From the study:
There is a high incidence of low back pain (LBP) associated with occupations requiring sustained and/or repetitive lumbar flexion (SLF and RLF, respectively), which cause creep of the viscoelastic tissues. The purpose of this study was to determine the effect of creep on lumbar biomechanics and facet joint capsule (FJC) strain. Specimens were flexed for 10 cycles, to a maximum 10 Nm moment at L5-S1, before, immediately after, and 20 min after a 20-min sustained flexion at the same moment magnitude. The creep rates of SLF and RLF were also measured during each phase and compared to the creep rate predicted by the moment relaxation rate function of the lumbar spine. Both SLF and RLF resulted in significantly increased intervertebral motion, as well as significantly increased FJC strains at the L3-4 to L5-S1 joint levels. These parameters remained increased after the 20-min recovery. Creep during SLF occurred significantly faster than creep during RLF. The moment relaxation rate function was able to accurately predict the creep rate of the lumbar spine at the single moment tested. The data suggest that SLF and RLF result in immediate and residual laxity of the joint and stretch of the FJC, which could increase the potential for LBP.
This study is largely confirmation that both sustained and repeated spine flexion decreases passive integrity of the spine. The take home message is that people with low back pain, and people that don’t want low back pain, should not sit prolonged in chairs with no lumbar support, should avoid stooped postures with a flexed spine (rounded back), should not exercise with movements into spine flexion (like situps, crunches, and stiff legged dead lifts) and should avoid stretches into spine flexion (like toe touches, posterior pelvic tilts, and knee to chest stretches). What they should do, and what I generally teach in physical therapy is the maintenance of a neutral spine while sitting with good support from chairs, proper adjustments of seating position while driving, and exercises to increase core and extremity strength all performed with the spine neutral and movement taking place at the hips and shoulders, rather than the waist. Exercises like standing cable rows and presses, mat exercises with a neutral spine, squats and RDLs. If the patient has too much pain for active exercise at first, I will start with electric muscle stimulation not just to the painful region but concurrently throughout the abdominal region which gives a 2 for 1 benefit of immediate pain reduction while improving core strength.
All of the above largely complements much of the Stuart McGill research that I am a fan of. However what was new to me was a citation that it is facet joint strain from flexion stretches that most likely contributes to muscle spasms. This agrees with my clinical observation that most often when you correct postures and improve core/hip motor control, strength and endurance, muscle spasms and “trigger points” go away. However if you just massage them or poke them with acupuncture or dry needling you are merely treating the symptom but not the cause, and if a physical therapist gives the patient typical spine flexion exercises like knee to chest and pelvic tilts, you are actively making the patient worse. What’s unfortunate is that I know a number of “back pain specialists” who still adhere to 1930s based Williams flexion exercises, and 1980s based McKenzie exercises (generally the latter part of his program only) both of which stretch the spine into flexion.
As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.
Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.