Flexion-Relaxation Response Returns with Treatment
Most people know it's better for their back to squat down than it is to bend (flex) over. Even so, most of us bend over to pick something up or to look in the refrigerator. Why? Because it's easier. Why is it easier? Because of something called the flexion-relaxation phenomenon (FR).

FR is the pattern of muscle activity in the back when bending over. First the muscles contract. But when the spine reaches a certain point, the muscles relax. At this point (the FR point), there is no muscle effort. The back is using ligaments to hold the position. People find that it's easier to hang on the ligaments than use active muscle control to hold a bent posture.

Scientists have known about FR since the early 1950s. They hope to find out enough about FR to use it during rehab for back injuries. This is the first study to show that people with chronic low back pain can get a normal FR back with treatment.

It turns out that full flexion motion of the low back occurs at FR. In this study patients who are work-disabled because of chronic back pain were tested for FR. The FR was compared to their range of motion measurements. All measures were taken before and after treatment.

The authors suggest that once a patient regains FR, rehab can move right into strength training and endurance. This will reduce costly and lengthy treatment programs. Suggestions were made for treatment to restore the FR. Doctors can also use FR in making decisions about disability ratings.
Randy Neblett, MA, LPC, BCIA-C, et al. Quantifying the Lumbar Flexion-Relaxation Phenomenon: Theory, Normative Data, and Clinical Applications. In Spine. July 1, 2003. Vol. 28. No. 13. Pp. 1435-1446.