Journal of Science and Medicine in Sport 21 (2018) 1162–1167
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Journal of Science and Medicine in Sport journal homepage: www.elsevier.com/locate/jsams
Review
A method for developing organisation-wide manual handling based physical employment standards in a military context Greg L. Carstairs ∗ , Daniel J. Ham, Robert J. Savage, Stuart A. Best, Ben Beck, Daniel C. Billing Land Division, Defence Science and Technology Group, Australia
a r t i c l e
i n f o
Article history: Received 13 September 2017 Received in revised form 7 February 2018 Accepted 17 February 2018 Available online 2 March 2018 Keywords: Trade task analysis Physical test development Physical demands Task performance Ergonomics Work
a b s t r a c t The benefit of job-related employment standards in physically demanding occupations are well known. A number of methodological frameworks have been established to guide the development of physical employment standards for single job functions. In the case of an organisation comprised of multiple and diverse employment specialisations, such as the Australian Army, it is impractical to develop unique employment standards for each occupation. Objectives: To present an approach to organisational level physical employment standards development that seeks to retain occupationally specific task characteristics by applying a movement cluster approach. Design: Structured methodological overview. Methods: An outline of the research process used in performing job tasks analysis are presented, including the identification, quantification and characterisation, and verification of physically demanding manual handling tasks. The methodology used to filter task information collected from this job analyses to group manual handling tasks with similar characteristics (termed clusters), across a range of employment specialisations is given. Finally, we provide examples of test development based on these key manual handling clusters to develop a limited suite of tests with high content, criterion and face validity that may be implementable across a large organisation. Results: Job task analysis was performed on 57 employment specialisations, identifying 458 tasks that were grouped into 10 movement based clusters. The rationalisation of criterion tasks through clustering informed the development of a limited suite of tests with high content, criterion and face validity that may be implementable across a large organisation. Conclusion: This approach could be applied when developing physical employment standards across other multi-occupation organisations. Crown Copyright © 2018 Published by Elsevier Ltd on behalf of Sports Medicine Australia. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).
1. Introduction The most demanding occupational duties often involve manual material handling,1,2 and are a significant source of musculoskeletal injuries.3–5 Manual handling is defined as the exertion of force to hold and/or move objects from one location to another, predominately by hand. Manual handling tasks in the military are diverse,1,2 often not modifiable6,7 and require high levels of muscular strength and/or muscular endurance.2,6 The mismatch between workers physical capacity and the physical demands of the job may increase the incidence of musculoskeletal injury.8 The implemen-
∗ Corresponding author. E-mail address:
[email protected] (G.L. Carstairs).
tation of scientifically developed physical employment standards (PES) serves to address this mismatch and can lead to increased capability, and operational effectiveness.1,9 A number of frameworks have been developed9–11 for creating PES. A common approach includes the identification of physically demanding tasks through workshop(s) and/or surveys with experiential experts,12 followed by field observations, to measure and quantify task demand. This process yields a subset of tasks, known as criterion tasks, which typically represent those that are the most physically demanding and critically important.11,13 Physical tests that reflect the physical demands of one or more criterion tasks are then developed. While this approach is suitable for developing PES for a single employment category (e.g. infantry soldier, which in itself has multiple different distinct roles or sub-specialities), this frame-
https://doi.org/10.1016/j.jsams.2018.02.008 1440-2440/Crown Copyright © 2018 Published by Elsevier Ltd on behalf of Sports Medicine Australia. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).
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work becomes cumbersome and impractical at an organisational level, which can incorporate multiple distinct employment categories. For example, the Australian Army contains more than 50 diverse employment specialisations, making it impractical to implement a specific PES assessment test for each criterion task for each employment category. Since physical screening also occurs prior to employment specialisation, it is clearly advantageous to have a limited suite of broadly applicable PES assessments that can predict physical suitability across different employment categories and which may be adjusted, by altering key characteristics of the test such as the mass lifted or carried and/or the distance traversed. The purpose of this paper is to present a methodological approach of characterising manual handling tasks to support the development of evidence-based PES for an organisation comprised of multiple and diverse employment specialisations, such as the Australian Army. Firstly, we briefly describe the process of performing job task analysis for manual handling tasks. Secondly, we present a method to condense the vast amount of information collected from these job task analyses procedures to group manual handling tasks into a manageable set, termed clusters. Finally, using these clusters we provide examples of test development. While the greatest applicability of this approach is for a diverse organisation such as the military, these steps could be applied to other physically demanding occupations such as the emergency services, which can contain many different distinct roles or sub-specialities.
2. Task identification The first stage of the PES development was to develop an initial task list. A list of preliminary physically demanding tasks was identified by systematically reviewing employment profile manuals and doctrine and extracting tasks that were documented as requiring physical attributes for successful task completion. These lists were then used to initiate discussions with experiential experts from each of the employment categories during focus groups called Trade Task Workshops (TTW). Each TTW included experienced personnel covering a range of ranks and roles, from those who directly execute the execute the task, those that supervise personnel completing the task, and those that manage the relevant workforce, with an aim of at least three personnel from each category, as well as physiological and biomechanical researchers experienced in PES development. The purpose of this stage was to; (1) identify physically demanding tasks that personnel within the employment categories are expected to perform, (2) gain an understanding of the physical nature of job functions and (3) to create task descriptions and a physically demanding task list for each employment category. For each task identified, the scenario and the context of how, when and where the task could be performed were discussed with specific details of the task focusing on: the difficulty, duration and frequency of the task; the body worn equipment such as protective armour and; whether the task was self- or externally-paced; and possible work environments. More manual handling-specific information gathered included: equipment used; object dimensions and masses (if known); actions used (e.g., lifting and carrying); number of people involved and; distances covered. Generally, the information extracted from the TTW would be incomplete or lack fidelity, which necessitated the requirement to observe tasks actually been performed. Comprehensive details on the scenarios and context of tasks were sufficient for the researches to gain an appreciation of the task and to be able to work with experiential experts to set up accurate task observations. Australian Army personnel perform two key functions, firstly, a generic service requirement involving common soldiering tasks and secondly, employment requirements directly related to their trade specialisation. This dual nature role necessitated the forma-
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tion of two baseline levels for the generic service requirements, the All Corps Soldier and Combat Arms. The All Corps Soldier is the minimum level and is based on the performance of essential military duties, which are typically defensive in nature. The Combat Arms level is based upon the requirement to operate in a high threat environment and, if necessary, conduct direct tactical action against the enemy. At the conclusion of the TTW, each group of experiential experts confirmed that the formulated list of tasks was inclusive of all employment category-specific tasks with a perceived high physical demand. For the 57 employment categories in the Australian Army that underwent review, 583 tasks were identified, 458 of which were characterised as manual handling tasks. The high proportion of physically demanding tasks classified as manual handling (79%) underscores the importance of these activities to successful job performance.
3. Task quantification and characterisation The second stage of the PES development was conducting Trade Task Field Observations (TTFOs), with the purpose of objectively quantifying the physical demands of tasks identified in the TTWs. All physically demanding job tasks were observed and measured under ‘typical’ work conditions in the field and/or barracks, with experiential experts providing guidance on the most appropriate locations and scenarios. For each task, experienced senior soldiers and/or officers verified that the soldiers performing the simulations were competent and that the task scenarios appropriately represented the task to an ‘expected standard’ i.e. what would be expected reasonable of all soldiers within the employment category to perform and not on the extremes of tasks performance. The qualified soldiers performing these task simulations were all medically fit for duty and were encouraged to identify any other physically demanding tasks not recognised during the TTW. Manual handling task parameters were quantified according to a list of factors (described by Waters et al.,14 Snook and Ciriello,15 and Gallagher16 ) known to influence task difficulty. Specifically, the following object, movement and task parameters were measured: object mass and size; hand location and object coupling; vertical and horizontal distances; asymmetry; frequency; repetitions; quantity of items; duration; pacing; pushing and pulling positions and forces; postures (i.e. stand, stoop, kneel, sit, crouch); number of personnel involved; number of hands used; action used (i.e. carry, push, pull, drag, hold); surface type; and physiological cost. All items carried, lifted or dragged were weighed with platform scales or a portable force plate. Distances were measured using global-positioning system (GPS) units, a trundle wheel and/or a tape measure. Lifting heights and object dimensions including handle location were measured using a tape measure. Push and pull forces were measured using an inline force transducer. Time to task completion and work:rest ratios were collected with a stop watch and/or video camera. The body worn equipment was noted and weighed. To measure the physiological demands of repetitive manual handling tasks, heart rate and oxygen consumption were collected. Participants were also asked to rate their perceived exertion (RPE) on a 15-point Borg scale (6–20)17 during certain tasks to subjectively compare the physical demands of different tasks within the same employment category. To demonstrate examples of some of the key task characterisation measures, three manual handling tasks; pack lift and place, stretcher carry, and bombing up an M1 Abrams main battle tank have been selected and presented in Table 1. Lifting one’s own field pack to the back of a common Australian military vehicle (height 1.50 m) is a discrete muscular strength task required by all Australian Army personnel, where the mass of the
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Table 1 Example of task characteristics for three tasks during trade task field observations.
Object characteristics
Lift/carry positions
Task parameters
a
Mass (kg) Dimensions (m) Coupling Handle height (m) Start Mid End Personnel Carry distance Duration Pace Work:rest Repetitions Number of hands Worn equipment
Combat arms pack lift and place
All corps soldier stretcher carry
Bombing up an M1 tank
22.1 (field pack) 0.80 × 0.65 × 0.30 Poor None Ground – in front of body Waist/chest – in front of body 1.50 m platform – in front of body One None/stationary ∼5 s NA NA 1 2 Fighting ordera
90.4 (casualty and stretcher) 2.29 × 0.54 Good 0.12 Ground – side of body Knuckle height – side of body Ground – side of body Four 100 m in 25 m bouts 01:40 min 4.5 km h−1 (4:1) carry 25 m in 20 s, 5 s rotate 4 x 25 m 1 swap every 25 m Fighting ordera
23 (ammunition shell) Diameter 0.12, length 0.98 Poor None 0.10, 0.30, 0.50 m – side/front of body Waist or chest height 1.70 m, can be lifted higher One 10 m loaded walk, 10 m unloaded 10–15 min 3.6 km h−1 1:1 36 shells 2 Disruptive pattern combat uniform
Fighting order is in additional to wearing standard combat uniform and boot consist of body armour, webbing, helmet and weapon (20–22 kg).
pack varies depending on the employment category. For example, the minimum required mass for an All Corps soldiers pack was 20.0 kg, while Combat Arms and Infantry soldiers require a 22.1 kg and 32.0 kg pack, respectively. While in many cases the mass used on operations may exceed this; these masses represent baseline levels required of all soldiers in these employment categories as defined by the load list. Performing a stretcher carry is an essential muscular endurance task required by all Australian Army personnel, where the expected mass, carry distance and type of stretcher varies across employment categories due to the different scenarios/contexts and threat profile. The casualty tasks were profiled using GPS to measure distances, speeds and work:rest ratios (as described by Silk and Billing18 ) on multiple patrols performing mock assaults and casualty evacuations through different terrain over different distances. The All Corps soldiers’ requirement was to participate in a 100 m carry of a 90.4 kg stretcher (average Australian soldier mass of 83.3 kg and 7.1 kg stretcher mass), the Combat Arms requirement was a 300 m carry of 108.8 kg stretcher (additional fighting order mass on casualty), and the Infantry requirement was a 750 m carry of a 110.6 kg stretcher. The All Corps and Combat Arms stretcher carry was performed with a rigid stretcher in a team of four. The Infantry stretcher carry was performed with a soft stretcher in a team of six, where four soldiers carry the stretcher at a time, while the other two provide covering fire. The six soldiers rotate roles to perform at least three 150 m carry efforts. Bombing up an M1 tank was completed in a team where a soldier would repeatedly pick up an ammunition shell from a tray, carry it 10 m, and then pass it up to another soldier standing on the tank, who would then pass it to another soldier standing in the turret, who would pass it to yet another soldier inside the tank for storage. The soldier performing the first part of the task was judged to have the most physically challenging role, due to the requirement to perform 23 lift and carry repetitions of the ammunition shell (23 kg), with a final lift height of 1.70 m at the end of each repetition, requiring both muscular strength and muscular endurance. The pack lift, stretcher carry and bombing up tasks each have a lifting load of 22–23 kg but the physical demands vary according to the different task parameters, highlighting the need to quantify all components of the task, rather than only quantifying the mass of a lift. As a result of the TTFOs, alterations to task characteristics could be made to the original task lists.
4. Task verification The third stage of the PES development involved the conduct of follow-up focus groups, via a Trade Task Confirmation Workshop
(TTCW), with a group of experiential experts that had a breath of understanding of the requirements of their employment category. The composition of these experiential experts mimicked that of the initial TTW as closely as possible. The purpose of this stage was to; (1) receive confirmation and endorsement of the physically demanding task list and descriptions, (2) confirm task parameters and (3) select criterion tasks. Researchers presented updated task descriptions of all relevant task characteristics and parameters based on the outcomes of the observations for all tasks, to confirm descriptions, and that tasks were conducted in the appropriate context. To characterise variation, tasks were observed being performed under different simulated operational scenarios and environmental contexts. These variations were presented to experiential experts to identify the most appropriate scenario(s) for their employment category, allowing parameters to be established. Experiential experts were able to identify differences between work practices observed during TTFOs and expected methods, allowing tasks to be adjusted accordingly and re-quantified where necessary. For example, lifting a 72 kg generator onto a trailer was an observed task performed by two soldiers from the Royal Australian Corps of Signals during the TTFO, however during the TTCW experiential experts indicated that there was no operational requirement for this and the task could be performed by four soldiers. Tasks were presented and grouped together as muscular strength, muscular endurance or requiring high levels of both based on the physical capacity or attribute that was likely to fatigue and/or fail first and limit continued task performance, to focus attention on one grouping of tasks at a time. In this context, muscular strength is the ability of a specific muscle or muscle group(s) to generate sufficient force for successful task completion, while muscular endurance is the execution of repeated isotonic contractions or a sustained isometric muscular contraction. Together researchers and experiential experts identified task(s) within each physical capacity to be criterion tasks for each employment category. The selection of criterion tasks was ultimately based on two key criteria (1) the task was physically demanding relative to others that were classified in the physical capacity or attribute group, researcher led decision (based from the objective data collected during TTFOs) and (2) all members within the employment category were expected to be able to safety and successfully execute the task, experiential experts led decision. Multiple criterion tasks for each physical capacity were selected when tasks were demanding and vastly different, for example the Infantry muscular strength criterion tasks chosen were a 32 kg pack lift and individually performing a 109 kg casualty drag over 10 m.
G.L. Carstairs et al. / Journal of Science and Medicine in Sport 21 (2018) 1162–1167 Table 2 Cluster allocation of all manual handling tasks and the criterion manual handling tasks. Cluster
All tasks
Criterion tasks
Lift to platform Lift to an anatomical height (without carry) Lift and hold Lift and twist Seated, crouching or kneeling lift Lift-carry-lower Lift-carry-lift Drag Push/pull Dig/hammer Other
198 34 54 10 9 100 40 13 38 30 13
49 4 2 1 0 25 9 3 6 5 2
Total 1 cluster 2 clusters 3 clusters 4 clusters
458 374 62 6 2
88 69 16 1 0
At the conclusion of each TTCW, experiential experts confirmed the formulated task list and selection of criterion tasks. Across the different employment categories investigated, 88 criterion tasks were identified from 458 manual handling tasks. The dominant physical capacity of criterion tasks was identified as muscular strength for 49 (55.7%) as muscular endurance for 44 (50.0%) while five (5.7%) were in both. 5. Clustering tasks across job functions Given the large number of criterion tasks identified and the need to provide a suite of physical tests that could be implemented on an organisation-wide level, developing specific individual PES assessments according to each occupational speciality was not feasible. In order to balance scientific integrity by maintaining the link between the task and the test with the successful service wide introduction of PES, a filtration approach was used to cluster tasks with similar characteristics. The research team methodically evaluated each task using a structured approach utilising the IDEA protocol19 to improve the accuracy of expert judgements and included several key steps including – investigate, discuss, estimate and aggregate. Task characteristics and parameters were discussed and data entry accuracy was checked, with the aid of video recordings, photographs, notes and first-hand observational insights collected during the TTFO and workshops. All task characteristics and parameters collected during TTFOs for all manual handling tasks from the 57 employment categories investigated, were tabulated in Microsoft Excel. Major column headings were based on the list of factors known to influence task difficulty as earlier identified in the task quantification and characterisation section. Through this process, a pattern of common movements and actions emerged that could lay the foundation of task simulation test design. Initially the team found four clear groupings with the following components: (1) vertical lift; (2) locomotion with load; (3) pushing and/or pulling and; (4) repetitive striking. These initial clusters were then further separated into 10 discrete clusters, with the majority of tasks (82%) placed into one cluster and a small portion falling into more than one cluster (14%) (see Table 2). Lifting was the most commonly performed manual handling task. The most common lifting cluster ‘lift to a platform’ involved a fixed-height external feature (such as a vehicle or work bench) that dictated the height of the lift. Additionally, there were a number of lifts that finished at an anatomically defined position ‘lift to an anatomical height without carry’, such as full arm extension overhead, hand at shoulder height or knuckle height (i.e. arms are by the side during standing). This cluster focused on the end position
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of the lift and not the carry component as most carry positions were governed by anatomy of the lifter. The next lifting cluster identified was ‘lift and hold’ where soldiers were often holding and operating tools and machinery for a prolonged period of time. The last two lifting clusters were ‘lift and twist’ and ‘seated, crouching or kneeling lift’. A lift was classified ‘lift and twist’ when there was 90◦ of rotation of the body in moving the item where the lower body was fixed in place, which often occurs when someone is seated. The ‘seated, crouching or kneeling lift’ was applicable to tasks where a soldier performed the lift in one of these postures which often occurred in a confined space such as inside a vehicle loading munitions. Locomotion with load tasks predominantly involved carrying equipment. Tasks were deemed to be a carry when items were lifted and moved a distance of 10 m or more. While many lifting tasks require movement of a few metres to complete the lift, it was deemed that the carry component was unlikely to limit task performance. Carries were divided into ‘lift-carry-lift’ and ‘liftcarry-lower’. When the item was lifted at the end of the carry above 0.8 m (representing a height requiring a lift above knuckle height of military personnel20 ) this was classified as ‘lift-carry-lift’, such as when loading a vehicle. The vast majority of carries ended with the item back on the ground or below knuckle height representing ‘lift-carry-lower’. The last cluster within locomotion was ‘drag’ which predominantly related to dragging a casualty, but could also include items such as heavy chains. Another cluster established was the ‘push/pull’ cluster as many tasks could be performed by either pushing or pulling the item, or require both actions (e.g., using a hydraulic pump). The last cluster, ‘dig/hammer’, included tasks that soldiers would do in setting up a field position such as hamming in star pickets and digging shell scrapes. A very small number of tasks (13 in total), such as manoeuvring in an explosive ordnance suit, did not fit within the 10 clusters and were classed as ‘other’. Once all tasks were clustered, the development of PES based on clusters rather than individual criterion tasks could be realised.
6. Development of test options Focusing on the cluster characteristics allowed for the targeted development of a limited number of fitness assessments that could predict performance across a range of criterion tasks. To establish relationships between tasks and test options, a number of representative criterion tasks were selected from each cluster. These representative cluster tasks were chosen to provide coverage of the range of tasks within the cluster that exhibited the important differences in object, movement and task parameters that occur within the cluster. For example, there were multiple criterion tasks of varying masses that required a solider to, individually lift an item, with good coupling, from the ground to a 1.5 m platform, once. These common features allowed a single criterion task to be used to represent a cluster of like tasks. Task simulations were devised for each of the chosen representative cluster tasks that were measurable and scalable, (e.g., the mass of a representative cluster task could be readily altered). Participants performed each representative cluster task and test maximally for task-to-test development (Fig. 1). Pearson’s product-moment correlations or coefficients of determination were used to investigate the relationships developed. Sensitivity and specificity analyses were used to investigate the ability of a test to correctly classify an employee’s performance on a representative cluster task. The lift to platform cluster led to the development of a box lift and place test which assesses muscular strength across multiple representative cluster tasks. The establishment of the box lift and place as a possible task related predictive test was firstly identified through investigations that found a strong relationship to
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Fig. 1. A schematic example of manual handling task-to-test development methodology.
lifting capacity, with different lift to platform cluster heights.21 This finding allowed for the development of a single box lift and place test to 1.50 m, ensuring content and face validity. Relationships were then developed that could explain the variation in task demands of the criterion tasks using the box lift and place test to 1.50 m as a reference point. Representative cluster tasks were performed maximally by participants to examine the impact of the different lifting characteristics: repetition,22 object type,6,23,24 posture,25 number of lifters24 and repetitive lift-carry-lifts to a platform.6,26 These representative cluster tasks provided coverage of the different lifting characteristics present within the cluster. Task-to-test relationships were then developed to ensure criterion validity, where strong relationships were found between representative cluster tasks and the box lift and place test.6,25,27 Multiple representative cluster tasks within the lift-carry-lower cluster were investigated, with specific focus on the stretcher carry criterion tasks, which ultimately resulted in the development of the jerry can carry test that assesses muscular endurance. Possible tests were designed to be completed individually, while faithfully representing as many of the stretcher carry parameters as possible (e.g. mass, lift and carry position, and work:rest periods) to maximise content and face validity. Unilateral carries were excluded as potential test options, as although they may have strong face validity for stretcher carry performance, unilateral carries have been shown to increase spinal compression and shear forces when compared with bilateral carries,28 and the majority of criterion lift-carry-lower tasks were determined to be bilateral. Using the stretcher carry as the reference point, strong task-to-test relationships were developed for a range of possible bilateral task-related predictive tests. By assessing the sensitivity and impact of altering key test characteristics such as mass,29 speed30 and item type,30 we were able to ensure criterion validity. Having the stretcher carry as a stable constant allowed for the understanding of the impact of these different carry characteristics, which could allow comparison amongst other criterion tasks within the lift-carry-lower cluster. While extensive research is required to first understand the separate effects of multiple factors on performance in the tasks and
tests, the use of the clustering method quickly highlighted points of parity and points of difference. As a result, concentrated effort could be directed at understanding and evaluating the key variables that differed amongst the criterion tasks and then develop task-to-test relationship with a sample of representative criterion tasks. With task-to-test relationships developed and the impact of different factors within the cluster known, scaling could then be confidently applied to other criterion tasks to set standards without needing to test them directly. This also builds in the capacity to adjust standards should the task requirements change in the future. Another key advantage is that knowledge of the impact of different tasks characteristics on task and test performance is often transferable to other clusters. This cluster approach provides broad coverage of the criterion tasks, thereby maximising scientific defensibility by ensuring recommended tests that have high content, criterion and face validity. However, this cluster approach may not provide highresolution sensitivity for all criterion tasks compared to what could be achieved by developing custom tests for each criterion task.
7. Conclusion This paper outlined a framework and the processes in which manual handling tasks were profiled, and appropriate physical testing measures were established, within the Australian Army. Through a rigorous process of subjective and objective research procedures, a task list of 458 manual handling tasks and 88 manual handling criterion tasks was established. The practical challenges associated in the development of PES for a multi-trade organisation; in profiling the vast physical task duties of a service and the development a limited suite of assessments were addressed. By utilising a clustering and filtration approach we provide a method of developing task-to-test validity by narrowing down a large and diverse task list to more manageable clusters of like manual handling tasks. Criterion referenced performance standards can then be developed based on the physical requirements of the array of
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soldiering tasks. These processes can be followed when developing PES for manual handling tasks in other occupations. Acknowledgements The authors would like to acknowledge and thank the members of the Physical Performance Team at Defence Science and Technology Group that assisted with data collection, be it leading or participating in running workshops or field observations. References 1. Rayson M. The development of physical selection procedures. Phase 1: job analysis, In: Contemporary Ergonomics., 1998. p. 393––397. 2. Sharp M, Rosenberger M, Knapik J. Common military tasks: materials handling, In: North Atlantic Treaty Organisation Research and Technology Organisation Research Technical Group-019 Optimizing Operational Physical Fitness., 2006, 5-1. 3. Lötters F, Burdorf A, Kuiper J et al. Model for the work-relatedness of low-back pain. Scand J Work Environ Health 2003:431–440. 4. Putz-Anderson V, Bernard BP, Burt SE et al. Musculoskeletal Disorders and Workplace Factors, vol. 104. National Institute for Occupational Safety and Health (NIOSH), 1997. 5. Roy T, Ritland B, Knapik J et al. Lifting tasks are associated with injuries during the early portion of a deployment to Afghanistan. Mil Med 2012; 177(6):716. 6. Carstairs GL, Ham DJ, Savage RJ et al. A box lift and place assessment is related to performance of several military manual handling tasks. Mil Med 2016; 181(3):258––264. 7. Sharp M, Legg S. Effects of psychophysical lifting training on maximal repetitive lifting capacity. Am Ind Hyg Assoc J 1988; 49(12):639. 8. Rosenblum KE, Shankar A. A study of the effects of isokinetic pre-employment physical capability screening in the reduction of musculoskeletal disorders in a labor intensive work environment. Work 2006; 26(2):215––228. 9. Taylor NAS, Groeller H. Work-based physiological assessment of physicallydemanding trades: a methodological overview. J Physiol Anthropol Appl Hum Sci 2003; 22(2):73––81. 10. Payne W, Harvey J. A framework for the design and development of physical employment tests and standards. Ergonomics 2010; 53(7):858––871. 11. Tipton M, Milligan G, Reilly T. Physiological employment standards I. Occupational fitness standards: objectively subjective? Eur J Appl Physiol 2013; 113(10):2435–2446. 12. Zumbo BD. Standard-setting methodology: establishing performance standards and setting cut-scores to assist score interpretation. Appl Physiol Nutr Metab 2016; 41(6):S74–S82.
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