Spontaneous vertebral fractures are a large and growing health care problem. Biomechanical factors, specifically, abnormal posture or gait‐related spinal motion may interact with age‐weakened bone to induce altered spinal biomechanics that in turn increase the likelihood of vertebral body fracture. This research takes steps towards the goal of reducing the number of vertebral fractures in two phases: 1) Validation of a noninvasive spinal motion measurement system in cadaver torsos and 2) Application of the measurement system in human subjects. The cadaver study compared vertebral motion at 4 levels (T7,T12,L3,L5) as measured by adhesive skin markers versus motion measured by bone pins implanted into the vertebrae. Cadaver torsos were tested in lateral‐bending, flexion and axialrotation. Mean differences in vertebral body angular motion between skin markers and bone pin markers were <0.5° around the anterior‐posterior and medial‐lateral axes and <0.9° around the superior‐inferior axis. This measurement method was able to accurately quantify vertebral body motion in cadaver torsos thus allowing for application to human subject testing. X‐rays and 3D motion capture were employed to quantify spinal posture and motion parameters during gait in 12 older and 12 younger normal, females. Vertebral motion around 3 axes was measured at 4 levels (T7,T10,T12,L2) using noninvasive retroreflective markers during treadmill gait at 3 speeds (0.5,0.7,0.9m/s). The average angular motion of all gait cycles at each speed was determined for each level. The triplanar ranges of motion and variability of motion were compared as a function of age. Older subjects had 31.7% larger frontal Cobb angles and up to 30.9% and 33.5% smaller ranges of spinal motion in the frontal and sagittal planes. Variability of motion in the sagittal plane was up to 42.9% less in older subjects. Decreased ranges of motion and variability of spinal motion observed in older subjects may imply that vertebral loading in these subjects may not be as uniformly distributed across the vertebrae as in younger subjects. Greater stresses may result from the abnormal motion, thus increasing fracture risk. Confirmation of this hypothesis requires a longitudinal study, but if verified, may lead to the development of inexpensive countermeasures to prevent fractures.

Currently, low back disorder (LBD) research focuses primarily on mechanical variables to assess whether acute or cumulative task demands exceed the capacity of the tissue; however, it is important to assess how other non-mechanical variables affect tissue capacity in a time-dependent manner. The current investigation sought to explore physiological responses to an acute lifting task (similar to a typical assembly line task), as lifting has been implicated as a risk factor in the development of LBDs. Twelve participants completed two experimental sessions of two hours of repetitive symmetrical lifting from floor to knuckle height under a low force, high repetition condition (LFHR; box weighted at 5% maximum lifting strength, five lifts per minute) and a high force, low repetition condition (HFLR; 25% maximum lifting strength, one lift per minute), such that the external biomechanical work was equivalent between conditions. These sessions were completed one week apart, with full-body motion capture and ground reaction forces measured throughout. Systemic inflammation was assessed with blood sampling at baseline, 0, 4 and 24 hours post-lifting on both days, and samples were assayed using an ELISA for interleukin 6 (IL-6) and interleukin 8 (IL-8). Participants also completed psychological questionnaires including the Tampa Scale for Kinesiophobia-General (TSK-G), Pain Catastrophizing Scale, Visual Analogue Scale (VAS, participants 1-4) and Borg CR-10 Scale of Exertion (participants 5-12). There was a significant main effect of time on both IL-6 and IL-8 (Baseline, 0, 4, 24 hours), as well as interaction effects of condition (HFLR and LFHR) and time. The LFHR condition caused greater inflammation in both IL-6 and IL-8 at 0 and 4 hours post-lifting, likely due to significantly higher cumulative spinal loading in this condition. Significant correlations between body fat percentages, peak and cumulative loading were found to exist in both the LFHR condition and the HFLR condition, lending strength to the hypothesis that some of these measures may be able to predict physiological responses to acute stresses, and subsequently, risk of acute injury.

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