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Quote: “In order to be wealthy, you must be healthy”

Does the leg press and hack squat place less stress on the back than regular squats?

No, both machines can impose more harmful stress on the spin than proper squatting! The user has the ability to rely more on the machine than their capabilities for spinal stability. Back strength is a major limiting factor in performing a squat, where it is not so in the hack squat or leg press. The users whose legs are equipped to handle high loads on these machines, but whose backs are much weaker in relation to the legs, can become especially susceptible to back strain. Also, the user tends to allow the load to move too far down creating an extremely rounded lumbar spine.

The rigid movement, 2 linear path of direction and diminished use of stabilizing muscles (stomach, back and deep segmental rib cage muscles) create strong legs and a weak core. This leads the user to build deceptively strong legs but a weak mid section due to the fact that they are lying down supported against a back support or standing up against a back support and not engaging the core muscles. “You are only as strong as your weakest link”, further more it does not allow you to allow for natural spinal curvature, which supports your spine, and back more safely.

The natural curvature of the spine has been shown to reduce stress and compression of the vertebrae disks. When the spine is fixed in an unnatural straight position, this although supported by external factors (back support) will not automatically decrease spinal strain and compression. Additionally, the extreme rounding of the lower back in the descending position tends to extremely stress the vertebrae. The spine is designed to have a natural curve enforcing a rigid straight back support to help support the spine actually hinders support of the spine. A rigid back support will not only create a less natural curvature of the spine but it will disengage the surrounding stabilizing muscles that are strong bridges to supporting the spine.

The spine and the body were made to work together relying on artificial supports may hurt you more than help you! Using the leg press and hack squat machines may be harming you more than helping you!  

By: J. D. Reber M.S. & B.S. Exercise Science, CSCS & NASM- CFT

References:

Dr. Mel Siff Facts and Fallacies of Fitness 2003, 55,66
Essentials of Strength and Conditioning 2 edition 2004 48,49

Remember, eat healthy and live wealthy!

Personal training in Lenox, MA