Combining camera and inertial data to optimise human movement

Kim Duffy, life science product manager at Vicon, discusses the uses of motion capture technology in medtech. 

Over the last decade, the use of motion capture technology by sporting bodies, research institutions and scientists across the globe has risen significantly. Motion capture was first used in the life science market for gait analysis in the early 1970s. Forty-or-so years later, biomechanics research remains the technology’s most common application.

The technology has made waves in academic and medical research and is at the frontline of cutting-edge clinical movement research. It is critical to the work of leading research centres, universities, hospitals and private medical practices across the globe, and is helping in various ways, from the rehabilitation of wounded soldiers to analysing the effect of low gravity on the spine.

The technology soon drew the attention of sports scientists looking to combat the huge costs occurred from player injury. According to PremierInjuries, in January 2020 the English Premier League reported 95 injuries that have cost clubs a collective £16.5 million. Undergoing high impact training programmes and endless travel means sports professionals are constantly facing the risk of a serious injury, and subsequent re-injuries.  

Sporting bodies have therefore turned to motion capture technology as a method of collecting key data that can be used in order to speed up return to play and help the prevent the risk of re-injury. This was just the entry point of motion capture into sports however, and now the technology has also been used to support technique training and player performance analytics across a wide variety of sports.

For those working in the broad biomechanics field, motion capture is a true facilitator — a tool that empowers users with more data-driven methods to interpret how their subjects move. The increasing proliferation of the technology is giving medical decision-makers access to far more data than previously possible and as a consequence, it’s helping to improve the quality of not just patient care, but also quality of life for hundreds of thousands of patients and athletes around the world.

The rise of inertial data

Traditionally, motion capture technology was used solely in the form of ‘optical solutions’- camera-based systems designed to track the position and motion of joints and limbs using markers placed across the subject. These systems are used in a variety of applications. For example, gait analysis helps medical practitioners to gain a deeper understanding into the movement of the lower limbs. In motor control and neuroscience motion capture technology is enabling big advances in the treatment of patients with a range of complex neuro-musculoskeletal injuries, like cerebral palsy and myelomeningocele.

However, with the enhanced specification and miniaturisation of sensors, as well as lower costs, we are seeing the rise of lightweight, easy to use, flexible and reliable wearable ‘inertial’ systems. These use a combination of accelerometers and gyroscopes to capture more data on joint impacts, limb movement and limb loads, enabling access to new insights and analysis into human performance.

What’s particularly interesting is the breakthrough in exceeding previous accelerometer threshold limits – enabling field-based inertial measurement of impacts and loads up to 200G. By capturing the highest speed and highest impact, sporting movement researchers and coaches are able to quantify and gain a better understanding of key movements such as sprinting, cutting, deceleration, landing and.

While these devices still remain quite new to the industry, it is likely that over the next couple of years we will see them move into more mainstream use.

Combining for success

While optical and inertial capture technologies can be used as standalone systems for focused applications, the future lies in how the combination inertial and optical motion capture will help deepen our understanding of movement tracking.

Optical technology has traditionally been limited to a lab environment, but inertial technology allows motion capture technology to be taken out to the field. While inertial data can be analysed in real-time during a training session, integrating the most accurate, real-life data from “in the wild” into the lab for further study will bring a new depth to biomechanics research.

The ability to compare motion capture data from both lab and external settings is on the rise, giving life sciences professionals insights which were previously unobtainable – or very difficult to attain. Utilising simultaneous capture techniques, users can now conduct on-the-spot comparisons and technology tests in the same software platform. The data collection capabilities of these new integrated inertial and optical solutions is unprecedented, and users are now able to harness both data streams concurrently or separately.

We can see so much potential here. This could take the form of different data visualisations, granting coaches or researchers the access needed for clearly understandable and actionable tracking results, or it could even be more automated audio or visual cues delivered via apps which will give clear prompts to users when certain values have been reached.

Although we are still in early days of understanding of how these two motion capture technologies will work together, progress in this area is likely to be fast. Real-time feedback will become the new normal as human-sensor technology continues to evolve. As such, the combination of optical and inertial technologies will contribute to improving the performance of athletes and the efficiency of researchers far more in the near future.