Squats are one of the most functional and popular exercises performed for fitness and sports conditioning. But because squats incorporate multiple joints and muscles, faulty exercise technique can place undue stress on your low back. A few minor changes in execution can correct your form and take away the strain and pain.
Anatomy of a Squat
The squat is a compound exercise that involves muscle action at three separate joints. Muscles involved include the gluteus maximus that acts at the hip, the quadriceps and hamstrings that act at the hip and knee, and the posterior tibialis, gastrocnemius and soleus of the calf, and smaller muscles of the foot that act at the ankle. The abdominal and trunk extensor muscles are activated isometrically to stabilize the pelvis and protect the spine. When executed properly, coordinated contraction of the muscles will yield optimal results with minimal stress to your joints. Spinal alignment, bar position and execution speed are key factors that influence the compression forces placed on your lumbar spine during squats.
According to a 2010 review by Brad J. Schoenfeld, CSCS, published in the "Journal of Strength and Conditioning Research," the joints of the spine are the most vulnerable to injury during squatting. Avoid forward trunk flexion and maintain a normal lordotic curve in the low back, keeping your spinal column rigid throughout the movement. Look straight ahead or gaze slightly upward to reduce your tendency for unwanted forward flexion. Maintain a tight contraction of the abdominal and hip extensor muscles to stabilize the spine and pelvis.
Three common bar positions are low back, with the bar placed slightly below the acromion, a bony process at the top of the shoulder blade; high back, with the bar placed just above the acromion; and front, with the bar held in front of the clavicle, or collarbone. According to strength and conditioning specialist Brad Schoenfeld, when the bar is positioned on your back you experience greater forward lean of the trunk, placing more stress on your lumbar spine. Front squats produce less lumbar stress and may be a better alternative for individuals with back pain.
The speed with which you execute your squats has a direct correlation to the amount of stress placed on your joints, with faster speeds generating greater joint forces. On the spine, peak compression forces double when squats are performed rapidly. To reduce spinal stress, execute your squats slowly in both the upward and downward phases. Maintain control in the downward phase using a two- to three-second tempo.
Other factors that can compromise your squat execution and lead to back pain are muscle weakness, particularly of the abdominals and trunk extensors, poor flexibility that limits your range of motion, and muscle fatigue that can lead to faulty execution and injury. Balance out your training program by working your core muscles, stretching regularly, and getting plenty of rest between training sessions.