You thought walking would keep your spine strong, but...
Dr. Dafne Zuleima Morgado Ramirez is based at the Interaction Centre (UCLIC) at University College London and is a member of the Global Disability Innovation Hub. She tweets at @zuleimamorgado. She has recently published work in Age and Ageing journal.
Walking has been promoted as a way of reducing the risk and progression of osteoporosis. Yet clinical studies have shown that walking does not increase bone mineral density at the spine unless it is performed along with other physical activities, and that even then, improvement is minimal. Physical activity produces vibration that is transmitted from the feet up to the head through the body. Although there is clear evidence that bone formation and resorption are responsive to mechanical stimulation, such as vibration, currently there is limited understanding of the vibration that is transmitted through the lumbar and thoracic spine during walking.
This was the first experimental study to examine how vibration signals were transmitted through the lumbar and thoracic spine during walking in older adults (with or without osteoporosis) compared to young, healthy adults. We wanted to understand how osteoporosis and ageing affect vibration transmission in regards to signal magnitude, frequency and transmission percentage. Vibration transmission was measured through inertial sensors, attached with adhesive tape to the skin over four locations along the spine. Older adults then walked in a straight line at their comfortable walking speed whilst wearing the sensors below their clothes.
The vibration transmission was found to be predominately amplified at low frequencies, and different between lumbar and thoracic spines. At these frequencies, walking produced vibration that was significantly amplified by the lumbar spine but attenuated in the thoracic spine. Ageing and osteoporosis reduced the magnitude of the vibration transmitted at the thoracic spine. Osteoporosis amplified the vibration transmitted to the lumbar spine, only between 4 to 6 Hz. No significant differences in vibration transmissibility were found between older adults with osteoporosis and without it. This indicates that vibration transmission is significantly affected by ageing but not osteoporosis.
In this study we observed that the thoracic spine transmits much less vibration compared to the lumbar spine, which as a result may be the reason why osteoporosis and vertebral fractures are more common at the thoracic spine. Clinicians need to find a way of stimulating bone growth in older spines through exercise, taking into account the observed reduced transmission of vibration at the thoracic spine. Our measurement technique could be employed to help clinicians identify exercises with the greatest potential to stimulate bone growth at the spine, by choosing those exercises that transmit the greatest percentage and magnitudes of vibration. A potential future clinical application (which requires additional research) would be to correlate the characteristics of vibration signals with effective and safe stimulation of bone growth in the spine, as part of an osteoporosis prevention and treatment programme containing a mix of therapeutic interventions and exercise.