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Postural assessments of the lumbar spine lack valuable information about its properties. The purpose of this study was to assess neutral zone (NZ) characteristics via in vivo lumbar spine passive stiffness and relate NZ characteristics to standing lumbar lordosis. A comparison was made between those that develop low back pain during prolonged standing (pain developers) and those that do not (nonpain developers). Twenty-two participants with known pain status stood on level ground, and median lumbar lordosis angle was calculated. Participants were then placed in a near-frictionless jig to characterize their passive stiffness curve and location of their NZ. Overall, both pain developers and nonpain developers stood with a lumbar lordosis angle that was more extended than their NZ boundary. Pain developers stood slightly more extended (in comparison to nonpain developers) and had a lower moment corresponding to the location of their extension NZ boundary. Overall, in comparison to nonpain developers, pain developers displayed a lower moment corresponding to the location of their extension NZ boundary which could correspond to greater laxity in the lumbar spine. This may indicate why pain developers have a tendency to stand further beyond their NZ with greater muscle co-contraction.

Occupations requiring prolonged periods of static standing are associated with the development of low back pain (LBP). Certain individuals are susceptible to LBP development during prolonged standing (pain developers, PDs) while others are not (non-pain developers, NPDs). Linear centre of pressure (COP) measures suggest that standing balance control is negatively influenced following prolonged standing, and that PDs and NPDs may be differentially affected. The objective of this study was to determine if nonlinear standing balance control, quantified on COP, using sample entropy, is altered after 2-h of standing. Thirty two participants stood for 2-h. Separate 2-min standing trials, performed with eyes open and eyes closed, were collected before and after the 2-h standing protocol. Sample entropy, median power frequency and RMS amplitude of the COP time-series, was calculated from the 2-min standing trials for all participants. For comparison, participants were classified, post hoc, as PDs or NPDs according to visual analog scale pain scores. Sample entropy decreased after 2-h of standing for both PDs and NPDs, however, the decrease for NPDs was only 21% of the decrease observed in PDs. This study demonstrated that nonlinear control of upright standing changes after 2- hours of standing, resulting in an increase in COP regularity post 2- hours of standing for both PDs and NPDs. PDs displayed a greater change in COP regularity, which is supported by the theory that increased COP regularity occurs with pain/pathology., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Along with quantitative measures, pain symptoms may help inform early interventions to prevent prolonged standing induced low back pain (LBP); however, the relationship between quantitative and qualitative measures has not been assessed., Objective: Determine the relationship between qualitative and quantitative measures of pain development during prolonged standing induced LBP development., Methods: Thirty-five participants performed two-hours of standing. A visual analog scale (VAS) and the Short-Form McGill Pain Questionnaire were used to assess the participant's LBP every 7.5-minutes. Participants were classified as a pain developer (PD) based on VAS scores or three consecutive pain symptom reports., Results: Pain symptom reports occurred 31.3 (±24.8) minutes earlier than the VAS reports. Eight participants (44%) were non-PDs with the VAS and PDs with the symptom method (p = 0.0047)., Conclusions: A subset of participants who were not categorized as LBP developers during prolonged standing using the VAS method still report LBP symptoms. The inclusion of pain symptom reporting could provide additional information for practitioners when identifying individuals who would benefit from early interventions for standing induced LBP.

Purpose: Standing workstations have recently been promoted as a healthy alternative to sitting. However, it is unknown how prolonged standing affects arterial stiffness, a prognostic indicator of cardiovascular health. The purpose of this study was twofold: to observe changes in arterial stiffness, as assessed by pulse wave velocity (PWV), with a 2-h bout of standing, and to determine if short, intermittent walking bouts provide a comparative advantage to standing alone., Methods: Nineteen adults had arterial stiffness assessed by pulse wave velocity. Central (C PWV ), upper peripheral (U PWV ), and lower peripheral (L PWV ) PWV were assessed before (supine), during standing (min 10, 60, and 120), and after (supine) the 2-h standing bout. In one trial, the participants stood at a standing desk immobile for 2 h. In the other trial, participants performed 5-min walking breaks after every 25 min of standing., Results: After 2-h of standing, supine (85.8 ± 90.1 cm/s) and standing (303.4 ± 390.2 cm/s), L PWV increased independent of trial (i.e., main effect of time; p < 0.001). Walking breaks during 2 h of standing did not significantly attenuate these changes. In addition, standing C PWV decreased over time (- 38.5 ± 61.5 cm/s; p = 0.04). Yet, U PWV , standing or supine, did not change over the course of standing (p > 0.05)., Conclusions: These findings indicate that prolonged standing increases the measures of arterial stiffness and there is no evidence that walk breaks attenuate this response.

Minimal data exist on the neutral position for the lumbar spine, trunk, and thighs when adopting a hybrid posture. This study examined sex differences in the neutral zone lumbar stiffness and the lumbar and trunk-thigh angle boundaries of the neutral zone, and determined if the standing lumbar angle fell within the neutral zone. Passive lumbar flexion and extension moment-angle curves were generated for 31 participants (13 M, 18 F), pooled from two datasets, with trunk-thigh angles available for 10 participants. The neutral zone was defined as the low stiffness zone from both the flexion and extension curves. Males demonstrated significantly greater extensor stiffness. Neutral lumbar and trunk-thigh angles ranged on average −22.2 to 0.2° and 124.2 to 159.6° for males and −17.8 to −1.3° and 143.2 to 159.5° for females, respectively. Standing lumbar angles fell outside the neutral zone for 44% of participants. These neutral zone boundaries may inform kinematics for hybrid chair designs. Practitioner summary: Adoption of a neutral spinal posture may be achieved through hybrid chair design, yet minimal data exists on a physiologically defined neutral zone. Using measures of in vivo lumbar stiffness, the lumbar and trunk-thigh angular boundaries of the neutral zone were defined for both males and females. Abbreviations: EMG: electromyography; MVC: maximal voluntary contraction [ABSTRACT FROM AUTHOR]

Background Lumbar lordosis measures are poorly related to clinical low back pain, however using a controlled exposure such as prolonged standing to identify pain groups may clarify this relationship. The purpose of this study was to determine the distribution of lumbar intervertebral angles in asymptomatic persons who do (pain developers) and do not (non-pain developers) develop low back pain during standing. Methods Sagittal plane lumbar spine radiographs of eight pain developers and eight non-pain developers were taken in three poses: upright standing, full extension and full flexion. Measures of vertebral end plate orientations from L1 to S1 were taken in each pose to compute: intervertebral angles, contribution of each level to the total curve, total lordosis, ranges of motion, relative pose positioning within the range of motion, vertebral shape, and lumbar spine recurve. Measures were compared between pain groups and lumbar levels. Findings Pain group differences in intervertebral angles and level contributions were greatest in the full extension pose, with pain developers having greater contributions from higher lumbar levels and fewer contributions from lower levels than non-pain developers. Pain group differences in intervertebral angle distributions were less pronounced in upright standing and non-existent in full flexion. No other measures differentiated pain groups. Interpretations Although participants had similar gross-lumbar spine curvature characteristics, non-pain developers have more curvature at lower levels in upright standing and full extension. These differences in regional vertebral kinematics may partially be responsible for standing-induced low back pain. [ABSTRACT FROM AUTHOR]

While alternating standing position on a sloped surface has proven successful at reducing low back pain during standing, the purpose of this study was to evaluate standing solely on a declining surface to isolate the influence of the postural change. Seventeen participants performed two 75-min prolonged standing occupational simulations- level ground and declining surface. Fifty-three percent of participants (9/17) were categorized as pain developers during the level ground standing condition. For these same pain developers, their average maximum pain scores were 58% lower during sloped standing. All participants showed greater hip flexion, trunk-to-thigh angle flexion, and posterior translation of the trunk center of gravity when standing on the sloped surface. These postural changes could cause the muscles crossing the hip posteriorly to increase passive stiffness and assist with stabilizing the pelvis. This study stresses the importance of hip kinematics, not just lumbar spine posture, in reducing prolonged standing induced low back pain. [ABSTRACT FROM AUTHOR]

Background Approximately 50% of a sample population will develop prolonged standing induced low back pain. The cause of this pain may be due to their lumbar spine posture. The purpose of this study was to investigate differences in lumbar posture between 17 participants categorized as a pain or non-pain developers during level ground standing. A secondary purpose was to evaluate the influence of two standing aids (an elevated surface to act as a foot rest and declined sloped surface) on lumbopelvic posture. Methods Four sagittal plane radiographs were taken: a normal standing position on level ground, when using an elevated foot rest, using a declined sloped surface, and maximum lumbar spine extension as a reference posture. Lumbosacral lordosis, total lumbar lordosis, and L1/L2 and L5/S1 intervertebral joint angles were measured on each radiograph. Findings There was a significant difference between the lumbosacral lordosis angle and L5/S1 angles in upright versus maximum extension; however, this was independent of pain group. The elevated surface was most effective at causing lumbosacral spine flexion. Interpretation Potentially successful postures for eliminating low back pain during prolonged standing mainly influence the lower lumbar lordosis. Future work should assess the influence of hip posture on low back pain development during standing. [ABSTRACT FROM AUTHOR]

With the recent attention to ‘sitting disease’, health practitioners and scientists are promoting standing in the workplace to decrease sedentary time, despite a high prevalence of low back pain (LBP) development during prolonged standing. The purpose of this study was to assess how a seated break inserted between bouts of prolonged standing would influence LBP development, posture and movement. A total of 20 participants stood for 45 minutes, sat for 15 minutes and repeated this sequence while lumbar and thoracic angles were measured, and LBP visual analogue scale reports were taken. Of the sample, 55% participants reported LBP in standing. A stand to sit ratio of 3:1 did not provide lasting recovery of LBP from standing and pain developers utilised a limited range of their lumbar spine angle and increased thoracic extension, resulting in static postures that caused tissue aggravation that was not resolved after 15 minutes of sitting. Prolonged standing in the workplace has the potential to result in LBP for some workers and alternate ways to reduce sedentary time should be investigated. Practitioner Summary:Recommending standing to replace sitting should be undertaken with caution. A ratio of 3:1 (stand to sit) did not mitigate standing induced LBP. Practitioners should consider the interplay between standing and seated work and provide a variety of activities to reduce sedentary time tailored to work, preference and tolerance for an activity. [ABSTRACT FROM PUBLISHER]

Abstract: Previous literature has shown that individuals can develop transient low back pain (LBP) during a 2-h bout of unconstrained prolonged standing. The purpose of this study was to investigate the postural changes of individuals who develop LBP during standing (PD) and those who do not (NPD). Forty-one subjects (20 male, 21 female) participated in a 2-h prolonged standing occupational simulation and recorded their ratings of perceived LBP on a visual analog scale (VAS). Center of pressure changes (shifts, drifts, and fidgets) and body weight shifts were determined for each subject. All subjects showed an increase in the BW shift frequency and a decrease in average shift duration over the 2-h protocol. All NPD and female PD were consistent for many of the variables; however, male PD did not show similar patterns to the other groups, especially for anterior–posterior (AP) shift amplitude and total body weight asymmetry. Although gender differences between the pain groups were found, PD and NPD do not use different postural changes during unconstrained standing, showing that changes to postural control may be an “adaptive”, rather than “causative” response to their LBP development. Future works should concentrate on bridging the literature seen in quiet standing before and after prolonged standing and the response of PD, as well as the effect of an exercise intervention on postural control, especially for male PD. [Copyright &y& Elsevier]