RESEARCH
Muscle
Functional significance of Spinal Memory:
“It would appear protective to avoid loading immediately after a bout of prolonged flexion. In the occupational world this has relevance to ambulance drivers, for example, who drive to an accident scene without the luxury of time to warm up (or reset the passive tissues ) before lifting. They would be wise to sit with a lumbar pad to avoid lumbar flexion and the associated creep. The athletic world provides good examples as well, such as sitting on the bench before engaging in play. Those with sensitive backs would do well to avoid sitting on the bench with a flexed lumbar spine while waiting to perform.”
McGill , Stuart. Low Back Dissorders Eidence-based Prevention and Rehabilitation. 2. Champaign,IL: Human Kinetics, 2007.97
“Reduced reflex may indicate that the spine is less stable following prolonged flexion-relaxation and, therefore, susceptible to injury. The absence of recovery in reflex after a substantial time indicates that increased low back pain risk from flexion-relaxation may persist after the end of the flexion task.”
Ellen L. Rogers and Kevin P. Granata, Disturbed Paraspinal Reflex Following Prolonged Flexion-Relaxation and Recovery.
“The creep induced in the viscoelastic tissues of the spine as a result of cyclic loading desensitizes the mechanoreceptors within, which is manifest in dramatically diminished muscular activity, allowing full exposure to instability and injury, even before fatigue of the musculature sets in.”
Solomonow, Moshe PhD, MD(hon); Zhou, Bing-He EE; Baratta, Richard V. PhD; Lu, Yun MD; Harris, Mitchel MD Spine. 24(23):2426, December 1, 1999. 1999 Volvo Award Winner in Biomechanical Studies: Biomechanics of Increased Exposure to Lumbar Injury Caused by Cyclic Loading: Part 1. Loss of Reflexive Muscular Stabilization. (C) 1999 Lippincott Williams & Wilkins, Inc
Joint
“…Concluded that the increased progression of forces in the tissues of the lumbar intervertebral joints in the flexed seated posture would likely result in increased degenerative changes in these joints.”
Hedman TP, Fernie GR. Mechanical response of the lumbar spine to seated postural loads. Spine. 1997; 22: 734-743.
Disc
“Damage to the annulus of the disc (herniation) appears to be associated with fully flexing the spine for repeated or prolonged period of time. In fact, herniation of the disc seems almost impossible without full flexion. This has implications for exercise prescription particularly for flexion stretching and sit-ups or for activities such as prolonged sitting, all of which are characterized by a flexed spine. Some resistance exercise machines that take the spine to full flexion repeatedly must be reconsidered for those interested in sparing the post annulus portions of their discs. Furthermore the mechanism by wich the process can be interrupted appears to be postural dependant, providing more insight into the mechanism of the Mckenzie approach.”
McGill, Stuart. Low Back Dissorders Eidence-based Prevention and Rehabilitation. 2. Champaign,IL: Human Kinetics, 2007.47
“Clearly Herniations are a function of repeated full-flexion motion cycles.”
McGill, Stuart. Low Back Dissorders Eidence-based Prevention and Rehabilitation. 2. Champaign,IL: Human Kinetics, 2007.46
“We have found that the herniation process begins from failure in the innermost annulus rings and progresses radially outward. The layers of the annulus delaminate and fill with nucleus material . We now have proof that the extended posture can drive the nucleus material that is in the delaminated pockets of the posterior nucleus back tward the central part of the disc.”
Scannell, J., and McGill,S.M.(2005) Spinal Disc Prolapse caused by flexion can be reduced by extension: an into study of disc mechanics. Canadian Biomaterials Society, Waterloo: May 26-28.
“It would appear that the disc must be bent to the full end range of motion in order to herniated.”
Adams ,M.A., and Hutton,W.C. Prolapsed intervertebral discs: A hyperflexion injury Spine,7:184
“Disc herniation is associated not only with extreme deviated posture, either fully flexed or bent, but also with repeated loading in the neighborhood of thousands of times, highlighting the role of fatigue as a mechanism of injury.”
Gordon,S.J., et al.(1991)Mechanism of Disc Rupture- a preliminary report. Spine 16:450
“Epidemiological data link herniation with sedentary occupations and the sitting posture.”
Videman, T.,Nurminen,M., and Troup, J.D.G.(1990) Lumbar spinal pathology in cadaveric Material in relation to history of back pain, occupation and physical loading. Spine,15(8):728
Creep
“Connective tissues demonstrate properties of extensibility. The dense regular connective tissues are viscoelastic displaying both viscous and elastic rheologic properties with both time and frequency dependent properties.”
Wainwright SA, Biggs WD, Curry JD, Gosline JM. Mechanical design in organisms. London: Edward Arnold, Princeton University Press;1976. Dorrington K. In: Vincent JFV, Currey JD,eds. The theory of viscoelasticity in biomaterials. 1980: 289-314 Cambridge University Press.
“Mechanical creep, defined as elongation of tissue beyond it’s intrinsic extensibility resulting from a constant load over time.”
Wilhelmi BJ, Blackwell SJ, Mancoll JS, Phillips LG. Creep vs. Stretch: A review of viscoelastic properties of skin. Ann Plast Surg. 1998; 41:215-219
“A property common to extensible soft tissues is that they become stiffer as they are extended due to the reorientation of collagen fibers. A stretch of a magnitude of 3-8% causes tearing and inflammation while applying a lesser stretch of 1-1.5% (load deformation) will have a similar affect.”
Currier DP, Nelson RM. Dynamics of human Biologic Tissues Philadelphia:FA Davis Co; 1992
“Sitting with the back slouched for as little as 20 minutes can result in increased laxity of the posterior spinal ligaments. It may take 30 minutes or more for these ligaments to regain their previous level of stiffness.”
McGill SM, Brown S. Creep response of the lumbar spine to prolonged full flexion. Clinical Biomechanics. 1992; 7: 43-46.
“It was concluded that sustained static or cyclic loading of lumbar viscoelastic tissues may cause micro-damage in the collagen structure, which in turn reflexively elicit spasms in the multifidus as well as hyperexcitability early in the recovery when the majority of the creep recovers. The micro-damage, however, results in the time dependent development of inflammation. In all cases, the spasms, initial and delayed hyperexcitabilities represent increased muscular forces applied across the intervertebral joints in an attempt to limit the range of motion and unload the viscoelastic tissues in order to prevent further damage and to promote healing. It is suggested that a significant insight is gained as to the development and implications of a common idiopathic low back disorder as well as to the development of cumulative trauma disorders.”
M. Solomonow, a, R. V. Barattaa, B. -H. Zhoua, E. Burgera, A. Zieskeb and A. Gedaliac Muscular dysfunction elicited by creep of lumbar viscoelastic tissue_a Occupational Medicine Research Center, Bioengineering Laboratory, Department of Orthopaedic Surgery, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA_b Department of Pathology, Louisiana State University Health Sciences Center, New Orleans, LA
70112, USA_c Departments of Pediatrics and Rheumatology, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA _Received 24 July 2002; revised 14 November 2002; accepted 19 November 2002. ; Available online 22 May 2003.
“Static flexion of the lumbar spine with constant load applied to the viscoelastic structures for 20 minutes and for 50 minutes resulted in development of spasms and inhibition in the multifidus muscles (e.g., deep erector spinae) and in creep of the supraspinous ligament in the feline model. The development of spasms and inhibition was not dependent on load magnitude. It is suggested that occupational and sports activities which require prolonged static lumbar flexion within the physiological range can cause a “sprain”-like injury to the ligaments, which in turn reflexively induce spasms and inhibition in some erector spinae muscles. Such disorder may take a long time to recover, in the order of days to weeks, depending on the level of creep developed in the tissues.”
M. Solomonow, , B. Zhou, R. V. Baratta, M. Zhu and Y. Lu Neuromuscular disorders associated with static lumbar flexion: a feline model _Occupational Medicine Research Center and Bioengineering Laboratory, Department of Orthopaedic Surgery, Louisiana State University Medical Center, New Orleans, LA 70112, USA _Received 12 April 2001; revised 16 August 2001; accepted 28 September 2001 Available online 28 November 2001.