The effect of physical activity lifestyle on in-vivo passive stiffness of the lumbar spine

The passive stiffness of the lumbar spine has direct implications on one’s risk of injury and spinal instability. Therefore, the effects that physical activity lifestyle may have on the lumbar spine’s passive stiffness was assessed. Participants were classified as active (n = 20) or inactive (n = 21) after completing a physical activity questionnaire. Passive lumbar flexion and extension trials were completed on a custom passive jig. The participant’s moment–angle curves were determined, and their lumbar spine passive stiffness was analyzed by partitioning the curve into three linear stiffness regions of increasing stiffness. Stiffness in the low stiffness zone of the moment–angle curve was significantly lower in the inactive group (p = 0.014). Furthermore, time spent sitting in an office chair significantly predicted the stiffness in their low stiffness zones across all participants (p = 0.011). These findings suggest that physical activity lifestyle may be a potential avenue through which one’s lumbar spine passive stiffness may increase, improving spinal health and stability in the population.