Integrating EMG with Motion Capture Systems

Synchronization of the data is of the utmost importance in 3D motion capture and analysis and yet it's often overlooked when planning a motion capture laboratory. It's common to assume that because all the data is collected at once then it will be automatically synchronized.

However, many EMG systems have significant internal delays built into their data processing systems that can delay the EMG signal causing the recorded EMG data to lag the 3D motion data by many 3D frames with an associated loss of data synchronization.

All Motion Lab system EMG systems guarantee that the signal delay will be less than 2ms (1/500th of a second) at 1kHz.

Multi channel electromyography (EMG) systems are often used with 3D Motion Capture systems from other manufacturers to provide the physicians and therapists with muscle activation and timing information to aid in the electromyographical analysis of the subjects condition. Motion Lab Systems has extensive experience with with the integration of EMG signals and Motion Capture data and can offer a solution for almost any data collection system or situation.

When EMG data is to be analyzed in conjunction with 3D trajectory data it is vital that all of the data streams (trajectory, electromyography and force data) are synchronized. All Motion Lab Systems EMG systems provide a real-time analog signal that can be directly sampled by any Motion Capture system. This allows the Motion Capture system to ensure that all of the analog data streams are perfectly synchronized with the 3D positional data by placing the entire data collection process under the control of a single application.

Unlike some competing manufacturers, all Motion Lab Systems EMG products include real time analog outputs at no extra charge, allowing the end-user complete access to their data.

Real Time Data Display

Motion Lab Systems products work with virtually any analog data recording system, including those supplied with most major motion capture systems used in Motion Analysis and Biomechanics Laboratories.  However, the data acquisition systems that are supplied as part of the motion capture system usually do not offer any facility to view electromyography data in real-time. Most 3D system allow the user to view live analog data at sample rates that are far too low to allow the user to accurately assess the quality of the EMG data prior to the actual collection.

We strongly recommend that serious electromyographers review the subjects EMG signals prior to data collection to ensure that any subsequent data analysis with be accurate and valid. This can be done using the MA-720 (via either USB or network) to display real-time EMG data on your PC as the subjects muscles contract. This offers substantial advantages over the traditional record and review afterwards approach and results in decreased post-process analysis times.

The compact MA-720 data units can be connected via the USB port, or via the network, offering simple plug-and-play connections to a PC or laptop with hot-swap capability. The high speed (200kHz sampling rate) and convenient design of the MA-720 makes it ideally suited for EMG signals. In benchmark testing using a 600MHz Pentium computer, the systems supported one-channel 16-bit resolution at 250 kHz; two channels at 222 kHz; and three or more channels at 231 kHz.

The ability to view the raw EMG data is provided with the purchase of the MA-720 hardware - additional software (WINDAQ/PRO) is only required when a stand alone data recording function (independent of the Motion Capture system) is needed.