Published on 8 November 2022
Generally known for its use in films, motion capture is also a research tool. At IMT Mines Alès, health and sports studies are being carried out using this technique to accurately visualize and diagnose body movements and health problems.
A person is asked to walk in a room with markers attached to his thighs and ankles. Bending, jumping, stepping – every movement is recorded by cameras positioned around the room. A few meters away from the subject, researchers observe his digital twin performing the same actions live on 3D software. Their aim is not to produce a fictional character in computer-generated images, but to study the person’s gait.
This scene takes place at IMT Mines Alès on part of the aIHM (Alès Imaging and Human Metrology) platform, an interdisciplinary project dedicated, amongst other issues, to studying the human body and movement using techniques such as motion capture. “On this platform, we want to focus on using motion capture, but not just in a dedicated room, as is usually the case. The entire system is mobile and can be moved to other environments“, says Pierre Slangen, an imaging researcher at IMT Mines Alès. “One of the AIHM’s missions is to characterize people’s movements in order to diagnose their health problems,” he continues. AIHM is one of the UMR EuroMov Digital Health in Motion platforms, created in a partnership between IMT Mines Alès and the University of Montpellier.
At IMT Mines Alès, a person equipped with motion sensors performs gestures that are digitally translated into an animated skeleton (bottom screen), providing the data needed to animate a live 3D virtual-reality avatar.
With motion capture, movements such as the rotation of an arm or the bending of a leg can be quantified, which is impossible with the naked eye. This makes it possible to study a person’s movements precisely and link them to their brain activity, which can be visualized by combining motion capture with an electroencephalogram or infrared spectroscopy.
Researchers at AIHM are also studying musculoskeletal disorders in Industry 4.0. With motion capture, scientists hope to be able to analyze warehouse workers’ movements with precision. The aim here is to offer advice on how to optimize workers’ movements in order to reduce their health problems. This could involve considering how people can improve their posture when carrying a parcel and moving around with it, for example. These studies may also elicit suggestions on how to improve the layout of workspaces.
This technology is also useful for analyzing athletes’ movements. In this field, the aim is not only to prevent injuries but also to improve athletes’ performance. “Previously, the coaches of elite sportsmen and women were responsible for diagnosing athletes’ postures to help them improve their performance,” explains Pierre Slangen. “Today, tools such as motion capture allow coaches to conduct more detailed analyses“, continues the researcher.
“Single-camera” motion capture was even used at IMT Mines Alès back in 2004 to optimize the running prosthesis of Dominique André, a medal-winning Paralympic sprinter. Currently, multi-camera motion capture is also being applied to cycling, and is also used in the optimization of walking prostheses for everyday use.
With motion capture, digital twins of the person being filmed can be produced, which enables subjects to be shown what is happening during their activity. “This visual perception is highly motivating because we can show the amplitudes of movement to subjects and to athletes“, says the researcher. This also facilitates psychological reinforcement. Viewing their movements on a screen encourages sportspeople and users to reproduce the movements best suited to their activity.
According to Pierre Slangen “the added value of the AIHM platform is that it brings together engineers and doctors from different disciplines such as optics, physics and computer vision“. Some of these professionals are experts in metrology (the science of measurement) in their particular field, so they can critically appraise the measurements taken during the experiments. “They are able to qualify and quantify measurements and their validity,” points out Pierre Slangen. In this way, the tests are constantly being improved to obtain increasingly reliable results.
The design of the AIHM platform is based on the principle of combining different technologies and disciplines to study a subject (or an object) from different angles during the course of an activity. “The idea, for example, is to combine the analysis of an individual’s movement using motion capture with a synchronized electroencephalogram and electromyogram,” explains Pierre Slangen. “Electromyograms provide a detailed picture of the individual’s muscular activity, while neurophysiological sensors allow us to visualize the person’s comfort from a cerebral perspective, in environments where sound and light can be controlled on our platform,” he adds.
“The equipment required for motion capture can cost between €60,000 and €100,000 ,” says the researcher. This high financial cost is largely due to the number of cameras involved and the types of camera used. Some can be used in hostile environments (underwater or outdoors) or at high speed, for example, which implies that they would cost much more than a conventional camera used for motion capture.
For the healthcare sector, Pierre Slangen would like to see motion capture devices become financially accessible, to enable hospitals, clinics and nursing homes to acquire them. To this end, it is a question of selecting the tools best suited to doctors’ needs. “A physiotherapist does not necessarily need a device capable of millimetric accuracy“, is an example given by Pierre Slangen.
At present, theses and work by Master-level students at IMT Mines Alès are actively contributing to the development of the AIHM platform, in direct collaboration with the “EuroMov Digital Health in Motion” Joint Research Unit (UMR) and other departments at the University of Montpellier, with the aim of popularizing the benefits of this technology outside the cinema.
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