Le Brook, Davidson Bradley, Solomonow Deborah, Zhou Bing He, Lu Yun, Patel Vikas, Solomonow Moshe
Musculoskeletal Disorders Research Laboratory, Bioengineering Division, Department of Orthopedic Surgery, Health Sciences Center, Denver, Colorado 80045, USA.
Muscle Nerve. 2009 Jan;39(1):71-82. doi: 10.1002/mus.21214.
Neuromuscular control of lumbar stability following exposure to prolonged static work, under low and high loads, was assessed in the in vivo feline model. Six sessions of 10 min work at 20N with 10 min between rest was compared to a group subjected to the same protocol but carrying high loads of 60N. Displacement and tension developed in the spine at the instant the multifidus muscles applied stabilizing contractions, and their amplitudes were obtained from their electromyogram (EMG). Significant (P < 0.001) laxity developed in the various viscoelastic tissues of the lumbar spine that did not recover during and up to 7 h of rest postwork. Simultaneously, there was a significant (P < 0.001) decrease in muscular activity in the 3-4 h immediately postwork under low load but only during the first hour in the high load group. After that period the musculature compensated for the laxity of the viscoelastic tissues by a significant (P < 0.001) increase in activity in the high-load group and a nonsignificant increase in the low group. It was concluded that during 1-3 h immediately poststatic work a significant decrease in the stabilizing function of viscoelastic tissues together with a significant decrease in muscular activity is present, and they render the spine unstable and exposed to high risk of injury. Performance of prolonged static work under low loads, while not harmful during the work, cannot be designated as a "no-risk" condition, as it may result in injury postwork.
在活体猫模型中，评估了在低负荷和高负荷下长时间静态工作后腰椎稳定性的神经肌肉控制情况。将以20N进行6组10分钟工作且每组工作间休息10分钟的情况，与采用相同方案但负荷为60N的高负荷组进行比较。在多裂肌施加稳定收缩瞬间脊柱产生的位移和张力，以及它们的幅度，从其肌电图（EMG）中获取。腰椎各粘弹性组织出现了显著（P < 0.001）的松弛，在工作期间及工作后长达7小时的休息时间内都未恢复。同时，低负荷组在工作后立即的3 - 4小时内肌肉活动显著（P < 0.001）下降，而高负荷组仅在工作后的第一小时内出现这种情况。在此之后，高负荷组肌肉组织通过显著（P < 0.001）增加活动来补偿粘弹性组织的松弛，低负荷组活动增加不显著。研究得出结论，在静态工作后立即的1 - 3小时内，粘弹性组织的稳定功能显著下降，同时肌肉活动也显著下降，这使得脊柱不稳定并面临高损伤风险。低负荷下长时间静态工作，虽然在工作期间无害，但不能被认定为“无风险”状态，因为它可能在工作后导致损伤。
