Mockup showing a laptop with prototype, 2 posters designed for masonry and pocket cards on a table

Reducing Muscle Injury Risk for Apprentice Masons

PRODUCT DESIGN • USER RESEARCH • STATISTICAL ANALYSIS • VISUAL DESIGN

ROLE

Product designer

Training software & educational resources delivered to Ontario Masonry Training Centres

TIMELINE

Sept 2019 – 2021

TEAM

Full stack developer

RESULT

Overview

Product Design at a Glance

The construction industry is one of the industries with the highest rates of musculoskeletal disorders. Masons are particularly susceptible to overexertion and back injuries due to the physical demands of their jobs. Previous research has shown that 1st and 3rd year apprentices are at the highest risk for injury, while expert masons have lower risk for injury and have the highest productivity. To tackle the challenge of "how we might reduce muscle injury risk in apprentice masons", I collaborated with stakeholders from the Canadian Masonry Design Centre and the Ontario Masonry Training Center and designed a comprehensive training system with a training tool and educational resources. The system teaches apprentice masons how to model expert working behaviour, which is associated with lower stress on the body and higher productivity.

Onsite Training Tool

Uses motion capture to identify high risk movements and provide recommendations

In-Class Learning Modules

Lecture slides, speaking notes and discussion prompts for instructors

Mockup of a powerpoint presentation on reducing muscle injuries in masonry

Additional Resources

Posters and pocket cards to reinforce learning

Mockup of poster and pocket card designs for safe lifting techniques and an example warm up routine

Continue reading to take a deeper look at the design process

Problem Space

Apprentice Masons Experience High Rates of Muscle Injury

Workers in the construction industry have a 50% higher risk of muscle injury compared to workers in other sectors. Masonry has one of the highest rates of both overexertion and back injuries in construction. Masonry apprentices are often assumed to be healthy as new workers in the trade; however, a recent study found that 78% of apprentices reported muscular symptoms (Anton et al., 2020).

Muscle injuries are a large burden to the healthcare and compensation system across Canada. In Ontario alone, they are the number one cause of lost-time injuries. But beyond that, work related injuries negatively impact individuals’ health and quality of life.

$19.7 billion

$72 million

Direct and indirect cost on Canadian economy

Direct costs on Ontario Employers

Project Inspiration

Turning Research into Solutions

When I joined the Masonry Work Systems research group, they had been studying the impact of masonry work on masons with different experience levels. Their data told a clear story:

Apprentice and expert masons work differently
Experts are both more productive and have a lower risk of muscle injury.

What was it about the way experts worked that lowered injury risk and how could we teach it to apprentices?

The research group lacked an indepth understanding of the work techniques that caused these differences and how it correlated to injury risk, as well as a practical and impactful way to apply this knowledge on a larger scale to reduce injury risk for Ontario masons.

🙋 This is where I come in...

Solution

Designing an Enhanced Training System for Apprentice Masons

I decided to research the differences in work techniques and design a tailored, evidence-based, industry-relevant, training system to improve apprentices’ lifting techniques and increase overall awareness and education on muscle injury risk.

Needs Assessment

The research group had previously developed an ergonomic assessment tool to assess body loads of masons onsite. The tool uses motion capture data to calculate forces and generates a report of the critical points where the loads exceed an established threshold. The tool identifies and displays evidence of the high forces experienced by masons. Other than the tool provided by our research group, the Ontario Masonry Training Centre lacked any formal training on ergonomics and muscle injury prevention.

Gaps in Previously Developed Onsite Assessment Tool

While the tool can identify high joint loads, those without technical knowledge may have difficulty translating that information into actionable steps to reduce injury risk in the workplace. Therefore, there are still large gaps in the value this tool can provide. Examples of deficits in the assessment tool include the following:

Lack of evidence-based criteria for critical points
Presentation of raw data is not meaningful to masons
Unable to identify causes of high forces or postures
Unable to recommend specific actions to reduce risk

Proposal for Enhanced Training Tool & System

To augment the benefits of the tool and improve its practicality for implementation in masonry training centers, I proposed that the tool be redesigned for training. Rather than create new software from scratch, I could repurpose the 3D human model to generate greater value and ship the final product more quickly.

My idea was to use the training tool to reduce forces on the body by identifying high risk postures and providing recommendations for improvement. To achieve this, I needed to establish what constituted high risk forces, high risk postures and both desirable and undesirable lifting techniques. Then I needed to translate this into quantitative inputs and qualitative outputs for the software.

This training tool could then be leveraged as part of an overall training system, comprised of the onsite training tool, and accompanied by in-class educational modules and additional resources for learning and implementation.

Goals

The primary goal is to design and develop a practical training system for apprentice masons, which teaches safe lifting techniques and reduces muscle injury risk. The following list outlines secondary research and design goals:

Understand expert and apprentice lifting techniques

Develop criteria for high risk postures

Create a scoring system for high risk forces

Design training tool based on results of goals 1-3

Develop educational resources and system structure

Project Scope & Constraints

Scope

Redesign the existing assessment tool for a training context
Focus of lifting analysis and recommendations on building a standard wall
Other masonry tasks not included in analysis and recommendations

Project Constraints

Improvements to tool constrained within the framework of the original technology
Research and design was completed under Covid-19 restrictions. No new in-person experiments could take place and user evaluation of the training system was unable to occur while I was working on the project

Training System Constraints

Training must integrate into existing course structure
Total training time must not exceed 7 hours
Test apprentices at the beginning and end of course
Include information about stretching and warm-up
Images should feature masons where possible

Secondary Research

Leveraging Knowledge across Multiple Disciplines

I conducted a comprehensive research review to survey the best principles for training. I included research from the fields of ergonomics, athletic performance, motor learning, adult learning, health promotion and construction health and safety.

Key Takeaways

Workers should be trained in an occupational context
Practice, reinforcement, and customization are essential
Expert work strategies can inform training
Training should implement best principles from motor learning, adult learning and behavioural change models
Younger students may be more receptive to new strategies since they have not yet been socialized into certain behaviours within the construction culture

To better inform the criteria for high risk postures, I also looked at existing thresholds in the literature from experimental and epidemiological studies, assessment tools and guidelines. This gave me a jumping off point to establish numeric values for high risk joint angles later on and would compliment the findings from my primary research.

Primary Research

Understanding Lifting Techniques Across Expert and Apprentice Masons

I used three analysis methods to gain insight into the movement strategies of the different groups of masons: predictor screening, statistical analysis and k-means clustering. All three analyses had complementary roles, and each provided some insight into how masons’ techniques influence joint forces.

Experiment 1: Experts vs Apprentice Movement Strategies

Image of a wall made of concrete blocks with a man standing behind it wearing a motion capture suit to display the experimental set up

Data Collection

I used motion data previously collected from 66 masons of different experience levels while building a standard wall (task shown in the figure above). Participants included:

17 novices with no prior masonry experience
19 first year apprentices
16 third year apprentices
14 were experts with ≥ 20 years of experience

Data was collected using a wireless motion capture suit with 17 sensors attached to the head, back, shoulders, upper and lower arms and legs, hands, and feet.

Graph showing the top ten contributors to low back forces

Analysis 1: Predictor Screening

Predictor screening uses machine learning to determine the contribution of different variables to an outcome. In this case, I predicted which movements had the greatest impact on forces at the areas of concern: the low back and shoulders.

Key Takeaways

The main movements which affected the forces at the low back and shoulders were:

Bending of the back, neck, and hips
Raising their arms to the side
Positioning of their feet
How far they carried the block away from their body and above the ground

Graph showing the effect of masons' experience level on bending at the hip at different heights

Analysis 2: Statistical Analysis

I used statistical analysis to determine how experience level affected how masons lift, such as movements at each of the joints, and how far they lift the block away from their body.

Key Takeaways

Differences between experience groups are amplified at lower heights
Apprentices bend and twist their torso to one side and bend their neck more
Experts bend at the hips instead of bending their backs

Stick figure of an apprentice posture being compared to a stick figure of an expert posture

Analysis 3: K-means Clustering

Machine learning was used to categorize postures into apprentice versus expert dominated clusters. This revealed how postures differ between experience groups.

Key Takeaways

Experts adopt unique work techniques compared to apprentices
Differences between experience groups are amplified at lower heights
Experts adopt different postures at different times during the lift
No singular correct technique in experts
Apprentices use more complex and varied techniques

Experiment 2: Joint Loads Experienced by Experts

7 tasks completed by masons in the experiment with a figure showing each of the tasks

Data Collection

I used data previously collected from 8 healthy masonry experts completing 7 different masonry tasks (shown above) that represent the variety of physical demands in masonry.

Low Back Loads

I modeled expert behaviour by analyzing the peak force profiles of expert masons during 7 masonry tasks. The above figure shows the low back loads experienced by those masons.

Peak Upper and Lower Body Loads

The above figure shows the peak upper and lower body loads experienced by expert masons across 7 different masonry tasks for the right side of the body.

Application of Findings for Training Tool

Joint Angle Thresholds

Based on the key findings from the postural analysis, and existing thresholds in the research literature, I established maximum joint angle thresholds for undesired movements that would trigger participant feedback in the training tool.

A skeleton with lines connecting joints on the body to a box with information on the force thresholds the respective body part

Joint Load Thresholds & Scoring Equations

I averaged the peak forces experienced by expert masons to develop force thresholds at each of the joints (above). I used a ratio to establish female equivalent thresholds. I developed two equations to compare measured forces from apprentices with the expert thresholds to provide a final score for the whole body and each of the joints.

Figure of a scale that shows forces from low to high alongside a corresponding score and descriptive text for each level of force.

Scoring System

I created a scoring chart to provide context and make the scores more meaningful to apprentices. The scoring system* is useful because it provides apprentices with feedback on the forces their bodies experience, which correlates with changes in their technique over time, allowing them to track their progress during training.

*Scoring system lacks epidemiological evidence. Therefore, has no direct implication for injury risk. The scoring system models expert behaviour which correlates with reduced exposures and potentially safer behaviour.

User Interviews

Understanding Safety Culture in Masonry & Instructors' Training Needs

I conducted user interviews with 8 instructors from the Ontario Masonry Training Center with an average of 23.9 years of experience. I gathered their perspectives on the current state of safety culture and their opinions on the proposed training system. Gaining this insight into the industry’s culture and the unique perspectives of the instructors was critical to developing both my understanding of and empathy with the end users.

Thematic Analysis

I analyzed analyzed the interviews using a template methodolgy. I completed preliminary coding and annotation to capture relevant information. I clustered a priori and emerging themes together to create an initial template. The template was then applied to all the data and altered as necessary to best fit the data. After further changes I established the final templates (below).

Thematic Analysis Map of Safety Culture in Masonry

The thematic analysis map above shows the primary themes and sub-themes identified for safety culture in masonry.

Thematic analysis map showing common themes from interviews with masonry instructors about the training tool and program design. Large themes are connected with lines to subcategories.

Thematic Analysis Map of Training System Feedback

The thematic analysis map shown above depicts the central themes and sub-themes regarding training system feedback.

Safety Culture in Masonry

Injuries Are Part of the Job

There is a belief within the trade that injuries are just part of the job, however, those beliefs are changing over time. Instructors suggested that implementing a formal training program on ergonomics can help change the culture.

“Nobody used to talk about it. It was one of those things, that years ago in construction, you just had to --your knees or your back will go, that's how it is and then you have to find something new to do [...] And that's no longer acceptable, which is good, it shouldn't be.”

Thinking They're Invincible

Young masons will believe they are invincible; therefore, long-term cumulative damage needs to be directly connected to their present actions.

“Everyone is young and that so, you know, you're gonna beat your body up because you're invincible.”

Lifting Past Their Capacity

Apprentices may lift past their capacity for a number of reasons including pride, to impress, out of respect, laziness or for speed and productivity. These should be highlighted as pitfalls to avoid. Safety and ergonomics should also be discussed within the context of productivity since productivity is a major driver in lifting past capacity due to financial incentives.

“So much is judged on your output and for myself, my income is judged on my output so I do pull [more than I probably should] and until I get to that point where I feel sore, I probably go past where I should physically.”

Passing on Knowledge

Expert masons are critical in exchanging knowledge to the younger generation because the apprentices look up to them and respect them. Therefore, instructors should be encouraged to talk about their own experiences with injury and share advice, anecdotes and knowledge.

“Which again goes to stuff you learn from other masons, [them] teaching you stuff and it's just something's quicker and faster and easier on your body”

Preventing Injury Risk in Apprentices

Instructors thought that knowledge and training, good technique, warming up, stretching, and awareness and attentiveness could reduce the risk for injury in apprentices.

“Whether it's a few hours presentation or whether it's a day thing… like I don't wanna exaggerate it, but certainly like I say, the better off people are with anything they do in life, information is key. We put so much emphasis on working at heights, we put so much emphasis on WHMIS [...] we should be putting emphasis, I feel, on your body, your muscles.”

Training System Recommendations

Instructors offered valuable insight into how the training system should be designed to seamlessly integrate into the masonry skills courses. It was particularly important to understand their needs and desires as the end users of the system and the experts on teaching apprentices.

Instructors thought that the training system should:

Be engaging
Include contextual information
Employ visual or hands-on teaching
Tailor messages
Break down the content
Provide extra resources
Start at year 1 but refresh at years 2 & 3

With regards to the proposed training tool, the instructors thought that it should:

Be user-friendly and easy to use
Illustrate direct connections between risky postures and outcomes
Use numeric scoring for joint loads
Minimize technical knowledge and time requirements

Design Process

Explorations & Ideations

I designed the training system and developed the content based on my research findings. I explored a number of visual design options for the training tool and educational resources.

Exploration 1: Training Tool Design

Two wireframe sketches for a potential design of the risk overview section

Initial Overview Section Sketches

For the overview section, I played with the idea of showcasing the risk report visually based on body location. However, I thought that it would quickly become visually busy when trying communicate the different levels of force and scores per joint and the whole body.

Sketch of the wireframe for the overview section compared to the final overview section design in the prototype

Overview Section Sketch to Final Design

The next idea I brainstormed, was presenting the information descriptively in sections, prioritized by force level and organized by whole body and then individual joints. Instead of laying the information out visually, I used illustrations to represent each of the joints. I felt that this option better organized and communicated all the necessary information.

For the final design, I chose the latter of my two initial sketches. The above image shows how I turned the initial sketch into a high-fidelity prototype.

Sketch of a wireframe for the overview section with recommendations for the shoulder and a screen capture of the final prototype design of the same screen

Recommendation Sketch to Final Design

When it came to recommendations, I decided to include previews in the overview section (shown in the original sketch above), so that the user could see which joints were at higher forces, immediately read which actions they could take and directly navigate to more in-depth detail about the recommendations.

In the final prototype design, I integrated recommendations for individual joints into their respective cards in the overview section.

Two sketches of wireframes for the recommendations section compared to the final prototype design for the recommendations section

Recommendation Section Sketch to Final Design

I also thought that it would be useful to have a section where the user could see all of the listed recommendations in one place. In a further iteration, I organized recommendations into sections by highest priority (highest forces) and by individual joints.

In the final prototype design, I provided a separate section with all of the recommendations in one location.

Exploration 2: Visual Design of Poster

Two sketches of potential poster designs for the safe lifting poster.

Initial Lifting Poster Sketches

The first option (left) focuses on individual body parts showing the desired and undesired posture with additional notes. The second option (right) focuses on the correct lifting technique and has little images at each body part to contrast the desired and undesired movement.

Two sketches of potential poster designs for lifting safely

Initial Lifting Poster Sketches (cont.)

The third option (left) shows the desired and undesired postures side by side. It would have additional notes pointing out the specific characteristics of good or poor technique. The fourth option (right) focuses on a mason building a wall within the masonry context and only visually shows the desired posture.

I decided to move ahead with the fourth option because it framed the information within a masonry context, which was a major goal throughout the design process. It also emphasizes how apprentices can achieve the correct technique rather than just pointing out incorrect lifting patterns. Lastly, this design had good visual appeal as a poster.

Potential poster design for safe lifting techniques. The text is condensed on the top of the poster and there is an image of a mason lifting a block.

Further Lifting Poster Explorations

In this option, the text is easy to find and read at the top of the poster. However, this causes the poster to be text heavy on the top half and the number system requires the viewer to spend time searching to match the number pairs in the text and illustration.

Potential poster design for safe lifting techniques. There is an image of a mason lifting a block. There is text around the mason showing safe lifting tips.

Further Lifting Poster Explorations (cont.)

The centred illustration gives this option a visually balanced design and draws the viewer’s eye to the center of the poster. The lines help the viewer immediately connect the text to the location on the figure without requiring additional effort.

Lifting poster design for safe lifting techniques alongside a potential design of the corresponding pocket card for the same information.

Further Lifting Poster Explorations (cont.)

In this iteration I experimented with adding green circles to draw visual interest and further focus the eye on each area of the body associated with the coaching cues. This provided visual consistency between the poster and an earlier iteration of the pocket card. However, I ultimately felt this design was too busy and distracting.

Image of a mason lifting a block with accompanying text pointing out safe lifting techniques

Final Design of Lifting Poster

For the final design I went with the option shown above. The main illustration used for the lifting poster was based off a video still of an expert mason from the data collection to further tailor the content. Simple concise phrases with easy-to-understand language were used to provide additional details about the coaching cues. I modified some of the colours for better visual contrast and revised some of the wording.

Design Decisions

Incorporating Best Practices from Multidisciplinary Research Literature

In the design of the training system I followed best practices for manual handling training, motor learning and adult learning and incorporated principles for behavioural change models for health promotion.

For example, some best principles include observing workers in working environment, tailoring the training to particpants, and comparing strategies of expert and novice workers. All of the recommendations for lifting technique were informed by primary research about expert and novice masons while building masonry walls. Additionally, the content of the training tool and educational modules were tailored to masonry apprentices.

Research over the past 15 years has shown that an external focus of attention (impact on the environment) improves motor performance and learning more than focusing attention internally (within the body). When developing the coaching cues, I aimed to use an external focus of attention where possible, such as in the following example:

Internal Focus

Keep your neck neutral!

External Focus

Keep your hard hat towards the ceiling!

Avoid bending your neck too much!

Expert Validation & Stakeholder feedback

To validate the content of the training system, I reviewed the warm-up routine and the coaching cues description with an NSCA-Certified Personal Trainer®.

The educational modules and resources were reviewed by one of the stakeholders, a subject matter expert who was familiar with both the industry and the end users. The main feedback I recieved could be categorized as revising content to make it tailored to the industry, modifying language to reduce technical jargon and improving representation. I took this feedback and made design changes to address each of the stakeholder’s comments.

Design Changes

Tailoring Content to Industry Context

One of the reasons the feedback from the stakeholder was so valuable was because they were able to evaluate the designs from a unique insider perspective on the industry. The stakeholder was able to provide feedback specific to the industry to make sure the content was relevent, tailored to masonry and useful.

Improving Relevance of Educational Modules

Providing Industry Specific Information

When discussing examples of how one could “replace the risk” in masonry, I suggested using a light-weight block, using H- and A-shaped blocks or using blocks made from autoclaved aerated concrete. When I reviewed the modules with the stakeholder, they pointed out that use of autoclaved aerated concrete tried to expand to Canada at one point, but it wasn’t sucessful. Therefore, it wasn’t really an option in Canada. With this feedback, I was able to remove the suggestion and better target the information.

Reducing Technical Jargon

It was important to make sure the language I used in the content of the educational modules was not only understandable for apprentices but also relateable and using the correct terminology used in the trade. In several cases, use of technical terms were pointed out that might not be well understood by masons, and I was able to reword them to improve comprehension.

Figure showing the hierarchy of controls for health and safety as described by the National Institute for Occupational Safety and Health

Modifying Language in Educational Modules

In health and safety, the hierachy of controls is a well known concept. The image above was the original image I sourced from NIOSH (2015) that depicts the concept. However, the wording used may not be easily understandable to a layman.

Figure explaining actions an employer can take to reduce muscle injury risks in the workplace.

Revised Language in Figure

I recreated the figure and modified the wording to make it easier to understand (shown above). For example, instead of saying “hierarchy of controls” I said “actions your employer can take”. I replaced “elimination, substitution, engineering controls and administrative controls” with “remove, replace, isolate and work practices”.

Improving Representation

Throughout the project it was important to make sure the visuals represented masons and were contextually relevant. This was evident in the stakeholders’ request that images should feature masons where possible. Another opportunity for representation was also in the visual design of the posters and pocket cards.

Poster design showing male masons doing different warm up exercises

Female Representation in Poster and Pocket Card Design

In my original poster design of the warm-up routine (shown above), it was important to be inclusive in the visual design. For this reason I included different skin tones for the illustrations of the masons. However, I overlooked the inclusion of both males and females in the illustrations, because masonry is such a male dominated field.

Poster design showing male and female masons doing different warm up exercises

Revised Poster Design

Following the recommendation from the stakeholder, I revised the poster and pocket-card illustrations to depict both male and female masons for the final design (shown above).

Final Design

Prototype Features & Design

The training system is comprised of three components: the onsite training tool, the in-class learning modules and additional resources for education and implementation.

Onsite Training Tool

The onsite training tool uses motion capture while the apprentices are working to identify high risk movements and provide recommendations to reduce injury risk.

Dashboard

The dashboard gives a high-level overview of forces acting on the whole body as well as the level of forces experienced at each of the joints in one convenient location.

Each of the individual joints with their risk score are then shown by level of risk*, with a summary of the recommended actions to improve their technique. The risk score acts as a way to contextualize the level of risk and benchmark apprentices’ training progress.

*Simplified language used to communicate ideas. The scoring system models expert behaviour which correlates with reduced exposures and potentially safer behaviour.

Recommendations

The recommendations section provides coaching cues to improve lifting technique.

A video provides visual feedback for the apprentice about their posture, and a stick figure model shows where the forces acted on the body. The recommendation explains which movement caused high forces, how it can lead to injury and which posture the apprentice should adopt instead. Visual examples of good and poor postures are also provided.

View Full Prototype in Figma

In-Class Learning Modules

The in-class learning modules includes lecture slides, speaking notes and discussion prompts for instructors.

PowerPoint Presentation

The learning modules emphasize discussion and application of knowledge. Five learning modules cover muscle injuries in masonry, how to prevent muscle injuries, the importance of and how to warm up, safe lifting techniques and an overview of the training tool. Additional information is included in the speaking notes.

Additional Educational Resources

I designed posters and pocket cards to reinforce apprentices’ learning and act as daily reminders. I also provided a guide for training system implementation.

Safe Lifting Poster

I designed a poster for the wall of the training center reminding masons of the key movements involved in safe lifting. The image was based off the form of an expert mason observed during data collection.

Warm-up Poster

I created a sample warm-up routine to target the mainbody parts engaged during masonry work, and designed an easy to follow poster for the wall of the training center.

Pocket card designs showing safe lifting techniques and an example warm up routine

Pocket Cards

I designed pocket cards for the apprentices with reminders about safe lifting and warming up that would accompany the pocket cards they receive for other safety topics. Two sizing options were provided for each topic.

Two pieces of paper with print. The paper's title says "8-week training course on muscle injuries". The pages are too small to read the body text.

Implementation Guide

A description of the training system components, how to use them, program timelines and additional implementation information is provided to instructors in this handy guide.

Next Steps

Future Project Improvements

Evaluate the usability and efficacy of the training system with the target users.

Improve product design. The goal of this project was to provide a minimum viable product. Future work should explore some of the other desires outlined by the masonry instructors in the user interviews as well as full automation of the training tool. The visual design and image content of the recommendations section could also be improved.

Demonstrate financial value and productivity gains through cost-benefit and return-on-investment analyses. This would act as a greater driver for adoption in masonry and the adoption of similar programs in other construction trades.

Reflection

Lessons Learned

Overall, this design-a-thon was a great experience and I learned a lot working with my co-designer on product design as well as leading the user researchers. Not only did I learned more about accessibility challenges for online websites and lack of resources within content management systems, but I also learned more about design processes.

Balancing Competing Priorities in Product Design

One of the most important lessons I learned from this project was how to balance the needs of the stakeholders, and the users’ desires with product feasibility, development speed and technological restrictions. I had to work with a number of constraints to design a minimum viable product that would satisfy multiple stakeholders and users. This was a clear example of how the design process must account for practical limitations.

Insights from Users’ and Subject Matter Experts are Critical

In this project, I had to design for the masonry instructors and apprentices. The structure and culture of the trade was something I was originally, very unfamiliar with, but in order to design a solution that would fit their needs, I needed to understand the ins and outs of the system and empathize with the users. This was where the interviews with the instructors were so critical into gaining insights into the culture and understanding their perspectives. Furthermore, despite my insight into the trade, there were still gaps in my knowledge that could only be filled by an insider or expert in the field. This is where consulting with a stakeholder, who was also subject matter expert was so valuable to the final product design.

Research Limitations

There were a number of limitations to the research and final design including a lack of female representation in datasets, lack of epidemiological support for the scoring system, the limited scope for postural analysis and that the quantification of the postural analysis does not fully capture expert knowledge.