MotionMetrix – Markerless Motion Capture

MotionMetrix is a system that was originally design for runners…elite runners. However, is has now being adapted for walking so that those who have problems relating to walking and day to day activities can now be evaluated via a similar process. In short, MotionMetrix has the potential to assess your movement through walking or running in a matter of minutes.

At Ashburnham Foot and Ankle Centre, we can take this data, combine it with a thorough clinical evaluation and relevant medical history to provide a comprehensive picture of you gait, movement lower and foot problems.

Through the use of 2 depth sensitive cameras, MotionMetrix is able to derive a wide range of information about a runner's stride performance, kinematics, running economy, and joint loading.  MotionMetrix is validated against traditional "markered" motion capture systems, and is comparable with those systems in the sagittal and frontal planes. 

Gait Characteristics

MotionMetrix provides significant insight into runners' gait characteristics.  This includes detailed information about the symmetry and motion of the lower limbs at different stages of the stride and in different anatomical planes.  This includes a magnified view of an animated segment model, which serves as visual support for the calculated parameters.  As is the norm with MotionMetrix, all parameter data are put in context via relation and comparison to elite performance and the normal population.  

A depth sensitive camera is like an ordinary digital camera but each pixel also contains information about the distance to the object. Therefore, you can digitally reconstruct any object or scene in 3D, quickly and with millimeter precision. We use these cameras to capture running motion.

In contrast to traditional motion capture systems, depth cameras do not rely on physical body markers. Instead, they use a pattern of near-infrared light to perceive depth. In a way, one can say that a depth camera generates its own body markers made of light. Therefore, no special suits or body stickers need to be worn which makes running analysis with MotionMetrix very fast and easy. You just need to step on the treadmill and run and that’s it.

Most depth cameras have built-in motion tracking functionality and it works well for general purpose applications where precision and speed is less crucial. For running, however, the built-in tracking is simply not adequate. This is why MotionMetrix uses its own algorithms for 3D reconstruction and recognition of individual body segments so that the running motion can be described with the highest possible accuracy.

How accurate you may ask? Well, sufficiently accurate to compete with world-leading marker-based solutions.

Biomechanical assessment

In our opinion, the true strength with MotionMetrix is neither in the innovative idea of using depth cameras to collect running motion data nor the unique body segment detection algorithms of unparalleled quality. It is when the 3D segmental model of the runner has been established that we finally can get down to what we do best – make sense out of your running mechanics. We look at three biomechanical categories:

  • Running economy and stride performance
  • Gait symmetry
  • Joint loading

All categories rely on rigorous kinematic and kinetic calculations to extract the angles, forces, timing parameters and everything else that matters for a complete running mechanics assessment. Before, you needed to visit a fully equipped biomechanics lab and spend a day to get the same parameters. With MotionMetrix you get it in minutes, all in one tool. It’s your own biomechanics lab. If you don’t consider yourself an expert biomechanics, no problem. MotionMetrix helps you interpret the parameters and guides you in your assessment.

Validation

When introducing a new technology, it is essential to demonstrate that it fulfils its intended purpose. Best practice is to do this by third party validation. MotionMetrix have successfully validated all the relevant parameters used in MotionMetrix at different independent institutes using standardized reference equipment, for instance

  • Position, angles and stride parameters against Qualisys Oqus 4 marker-based motion capture system
  • Forces and temporal parameters against Kistler Gaitway system
  • Running economy against VO2 using Oxycon Pro

Can MotionMetrix help prevent injuries?

MotionMetrix measures a number of different loading variables on you knee and hip joints and then compares them with the normal distribution for a group of over 600 runners. If a loading variable, for instance the frontal moment at the left knee, is found to be significantly higher than the mean, then that variable can be considered a potential risk factor for injuries.

  1. Next step is to relate the excessive loading variable to characteristic features in your running stride. For this, we use MotionMetrix’s unique correlation database that connects loading variables to specific stride parameters and anthropometrics. When a match is found, the loading variable can in most cases be tuned down by a targeted correction to your stride but may in some cases require physiotherapeutic interventions, strength training, altered footwear and so on. Whatever action is taken, it is crucial to verify that it has the desired effect by executing the final step 3.
  2. Make a re-test to verify that the corrective action has had the desired result.