Are flexibility and muscle-strengthening activities associated with a higher risk of developing low back pain? (2013)

The researchers followed 4610 adults and compared their exercise program and incidence of low back pain over an average of 4.9 years.

Quotes from the study:
“CONCLUSIONS: In this sample, stretching or use of weight training machines is associated with increased risk of developing low back pain compared to use of free weights, calisthenics or exercise classes.”

“Our data show that participants, who report regular stretching were at a greater risk of developing low back pain than those who did not.”

“We found participants who regularly used weight training machines were at a higher risk of developing LBP, but this association was not found in people who used free weights”

“One argument often given in favor of free weights over machines is that it allows not only for the development of the main target muscle group, but also surrounding stabilizing muscles, such as those in the back and abdomen. However, when using machines, the ROM is defined by the machine, providing isolation of the movement in one plane, meaning the deep paraspinal stabilizing muscles may not be engaged as much as they are with free weights, and subsequently underdevelop.”

Chad’s comments:

For the most part this study agrees with my observations. I put it under the category of vindication that I was right and others wrong when I was a physical therapy student in the 90s. The researchers cite muscle cytoskeleton damage as why they think the stretching leads to increased low back pain, but my feeling is that modern society puts people in repeated and prolonged spine flexion, which over time leads to degenerative disc disease. Most stretching programs either purposely or accidentally put people into further spine flexion, repeatedly, worsening the condition. So I don’t doubt that stretching programs increase the risk of low back pain, particularly if they are stretching the spine itself. I just don’t see many patients complaining of low back pain that I would diagnose with cytoskeletal muscle damage. The general theme of flexibility of the spine causing more harm is in accordance with lumbar spine researcher Stuart McGill’s recommendations, which I am also largely in agreement with.

As for their rationale as to why machine training led to increased incidence of low back pain while free weights did not, I think the researchers are pretty close to the mark. I would add that unlike most machines, free weights generally require you to coordinate many joints together using the body as a single unit, such as in a squat or deadlift. With good technique, this imparts not just strength and endurance but also better motor control of the spine, all of which are protective. Furthermore, most abdominal weight machines require repeated spine flexion or twisting, both of which have been shown to be pathologic stresses to the spine. These muscles are better strengthened isometrically which happens both explicitly and implicitly with a lot of free weight exercises. Certain weight machines in my opinion are often very useful and can play a role in everyone’s fitness program but the advantages and disadvantages of their use should be kept in mind and they are probably best worked into a program combined with free weight exercises for optimal function.

Likewise I do think some stretching has its place, but it should not be a foundation of one’s exercise program. People fall and break hips because they are not strong enough to prevent the fall. Generally nothing bad happens if you can’t bend over and touch your toes; plus, the posterior direction of herniation in peoples’ discs indicates that they bend forward too much as is and don’t need any special stretches in the same direction. Unfortunately many physical therapy clinics base their lumbar rehabilitation programs on traditional wisdom and start their patients with supine knees-to-the-chest stretches (which is only more spine flexion) and posterior pelvic tilts (which are also more spine flexion), which is probably not the best thing to do. As they say, traditional wisdom is often long on tradition and short on wisdom.