The effects of upper limb loading on spinal shrinkage during treadmill walking

Watson, Hugh and Simpson, A and Riches, Philip (2012) The effects of upper limb loading on spinal shrinkage during treadmill walking. European Spine Journal, 21 (12). pp. 2688-2692. ISSN 0940-6719 (https://doi.org/10.1007/s00586-012-2377-x)

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Abstract

Everyday activities such as walking either loaded or unloaded may elicit spinal shrinkage in an order of magnitude that has been related to lower back pain. The present study aims to compare the effects of unloaded treadmill walking with walking carrying loads representing everyday shopping tasks. Walking tasks were performed on 7 healthy males, consisting of unloaded walking and walking carrying 7.5% and 15% of body weight. Motion analysis was used to track four reflective markers at 100Hz, dividing the spine into three segments and static data was collected in 5 minute intervals over a 30 minute period. Total spine and segment length changes were compared to original length in the sagittal plane and the effects of load, time and their interaction were analysed using ANOVA. Total spinal length and lumbar segment decreased with respect to time (p < 0.001). Load affected the percentage length change at each spinal segment (p < 0.005), with the lumbar segment showing greatest height loss at the highest load. Inter-segmental variations in length resulted in the non-significant effect of load on the percentage length change of the total spine (P = 0.263). The upper and lower thoracic segments showed greater anterior lean with the heavier loads (p = 0.000) and the lumbar segment showed the opposite trend (p = 0.000). Results suggest that the body adopts less anterior lean with an immediate load bearing demand, to decrease the flexion moment arm of the load about the lumbar spine and thus decrease the necessary extension moment generated by the spinal extensors for spinal stability. Further postural alteration in the same direction is observed with prolonged loading. In combination with lumbar spinal shrinkage, such postural changes are likely to increase the loading on the facet joints with potential deleterious consequences for low back pain