Determining whether biomechanical variables that describe common 'safe lifting' cues are associated with low back loads.

Lift technique training programs have been implemented to help reduce injury risk, but the underlying content validity of cues used within these programs is not clear. The objective of this study was to determine whether biomechanical variables, that commonly used lifting cues aim to elicit, are associated with resultant low back extensor moment exposures. A sample of 72 participants were recruited to perform 10 repetitions of a floor-to-waist height barbell lift while whole-body kinematics and ground reaction forces were collected. Kinematic, kinetic, and energetic variables representative of characteristics commonly targeted by lifting cues were calculated as predictor variables, while peak and cumulative low back moments were calculated as dependent measures. Multiple regression revealed that 56.6-59.2% of variance in low back moments was explained by predictor variables. From these regression models, generating motion with the legs (both greater hip and knee work), minimizing the horizontal distance of the body to the load, maintaining a stable body position, and minimizing lift time were associated with lower magnitudes of low back moments. These data support that using cues targeting these identified variables may be more effective at reducing peak low back moment exposures via lift training.

The Influence of Contextual and Theoretical Expertise on Generic and Occupation-Specific Lifting Strategy.

OBJECTIVE: To determine whether (i) low back loads and/or (ii) kinematic coordination patterns differed across theoretical expert, contextual expert and novice groups when completing both generic and occupation-specific lifts. BACKGROUND: Experience has been proposed as a factor that could reduce biomechanical exposures in lifting, but the literature reports mixed effects. The inconsistent relationship between experience and exposures may be partially attributable to the broad classification of experience and experimental lifting protocols not replicating the environment where experience was gained. METHODS: Purposive sampling was used to recruit 72 participants including theoretical experts (formal training on lifting mechanics), contextual experts (paramedics), and novices. Participants performed 10 barbell and crate (generic) lifts, as well as backboard and stretcher (occupation-specific) lifts while whole-body kinematics and ground reaction forces were collected. Peak low back compression and anteroposterior shear loads normalized to body mass, as well as kinematic coordination patterns, were calculated as dependent variables. RESULTS: No significant differences in low back loads were observed across expertise groups. However, significant differences were seen in kinematic coordination patterns across expertise groups in occupation-specific lifts, but not in generic lifts. CONCLUSION: Increasing expertise is unlikely to minimize low back loads in lifting. However, contextual expertise did influence lifting kinematics, but only when performing occupationally specific lifts. APPLICATION: Contextual expertise may help lifters adopt lifting kinematics that enhance the tolerance of their musculoskeletal system to withstand applied loads, but does not seem to reduce the applied low back loads relative to noncontextual expert groups.

Increased Ability to Perceive Relevant Sensory Information Minimizes Low Back Exposures in Lifting.

We have previously shown evidence that some individuals seem to consistently minimize low back loads when lifting, while others do not. However, it is unknown why. Individual differences in ability to perceive relevant sensory information may explain differences in minimization of low back loads during lifting, consistent with considering load reduction in one's movement objective in an optimal feedback control theory framework. The purpose of this study was to investigate whether individuals' ability to perceive proprioceptive information (both force- and posture-senses) at the low back was associated with peak low back loads when performing generic or occupation-specific lifts. Seventy-two participants were recruited to perform 10 barbell (generic) and backboard (occupation-specific) lifts, while whole-body kinematics and ground reaction forces were collected. Peak low back compression and anteroposterior shear forces normalized to body mass were calculated as dependent variables. Both posture matching ability and force matching ability at the heavier force targets were associated with lower means and variability of peak low-back loads in both lift types, albeit with small effect sizes (R2 ≤ .17). These findings support the utility of an optimal feedback control theory framework to explore factors explaining interindividual differences in low back loads during lifting. Further, this evidence suggests improving proprioceptive ability may be a useful strategy in lift training programs designed for workplace injury prevention.

Factors influencing the likelihood of females passing the Ottawa paramedic physical ability test.

The Ottawa Paramedic Physical Ability Test (OPPAT) was launched in Ontario as a physical employment standard for front-line paramedics. When considering pass rates based on sex, males had a higher likelihood of passing than females. To help understand how to improve pass rates among females we aimed to understand if factors such as participant demographics, college type, employment status and/or peak heart rate (a surrogate of fitness level) were related to OPPAT pass rates. Females who were employed, who were educated in a public paramedic college, and who had higher body mass were more likely to successfully complete the OPPAT. Those educated in a public paramedic college were more than twice as likely to pass relative to those educated in a private college program. This may underscore a need to further explore different modes of paramedic education to understand why public college program trained students are more likely to pass.

Quantifying the Importance of Active Muscle Repositioning a Finite Element Neck Model in Flexion Using Kinematic, Kinetic, and Tissue-Level Responses.

PURPOSE: 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 achieve a desired head and neck position generating initial loads and deformations in the tissues. In the present study, a new muscle-based repositioning method was compared to traditional applied BCs using a contemporary FE neck model for forward head flexion of 30°. METHODS: For the BC method, an external moment (2.6 Nm) was applied to the head with T1 fixed, while for the muscle-based method, the flexors and extensors were co-contracted under gravity loading to achieve the target flexion. RESULTS: The kinematic response from muscle contraction was within 10% of the in vivo experimental data, while the BC method differed by 18%. The intervertebral disc forces from muscle contraction were agreeable with the literature (167 N compression, 12 N shear), while the BC methodology underpredicted the disc forces owing to the lack of spine compression. Correspondingly, the strains in the annulus fibrosus increased by an average of 60% across all levels due to muscle contraction compared to BC method. CONCLUSION: The muscle repositioning method enhanced the kinetic response and subsequently led to differences in tissue-level responses compared to the conventional BC method. The improved kinematics and kinetics quantify the importance of repositioning FE neck models using active muscles to achieve non-neutral neck positions.

Differential effects of sex on upper body kinematics and kinetics during fatiguing, Asymmetric lifting.

This study quantified sex-specific biomechanical adaptations to fatigue in asymmetric lifting. Twenty-one females and fifteen males performed a prolonged asymmetric lifting protocol while upper body, trunk and pelvis kinematics were collected. Features of movement identified with principal component analysis, and peak joint angular velocities and moments were calculated. Sex-specific kinematic adaptations to fatigue included females adopting a 'stoop-like' lifting strategy to a greater extent than males. Additionally, females exhibited higher vertical elbow positions during load rotation, moved their body toward the destination for load deposit, and did not reduce peak right shoulder flexion velocities, in contrast to male participants. Females also had greater low back and shoulder peak normalized joint moments. When fatigued, females adopted an asymmetric lifting strategy that minimized metabolic demand as supported by smaller decreases in maximum voluntary contractions. However, females' fatigue-related adaptations increased biomechanical exposures associated with injury risk.

Throwing Shoulder Range of Motion and Hamstring Flexibility in Adolescent Baseball Players: A Pilot Study.

Overhead throwing athletes with limited hamstring flexibility should be counseled appropriately regarding their risk for shoulder injury. Baseball players should stretch and prepare their bodies to throw to reduce the compensatory mechanisms that may occur from hamstring stiffness. We aim to identify the association between the contralateral hamstring-popliteal angle and throwing shoulder total range of motion (ROM) in high school baseball players. Fifteen high school varsity baseball players (ages 14-18 years old) volunteered for this observational study. All the athletes played five times a week and played different positions. Bilateral hamstring and throwing shoulder total ROMs were measured using a goniometer by the same examiner. Three examiners determined the maximum ROM by joint end feel for each measurement to ensure quality control. Contralateral hamstring flexibility was measured using the popliteal angle test. These measurements were compared to the throwing shoulder total ROM to determine the presence of an association. The relationship between the contralateral hamstring flexibility and throwing shoulder total ROM was determined using a linear regression analysis. The correlation coefficient (r) was +0.3928, indicating a positive linear relationship. We conclude that higher contralateral hamstring-popliteal angles may cause a compensatory increase in throwing shoulder total ROM. We highlight the role hamstring stiffness may play in shoulder injury development in adolescent baseball players.

Quantifying how functional and structural personal factors influence biomechanical exposures in paramedic lifting tasks.

It is unknown how structural (sex, stature, body mass) and functional (strength, flexibility) personal factors influence lifting strategy in paramedic work. We explored whether variance in peak low back forces and kinematic coordination patterns could be explained by structural and functional personal factors in paramedic lifting tasks. Seventy-two participants performed backboard and stretcher lifts. Peak low back forces normalised to body mass, as well as kinematic coordination patterns, were calculated as dependent variables. Being female, stronger, shorter, having higher body mass, and/or having greater lower body range of motion (ROM) were all independently associated with lower normalised low back forces across backboard and stretcher lifting. Females and stronger individuals seemed to define a movement objective to consistently minimise compressive forces, while individuals with greater hip ROM consistently minimised anteroposterior shear forces. The efficacy of improving strength and hip ROM to reduce low back forces in paramedic lifting should be investigated.Practitioner summary: Females, stronger individuals, and individuals with greater hip range of motion consistently exhibited lower normalised low back forces in paramedic lifting. Improving strength and hip range of motion via training is a potential proactive ergonomics approach to reduce peak low back forces in paramedic lifting tasks.

The Value of Interdisciplinary Collaboration in Lateral Medullary Syndrome Rehabilitation: A Case Report.

Wallenberg's syndrome, also known as lateral medullary syndrome (LMS), is a neurological condition resulting from damage to the lateral portion of the medulla oblongata. We present a case of a 64-year-old man with Wallenberg's syndrome who presented for acute rehabilitation after sustaining a cerebrovascular accident (CVA). As seen in our patient, common symptoms of LMS include difficulty swallowing, hoarseness, ipsilateral weakness, and ipsilateral loss of sensation or numbness. Although the prognosis following infarction is often good, dysfunction in swallowing is one of the key deficits that have a long-term impact on patient quality of life. We aim to emphasize the significance of the interdisciplinary approach to achieving favorable health outcomes in patients with LMS.

Managing Chronic Regional Pain Syndrome: The Potential Impact of the Food and Drug Omnibus Reform Act.

Complex regional pain syndrome (CRPS) is a neurological disorder characterized by persistent limb symptoms. With there being no definitive tests, diagnosis can be challenging. The Budapest criteria are the standard for diagnosis. The underlying mechanisms of CRPS involve changes in skin innervation, sensitization of the nervous system, inflammatory cytokines, and genetic and psychological factors. Treatment typically involves a multidisciplinary approach. We present a case of a 71-year-old male with CRPS involving the right upper extremity and a complex history of management including physical therapy, oxycodone, muscle relaxers, non-steroidal anti-inflammatory drugs, and multiple stellate ganglion blocks. The patient manages his pain with off-label medications, including methadone, duloxetine, and pregabalin. In the United States, the management of chronic pain may be affected by potential usage restrictions imposed by the Food and Drug Omnibus Reform Act (FDORA). Under this new act, physicians may face limitations in prescribing off-label medications for specific diagnoses. We aim to highlight the need for prioritizing patient care and individualized treatment in healthcare policy decision-making.

Identifying the critical physically demanding tasks performed by personal support workers in Canada.

Due to increased work demands, personal support workers (PSWs) are experiencing more work-related injuries. However, little is known about PSW work tasks and their corresponding physical demand. The purpose of this study was to identify critical tasks that are physically demanding and completed frequently as identified by PSWs. Additionally, we identified contextual factors (i.e., environmental-, situational-, patient-related) that influenced physical demands. We surveyed 443 community-based PSWs working in Canada who rated the physical demand associated with client care tasks and identified contextual factors that can increase task specific physical demands. Transferring/repositioning patients, dressing, and bathing were perceived as most demanding. Patient weight and mobility influenced the level of physical demand required for most tasks. These data provide a foundation to develop physical employment standards and task specific education and training to prevent PSW injuries.

Long-Term Retained Lippes Loop Intrauterine Device Causes Vesicouterine Fistula.

This case report discusses a 77-year-old female patient who presented to an outpatient clinic with urinary symptoms and recurrent UTIs. Imaging revealed a foreign body, which was later confirmed as a retained intrauterine device (IUD) that had caused a vesicouterine fistula (VUF). The patient had a medical history of cervical cancer treated with radiation therapy, during which her IUD's string could not be located, leading to the decision to proceed with radiation therapy without removing the IUD. The patient opted to manage her condition medically rather than undergo surgical removal due to concerns about worsening the vesicouterine fistula. This case highlights the potential risks and complications of retained IUDs, and the importance of careful consideration and communication among clinical teams and patients when managing these situations.

Head supported mass, moment of inertia, neck loads and stability: A simulation study.

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 moments; (ii) more muscle activation is required to stabilize the head with HSM; (iii) the position of the HSM centre of mass (COM) induces gravitational moments; and (iv) the added moment of inertia (MOI) from HSM increases neck loads during head repositioning tasks. We performed a sensitivity analysis on the C5-C6 compression evaluated from a 24-degree freedom cervical spine model in OpenSim for static and dynamic movement trials. For static trials, we varied the magnitude of HSM, the position of its COM, and developed a novel stability constraint for static optimization. In dynamic trials, we varied HSM and the three principle MOIs. HSM magnitude and compression were linearly related to one another for both static and dynamic trials, with amplification factors varying between 1.9 and 3.9. Similar relationships were found for the COM position, although the relationship between C5-C6 peak compression and MOI in dynamic trials was generally nonlinear. This sensitivity analysis uncovered evidence in favour of hypotheses (i), (ii) and (iii). However, the model's prediction of C5-C6 compression was not overly sensitive to the magnitude of MOI. Therefore, the HSM mass properties may be more influential on neck compression than MOI properties, even during dynamic tasks.

Exploring the relationship between kinematic variability and fatigue development during repetitive lifting.

To investigate the variability-fatigue and repeaters-replacers hypotheses, motor variability (MV) and indicators of fatigue were assessed during repetitive lifting. Eighteen participants performed sequential repetitive bouts of lifting divided into a short bout, and three phases of a prolonged bout until volitional fatigue (or until a 1-h time limit). Whole-body kinematics were collected to calculate variability in three-dimensional joint angles and in continuous relative phase (CRP) of sagittal joint angle couplings, which were summed for the upper and lower body, and whole-body. Excellent individual consistency (ICC = 0.95-0.97) was demonstrated across lifting bouts as fatigue developed. Therefore, strong evidence was obtained for MV as an individual trait in support of the repeaters-replacers hypothesis. Associations were found for endurance and baseline effort with lower body variability, while no associations were found for rate of fatigue. Thus, some support was found for the variability-fatigue hypothesis which suggests that repeaters are less fatigue-resistant than replacers.

The effects of whole-body vibration and head supported mass on performance and muscular demand.

For military rotary-wing aircrew, little is known about the interactive effects of vibration exposure and the addition of head supported mass (HSM) on target acquisition performance, head kinematics, and muscular demand. Sixteen healthy male participants wore an aviator helmet with replica night vision goggles and completed rapid aiming head movements to acquire visual targets in axial and off-axis movement trajectories while secured in a Bell-412 helicopter seat mounted to a human-rated shaker platform. HSM configuration (with or without a counterweight (CW)) and vertical whole-body vibration (WBV) conditions (vibration or no vibration exposure) were manipulated as independent variables. WBV exposure degraded target acquisition performance and lengthened time to peak velocity of head movements. For yaw peak velocity in the axial movement trajectory, peak velocity was 9.9%, 11.6%, and 8.4% higher in the noCW + WBV condition compared to the CW + WBV, CW + noWBV, and noCW + noWBV conditions, respectively.Practitioner summary: The majority of military helicopter aircrew use a counterweight to counteract the anteriorly displaced load of night vision googles. This study was undertaken to better understand how helicopter vibration and counterweight use interactively affect performance and health-related measures during rapid scanning head movements.

A response surface methodology to determine the optimal objective function weightings within a multi-objective optimization digital human model used to predict postures.

Multi-objective optimization digital human models permit users to predict postures that follow performance criteria, such as minimizing torques. Currently, it is unknown how to weight different objective functions to best predict postures. Objective one was to describe a response surface method to determine optimal objective function weightings to predict lift postures. Objective two was to evaluate the sensitivity of different error calculation methods. Our response surface approach has utility for determining optimal objective function weightings when using a digital human model to evaluate human-system interactions in early design stages. The approach was not dependent on variations in error calculation methods.

Detecting subject-specific fatigue-related changes in lifting kinematics using a machine learning approach.

Individual responses to fatigue have been observed in lifting kinematics, suggesting a subject-specific approach is necessary for fatigue identification. One-class support vector machines (OCSVM) may provide an objective method to classify fatigue-related kinematic changes during repetitive lifting. Participants completed a repetitive lifting protocol while motion capture recorded lifting motions. Subject-specific kinematics from participants' first 35% of lifts trained OCSVM decision boundaries. The remaining lifts were separated into test sets and classified against the decision boundary to identify the percentage of outlier lifts within each test set. Spearman's correlation assessed if the test sets' percentage of outlier lifts increased concurrently with participants' rating of perceived exertion (RPE). Significant positive associations were found for participants who demonstrated evidence of fatigue, while no significant associations were found for participants who did not demonstrate evidence of fatigue. These results demonstrate the prospective efficacy of an outlier detection tool for fatigue detection during repetitive lifting.Practitioner Summary: An objective subject-specific fatigue detection method is desired for workplace tasks, such as lifting. An outlier detection machine learning approach was identified when lifting movement patterns changed from baseline throughout a repetitive lifting protocol. Participants who demonstrated an increase in outlier movement patterns had a concurrent increase in self-reported fatigue.

Exploring the role of task on kinematic variability and assessing consistency in individual responses across repetitive manual tasks.

To gain a greater understanding of motor variability (MV) as an individual trait, the effect of task type on MV and individual consistency in MV across three tasks was investigated. Twenty participants performed repetitive carrying, lifting, and simulated sawing tasks. MV was assessed using the linear measure of mean point-by-point standard deviation in three-dimensional upper body joint angles. Task type affected MV, where carrying showed higher MV compared to sawing (23-29%) and lifting (12-19%). Furthermore, MV was higher in lifting compared to sawing (12-25%). Poor to moderate individual consistency (ICC = 0.42-0.63) was found across tasks. Task type determined MV and only some support for MV as an individual trait across tasks was found. Based on this work, differences in degrees of freedom afforded by the task influence the opportunity to exploit MV, and possibly individual consistency in MV magnitude is specific to the degrees of freedom afforded by the task. Practitioner summary: In repetitive tasks, movement variability has been proposed as an individual characteristic independent of task characteristics, where repeaters show consistently low variability, while replacers show consistently high variability. In the current study, only moderate support was demonstrated for variability as a consistent individual characteristic across different manual tasks.AbbreviationMV: Motor variability; WRMSDs: Work-related musculoskeletal disorders; DOF: Degrees of freedom; meanSD: Mean standard deviation; SD: Standard deviation; H: Handle (of simulated sawing setup); T: Track (of simulated sawing setup); F: Frame (of simulated sawing setup); ICC: Intraclass correlation; UE: Upper extremity; MMH: Manual material handling; EMG: Electromyography.

Comparison of machine learning classifiers for differentiating level and sport using movement data.

The purposes of this study were to determine if 1) recurrent neural networks designed for multivariate, time-series analyses outperform traditional linear and non-linear machine learning classifiers when classifying athletes based on competition level and sport played, and 2) athletes of different sports move differently during non-sport-specific movement screens. Optical-based kinematic data from 542 athletes were used as input data for nine different machine learning algorithms to classify athletes based on competition level and sport played. For the traditional machine learning classifiers, principal component analysis and feature selection were used to reduce the data dimensionality and to determine the best principal components to retain. Across tasks, recurrent neural networks and linear machine learning classifiers tended to outperform the non-linear machine learning classifiers. For all tasks, reservoir computing took the least amount of time to train. Across tasks, reservoir computing had one of the highest classification rates and took the least amount of time to train; however, interpreting the results is more difficult compared to linear classifiers. In addition, athletes were successfully classified based on sport suggesting that athletes competing in different sports move differently during non-sport specific movements. Therefore, movement assessment screens should incorporate sport-specific scoring criteria.

Relationship between occupational stress injury score and simulated patient-care scenario performance among experienced paramedics.

BACKGROUND: It is well-known that psychosocial health status of paramedics may be altered by their job demands. However, it is unknown whether psychosocial health status can affect occupational performance. OBJECTIVE: The goal of this study was to explore whether a paramedic's symptom severity of Occupational Stress Injury (OSI) was related to simulated patient-care performance. METHODS: Nineteen paramedics with 15.0±8.7 years of paramedic experience participated in this study. Participants completed both an OSI symptom severity questionnaires, and a patient-care simulation. Vagal activity was also collected during the patient-care simulation. The simulation was used to assess experienced paramedics in a realistic stressful setting. Based on the provincial standard in New Brunswick, an experienced paramedic instructor graded the patient-care simulation using the provincial standard charts, observing performance videos and assessing data from the manikin. RESULTS: The current study suggests that paramedics who self-reported elevated symptoms of OSI were less likely to successfully complete the simulated patient-care scenario. CONCLUSION: This research suggests that the presence of self-reported elevated symptoms of OSI negatively impacts paramedics' performance during a stressful work task simulation. Therefore, to help paramedics maintain optimal performance, it may be important to ensure that paramedics have access to appropriate resources to monitor and improve their psychosocial health.