Popa Traian, Bonifazi Marco, Della Volpe Raimondo, Rossi Alessandro, Mazzocchio Riccardo
Scuola di Dottorato in Scienze Neurologiche Applicate, Universita' di Siena, Siena, Italy.
Exp Brain Res. 2007 Mar;177(3):411-8. doi: 10.1007/s00221-006-0683-4.
Chronic low back pain (CLBP) patients achieve postural stability during challenging stance conditions by increasing sway speed. We investigated the mechanisms underlying this behavior, and whether postural strategy selection may be influenced by short-term experience of postural perturbation. Thirteen CLBP patients and thirteen age-matched controls underwent posturography tests. Subjects were asked to stand quietly: (a) with eyes open and eyes closed, and (b) while expecting a series of four backward translations of the support surface. Data from condition (a) was subjected to sway density analysis (SDA). This computes the number of consecutive spaces and respectively time samples during which center of pressure (COP) displacements remained inside a 2.5 mm radius. Three parameters of this analysis were considered: the mean number of peaks (MP), reflecting the time spent by COP in regions of stability, the mean time between peaks (MT) relating to the rate of production of posturographic commands, and the mean spatial distance (MD), reflecting the distance between stable regions. In condition (b) the mean COP positions were analyzed during the time (500 ms) preceding each translation. The MD was significantly increased in the CLBP group as compared to controls (P < 0.01), while the MP and MT did not present any significant difference. The expectation of backward translations initially produced a different COP positioning between the two groups (P < 0.0001) which decreased with repetition of platform translations (controls: PDelta1-4 < 0.002; patients: PDelta1-4 < 0.005). The findings show that the timing and the rate of the balance motor commands is comparable between the two groups. On the other hand, there is greater distance between regions of stability in the patient group. Such modification of motor control patterns might be the consequence of a reweighting of sensory input, possibly due to a deterioration of its reliability. Platform translation findings show that both groups aimed at optimizing their posture selection strategy based on prior testing experience. CLBP patients make use of a different postural motor strategy to maintain quiet stance. This is probably the consequence of an imprecise internal estimate of body sway, due to reduced accuracy in the sensory integration process.
慢性下腰痛（CLBP）患者通过增加摇摆速度在具有挑战性的站立条件下实现姿势稳定性。我们研究了这种行为背后的机制，以及姿势策略的选择是否可能受到姿势扰动的短期体验的影响。13名CLBP患者和13名年龄匹配的对照组进行了姿势描记测试。受试者被要求安静站立：（a）睁眼和闭眼，以及（b）在预期支撑面进行一系列四次向后平移时。条件（a）的数据进行了摇摆密度分析（SDA）。这计算了压力中心（COP）位移保持在半径2.5毫米范围内的连续空间数量和相应的时间样本。考虑了该分析的三个参数：峰值平均数（MP），反映COP在稳定区域所花费的时间；峰值之间的平均时间（MT），与姿势描记指令的产生速率有关；以及平均空间距离（MD），反映稳定区域之间的距离。在条件（b）中，分析了每次平移前500毫秒内的平均COP位置。与对照组相比，CLBP组的MD显著增加（P < 0.01），而MP和MT没有显著差异。对向后平移的预期最初在两组之间产生了不同的COP定位（P < 0.0001），随着平台平移的重复，这种差异减小（对照组：PDelta1 - 4 < 0.002；患者组：PDelta1 - 4 < 0.005）。研究结果表明，两组之间平衡运动指令的时间和速率相当。另一方面，患者组中稳定区域之间的距离更大。这种运动控制模式的改变可能是感觉输入重新加权的结果，可能是由于其可靠性下降。平台平移结果表明，两组都旨在根据先前的测试经验优化其姿势选择策略。CLBP患者采用不同的姿势运动策略来维持安静站立。这可能是由于感觉整合过程中准确性降低导致身体摇摆的内部估计不准确的结果。
