Diana E. De Carvalho

Lumbar Spine and Pelvic Posture Between Standing and Sitting: A Radiologic Investigation Including Reliability and Repeatability of the Lumbar Lordosis Measure

OBJECTIVE Sitting has been identified as a cause of mechanical low back pain. The purpose of this study was to use plain film x-rays to measure lumbar spine and pelvic posture differences between standing and sitting. METHODS Eight male subjects were radiographed standing and sitting in an automobile seat. Measures of lumbar lordosis, intervertebral disk angles, lumbosacral angle, lumbosacral lordosis, and sacral tilt were completed. One-way analysis of variance (alpha = .05) was conducted on the variables stated above. A Bland-Altman analysis was conducted to assess agreement and repeatability of the lumbar lordosis angle using 2 raters. RESULTS Lumbar lordosis values in standing (average, 63 degrees +/- 15 degrees ) and sacral inclination (average, 43 degrees +/- 10 degrees ) decreased by 43 degrees and 44 degrees , respectively, in sitting. Intervertebral joint angles in sitting underwent substantial flexion (L1/L2-5 degrees [+/-3 degrees ], L2/L3-7 degrees [+/-3 degrees ], L3/L4-8 degrees [+/-3 degrees ], L4/L5-13 degrees [+/-3 degrees ], and L5/S1-4 degrees [+/-10 degrees ]). Measures of lumbar lordosis; intervertebral disk angles between L2/L3, L3/L4, and L4/L5; lumbosacral lordosis; lumbosacral angle; and sacral tilt were significantly decreased between standing and sitting (P < .001). Intervertebral disk angle between L5/S1 was not significantly different. Analysis using the Bland-Altman technique found good agreement and stable repeatability of measures with no statistical significant differences between or within raters (R1, P = .8474; R2, P = .4402; and R-R2, P = .8691). CONCLUSION The significant differences in lumbar and pelvic measures from standing to sitting further emphasize the range of motion experienced at vertebral levels in sitting. Based on the results of this study, interventions to return motion segments to a less flexed posture should be investigated because they may play a role in preventing injury and low back pain.

Is Standing the Solution to Sedentary Office Work

There has been a major shift toward office workstations that accommodate standing postures. This shift is attributable to negative health and musculoskeletal issues from sedentary exposures. However, changing exposures from sitting to standing does not eliminate these issues, as evidence indicates prolonged standing also induces problems. Reducing seated exposure and rotating frequently between sitting and standing has been shown to result in positive health outcomes, reduced discomfort, and increased work performance. Implementing sit-stand workstations has promise to mitigate work-related health issues, if the users are provided with training that includes accommodations for individual work patterns and preferences.

Evaluating Abdominal and Lower-Back Muscle Activity While Performing Core Exercises on a Stability Ball and a Dynamic Office Chair:

Objective: The purpose of this study was to evaluate the ability of a dynamic office chair to activate the core muscles while participants performed exercises sitting on the chair compared to a stability ball. Background: Prolonged sitting has become an accepted part of the modern office. However, epidemiological evidence suggests that sedentary postures are linked to many adverse effects on health. The concept of dynamic or active sitting is intended to promote movement while sitting to reduce the time spent in prolonged, static postures. Methods: Sixteen participants performed four pelvic rotation exercises (front-back, side-side, circular, and leg lift) on both a dynamic office chair and a stability ball. Muscle activity from 12 torso muscles were evaluated with surface electromyography. Results: For all exercises, trunk muscle activity on the chair was comparable to that on a stability ball. The right external oblique was the only muscle to produce greater peak activity (p = .019) when using the ball compared to the chair (21.4 ± 14.0 percent maximal voluntary excitations (%MVE) and 14.7 ± 10.8 %MVE for the ball and chair, respectively). The left thoracic erector spinae produced greater average activity (p = .044) on the chair than on the ball. Conclusion: These findings suggest that this dynamic sitting approach could be an effective tool for core muscle activation while promoting movement and exercise while sitting at work. Application: Muscle activations on the dynamic chair are comparable to those on a stability ball, and dynamic office chairs can promote movement and exercise while sitting at work.

Spine Posture and Discomfort During Prolonged Simulated Driving With Self-Selected Lumbar Support Prominence

Objective: We examined magnitude preference, subjective discomfort, and spine posture during prolonged simulated driving with a self-selected amount of lumbar support. Background: The general use of lumbar supports has been associated with decreased reports of low-back pain during driving exposures; however, minimal data exist regarding occupant magnitude preference. Method: Participants chose between five discrete levels of lumbar support (0–4 cm). Time-varying postural and discomfort responses were then monitored throughout 2 hr of simulated driving. Results: There were no significant effects of gender or time on posture. Women preferred larger amounts of support than men (3.25 cm ± 0.71 and 2.56 cm ± 0.88, respectively, p = .048). All participants exhibited significant increases (p = .003) in pelvic discomfort throughout the 2-hr trial regardless of the level of support chosen. Discomfort related to various aspects of the lumbar support increased significantly over time. Retrospectively, no participants desired a setting beyond 4 cm, and the majority of respondents indicate had they been able to change their initial selection, they would choose a setting between 2 and 3 cm. Conclusion: The results suggest that occupants would prefer increasing the excursion capability of automobile lumbar supports beyond 2 cm. Application: Excursion capability and adjustability of automobile lumbar supports are important features to better meet end-user preference and to reducing lumbar flexion in sitting.

The Effect of Wallet Thickness on Spine Posture, Seat Interface Pressure, and Perceived Discomfort During Sitting

OCCUPATIONAL APPLICATIONS Occupational sitting has been associated with an increased risk for developing low back pain. The present investigation examined the effects of asymmetrical sitting surfaces induced by a wallet on acute changes in spine/pelvis posture, interface pressure, and discomfort. Compared to level sitting, sitting on a wallet resulted in greater sagittal and lateral spine flexion, a smaller total contact area with the seat pan, and greater gluteal discomfort. At wallet thicknesses of 22 mm and thicker, seat pan contact pressure area decreased and thoracic spine and pelvic angles deviated laterally compared to the no-wallet condition. At a 32-mm wallet thickness, gluteal discomfort increased. These results indicate that sitting for brief periods (15 minutes) on an uneven seating surface greater than 32 mm in thickness causes postural deviations from neutral spine positions and increases gluteal discomfort. This study supports the removal of rear pocket items, especially larger ones, during sitting. TECHNICAL ABSTRACT Background: Occupations in mobile or office settings can involve prolonged seated exposures, increasing the likelihood of low back pain development. The seat-occupant interface can be impeded by wallets or other objects (cell phones, paper documents, etc.) placed in the rear pocket, potentially increasing the risk of developing low back pain directly (nerve compression) or indirectly (altered kinematics). However, there are no published studies that have examined the effect of an uneven seating surface. Purpose: This study aimed to quantify the outcomes of a non-level sitting surface on trunk kinematics, seat pan pressure distribution, and discomfort. Gender differences in responses were also examined. Methods: Twelve males and 12 females sat for 15 minutes each on 4 wallet thicknesses (0, 12, 22, and 32 mm). Sagittal and frontal plane angles of the thoracic, lumbar spine and the pelvis were measured. Seat pressure distribution (total pressure area) and discomfort using a 100-mm visual analogue scale were also collected for each thickness. Results: In the 22- and 32-mm conditions, there was greater pelvic posterior rotation, pelvic left lateral bending, thoracic flexion, and thoracic right lateral bending compared to the 0-mm condition. Males and females showed differences in the magnitude of lateral bend angles at all spine levels; however, both genders demonstrated the same directions of postural compensation. Total pressure area decreased and gluteal discomfort increased with thicker wallets, reaching significance in the 22- and 32-mm conditions, respectively. Conclusions: Sitting on wallets greater than 32 mm in thickness increased gluteal discomfort reporting after short duration exposures. Asymmetrical sitting promotes non-neutral spine postures and reduces seat pan contact area. Asymmetrical sitting is therefore not recommended, even for short duration exposures.

Semi-automatic Fisher-Tippett guided active contour for lumbar multifidus muscle segmentation

Rehabilitative Ultrasound Imaging or diagnostic ultrasound is used to measure geometric properties of the lumbar multifidus muscle to infer muscle strength or degeneration for back pain therapy. For this purpose, a novel semi-automatic approach (FTS: Fisher-Tippett Segmentation) based upon the Decoupled Active Contour is proposed to reliably and quickly segment the lumbar multifidus muscle in diagnostic ultrasound. To overcome speckle or hardly visible region boundaries in ultrasound images, we first propose a novel external energy functional to explicitly consider the underlying Fisher-Tippett distribution of ultrasound data. We then introduce a user-guided Hidden Markov Model trellis formation for improved segmentation of weakly-defined regions. Extensive experiments have shown that our approach not only improves the segmentation performance when compared to existing methods, but also does not rely on sub-specialized knowledge for segmentation.