common culprits. Lying on your stomach, it is easy to arch your back and lift your hips off the pad to help curl the weight. But this is exactly what you shouldn't do. Your hips, thighs and torso should remain stationary during the leg curl exercise. Curl your feet toward your buttocks as far as is comfortable. Pause for a count before slowly lowering the weight back to the starting position.

Low Back Involvement

If you arch your low back to help curl the weight up, the low back muscles become involved in the leg curl exercise. Your back should remain neutral with a natural lordotic, or inward, curve in the lumbar spine. If you feel your low back excessively arching, you are probably using too much weight. The hamstrings are not as powerful as the quadriceps so do not use the same weight you use for the leg extension exercise. Aim for hamstring strength equal to about two-thirds the strength of your quadriceps.

Hyperextension Pain

Excessively arching, or hyperextending, the low back, especially under a heavy load, can cause low back pain and possibly injury. According to the University of Maryland Medical Center, athletes and weightlifters who place excessive stress on the spine due to hyperextension, have higher risk spondylolysis, a spine condition that can cause chronic low back pain. Always use correct form when performing leg curls or any resistance exercise.