Jack Callaghan

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Verified

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• Professor
• Canada Research Chair in Spine Biomechanics and Injury Prevention at University of Waterloo

This study explored differences in activities and spine kinematics by transient low back pain status throughout a week of their usual office work. Using a 100-mm visual-analogue scale, twenty participants were classified as non-pain (NPD) and pain developers (PD; ≥10 mm). Tri-axial accelerometers measured sitting time and thorax, pelvis, and lumbar...

Background Active sitting chairs have been proposed as an effective approach for reducing sedentary behaviour in the workplace. Objective This cross-sectional study evaluated how an active sitting chair altered energy expenditure compared to a traditional office chair during seated computer work. Methods Sixteen participants (8M/8F) completed two...

Occupational applicationsAcross a series of standing single-handed exertions performed at different lateral angles, distances, heights, and loads, lumbar axial twist exceeded an angular threshold of 9° in select exertions. Specifically, 9° of rightward axial twist was exceeded for all exertions performed laterally (90° from the body midline). Addit...

Force plates are used as standalone measurement systems in research and practice to evaluate metrics such as jump height. Calculating jump height involves multiple procedural steps, but previous investigations aiming to improve calculation procedures have only considered the influence of a single procedural step in isolation. The purpose of this st...

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 s...

Study Design 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 compres...

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...

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 stand...

Non-neutral neck positions are important initial conditions in impact scenarios, associated with a higher incidence of injury. Repositioning in finite element (FE) neck models is often achieved by applying external boundary conditions (BCs) to the head while constraining the first thoracic vertebra (T1). However, in vivo, neck muscles contract to a...

Background context: Injury to the cartilaginous endplate (CEP) is linked to clinically relevant low back disorders, including intervertebral disc degeneration and pain reporting. Despite this link to clinical disorders, the CEP injury pathways and the modulating effect of mechanical loading parameters on the pace of damage accumulation remains poo...

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 sitti...

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. Summary of Background Data. The endplate is physiologically and functiona...

In vivo lumbar passive stiffness is often used to assess time-dependent changes in lumbar tissues and to define the neutral zone. We tested the hypothesis that flexing the hips would alter tension in hip and spine musculature, leading to a more extended passive stiffness curve (i.e., right-shifted), without changes in lumbar stiffness. Twenty parti...

Computational approaches for movement onset detection can standardize and automate analyses to improve repeatability, accessibility, and time efficiency. With the increasing interest in assessing time-varying biomechanical signals such as force–time recordings, there remains a need to investigate the recently adopted 5 times the standard deviation...

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 include...

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 designe...

Background: Sitting can induce transient low back pain (LBP) in healthy individuals. A rest from sitting should provide relief, however, the parameters of breaks (activity type, intensity, duration, and timing) are not currently known. Objective: The purpose of this study was to examine the effect of 2-minute walking breaks at 40-minute interval...

Background Spinal manipulation has been shown to affect muscle activity, posture, and pain. To date, no studies have examined the effect of manipulation on biomechanical factors during sitting. Therefore, the purpose of this study was to investigate the immediate effect of lumbar spinal manipulation on trunk muscle activation, spine posture and mov...

Occupations or activities where donning head-supported mass (HSM) is commonplace put operators at an elevated risk of chronic neck pain. Yet, there is no consensus about what features of HSM influence the relative contributions to neck loads. Therefore, we tested four hypotheses that could increase neck loads: (i) HSM increases gravitational moment...

Chair design features are typically compared using multiple seats, which can lead to confounding effects. Using a single chair, configurable to four designs (control, lumbar support, seat pan tilt and scapular relief), we investigated the effect of chair design on spine posture and movement, muscle activity and perceived pain in a sample of 31 asym...

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 s...

This study aimed to mathematically characterize the ultimate compression tolerance (UCT) as a function of spinal joint posture, loading variation, and loading duration. One hundred and fourteen porcine cervical spinal units were tested. Spinal units were randomly assigned to subthreshold cyclic loading groups that differed by joint posture (neutral...

Prolonged driving has been linked to the development of low back pain. Methods to examine time varying postural changes of the lumbar spine during driving have been scarcely investigated. Distinguishing postural variation as movement patterns such as lumbar shifts and fidgets may provide novel insight, which may otherwise be lost with analyses that...

Background: Spine manipulation has been shown to affect muscle activity, posture, and pain. To date, no studies have examined the effect of manipulation on biomechanical factors during sitting. Therefore, the purpose of this study was to investigate the immediate effect of lumbar spine manipulation on trunk muscle activation, spine posture and move...

The annulus fibrosus (AF) and endplate (EP) are collagenous spine tissues that are frequently injured due to gradual mechani-cal 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, t...

Although sitting on a stability ball has become an alternative to using an office chair, little is known about the increased potential for a fall on the deformable seat. This study examined differences in stability between sitting on a seat pan of a backless office chair and a stability ball during reaching tasks. Sixteen participants performed for...

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 flex...

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 c...

INTRODUCTION: Between 43 and 97% of helicopter pilots in the Canadian Armed Forces report neck pain. Potential contributing factors include the weight of their helmet, night vision goggles (NVG), and counterweight (CW) combined with deviated neck postures. Therefore, the purpose of this investigation was to quantify changes in neck loads associated...

Background: Chronic Neck Pain (CNP) among rotary-wing aircrew is thought to stem from night vision goggles (NVG) and counterweight (CW) systems which displace the centre of mass of the head. This investigation aimed to quantify the loads acting on the neck as a function of movement magnitude (MM), helmet conditions, and movement axes in rapid move...

Force plate analyses of various activities sometimes require the average (WPav) and standard deviation (WPsd) of force across the Weighing Phase (i.e., quiet period) to calculate kinetic, temporal and kinematic metrics. Yet, the influence of weighing phase duration on these analyses has been scarcely investigated. This study investigated the effect...

Complaints of musculoskeletal pain are common among employees who stand for prolonged periods. This study sought to determine if an anti-fatigue mat (AFM) could uniquely affect low back pain (LBP), low back posture, and foot-floor interface responses in individuals prone to developing LBP (termed pain developers (PDs)) during prolonged standing exp...

The facet capsule ligament (FCL) is a structure in the lumbar spine that constrains motions of the vertebrae. Subfailure loads can produce micro-damage resulting in increased laxity, decreased stiffness, and altered viscoelastic responses. Therefore, the purpose of this investigation was to determine the mechanical and viscoelastic properties of th...

Background Qualitative clinical assessments of spinal stiffness have been demonstrated to show moderate correlations with one-another. We hypothesized that these correlations would improve in an in vitro model of the functional spinal unit. If the stiffness of spinal units are different across loading regimes (e.g. flexion-extension versus shear),...

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. Constrai...

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 cap...

Background Historically, there has been a lack of focus on the lumbar spine during rear impacts because of the perception that the automotive seat back should protect the lumbar spine from injury. As a result, there have been no studies involving human volunteers to address the risk of low back injury in low velocity rear impact collisions. Method...

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...

Despite growing literature, limited research details the influence of passive upper limb exoskeletons on upper limb kinematics. Two bolting tasks and a tracing task were completed at two heights (overhead and between waist and overhead height) for four exoskeleton conditions (no exoskeleton, and 3 levels of exoskeleton assistance) by female partici...

Objective To explore how individual characteristics influence selected lumbar support prominence (LSP), seated lumbar flexion, seatback average pressure, contact area, and center of pressure (CoP) location before and after 1 hr of driving. Background An LSP can alter posture and may reduce low back pain during prolonged driving. Although LSP prefe...

Relatively few biomechanical models exist aimed at quantifying the mechanical risk factors associated with neck pain. In addition, there is a need to validate spinal-rhythm techniques for inverse dynamics spine models. Therefore, the present investigation was 3-fold: (1) the development of a cervical spine model in OpenSim, (2) a test of a novel sp...

As the prevalence of obesity grows worldwide, it becomes an increasing concern in working populations. Ergonomists are faced with the challenge of accommodating workplace layouts to include this worker demographic. This study investigated the relationship between shoulder and low back isometric joint strengths across body mass index (BMI) groups. A...

Study design: An in vitro biomechanics investigation exposing porcine functional spinal units (FSUs) to sudden impact loading while in a flexed, neutral, or extended posture. Objective: To investigate the combined effect of impact severity and postural deviation on intervertebral joint mechanics. Summary of background data: To date, no in vitr...

The relationship between externally measured and internal spine axial twist motion (rotation about a vertical axis) is not well understood. Ultrasound is a validated technique for measurement of vertebral axial twist motion and has the potential for measuring segmental vertebral axial twist in vivo. The objective of this study was to evaluate lumba...

The aim of this experimental study was to assess the biomechanical performance of a novel C1 posterior arch (C1PA) clamp compared with C1 lateral mass (C1LM) screws in constructs used to treat atlantoaxial instability. These constructs had either C2 pedicle (C2P) screws or C2 translaminar (C2TL) screws. Eight fresh-frozen human cadaveric ligamentou...

OCCUPATIONAL APPLICATIONS Military helicopter pilots around the globe are at high risk of neck pain related to their use of helmet-mounted night vision goggles. Unfortunately, it is difficult to design alternative helmet configurations that reduce the biomechanical exposures on the cervical spine during flight because the time and resource costs as...

Rotator cuff pathology typically originates in the supraspinatus tendon, but uncertainty exists on how combinations of glenohumeral elevation angle and load intensity influence responses of the intact, functional supraspinatus unit. This study exposed the supraspinatus tendon to mechanical loading scenarios emulative of derived muscle force and pos...

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 p...

A collision testing device used to simulate rear-end impacts on human volunteers was developed and validated. The testing device impact profile was designed using parameters obtained from real crash-test derived vehicle to vehicle rear-end collisions. Experimental results show the proposed testing device achieves repeatable impact parameters well w...

Inconsistent filtering of force plate data persists in published studies. Previous evidence suggests that low pass filtering produces the largest error when calculating jump height, but used jump height from unfiltered force plate data as the criterion. This study investigated the effects of low pass filtering on jump height calculated from force p...

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 an...

Accurate characterization of the mechanical response of collagenous tissues is critical for investigations into mechanisms of soft tissue injury. These tissues are inherently viscoelastic, exhibiting strain-rate dependent stiffnesses, creep, and stress-relaxation. The strain-rate features of the failure portion of the stress-strain curve are less w...

BACKGROUND: Mass, moment of inertia, and amplitude of neck motion were altered during a reciprocal scanning task to investigate how night vision goggles (NVGs) use mechanistically is associated with neck trouble among rotary-wing aircrew. METHODS: There were 30 subjects measured while scanning between targets at 2 amplitudes (near and far) and unde...

The lumbar extensor spinae (LES) has an oblique orientation with respect to the compressive axis of the lumbar spine, allowing it to counteract anterior shear forces. This mechanical advantage is lost as spine flexion angle increases. The LES orientation can also alter over time as obliquity decreases with age and is associated with decreased stren...

Repetitive trunk flexion can damage spinal tissues, however its association with low back pain in the workplace may be confounded by factors related to pain sensitivity. Muscle fatigue, exercise-induced hypoalgesia, and creep-induced neuromuscular changes following repetitive trunk flexion may all affect this assumed exposure-pain relationship. Thi...

Objective: To present and evaluate a method to objectively quantify the functional regions of joint lumped passive stiffness. Background: Joint passive stiffness has an important clinical role in constraining the degrees of freedom at a given joint. Links between passive stiffness and injury, pathology and function may be better understood if jo...

Viscoelastic creep generated in the lumbar spine following sustained spine flexion may affect the relationship between tissue damage and perceived pain. Two processes supporting this altered relationship include altered neural feedback and inflammatory processes. Our purpose was to determine how low back mechanical pain sensitivity changes followin...

This study evaluated early and frequent seated breaks from standing work to reduce low back pain (LBP) in known pain developers (PD). Twenty-four participants, classified as either PD or non-PD during a separate 2-hour standing session, performed 124 minutes of standing work with seated breaks at a 3:1 stand-sit ratio with increasing durations from...

Minimal footwear has become more ubiquitous; however, it may increase slip severity. This study specifically examined the slipping kinematics of flip-flop sandals. Invoked slips from standing were evaluated in dry and wet tile, and a unique wet footbed + wet tile condition, with 40, 50, and 60% bodyweight (BW) committed to the slipping foot. Water...

w Currently, there is no guidance on the training program approach that should be provided to new sit-stand workstation users to optimally integrate workstation usage patterns into their working day. The objective of this research study was to determine if a training program could influence long-term usage of sit-stand workstations. Thirty-five emp...

This study quantified the effect of compression load and duration on the deflection of five separate anti-fatigue flooring surfaces. Following standardized measurement of A Shore hardness, each sample underwent simulated single-leg stance indentation procedures that differed by compression load (45.3 kg, 90.7 kg, 136.1 kg) and duration (initial = 2...

The purpose of this investigation was to determine the effect of prolonged seated work, lift task, age and sex on normalized lumbar angles, thoracic angles, perceived effort and duration of lifts. A total of 17 young and 17 mature participants were recruited with an average (standard deviation) age of 23.8 (5.0) years and 63.7 (3.9) years, respecti...

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. Thirty-two porcine spinal units were randomly assigned to experimental groups t...

Spinal stiffness and mobility assessments vary between clinical and research settings, potentially hindering the understanding and treatment of low back pain. A total of 71 healthy participants were evaluated using 2 clinical assessments (posteroanterior spring and passive intervertebral motion) and 2 quantitative measures: lumped mechanical stiffn...

People developing transient low back pain during standing have altered control of their spine and hips during standing tasks, but the transfer of these responses to other tasks has not been assessed. This study used video fluoroscopy to assess lumbar spine intervertebral kinematics of people who do and do not develop standing-induced low back pain...

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 devel...

Introduction: Strains and sprains of soft tissues, including tendons and ligaments, are frequently occurring injuries. Musculoskeletal models show great promise in prediction and prevention of these injuries. However, these models rarely account for the viscoelastic properties of ligaments and tendons, much less their failure properties. Therefore...

Quantifying user behaviors at sit-stand desks is critical to understanding the efficacy of these workstations to reduce exposures to prolonged sitting or standing. A custom after-market desk-mounted sensor predicting sit-stand desk use by measuring desk floor heights, desk user distances, and the temperature in front of the desk was tested. We perf...

Background: Home care providers assisting with seniors' personal care often experience high rates of musculoskeletal disorders, particularly affecting the lower back. Assisting with bathing is consistently identified as one of their most physically demanding activities. Objective: To identify and describe care providers' procedures for assisting...

Objective The aim of this study was to determine the inter- and intrarater agreement of estimated wrist angles using video and to compare wrist angles from video analysis to electrogoniometers. Background Video analysis is used frequently in ergonomic assessments, but factors including parallax and complex angles may influence wrist angle estimate...

OCCUPATIONAL APPLICATIONS The aim of this project was to develop and test an application capable of quickly and repeatedly measuring trunk flexion angles during sagittal plane lifting tasks. The developed application uses the built-in accelerometer in mobile devices to approximate trunk flexion angle, as the user follows an operator as they perform...

Prolonged static sitting has been associated with a number of negative health consequences. In prior work investigating office seating designs, the main focus has been on lumbar supports and backrest recline angles. To date, however, there is very limited information on the impact of backrest height on physiologic responses to sitting. Thus, the pr...

Three-dimensional joint angles are most often quantified using Euler Angles. These measures are often easier to interpret if they are reported relative to a reference posture. However, since Euler Angles are not vectors, directly subtracting their values is difficult to justify mathematically. We compared four methods for subtracting a reference po...

Nerve compression due to intervertebral disc (IVD) bulging is a known mechanism for low back pain and typically occurs in the posterior region of the disc. Most in vitro studies are limited in the ability to quantify the magnitude of bulging on the posterior aspect of the disc due to the boney structures that occlude a direct line-of-sight in the i...

Objectives: This study compares people with recurrent low back pain (rLBP) and people with pre-clinical low back pain (standing-induced low back pain developers; PDs) to each other and back-healthy controls (non-pain developers; NPDs). Movement variability and muscular co-activity related to coordination are important for both rLBP and PDs, and the...

Axial twisting exposures have been repeatedly identified as a risk factor for occupational low back pain and injury, but there is a need for an improved understanding of the role of axial twist magnitude and associated joint moment as modifiers of the cumulative load tolerance of intervertebral joints. The purpose of this study was to mathematicall...

A computerised system for measuring radial displacement of the intervertebral disc (IVD) based on laser scanning was developed and validated. The system is designed to allow for quantitative analysis of changes in peak IVD displacement on the posterior and anterior side of the disc. This computerised system facilitates quantifying the magnitude of...

Ladder-related falls are common in many industries and lead to high rates of injury and hospitalization. This study aimed to establish safety criteria for ladder stability and potential for failure in the event of an operator fall when equipped with a fall arrest system that has been attached to the ladder as opposed to a fixed structure anchor poi...

Purpose: Cervical spine flexion is a common posture for those using computers, tablets, and smartphones; the latter being dubbed ‘text-neck’ in recent years. Coincidentally, flexion has been flagged as a significant mechanical risk factor for the development of chronic neck pain. Unfortunately, few modelling endeavors have attempted to quantify the...

Recently, the rate at which sit-to-stand workstations are being introduced into the workplace has seen a dramatic increase. Aside from adjusting the height of the desk when transitioning from sitting to standing, there is a lack of literature regarding the necessary adjustments to other equipment associated with the workstation. To better understan...

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 (i.e. large joint deviations) under physiological loading could be useful as it may help explain why vis...

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 (N = 20...

Nonlinear weighting adjustments were implemented to study low back injury potential associated with variable compression exposures. This in vitro study exposed porcine spinal units to cyclic compression paradigms that had consistent and variable peak amplitudes until failure was detected. When weighted, the tolerated compression was similar between...

This study examined the effect of inter-cycle loading variation on cumulative tolerance in isolated spinal units. An in vitro paradigm was used to compare custom sinusoidal waveforms (i.e., consistent vs. variable amplitude) constructed with control between specimens for an equal average peak amplitude and total cumulative load. Spinal units expose...

Various interventions, such as standing intermittently with one leg on a footrest, have been suggested to prevent low back pain (LBP) development during prolonged standing. To assess this standing intervention twelve participants stood for 80 min while cycling through three minute periods of level-ground standing divided by one minute periods with...

Repetitive movement is common in many occupational contexts. Therefore, cumulative load is a widely recognized risk factor for low-back injury. This study quantified the effect of force weighting factors on cumulative load estimates and injury prediction during cyclic loading. Forty-eight porcine cervical spine motion segments were assigned to expe...

Objective: Up to 50% of individuals involved in low-velocity motor vehicle collisions report low back pain (LBP). A major limitation in such cases is the lack of knowledge of injury mechanisms linking the collision characteristics to the pain and pathology associated with LBP reporting. Thus, the objective of this investigation was to characterize...