Background: Sitting is associated with loss of the lumbar lordosis, intervertebral disc (IVD) compression, and height loss, possibly increasing the risk of lower back pain. With a trend toward more sitting jobs worldwide, practical strategies for preventing lumbar flattening and potentially associated low back pain (LBP) are important.
Purpose: The purpose of this study was to determine the feasibility of using upright magnetic resonance imaging (MRI) and stadiometry to measure changes in height and configuration of the lumbar spine before and after normal sitting and a seated unloading exercise intervention.
Study design/setting: This is a hospital-based pilot study involving pre-post assessments in a single group.
Patient sample: The sample comprises six asymptomatic hospital employees involved in either general patient care or research writing/data collection.
Outcome measures: The outcome measures were lumbar total midsagittal cross-sectional IVD area, vertical height, lordotic angle derived from digitized MRI examinations, and seated body height measured directly with a stadiometer.
Methods: Midsagittal MRI scans were performed before sitting, after 15 minutes of relaxed sitting ("postsitting"), immediately after seated unloading exercises, and approximately 7 minutes after exercise. Subsequently, seated stadiometry assessments were performed after 10 minutes of supine recumbency, 15 minutes of relaxed sitting, and every 10 seconds after seated unloading exercises until three consecutive height measurements were identical. Digitized midsagittal images were used to derive MRI-based outcome measures. Measurements at postsitting were compared with the corresponding ones at other time points using multiple paired t-tests. The Bonferroni method was used to adjust for multiple pairwise comparisons.
Main results: After 15 minutes of sitting, mean total IVD area, lordotic angle, and vertical height of the lumbar spine decreased 18.6 mm(2), 6.2 degrees , and 12.5 mm, respectively, whereas after seated unloading exercises, these parameters increased by 87.9 mm(2), 5.0 degrees , and 21.9 mm, respectively. Similarly, mean seated height on stadiometry decreased by 6.9 mm after 15 minutes of sitting and subsequently increased by 5.7 mm after unloading exercises.
Conclusions: Seated upright MRI and stadiometry, as performed in this study, appear to be feasible methods for detecting compressive and decompressive spinal changes associated with normal sitting and, alternately, seated unloading exercises. Larger studies are encouraged to determine normative values of our study measurements and to determine if morphological changes induced by seated unloading predict treatment response and/or reductions in the incidence of sitting-related LBP.