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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 with posture, helmet, NVG, and CW.METHODS: Eight male subjects volunteered. They undertook one of five deviated neck postures (flexion, extension, lateral bending, axial rotation) times four configurations (no helmet, helmet only, helmet and NVG, and helmet, NVG, and CW). 3D kinematics and EMG from 10 muscles (5 bilaterally) drove a 3D inverse dynamics, EMG-driven model of the cervical spine which calculated joint compression and shear at C5-C6.RESULTS: The compression in the neutral posture was 116.5 (5.7) N, which increased to 143.7 (11.4) N due to a 12.7 N helmet. NVGs, weighing 7.9 N, also generated this disproportionate increase, where the compression was 164.2 (3.7) N. In flexion or extension, the compression increased with increasing head-supported mass, with a maximum of 315.8 (67.5) N with the CW in flexion. Anteroposterior shear was highest in the lateral bending [34.0 (6.2) N] condition, but was generally low (< 30 N). Mediolateral shear was less than 5 N for all conditions.DISCUSSION: Repositioning the center of gravity of the helmet with either NVGs or CW resulted in posture-specific changes to loading. Posture demonstrated a greater potential to reposition the head segment’s center of gravity compared to the helmet design. Therefore, helmet designs which consider repositioning the center of gravity may reduce loads in one posture, but likely exacerbate loading in other postures.Barrett JM, McKinnon CD, Dickerson CR, Laing AC, Callaghan JP. Posture and helmet configuration effects on joint reaction loads in the middle cervical spine. Aerosp Med Hum Perform. 2022; 93(5):458–466.

This study sought to compare and validate baseball pitching mechanics, including joint angles and spatiotemporal parameters, from a single camera markerless motion capture solution with a 3D optical marker-based system. Ten healthy pitchers threw 2-3 maximum effort fastballs while concurrently using marker-based optical capture and pitchAI

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 3:1 minute to 48:16 minutes. Back pain and spine posture measures showed no differences between PD and non-PD. Females had greater left glutaeus medius activation (8.4%MVC) than males (4.5%MVC) and greater glutaeus medius co-contraction. This protocol was successful at reducing LBP in PD to the level of non-PD, with mean pain scores (13 mm) only slightly exceeding the clinical LBP threshold of 10 mm. Early and frequent breaks within the first hour of standing work appear to be an effective solution to reduce the LBP that often occurs at the beginning of standing work.

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 estimates. Electrogoniometers are an alternative to video, but may not be reliable in complex postures. Given the limitations of each method, there is a need to determine the suitability of the measurement methods for field use. Method Ten participants performed frame-by-frame wrist (flexion–extension, radioulnar deviation) and forearm (pronation–supination) posture estimation for worker tasks from three camera views (top, side, and oblique). Workers were equipped with electrogoniometers to record wrist posture during the tasks. The video estimate data was compared between 2 days and to sensor data. Results Percent agreement between participants ranged from 53% to 81% across all ratings. Agreement was highest from the side view (66%, κ = 0.56) for flexion–extension and top view for radioulnar deviation (77%, κ = 0.52) and pronation–supination (69%, κ = 0.58). Video–electrogoniometer agreement was lower, with peak agreement from the top view for flexion–extension (57%, κ = 0.49) and radioulnar deviation (68%, κ = 0.30) and the oblique view for pronation–supination (53%, κ = –0.1). Conclusion Participant estimate agreement was moderate-substantial overall and aligns with previous reports. Disagreement between video and electrogoniometers may be attributed to camera angle and parallax effects and the small magnitude of wrist motions compared to other joints.

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.

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 mag...

Current methods for physical demands descriptions often lack detail and format standardization, require technical training and expertise, and are time-consuming to complete. A video-based physical demands description tool may improve time and accuracy concerns with current methods. Ten simulated occupational tasks were synchronously recorded using a motion capture system and digital video. Digital video was processed with a novel video-based assessment tool to produce 3D joint trajectories (PDAi), and joint angle and reach envelope measures were calculated from both data sources. These measures were compared to joint angle and reach envelope estimates from experienced ergonomists (3) and novice ergonomists (3) in a simulated traditional physical demands description format. The video-based joint estimated showed 62.5% agreement with motion capture data across 80 measures (8 summary measures x 10 tasks). Video-based posture estimates were equal or better than human raters for 72.5% of ratings, and were outright better than human groups for 32.5% of ratings. The high level of agreement between video-based and motion capture measures suggest video-based job task assessment may be a viable approach to improve accuracy and standardization of field physical demands descriptions and minimize error in joint posture and reach envelope estimates compared to traditional pen-and-paper methods.

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 point. All combinations of five variables were tested in a custom-built load drop apparatus: ground surface, leaning surface, force direction, operator tether method, and ladder type. Overall, all conditions tested in this investigation with a simulated worker falling from a ladder with the fall arrest device attached to the ladder rails or a rung resulted in a pass. While there were clear deformations to the aluminum ladders and there were 3 failures due to repeated drop tests on the same ladder, replication of failed tests on a new ladder passed the failure conditions. Given a ladder that is in good working condition, has not be subjected to prior falls or damage, is properly erected and secured - a worker with a mass below 113kg (250lb) would be safely restrained when tethered to the ladder as opposed to the lanyard being tied off to a structure or a lifeline based on the simulated mass drops performed in this study in controlled laboratory conditions.

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 ligamentous spine specimens (C0-C3) were tested under six conditions: the intact state, the destabilized state after a simulated odontoid fracture, and when instrumented with four constructs (C1LM-C2P, C1LM-C2TL, C1PA-C2P, C1PA-C2TL). Each specimen was tested in a spinal loading simulator that separately applied axial rotation, flexion-extension and lateral bending. In each test condition, displacement controlled angular motion was applied in both directions at a speed of 2 deg/s until a resulting moment of 1.5 Nm was achieved. The measured ranges of motion (ROM) of the C1-C2 segments were compared for each test condition using nonparametric Friedman tests. The destabilized state had significantly more C1-C2 motion ( p

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 endeavours have attempted to quantify the intervertebral joint loads throughout the cervical spine in flexion, while still accounting for muscular activation. Eight healthy male subjects undertook five trials beginning in a neutral posture, flexed to 45 degrees, and returned to a neutral posture. 3 D head-trunk angles and surface electromyography from 10 neck muscles (5 bilaterally) were used as inputs into an inverse dynamic cervical spine model based on a 50th percentile male to compute the compression and anteroposterior (AP) shear forces for this flexion task. In general, compression increases cranially to caudally throughout the cervical spine, but levels off at the C5-C6 level. Conversely, in a neutral posture, there is a constant 18 N of anterior shear at each joint level. Compression increased twofold throughout the cervical spine with flexion, whereas anterior shear increased fourfold in the upper cervical spine and dramatically decreased caudally. The dramatic change in joint kinetics provides some mechanical evidence for the role of posture and interplay with muscle activity in the development of chronic neck pain. Results from this study can reinforce the need for appropriate workstation and monitor configurations and support the increased loading hypothesised to occur in 'text neck' postures.

Ultrasound has potential for use in evaluation of bone and joint movement during axial twist of the lumbar spine both in vivo and in vitro. 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. In part 1, ultrasound transducer angle was confirmed to have no effect on sonogram point digitization. In part 2, 12 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°) were applied. Axial twist motion was tracked using an optical motion capture system and posterior surface ultrasound. Correlation between the two measurement systems was >0.903, and absolute system error was 0.01° 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.

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 spinal-rhythm technique based on minimizing the potential energy in the passive tissues, and (3) comparison of an electromyographically driven approach to estimating compression and shear to other cervical spine models. The authors developed ligament force–deflection and intervertebral joint moment–angle curves from published data. The 218 Hill-type muscle elements, representing 58 muscles, were included and their passive forces validated against in vivo data. Our novel spinal-rhythm technique, based on minimizing the potential energy in the passive tissues, disproportionately assigned motion to the upper cervical spine that was not physiological. Finally, using kinematics and electromyography collected from 8 healthy male volunteers, the authors calculated the compression at C7–T1 as a function of the head–trunk Euler angles. Differences from other models varied from 25.5 to 368.1 N. These differences in forces may result in differences in model geometry, passive components, number of degrees of freedom, or objective functions.

Background Current methods for describing physical work demands often lack detail and format standardization, require technical training and expertise, and are time-consuming to complete. A video-based physical demands description (PDD) tool may improve time and accuracy concerns associated with current methods. Methods Ten simulated occupational tasks were synchronously recorded using a motion capture system and digital video. The tasks included a variety of industrial tasks from lifting to drilling to overhead upper extremity tasks of different cycle times. The digital video was processed with a novel video-based assessment tool to produce 3D joint trajectories (PDAi), and joint angle and reach envelope measures were calculated and compared between both data sources. Results Root mean squared error between video-based and motion capture posture estimated ranged from 89.0 mm to 118.6 mm for hand height and reach distance measures, and from 13.5° to 21.6° for trunk, shoulder, and elbow angle metrics. Continuous data were reduced to time-weighted bins, and video-based posture estimates showed 75% overall agreement and quadratic-weight Cohen’s kappa scores ranging from 0.29 to 1.0 compared to motion capture data across all posture metrics. Conclusion and Application The substantial level of agreement between time-weighted bins for video-based and motion capture measures suggest that video-based job task assessment may be a viable approach to improve accuracy and standardization of field physical demands descriptions and minimize error in joint posture and reach envelope estimates compared to traditional pen-and-paper methods.

A postural evaluation of commercial licensed truck drivers was conducted to determine the ergonomic benefits of a truck seat prototype in comparison with an industry standard seat. Twenty commercially licensed truck drivers were recruited to perform a 90-min driving task. Postures were assessed using accelerometers and a backrest and seat pan pressure mapping system. Subjective discomfort measurements were monitored using two questionnaires: ratings of perceived discomfort (RPD) and the automotive seating discomfort questionnaire (ASDQ). Participants reported significantly higher discomfort scores when sitting in the industry standard seat. Participants sat with more lumbar lordosis and assumed a more extended thoracic posture when seated in the prototype. Pairing the gluteal backrest panel with the adjustable seat pan also helped reduce the average sitting pressure on both the seat pan and the backrest. The prototype provided several postural benefits for commercially certified truck drivers, as it did for a young and healthy population.

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 lumbar segmental axial twist in relation to external thoracopelvic twist from optical motion capture using an ultrasound imaging technique. Sixteen participants were tested in a custom-built axial twist jig, which isolated motion to the lumbar spine. Participants were moved from neutral to 75% of maximum axial twist range of motion in an upright kneeling posture. Thoracopelvic motion was recorded with a motion capture system and L1 to S1 vertebral axial twist was recorded using ultrasound. From motion capture, maximum thoracopelvic axial twist motion was 41.1 degrees. From ultrasound, 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 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 the distribution of motion across the lumbar spine suggests that classic use of L4-L5 to represent lumbar spine motion may not be appropriate for axial twist modelling approaches.

A postural evaluation during a prolonged driving task was conducted to determine the ergonomic validity of a new freely adjustable truck seat prototype. Twenty participants were recruited to perform two 2-h simulated driving sessions. Postures were assessed using motion capture, accelerometers and pressure pads. Subjective discomfort was also monitored in 15-min increments using ratings of perceived discomfort (RPD) and the Automotive Seating Discomfort Questionnaire. Participants had a more neutral spine posture during the first hour of the drive and reported lower RPDs while sitting in the prototype. Pairing the gluteal backrest panel with the adjustable seat pan helped reduce the average sitting pressure. The industry-standard truck seat may lead to the development of poor whole body posture, and the proposed ergonomic redesign of a new truck seat helped improve sitting posture and reduce perceived discomfort. Practitioner Summary: A new freely adjustable truck seat prototype was compared to an Industry standard seat to assess hypothesised improvements to sitting posture and discomfort for long haul driving. It was found that the adjustable panels in the prototype helped promote spine posture, reduce sitting pressure and improved discomfort ratings.

Background With the increase of tablet usage in both office and industrial workplaces, it is critical to investigate the influence of tablet usage on spine posture and movement. Objective To quantify spine kinematics while participants interacted with a tablet or desktop computer. Methods Fourteen participants volunteered for this study. Marker clusters were fixed onto body regions to analyze cervical and lumbar spine posture and sampled at 32 Hz (Optotrak Certus, NDI, Waterloo, Canada). Participants sat for one hour in total. Cervical and lumbar median angles and range of motion (10th to 90th % ile angles) were extracted from amplitude probability distribution functions performed on the angle data. Results Using a sloped desk surface at 15°, compared to a flat desk, influenced cervical flexion (p = 0.0228). Completing the form fill task resulted in the highest degree of cervical flexion (p = 0.0008) compared to the other tasks completed with cervical angles between 6.1°-8.5° higher than emailing and reading respectively. An interaction between device and task (p = 0.0061) was found for relative lumbar median spine angles. Conclusions Increased lumbar flexion was recorded when using a computer versus a tablet to complete various tasks. Task influenced both cervical and lumbar spine posture with the highest cervical flexion occurring while completing a simulated data entry task. A work surface slope of 15° decreased cervical spine flexion compared to a horizontal work surface slope.

Objective: We evaluated the effect of work surface angle and input hardware on upper-limb posture when using a hybrid computer workstation. Background: Offices use sit-stand and/or tablet workstations to increase worker mobility. These workstations may have negative effects on upper-limb joints by increasing time spent in non-neutral postures, but a hybrid standing workstation may improve working postures. Method: Fourteen participants completed office tasks in four workstation configurations: a horizontal or sloped 15° working surface with computer or tablet hardware. Three-dimensional right upper-limb postures were recorded during three tasks: reading, form filling, and writing e-mails. Amplitude probability distribution functions determined the median and range of upper-limb postures. Results: The sloped-surface tablet workstation decreased wrist ulnar deviation by 5° when compared to the horizontal-surface computer when reading. When using computer input devices (keyboard and mouse), the shoulder, elbow, and wrist were closest to neutral joint postures when working on a horizontal work surface. The elbow was 23° and 15° more extended, whereas the wrist was 6° less ulnar deviated, when reading compared to typing forms or e-mails. Conclusion: We recommend that the horizontal-surface computer configuration be used for typing and the sloped-surface tablet configuration be used for intermittent reading tasks in this hybrid workstation. Application: Offices with mobile employees could use this workstation for alternating their upper-extremity postures; however, other aspects of the device need further investigation.

Advances in police-specific technology have led to changes in work layout and physical occupational demands of mobile police officers. This study investigated the influence of police cruiser compartment configuration on perceived discomfort, muscle activation, shoulder kinematics, and typing performance during simulated police patrol. Participants completed a one-hour session including simulated driving and 2-min typing trials in a standard compartment configuration with a fixed mobile data terminal (MDT) location (ST), and in a modified compartment configuration with an MDT in front of the user and a rearward translated seat (MOD). The MOD configuration resulted in reductions of 55-65% in perceived shoulder discomfort, up to 3.4% MVC in shoulder muscle demands, and more neutral humeral orientations (shoulder elevation reduced by 13-25°). These improvements associated with the MOD configuration may have ergonomic implications for future police car designs, particularly as new technology is introduced in the mobile environment and advanced solutions are sought.

The purpose of this study was to identify occupational and car seat features causing discomfort in patrol officers, and to determine which body parts were experiencing the most discomfort. A Seat Features and Occupational Components Questionnaire, based on a 0 to 100 mm Visual Analog Scale (VAS), revealed that the duty belt was the occupational gear causing the most discomfort, followed by computer use within the car. The seat lumbar support was the seat feature causing the most discomfort. A Body Part Discomfort Questionnaire was administered at the beginning of the shift (T1), after six hours (T6), and at the end of the twelve hour shift (T12), for both day and night shifts. There were no significant differences in body part discomfort between the two types of shifts. There were, however, significant increases in body part discomfort ratings over the course of the working day, especially on the right side of the body. While some body parts experienced a significant increase in discomfort between the T1 and T6 (i.e., the neck, left upper back, right buttocks), some body parts only had a significant increase in discomfort after six hours (i.e., the lower back and mid back). The two body parts that experienced the highest levels of discomfort were the neck and lower back. A secondary purpose of the study was to identify the frequency of the activities that occur within the car. The largest portion of the workday and night were spent outside of the vehicle (46.1±10.8 % during the day, and 43.5±14.9% during the night). Left-handed driving occupied the most time in the car (26.3±10.1% during the day, and 25.7 ± 8.6% at night). A reduced or reconfigured duty belt, as well as decreased time spent in the car (doing paper work, computer work, and driving), could help decrease discomfort levels.

The introduction of mobile computing within a constrained vehicle environment has led to changes in the task demands of occupational groups such as professional drivers and law enforcement officers. The purpose of this study was to examine how mobile data terminal (MDT) use interacts with prolonged driving to induce postural changes or low-back discomfort. Eighteen participants (9 male, 9 female) completed two 120-min simulated driving sessions. Time-varying lumbar spine and pelvis postures, seat pan interface pressures and ratings of perceived discomfort were recorded at 15-min intervals. The introduction of a computer interface decreased pelvic posterior rotation by an average of 15° with respect to upright standing and increased peak average discomfort in the neck (5.9 mm), left shoulder (6.8 mm), midback (10.9 mm), low back (10.6 mm) and pelvis (11.5 mm) compared to driving alone. The incorporation of mobile computing warrants consideration in the design of vehicle work environments.

Police officers are at high risk for developing musculoskeletal injuries. This study aimed to determine differences in physical demands of patrol officers during day shifts and night shifts. Sixteen participants were recruited (10 males, 6 females) for in-vehicle observation over one full day shift and one full night shift. Dynamic pressure distribution when seated in the vehicle was assessed and compared between the first and last parts of each shift. Activity characterization and postural analyses were conducted from video that was recorded continuously for the duration of each shift to determine time spent in each task and corresponding postures. Postural analysis and cumulative joint loads were used to identify higher-risk tasks. Several activities caused the officers to adopt non-neutral postures of the neck, shoulders and back. Future work needs to focus on modifying the interior of the vehicle, as well as decreasing exposure time to activities resulting in non-neutral postures.

Mobile police officers perform many of their daily duties in their vehicles. Combined workspace inflexibility and prolonged driving create potential musculoskeletal injury risks. Limited research exists that quantitatively describes postural and load exposures associated with mobile police work. The purpose of this study was to characterize officer activity during a typical workday and identify opportunities for ergonomic intervention. Digital video of traffic officers (N = 10) was used to classify postures according to work activity. Cumulative time in 10 activities was calculated, and a time-history of driver activity documented. Most (55.5 ± 13.4%) time was out of the vehicle, and 22.3 ± 10.5% was spent in single-arm driving. On paper documentation and mobile data terminal use were identified as in-car activities that may benefit from targeted interventions. The primary contribution of this study is characterization of daily mobile police activity and the identification of possible intervention strategies to mitigate physical exposure levels.

Police officers spend large amounts of time performing duties within a police cruiser and report a high prevalence of musculoskeletal problems. This study evaluated the effects of driver seat and duty belt design on posture, pressure and discomfort. Ten male and 10 female university students attended two sessions involving simulated driving in a standard police seat (CV) and an active lumbar support (ALS) seat. Participants wore a full duty belt (FDB) or reduced duty belt (RDB) in each seat. Lumbar postures, driver-seat and driver-duty belt pressures and perceived discomfort were measured. Gender × Seat interactions were found for pelvic (p = 0.0001) and lumbar postures (p = 0.003). Females had more lumbar flexion than males and were more extended in the ALS seat (-9.8 ± 11.3°) than CV seat (-19.8 ± 9.6°). The FDB had greater seat pressure than the RDB (p0.0001), which corresponded to increased pelvis discomfort. This study supports the use of an ALS seat and RDB to reduce injury risk associated with prolonged sitting in police officers.Police officers report a high prevalence of musculoskeletal problems to the lower back, associated with prolonged driving and further investigation is needed to reduce injury risk. This simulated driving study investigated seat and duty belt configuration on biomechanical measures and discomfort. Seat design had the greatest impact, regardless of gender and males benefited more from a reduced belt configuration.

Prolonged occupational police driving combined with use of an in-vehicle computer elicits awkward, sustained postures in a scenario that lacks the adjustability to accommodate many mobile officer anthropometries and job-specific components. Twenty participants performed simulated police patrol sessions at five mobile data terminal (MDT) locations and using two seats: standard police vehicle seat and modified seat designed for police use. An MDT location self-selected prior to the session reduced perceived discomfort by up to 50% in the low back (p .0001) and 68% in the right shoulder (p .0001) compared to other tested locations, including the most common currently used location recorded from a representative police force. Muscle activity was lowest at the self-selected and current MDT locations for all muscles, significantly so for posterior deltoid (p .0001) and supraspinatus (p .0001). The modified seat reduced low back discomfort from the standard seat by 28% (p .0001). Combining a self-selected MDT location and modified driver seat generated lower discomfort and physical loading than the currently used configuration.