Abstract
Background: Prospective population studies demonstrate that poor paraspinal muscle endurance increases the risk of developing first-time LBP and many CLBP studies also document excessive paraspinal muscle fatigability. The question arises as to whether this could have predisposed to chronic symptoms, through impaired spinal instability, especially in light of the wide inter-individual variation observed in the constitutionally determined paraspinal muscle fibre-type composition, which governs contractile performance.
Objective: To determine whether CLBP-associated excessive paraspinal fatigue results from a paucity in the type I fibre content.
Design: Control comparison using male subjects.
Subjects: Thirty-five CLBP patients with Von-Korff Chronic Pain Scores of ≤ III (high level of residual function, despite pain, to negate effects of disuse atrophy), and 32 controls of similar age.
Outcome measures: Fatigue-induced median frequency (MF) declines in the surface EMG signal, monitored bilaterally at L4 level during Biering-Sorensen- and 60%MVC- isometric fatigue tests. Percutaneous para-spinal muscle biopsies permitted histomorphometric comparisons.
Results: Between-group differences were assessed using independent t-tests (p < 0.05). There were no differences for MF decline during the Biering-Sorensen -0.37(0.16) vs. -0.36(0.12), and the 60% MVC test −0.42(0.31) vs −0.51(0.29), and in the percentage number of type I fibres, 63.6% vs 64.3%, or percentage area occupied by type I fibres, 69.4% vs 67.2%, in the paraspinal muscles for patients and controls respectively (p> 0.05).
Conclusion: Impaired CLBP-associated endurance is not the result of a constitutionally ‘adverse’ fibre-type composition.
Abstracts prepared by Mr. A. J. Stirling, FRCS, and Miss A. Weaver. Correspondence should be addressed to Miss A. Weaver at the Research and Teaching Centre, Royal Orthopaedic Hospital, Northfield, Birmingham, B31 2AP, UK
BritSpine 2002, the second combined meeting of the British Association of Spinal Surgeons, the British Cervical Spine Society, The British Scoliosis Society and the Society for Back Pain Research, took place at the International Convention Centre in Birmingham UK between 27th February and 1st March 2002. The following presentations and posters were given and displayed.
