Portable Motion Capture – full body, 3D kinematics

 

Why 3D motion

Movement analysis or the analysis of the kinematics is a key part of biomechanics. As pretty much any movement can be analysed, there are multiple ways of technology that have been established.

2D video analysis is lowest price and “easiest” way of looking at movements. Especially when the person constantly moves in one movement plane with a fixed distance to the camera, tools like 2D marker tracking can be used to quantify the movement. One very good example for this a classic gait analysis on a treadmill. Here, 2D video analysis is great to get some first insights into range of motion and movement patterns.

As soon as the movement becomes more complex and includes rotations of segments, the limitations of 2D video become too big and perspective errors make a professional assessment impossible. This may occur when looking at directional movements like cuttings towards or away from the camera, as well as any movement that does not happen in one single plane.

Besides these perspective errors, occlusion (of markers or segments) is a huge issue for 2D video analysis. Besides others, especially the orientation of the pelvis is very hard to measure if the subject is wearing clothes, which are needed during field testing.

These two very crucial limitations can be eliminated by using 3D motion sensors like inertial sensors (IMUs). They can measure any orientation of the key whole body segments completely mobile and also calculate the 3D anatomical angles live. This can be done even at high speeds and without the limitation of the perspective errors or occlusion as the sensors can be worn underneath your clothes.

Having accelerometers built-in, they can also measure the person’s foot contacts automatically and create reports that look at the range of motion and movement patterns during gait, running, functional assessments and jumping.

 

Portable
A compact inertial sensor (IMU) mounted on any body segment measures the 3D angular orientation of the body segment.

Range of Motion
By attaching two IMU sensors to contiguous body segments, the intervening range of motion (ROM) of the joint can be determined.

Full Body
This concept is easily extended from a single joint to a simultaneous whole body measurement across all important joints. The software provides orientation data and / or linear acceleration data.

Virtual footswitch
Sensors on the feet capture heel down / toe off patterns during most gait and cycling activities. This allows the use of gait reports to synchronise and analyse data based on gait and cycling patterns.

  • Human movements with 3 DOF in a virtual reality environment/representation of the recorded human movement as avatar with 6DOF
  • Completely wireless without visual restriction
  • No measurement volume calibration required
  • Portable – can be used in the laboratory and field
  • Extendable from 2 to 16 inertial sensors (IMU)
  • Accuracy of +/- 1 degree in the sagittal and frontal plane and +/-2 degrees in the transverse plan
  • Interfaces to all Noraxon EMG wireless systems, MyoPressure systems and the MyoVideo 2D video analysis system
  • Returns orientation angles and linear acceleration data
  • Angular speeds available post hoc
  • Models of all major joints of the body: upper/lower limbs, trunk, head and feet
  • Two sensors each act as virtual goniometers

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