Traditional versus dynamic sitting: Lumbar spine kinematics and pain during computer work and activity guided tasks.

Dynamic sitting may mitigate low back pain during prolonged seated work. The current study compared pelvis and lumbar spine kinematics, pain, and work productivity, in traditional and dynamic sitting. Sixteen participants completed three 20-min blocks of computer work and activity guided tasks in a traditional office chair or backless and multiaxial rotating seat pan while kinematics were measured from accelerometers on the low back.

Lateral Pelvis and Lumbar Motion in Seated and Standing Office Work and Their Association With Transient Low Back Pain.

Objective: To assess frontal plane motion of the pelvis and lumbar spine during 2 h of seated and standing office work and evaluate associations with transient low back pain.

Background: Although bending and twisting motions are cited as risk factors for low back injuries in occupational tasks, few studies have assessed frontal plane motion during sedentary exposures.

Methods: Twenty-one participants completed 2 h of seated and standing office work while pelvic obliquity, lumbar lateral bending angles, and ratings of perceived low back pain were recorded.

Experimentally Dissociating the Acute Mechanisms of Endplate Fracture Lesions and Schmorl's Node Injuries Using a Porcine Cervical Spine Model.

Study Design: This is an in vitro biomechanical study.

Objective: This study evaluated the influence of localized trabecular bone strength deficits and loading rate as determinants of Schmorl's node and fracture lesion incidence. The failure load (ultimate compression tolerance [UCT]), loading stiffness, and failure morphology were assessed after acute compression loading and failure.

Exploring the Influence of Facet Orientation and Tropism on Neutral Zone Properties.

Lumbar spine pathologies have been linked independently to both neutral zone (NZ) properties and facet joint anatomical characteristics; however, the effect of facet joint orientation (FO) and tropism (FT) on NZ properties remains unclear. The aim of the present study was to investigate how axial plane FO and FT relate to NZ range and stiffness in the human lumbar spine and porcine cervical spine. Seven human lumbar functional spine units (FSUs) and 94 porcine cervical FSUs were examined.

Implementing an accelerometer-based pelvis segment for low back kinetic analyses during dynamic movement tasks.

An accelerometer-based pelvis has been employed to study segment and joint kinematics during scenarios involving close human-object interface and/or line-of-sight obstructions. However, its accuracy for examining low back kinetic outcomes is unknown. This study compared reaction moments and contact forces of the L5S1 joint calculated with an accelerometer-based and optically tracked pelvis segment.

Indentation mechanics and native collagen content in the cartilaginous endplate: A comparison between porcine cervical and human lumbar spines.

This study characterized the regional indentation mechanics and native collagen content in cartilaginous endplates (CEPs) from the porcine cervical spine, young human lumbar spine, and aged human lumbar spine. Seventeen endplates were included in this study: six porcine cervical, nine young human lumbar, and two aged human lumbar. Width and depth measurements were obtained using a digital caliper and used to size-normalize and identify the central, anterior, posterior, and lateral regions.

Increasing movement during office work at sit-stand workstations: A novel seating device to facilitate transitions.

A novel active office chair (Movably Pro) was designed to facilitate frequent sit-stand movement 1) through auditory and tactile prompts and 2) with minimal-to-no work surface adjustment when transitioning. The purpose of this study was to compare lumbopelvic kinematics, discomfort, and task performance between the novel chair and traditional sitting/standing. Sixteen participants completed three separate 2-h sedentary exposures.

Experimentally dissociating the overuse mechanisms of endplate fracture lesions and Schmorl's node injuries using the porcine cervical spine model.

Background: Compared to the documented overuse mechanisms of endplate fracture lesions, the cause of Schmorl's node injuries remains unknown, despite existing hypotheses. Therefore, this study aimed to examine and dissociate the overuse injury mechanisms of these spinal pathologies.

Methods: Forty-eight porcine cervical spinal units were included.

Mechanical work and energy of sit-to-stand and stand-to-sit transitions performed with traditional and dynamic office chair designs.

Background: Adherence to sit-stand workstation usage has been shown to decrease post-intervention, with the reported reasons related to fatigue, cumbersome workstation adjustments, and focus.

Objective: To characterize the mechanical work and total energy required to perform transitions from a traditional office chair and a dynamic chair designed specifically for sit-stand workstations. The whole-body, thigh, and shank centre-of-mass (CoM) were evaluated.

Incidence of Compression-Induced Microinjuries in the Cartilage Endplate of the Spine.

Study Design: In vitro biomechanical study.

Objective: This study investigated the incidence of microstructural endplate injuries caused by cyclic compression loading. The covarying effects of joint posture, loading duration, and peak compression variation were assessed.

Cyclic loading history alters the joint compression tolerance and regional indentation responses in the cartilaginous endplate.

This study quantified the effect of subthreshold loading histories that differed by joint posture (neutral, flexed), peak loading variation (10%, 20%, 40%), and loading duration (1000, 3000, 5000 cycles) on the post-loading Ultimate Compressive Tolerance (UCT), yield force, and regional Cartilaginous End Plate (CEP) indentation responses (loading stiffness and creep displacement). One hundred and fourteen porcine spinal units were included. Following conditioning and cyclic compression exposures, spinal units were transected and one endplate from each vertebra underwent subsequent UCT or microindentation testing.

Kinematic adaptations to restricting spine motion during symmetrical lifting.

When lifting an object from the ground a person has many possible whole-body movement solutions to accomplish the task. It is unclear why lifters use most of their available lumbar spine flexion range-of-motion despite many ergonomic guidelines advising against doing so. Experimentally restricting spine motion and observing compensatory movement strategies is one approach to address this knowledge gap.

Mechanically induced histochemical and structural damage in the annulus fibrosus and cartilaginous endplate: a multi-colour immunofluorescence analysis.

The annulus fibrosus (AF) and endplate (EP) are collagenous spine tissues that are frequently injured due to gradual mechanical overload. Macroscopic injuries to these tissues are typically a by-product of microdamage accumulation. Many existing histochemistry and biochemistry techniques are used to examine microdamage in the AF and EP; however, there are several limitations when used in isolation.

Characterizing Lumbar Spine Kinematics and Kinetics During Simulated Low-Speed Rear Impact Collisions.

Background: Recent work has demonstrated that low back pain is a common complaint following low-speed collisions. Despite frequent pain reporting, no studies involving human volunteers have been completed to examine the exposures in the lumbar spine during low-speed rear impact collisions.

Methods: Twenty-four participants were recruited and a custom-built crash sled simulated rear impact collisions, with a change in velocity of 8 km/h.

Strain Response in the Facet Joint Capsule During Physiological Joint Rotation and Translation Following a Simulated Impact Exposure: An In Vitro Porcine Model.

Low back pain (LBP) is frequently reported following rear impact collisions. Knowledge of how the facet joint capsule (FJC) mechanically behaves before and after rear impact collisions may help explain LBP development despite negative radiographic evidence of gross tissue failure. This study quantified the Green strain tensor in the facet joint capsule during rotation and translation range-of-motion tests completed before and following an in vitro simulation of a rear impact collision.

Reaction Forces and Flexion-Extension Moments Imposed on Functional Spinal Units With Constrained and Unconstrained In Vitro Testing Systems.

A mechanical goal of in vitro testing systems is to minimize differences between applied and actual forces and moments experienced by spinal units. This study quantified the joint reaction forces and reaction flexion-extension moments during dynamic compression loading imposed throughout the physiological flexion-extension range of motion. Constrained (fixed base) and unconstrained (floating base) testing systems were compared.

Regulating Movement Frequency and Speed: Implications for Lumbar Spine Load Management Strategies Demonstrated Using an In Vitro Porcine Model.

The relationship between internal loading dose and low-back injury risk during lifting is well known. However, the implications of movement parameters that influence joint loading rates-movement frequency and speed-on time-dependent spine loading responses remain less documented. This study quantified the effect of loading rate and frequency on the tolerated cumulative loading dose and its relation to joint lifespan.

Reconstructing an accelerometer-based pelvis segment for three-dimensional kinematic analyses during laboratory simulated tasks with obstructed line-of-sight.

Close interface between humans and inanimate objects (furniture, assistive devices, and external loads) can obstruct line-of-sight in biomechanics studies that utilize optoelectronic motion capture systems. This specific problem is frequently encountered with the pelvis segment. This study sought to compare joint and pelvis angles computed from a pelvis-fixed local coordinate system (LCS) that was constructed from optically tracked pelvis landmarks (gold standard) and landmarks derived from angular deviations calculated from triaxial accelerometer data.

Exploring the influence of impact severity and posture on vertebral joint mechanics in an in-vitro porcine model.

To date, no in vitro studies have been conducted to explore lumbar soft tissue injury potential and altered mechanical properties from exposure to impact forces. After a motor vehicle collision (MVC), the cause of reported acute onset low back pain is difficult to associate with potential soft tissue strain injury sites including the facet joint and innervated facet joint capsule ligament (FJC). Thus, the purpose of this investigation was to quantify intervertebral anterior-posterior (AP) translation and facet joint capsule strain under varying postures and impact severities.

Joint fatigue-failure: A demonstration of viscoelastic responses to rate and frequency loading parameters using the porcine cervical spine.

Fatigue-failure in low back tissues is influenced by parameters of cyclic loading. Therefore, this study quantified the effect of loading rate and frequency on the number of tolerated compression cycles. Energy storage and vertical deformation were secondarily examined.

Strain of the facet joint capsule during rotation and translation range-of-motion tests: an in vitro porcine model as a human surrogate.

Background Context: Prior data about the modulating effects of lumbar spine posture on facet capsule strains are limited to small joint deviations. Knowledge of facet capsule strain during rotational and translational intervertebral joint motion (ie, large joint deviations) under physiological loading could be useful as it may help explain why visually normal lumbar spinal joints become painful.

Purpose: This study quantified the strain tensor of the facet capsule during rotation and translation range-of-motion tests.

Spine loading during laboratory-simulated fireground operations - inter-individual variation and method of load quantification.

Spine loading data are needed to design low-back health-preserving ergonomic interventions for firefighters. Study objectives were to quantify spine loads during simulated fireground operations using simple (polynomial) and advanced (EMG-assisted musculoskeletal model) methods and to describe the variation in spine loads between performers ( = 20). Spine compression forces differed by as much as 5.

Examining endplate fatigue failure during cyclic compression loading with variable and consistent peak magnitudes using a force weighting adjustment approach: an study.

Repetitive movement is common in many occupational contexts. Therefore, cumulative load is a widely recognised risk factor for lowback injury. This study quantified the effect of force weighting factors on cumulative load estimates and injury prediction during cyclic loading.

Partitioning the total seatback reaction force amongst the lumbar spine motion segments during simulated rear-impact collisions.

. This study aimed to determine how the seatback force is distributed across lumbar spine motion segments during a simulated low-velocity rear-impact collision with and without the application of mechanical lumbar support. .