The stress-strain relationships of human spinal ligaments and\u00a0 muscles indicate that the spinal musculature play a major role in spine\u00a0 stability (1, 2). Low-loading rate, quasi-static assessments of\u00a0 posteroanterior (PA) spinal stiffness have correlated increased PA spine\u00a0 stiffness to voluntary contracture of the lumbar extensor muscles (3,\u00a0 4), No study, however, has examined the contributions of lumbar extensor\u00a0 muscle and high-loading rate dynamic PA spinal stiffness. The objective\u00a0 of this study was to quantify PA dynamic spinal stiffness at rest and\u00a0 during maximal voluntary contraction (MVC) efforts in patients with LBP.\u00a0 Twenty-two consecutive patients with LBP underwent dynamic spinal\u00a0 stiffness assessment in the prone resting position and during lumbar\u00a0 extensor muscle MVC, A hand-held Activator Adjusting Instrument equipped\u00a0 with an impedance head was used to deliver high-loading rate( < 0,1\u00a0 msec) PA manipulative thrusts (450 N) to the L3 spinous process for\u00a0 spinal stiffness assessment using a previously validated technique (5).\u00a0 Surface, linear enveloped, electromyographic (sEMG) recordings were\u00a0 obtained during the thrusts from electrodes (8 leads) located over the\u00a0 L3 and L5 erector spinae and data was normalized to subject individual\u00a0 MVC\u2019s. The accelerance (peak acceleration\/peak force, kg-1) or stiffness\u00a0 index was calculated for each of the thrusts and compared for the\u00a0 resting and active MVC trials using a 2-tailed, paired t-test. A\u00a0 significantly increased spine stiffness index (8.36%) (P=0.012) was\u00a0 found upon MVC trials compared to prone resting stiffness indices.\u00a0 Lumbar spine extensor MVC contributes to increased PA lumbar spine\u00a0 stiffness. These findings corroborate the findings of others and add\u00a0 support to the significance of the trunk musculature in providing spinal\u00a0 stability.<\/p>\n
Reference:<\/strong> Christopher J. Colloca, D.C.1<\/sup>, Tony S. Keller, Ph.D. 2<\/sup> Daryn E. Seltzer, D.C.3<\/sup>, Arlan w. Fuhr, D.C.1<\/sup>;\u00a0 Muscular and Soft-Tissue Contributions of Dynamic Posteroanterior\u00a0 Spinal Stiffness; Proceedings of the International Conference on Spinal Manipulation,\u00a0 Bloomington, MN September 21-23,2000.<\/p>\n 1<\/sup> Postdoctoral & Related Professional Education\u00a0 Department Faculty, Logan College of Chiropractic, St. Louis, MO, USA;\u00a0 National Institute of Chiropractic Research, Phoenix, AZ, USA; Private\u00a0 Practice of Chiropractic, Phoenix, AZ, USA. 2<\/sup> Professor, Department of Mechanical Engineering\u00a0 & Department of Orthopedics and Rehabilitation, The University of\u00a0 Vermont, Burlington, VT, USA. 3<\/sup> National Institute of Chiropractic Research, Phoenix, AZ, USA; Private Practice of Chiropractic, Phoenix, AZ, USA.<\/p>\n
\n