Shirley D, Hodges P W, Eriksson A E M, Gandevia S C
School of Physiotherapy, Faculty of Health Sciences, Univ. of Sydney, P.O. Box 170, Lidcombe, Sydney NSW 1825, Australia.
J Appl Physiol (1985). 2003 Oct;95(4):1467-75. doi: 10.1152/japplphysiol.00939.2002.
Posteroanterior stiffness of the lumbar spine is influenced by factors, including trunk muscle activity and intra-abdominal pressure (IAP). Because these factors vary with breathing, this study investigated whether stiffness is modulated in a cyclical manner with respiration. A further aim was to investigate the relationship between stiffness and IAP or abdominal and paraspinal muscle activity. Stiffness was measured from force-displacement responses of a posteroanterior force applied over the spinous process of L2 and L4. Recordings were made of IAP and electromyographic activity from L4/L2 erector spinae, abdominal muscles, and chest wall. Stiffness was measured with the lung volume held at the extremes of tidal volume and at greater and lesser volumes. Stiffness at L4 and L2 increased above base-level values at functional residual capacity (L2 14.9 N/mm and L4 15.3 N/mm) with both inspiratory and expiratory efforts. The increase was related to the respiratory effort and was greatest during maximum expiration (L2 24.9 N/mm and L4 23.9 N/mm). The results indicate that changes in trunk muscle activity and IAP with respiratory efforts modulate spinal stiffness. In addition, the diaphragm may augment spinal stiffness via attachment of its crural fibers to the lumbar vertebrae.
腰椎的后前向刚度受多种因素影响，包括躯干肌肉活动和腹内压（IAP）。由于这些因素会随呼吸而变化，本研究调查了刚度是否会随呼吸呈周期性调节。另一个目的是研究刚度与IAP或腹部及椎旁肌肉活动之间的关系。通过施加在L2和L4棘突上的后前向力的力-位移响应来测量刚度。记录了IAP以及L4/L2竖脊肌、腹部肌肉和胸壁的肌电图活动。在潮气量的极值以及更大和更小的肺容积下测量刚度。在功能残气量时（L2为14.9 N/mm，L4为15.3 N/mm），吸气和呼气时L4和L2处的刚度均高于基础水平值。这种增加与呼吸努力有关，在最大呼气时最大（L2为24.9 N/mm，L4为23.9 N/mm）。结果表明，呼吸努力引起的躯干肌肉活动和IAP变化会调节脊柱刚度。此外，膈肌可能通过其脚纤维附着于腰椎来增强脊柱刚度。
