(Lee & Evans, 1992)
Aims: Among others, to evaluate the effects of cyclic and sustained PA loadings, and on loading rate on PA mobility.
Method: N = 28, 18 – 23 yo, 50/50 male/female. Assessed mobility of L3-L5 (max 150N), three cyclic loadings on L4 (150N) and sustained loading on L4 (100N in two min). Displacements measured with transducers on level above and below. Pad put under applicator to minimize discomfort. Pad preloaded.
Results: No gender difference in spinal mobility. PA mobility together varied significantly between spinal levels, L5 most mobile, then L4 and L3. Cyclic and sustained load induced progressively more displacements. For sustained, most displacement seen in the first 30 seconds (69%) creep. For cyclic two first loading cycles showed more displacement (hysteresis / preconditioning). Slow rate of loading produced more displacement. However, effects of creep and preconditioning are temporary.
Limitations: Error of the measured displacement because of soft tissue compression. We do not know the actual vertebral displacement.
Lee, R., & Evans, J. (1992). Load-displacement-time characteristics of the spine under posteroanterior mobilisation. Australian Journal of Physiotherapy, 38(2), 115–123. https://doi.org/10.1016/S0004-9514(14)60556-0