Variability of spinal stiffness and its relation to daily activities: A prospective cohort study using a mechanical assisted indentation technique

Background: Spinal stiffness is a potentially important cause of spinal pain but we have limited knowledge of its variability in relation to daily activities. This study investigated the association between variability of spinal stiffness and body anthropometry, age, and different daily activities in a cohort of healthy participants. Methods: A cross-sectional study of a cohort of 25 healthy participants (median age 24 years; 52% male) was employed to collect stiffness measurements obtained through surface indentation of the lumbar and thoracic spine three times over the course of a single day. Daily activities (sitting, standing, and movement) were assessed using accelerometer data. Linear mixed models analyzed the associations between stiffness variability and body anthropometry, age, and activities. Findings: We observed significant variability in spinal stiffness among individuals, with greater variability in the lumbar region compared to the thoracic region. Both sedentary and standing activities influenced stiffness variability at a statistically significant level. However, body anthropometry and age was not associated with stiffness variability. Interpretation: Our study demonstrates that daily activities (i.e., sedentary and standing) contribute to the variability of spinal stiffness during the day. Age and sex did not significantly impact stiffness variability. Further investigations are warranted to explore the clinical implications of stiffness changes.