Marker-less Vision-Based Motion Capture for Ergonomics: A Review

EWI logo and technology for ergonomics

Vision-based motion capture technology has entered the realm of ergonomics and it’s got the potential to make some serious waves.

In our Technology for Ergonomics series, we break down our thoughts on using the best available advanced technologies for improving ergonomics. In this article, we discuss our experience with Kinetica Labsvision-based marker-less motion capture technology, one of the best that is currently available for use in the field.

Technology for Ergonomics

Widespread advancements in technology continue to make our work and personal lives better.

vision based motion capture technology for ergonomics on phone

Among these technologies, areas related to Artificial Intelligence (AI), machine learning, and data science seem to be among the top trends.

With these ongoing advancements, researchers and innovators have also been looking into using these technologies for ergonomics and human factors applications.

One area where technology has substantial value for ergonomic risk analysis is in using motion capture data for posture tracking, either with wearable sensors (e.g. Inertial Measurement Units (IMU)) or through vision-based approaches.

The idea is to track the subject’s posture as they move, providing feedback (potentially real-time) on the position of different body joints. This technology is also used for making visual effects in games and animations.

vision based motion capture technology for ergonomics. two people with sensors on them.

In an ergonomic risk analysis, vision-based technology works by capturing an image or video of a worker carrying out a task and then using computer vision algorithms to calculate body joint angles and provide feedback on body joint positions.

We can further break vision-based technologies down into marker-based, marker-less, and sensor-less. Kinetica Labs’ product is an example of a sensor-less technology, meaning it can work with normal videos taken on cameras or smartphones can be used. This greatly enhances its usefulness for adoption in job sites.

vision based motion capture technology for ergonomics worker being analyzed by video
vision based motion capture technology for ergonomics worker bending with lines indicating posture concerns

So far, we’ve used vision-based posture tracking in many projects, from manufacturing to housekeeping. Here are our main findings:

1. How can vision-based motion capture approaches provide value?

  • Remote assessments. Considering current COVID-19 health measures and the need to move many services online, this technology is excellent for remote ergonomic assessments. In fact, setup couldn’t be easier: anyone on-site can take a video of the work and then upload it so an ergonomist can carry out the analysis.
  • Reliable data collection. One of the biggest upsides to this and many other ergonomics technologies is that machines can potentially provide more accurate and less subjective data collection than human beings.
  • Decision-making. Instead of the more traditional approach of reporting some scores to management that they can’t really make sense of, we found that visualizing the outputs (e.g. superimposing colour-coded body joints on top of the video) makes it really easy for managers to see the risks and convince them of the need for change. The better they can understand the risks, the more engaged and willing to make changes they are.
  • Training and behaviour change. We found the technology highly effective when we used it to train workers and supervisors. Using visuals to illustrate the risks associated with how tasks are being performed is very effective and also accommodates a wider rage of learning styles. In this case, a picture (or video) really is worth a thousand words! By visualizing the problem, you make it easier for everyone to visualize the solution and know why they need to make a change.
  • Comparison. Technologies like this offer a new level of comparison between different methods of carrying out the same task and comparing the ergonomic risks. What’s unique here is the door this opens for assessing the effectiveness of interventions.
vision based motion capture technology for ergonomics neck risk comparison chart

2. Common pitfalls

Now, while we know nothing is perfect, the drawbacks of this motion capture technology are few and far between. Still, sometimes people felt drawn towards using technologies beyond what they are best suited for. In other words:  Don’t just use technology for the sake of using technology!

It’s no secret that a lot of people like to throw the term ‘AI’ and other buzzwords around. Yet, at the end of the day, these technologies are question-answering machines. If you don’t know what question you want to answer, you won’t get much out of it!

Currently, motion capture risk analysis is best when complemented by an ergonomist. Sure, the technology is amazing for data collection, but an ergonomist still needs to make the intervention.

In other words, the machine helps you identify what needs to be fixed. The ergonomist tells you how to fix it.

3. Recommendations for companies working on the tech side

Now that technologies for ergonomics are entering a new era, we need to bring the brilliant minds from the tech side into collaboration with ergonomists on the ground. The most ground-breaking developments are only going to happen if we involve ergonomics professionals right from the development and testing phases. What’s great in theory might falter in practice when you move it from a lab to a real job site.

4. Recommendations for ergonomists

If you’re an ergonomist, one of the best things you can do is keep up with the rapid advances in technologies and keep a basic understanding of the capabilities of what’s out there.

Not only does this prepare you for the future, it also helps you understand what the tech world is missing. Your innovative ideas are not going to be the same as those of the tech developers, who, presumably, have never done an ergonomic assessment.

5. Opportunities for improvement

By providing feedback on body joint angles, the existing technology is very effective for postural analysis. However, there is still room for improvement by potentially automating more of the manual data input.

For example, to analyze a task that involves manual handling or the use of tools, the weight of the object is typically required. With advancements in object detection, this can be a valuable addition to the existing vision-based technologies. By integrating such functions, these tools can eventually carry out a complete risk assessment and output the scores of existing risk assessment tools, improving their efficacy even further.

And we’ll be staying tuned because Kinetica has made it a priority to reduce manual data entry as much as possible by detecting many of the task variables from the video itself!

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