Axial twist of the lumbar spine: Mechanical responses to twisted postures and potential factors for workplace injury

While a link between magnitudes of spinal axial twist motions and the various modes of associated injury, pain reporting, and lost time claims has been tentatively established, there is need for greater investigation and understanding of the mechanical impact of axial twist motions. Researchers have compiled data sets demonstrating the relationship between twisting motions and moments and low back injury outcomes, but do not create a link to gross occupational exposures. Further, few studies can create a direct relationship between workstation design, trunk postures, and spine joint specific pain and failure mechanisms. When this limited mechanistic understanding is paired with injury prevalence statistics, they highlight a clear need to investigate the role of tissue-level axial twist exposures on occupational injury risk and workstation design guidelines to mitigate that risk. The global objective of this research was focused on developing a relationship between working axial twist postures and intervertebral joint injury risk. The four specific questions asked were (1) What is the relationship between externally measured thoracopelvic axial twist and the actual segmental axial twist motion of the intervertebral joints? (2) Can we use ultrasound as a modality to consistently and accurately measure vertebral axial twist motion? (3) What amount of lumbar axial twist presents an elevated injury risk for working populations? (4) What movement strategies do people use to perform reaching tasks at different hand locations, and how do task parameters impact these strategies? Study 1: Ultrasound has the potential for use to evaluate boney movement during axial twist of the lumbar spine in both in vivo and in vitro evaluations. Such segmental rotations could then be measured under controlled external thoracic axial twist conditions and in response to mechanical loading. The purpose of this study was to measure vertebral segmental rotations in a porcine model of the human lumbar spine using an ultrasound imaging protocol, and to validate use of this imaging technique with an optical motion capture system. Twelve porcine functional spinal units were fixed to a mechanical testing system, and compression (15% of compressive tolerance), flexion-extension, and axial twist (0, 2, 4, or 6 degrees) were applied. Axial twist motion was tracked using an optical motion capture system and posterior surface ultrasound. Correlation between the two measurement systems was greater than 0.903 and absolute system error was 0.014 across all flexion-extension postures. These findings indicate that ultrasound can be used to track axial twist motion in an in vitro spine motion segment and has the potential for use in vivo to evaluate absolute intervertebral axial twist motion. Study 2: The relationship between externally measured and internal spine axial twist motion is not well understood. Ultrasound is a validated technique (Study 1) for measurement of vertebral axial twist motion and has the potential for measuring segmental vertebral axial twist in vivo. The purpose of this study was to evaluate lumbar segmental axial twist in relation to external thoracopelvic twist using an ultrasound imaging technique. Sixteen participants kneeled in a custom-built axial twist jig which isolated motion to the lumbar spine. Participants twisted from neutral to 75% of maximum twist range of motion in an upright flexion-extension posture. Thoracopelvic motion was recorded with a motion capture system and L1 to S1 vertebral axial twist was recorded using ultrasound. Maximum thoracopelvic axial twist motion was 41.1 degrees. The majority of axial twist motion occurred at the L2-L3 (46.8% of lumbar axial twist motion) and L5-S1 (33.5%) intervertebral joints. Linear regression fits linking axial twist at each vertebral level to thoracopelvic axial twist ranged from 0.43 to 0.79. These findings demonstrate a mathematical relationship between internal and external axial twist motion, and suggest that classic use of L4-L5 to represent lumbar spine motion may not be appropriate for axial twist modeling approaches. Study 3: 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 moment as modifiers of the cumulative load tolerance of intervertebral joints. The purpose of this study was to mathematically characterize the relationship between axial twist motion magnitudes and the cumulative load tolerance of porcine cervical functional spinal units. Twenty-four porcine functional spinal units were fixed in a mechanical testing system under compressive load (15% of compressive tolerance) and in a neutral flexion-extension posture. Specimens were axially twisted to 5, 7.5, 10, 12.5, 15 or 17.5 degrees at 1 Hz until failure or 21 600 total cycles. Cumulative applied axial twist was recorded, and exponential functions were fit to the twist magnitude-cumulative twist moment recordings. Weighting-factor functions for cumulative axial twist moment injury risk were developed based on absolute axial twist magnitude and twist normalized to maximum range of motion. The non-linear weighting-factors have potential use in assessment of cumulative axial twist injury risk in occupational tasks. Study 4: The magnitude of axial twist in the lumbar spine in relation to reaching tasks is currently unknown. Therefore, the purpose of this study was to investigate lumbar spine axial twist during simulated occupational tasks across a range of forward and lateral reach distances, task heights, and exertion directions. Twenty-four participants performed single-handed, right-handed exertions against a load cell in three directions (upward, downward, forward push), at two heights (shoulder, elbow), and at 11 different hand target locations corresponding to current ergonomic reach guidelines. Thoracopelvic and right upper limb postures were recorded using an optical motion capture system, and trunk muscle activation was recorded using surface electromyography. Participants performed a contralateral twist at both the thoracopelvic spine and pelvis about the feet for directly forward hand targets, and twisted up to 19.9 degrees and 12.1 degrees at the lumbar spine and pelvis, respectively, at the most lateral hand target locations. Lumbar flexion and shoulder elevation each increased with reach distance to a maximum of 5.6 degrees and 64.9 degrees, respectively, at the furthest, directly forward hand target location. Hip and abdominal muscle activation exceeded 10% MVC for the most lateral hand target locations, and exhibited the highest activation for upward and forward push exertions. These findings suggest that future ergonomics guidelines should assess reaching and exertion tasks to hand target locations beyond 60-degrees from the midline of the body and consider them as non-optimal zones. The collection of studies in this thesis was structured to improve current ergonomics reach guidelines and provide a physiological and biomechanical basis for reach distance recommendations incorporating the low back. The findings from these studies have important implications for researchers, ergonomists, and clinicians assessing injury risk related to twisted occupational postures

Quantification and Evaluation of Physical Shoulder Exposures in Police Mobile Data Terminal Operators

Mobile police officers perform many of their daily duties within vehicles. Combined workspace inflexibility and prolonged driving exposure creates a risk for developing musculoskeletal issues. Limited research exists that quantitatively describes postural and load exposures associated with mobile police work. This study characterized officer activity during a typical workday and recommended a cruiser configuration that minimized musculoskeletal risk through laboratory quantification of physical loading during simulated police patrol tasks. A field study captured and analyzed digital video of traffic constables (N = 10) using custom Regional Enforcement Activity Characterization Tool (REACT) software. Mobile data terminal use represented over 13% of in-car activity time and was identified as a primary site for targeted design change. A laboratory study included 20 (10 male, 10 female) participants aged 18-35 with no recent history of right upper limb or low back disorder. Five mobile data terminal (MDT) locations and two driver seat designs were tested in two simulated police patrol testing sessions in a custom driving simulator. A self-selected mobile data terminal location reduced mean right shoulder elevation angle as well as perceived discomfort in both the low back and right shoulder relative to all other tested locations. Muscle activity was lowest at the self-selected location and current MDT location for all recorded muscles, with significant effects shown in posterior deltoid (p < .0001) and supraspinatus (p < .0001). Using a global ranking system, the self-selected location was identified as the best of all tested locations, followed by the current mobile data terminal location. The ALS driver seat effectively reduced discomfort (p < .0001) in the low back during a simulated police patrol session from 15.4mm in the Crown Victoria seat to 11.1mm on a VAS scale. Under these experimental conditions, a self-selected MDT and ALS driver seat reduced discomfort and physical loading compared to the current configuration

Explicit teaching of models to enrich physical science learning

Good teaching inducts students into science as a human endeavour and demonstrates that scientific knowledge arises from a process of model construction, testing and review. The historical evolution of scientific knowledge is the development and refinement of models to explain scientific observations. The explicit use of models in teaching facilitates metacognitive engagement, which can lead to improved conceptual understanding (Kenyon et al., 2008). The Science curriculum in Victoria, Australia is modelled on the Australian national curriculum and begins with an explicit aim of students developing an understanding of “the nature of scientific inquiry and the ability to use a range of scientific inquiry methods.” Models are mentioned frequently in the more detailed curriculum statements. For example, the curriculum strand “Science as a human endeavour” includes the following statement: “Scientific understanding, including models and theories, are contestable and are refined over time through a process of review by the scientific community.” In this work we present examples of the representation of models in the secondary physical science curriculum and highlight opportunities for enriching the teaching of science through the explicit introduction of the history and nature of the model, with an emphasis on linking to metacognition (Avargil et al., 2017). REFERENCES Avargil, S., Lavi, R., &amp; Dori, Y. (2017). Students’ Metacognition and Metacognitive Strategies in Science Education, in Y.J. Dori, Z.R. Mevarech, &amp; D.R. Baker (ed.). Cognition, metacognition, and culture in STEM education: Learning, teaching and assessment, Springer International Publishing AG, 33-64. Kenyon, L., Schwarz, C. &amp; Hug, B. (2008), The Benefits of Scientific Modeling. Science and Children, 46(2), 40-44

INVESTIGATING DRILL CONSTRAINT KINEMATICS IN MALE BASEBALL PITCHERS USING MARKERLESS MOTION CAPTURE

This study investigated the kinematic differences that pitching constraint drills elicit compared to a baseball pitch. 18 male baseball pitchers with average height (183.7 ± 5.2cm), weight (87.4 ± 9.6kg), and skill level (Professional (4), Collegiate (5), High School (9)) were included. Video was recorded using a single camera from the open side. Each pitcher threw 3 maximum effort pitches from a mound. Next, 3 maximum effort throws were recorded for 8 different throwing drills: medicine ball hook’em drill, pivot pickoff drill, foot-up rocker drill, walk-in drill, towel drill, janitor drill, drop-step drill, and long toss. Videos were processed using pitchAITM, a markerless motion capture solution. The medicine ball hook’em drill was the most different to a pitch, and the towel drill was the most similar. This work demonstrates the first collective approach to studying the biomechanics of frequently used baseball pitching constraint drills

DETERMINING RELATIONSHIPS BETWEEN KINEMATIC SEQUENCING AND BASEBALL PITCH VELOCITY USING MARKERLESS MOTION CAPTURE

The purpose of this study was to determine how the timings and magnitudes of peak pelvis rotational velocity, peak trunk rotational velocity, peak elbow extension velocity, and peak shoulder internal rotation velocity affect pitch velocity. Eighty pitchers (187.2 ± 8.2cm, 89.3 ± 13.0kg, 20.1 ± 3.3yrs) had a minimum of 3 fastballs recorded and video was processed using pitchAITM. Average pitch velocity was 38.1 ± 2.5 m/s. A multilinear regression generated a significant prediction for pitch velocity (R2 = 0.368 and p \u3c 0.01). Pitcher weight (β = 0.535, p \u3c 0.001), peak pelvis rotational velocity timing (β = -0.157, p = 0.001), peak elbow extension timing (β = 0.122, p = 0.006), and peak shoulder internal rotation timing (β = -0.113, p = 0.018), were significant contributors to the multilinear model. In conclusion, player weight and their kinematic sequence metrics from pitchAITM can be significant predictors of pitch velocity

Characterising encapsulated nuclear waste using cosmic-ray muon tomography

Tomographic imaging techniques using the Coulomb scattering of cosmic-ray muons have been shown previously to successfully identify and characterise low- and high-Z materials within an air matrix using a prototype scintillating-fibre tracker system. Those studies were performed as the first in a series to assess the feasibility of this technology and image reconstruction techniques in characterising the potential high-Z contents of legacy nuclear waste containers for the UK Nuclear Industry. The present work continues the feasibility study and presents the first images reconstructed from experimental data collected using this small-scale prototype system of low- and high-Z materials encapsulated within a concrete-filled stainless-steel container. Clear discrimination is observed between the thick steel casing, the concrete matrix and the sample materials assayed. These reconstructed objects are presented and discussed in detail alongside the implications for future industrial scenarios.Comment: 6 pages, 4 figure

Uptake and transport of novel amphiphilic polyelectrolyte-insulin nanocomplexes by caco-2 cells - towards oral insulin

“The original publication is available at www.springerlink.com”. Copyright SpringerPurpose: The influence of polymer architecture on cellular uptake and transport across Caco-2 cells of novel amphiphilic polyelectrolyte-insulin nanocomplexes was investigated. Method: Polyallylamine (PAA) (15 kDa) was grafted with palmitoyl chains (Pa) and subsequently modified with quaternary ammonium moieties (QPa). These two amphiphilic polyelectrolytes (APs) were tagged with rhodamine and their uptake by Caco-2 cells or their polyelectrolyte complexes (PECs) with fluorescein isothiocyanate-insulin (FITC-insulin) uptake were investigated using fluorescence microscopy. The integrity of the monolayer was determined by measurement of transepithelial electrical resistance (TEER). Insulin transport through Caco-2 monolayers was determined during TEER experiments. Result: Pa and insulin were co-localised in the cell membranes while QPa complexes were found within the cytoplasm. QPa complex uptake was not affected by calcium, cytochalasin D or nocodazole. Uptake was reduced by co-incubation with sodium azide, an active transport inhibitor. Both polymers opened tight junctions reversibly where the TEER values fell by up to 35 % within 30 minutes incubation with Caco-2 cells. Insulin transport through monolayers increased when QPa was used (0.27 ngmL-1 of insulin in basal compartment) compared to Pa (0.14 ngmL-1 of insulin in basal compartment) after 2 hours. Conclusion: These APs have been shown to be taken up by Caco-2 cells and reversibly open tight cell junctions. Further work is required to optimise these formulations with a view to maximising their potential to facilitate oral delivery of insulin.Peer reviewe

Proteomic profiling of neuronal mitochondria reveals modulators of synaptic architecture

Abstract Background Neurons are highly polarized cells consisting of three distinct functional domains: the cell body (and associated dendrites), the axon and the synapse. Previously, it was believed that the clinical phenotypes of neurodegenerative diseases were caused by the loss of entire neurons, however it has recently become apparent that these neuronal sub-compartments can degenerate independently, with synapses being particularly vulnerable to a broad range of stimuli. Whilst the properties governing the differential degenerative mechanisms remain unknown, mitochondria consistently appear in the literature, suggesting these somewhat promiscuous organelles may play a role in affecting synaptic stability. Synaptic and non-synaptic mitochondrial subpools are known to have different enzymatic properties (first demonstrated by Lai et al., 1977). However, the molecular basis underpinning these alterations, and their effects on morphology, has not been well documented. Methods The current study has employed electron microscopy, label-free proteomics and in silico analyses to characterize the morphological and biochemical properties of discrete sub-populations of mitochondria. The physiological relevance of these findings was confirmed in-vivo using a molecular genetic approach at the Drosophila neuromuscular junction. Results Here, we demonstrate that mitochondria at the synaptic terminal are indeed morphologically different to non-synaptic mitochondria, in both rodents and human patients. Furthermore, generation of proteomic profiles reveals distinct molecular fingerprints – highlighting that the properties of complex I may represent an important specialisation of synaptic mitochondria. Evidence also suggests that at least 30% of the mitochondrial enzymatic activity differences previously reported can be accounted for by protein abundance. Finally, we demonstrate that the molecular differences between discrete mitochondrial sub-populations are capable of selectively influencing synaptic morphology in-vivo. We offer several novel mitochondrial candidates that have the propensity to significantly alter the synaptic architecture in-vivo. Conclusions Our study demonstrates discrete proteomic profiles exist dependent upon mitochondrial subcellular localization and selective alteration of intrinsic mitochondrial proteins alters synaptic morphology in-vivo