Vibration transmission of the spine during walking is different between the lumbar and thoracic regions in older adults

Background: fractures occur more commonly in the thoracic than in the lumbar spine. Physical activity complemented with pharmacological interventions has been advocated as a preventive measure for osteoporosis. However, walking has been shown to produce only a small improvement in spinal bone mineral density. The characteristics of vibration transmission during walking at the lumbar and thoracic spines may be different, and this may help explain the relative incidence of fractures in the two spine regions. 

Objective: to determine how mechanical vibration is transmitted in the lumbar and thoracic spines in older adults with and without osteoporosis. 

Methods: 16 young healthy adults, 19 older adults without osteoporosis and 41 adults with osteoporosis were recruited. Inertial sensors were attached to the skin over the lumbar and thoracic spines for recording the vibration transmitted during level walking. Vibration characteristics were compared across lumbar and thoracic spines and across groups. 

Results: the lumbar spine generally amplified the vibration transmitted during walking, whereas the thoracic spine exhibited a much smaller amplification effect, except at the lowest frequency. The magnitude of vibration was generally reduced in the older spines. Osteoporosis had minimal effects on vibration transmission. 

Conclusions: the larger amplification of vibration in the lumbar spine may explain the lower incidence of vertebral fractures in this region when compared to the thoracic spine. Ageing alters the transmission of vibration in the spine while osteoporosis has minimal effects. Future research should determine the characteristics of vibration transmitted through the thoracic spine during other physical activities.