A Guide to Selecting the Right EMG System

Transcription

1 Motion Lab Systems, Inc Old Hammond Hwy, Baton Rouge, LA June 20, 2017 A Guide to Selecting the Right EMG System Everyone wants to get the best value for money and there are a lot of EMG systems available that are advertised at very low prices. Users often want to integrate these cheaper systems (usually described by their manufacturers as EMG biofeedback systems) with a 3D motion capture system but may not understand the limitations that make these systems inexpensive. This 10 page document attempts to explain in detail, some of the issues that are encountered when selecting a multi-channel EMG system for use in a research, biomechanics, or gait analysis environment to collect and analyze human motion in 3D. Synchronization In order to make an EMG system work effectively with a 3D Motion Capture system it is essential that the 3D data and the EMG data are collected simultaneously so that there is a clear relationship between the recorded motion, and the EMG data from the muscles that actually create the motion. Recorded EMG data is worthless without the assurance of accurate synchronisation between EMG and the 3D motion data. The only way to guarantee this synchronization requires: The 3D Motion Capture process to control the 3D data acquisition and record the EMG and other signals (such as Force Plate data) through an integrated analog data collection (ADC) system. While it s not required that all of the data is stored in one file, it is essential that one process controls the data collection process if synchronization is to be guaranteed from the start of the data to the end of the file. An EMG system with a signal delay (input to output) that is less than the 3D motion capture system frame rate - thus ensuring that the EMG data is synchronized with the 3D data. If the EMG signal is significantly delayed then the EMG data will be recorded later than the 3D data and, unless a post -collection synchronization is performed, will be associated with the wrong 3D points. A 3D frame lasts only 16.6ms at 60Hz (8.3ms at 120Hz) so it is important that the delay introduced by the EMG system is significantly lower than the 3D frame for accurate data. Unfortunately almost all of the cheaper EMG systems fail on one, and often both, of these measures. Almost all of the EMG systems that transfer their data to a computer via USB will produce individual EMG data files that require post processing to achieve synchronization with the 3D motion data. And, as everyone who has ever tried to do this will tell you, synchronization between two separate processes is far more complex than simply starting both data collections at the same time. Synchronization has to be maintained throughout the entire data collection period, on a frame by frame basis, not just at the beginning of data collection. Even when the EMG data is presented directly to the 3D Motion Capture system, signal delays within the EMG system (prior to the data being sampled by the ADC) can cause problems. Many common biofeedback EMG systems add significant delays into the EMG signal path either by excessive filtering or packet processing of the EMG data. These delays can make any attempt at subsequent 3D data synchronization and analysis almost impossible. EMG signal delays from 40ms to 300ms or more are not uncommon - and 40ms translates to a synchronisation error of almost three 3D frames at 60Hz and even more at higher video rates.

2 The latency of an MA EMG telemetry system is less than 2ms. Typical Wi-Fi packet based EMG telemetry latency is greater than 16ms. The illustrations above show the signal applied to the EMG system inputs (top trace - green), with the output signals from the EMG system below in blue - the delay between input signal and output signal is the system latency. While a high signal latency may not cause problems in simple biofeedback or stand-alone applications, signal delays can easily become huge liabilities when the EMG is recorded for analysis in a motion laboratory environment. 3D motion analysis works because all of the events (marker motion, force data and EMG data) are recorded simultaneously and synchronously - EMG systems that are designed primarily as "biofeedback" systems almost always add delays that violate this assumption in a 3D data collection environment - and in some cases the sensors on the same system may have radically different delays from each other. Motion Lab Systems EMG systems have a constant, fixed delay that is less than 2ms - this realtime performance makes our EMG systems ideal for any 3D data collection environment. USB based EMG systems Many EMG systems use a proprietary USB interface to avoid the expense of multiple analog output connections and circuitry for each individual EMG channel. At first sight this is an attractive solution for connecting multiple channels of data to a computer requiring only a single USB cable. However, a system that connects directly to a motion capture system via a USB connection presents several problems: When an EMG system is used with a 3D system, the Motion Capture system must load a USB driver before it can communicate with the EMG system. This means that the Motion Capture system must contain software specifically for the EMG system in order to communicate and this software may need to be upgraded by the 3D system manufacturer and the EMG system manufacturer if either system, or the computer operating system, is updated. The risk of this approach is that few manufacturers are willing to support old hardware when it requires writing new software because the PC operating system or motion capture system has been upgraded and there is no guarantee that the updated system will work in the same way as the original interface. Transferring real time EMG data into a computer via USB, and synchronizing it with real time collection of 3D Motion Capture data is not a trivial task. There may be internal delays associated with the USB system and the software drivers required by the 3D Motion Capture system, causing the EMG data to be buffered, re-sampled, or delayed during data collection. These delays are hard to measure and may vary under different operating conditions and different USB driver versions. Any delay here has the potential to cause loss of synchronization between the EMG data and the 3D motion data - making subsequent data analysis suspect at best, and invalid at worst.

3 Accurate synchronization of two separate data streams is a complex task that requires precise control of the two sample rates - the 3D frame rate and the faster EMG sample rate - to ensure that each 3D frame is stored with exactly the same number of EMG samples. It s no good storing 10 samples of EMG data for one 3D frame, followed by a frame with 11 EMG samples, and then 9 samples for the next frame. It is not uncommon for sampling errors to appear due to the complex interaction between USB drivers, the requirements of the 3D Motion Capture system, and the computer operating system storing the data. An example of EMG data that has been subtly corrupted due to a USB interface issue. The EMG signal corruption only becomes fully apparent when a spectrum analysis is performed on the recorded data. A system that works one day may be subtly changed by actions as simple as adding another USB device - e.g. a printer - to the computer, causing problems with data integrity that may only be discovered at a later date after the data has been collected and the subject has left the laboratory - this type of problem is illustrated above. Motion Lab Systems EMG systems produce raw analog signals that are sampled by the 3D Motion Capture system ADC - avoiding the pitfalls of USB based EMG data collection systems. Wireless Telemetry EMG systems There are several competitive EMG systems available that use various telemetry protocols to transfer data wirelessly using data packet protocols such as Wi-Fi, ZigBee and Bluetooth in the 2.4GHz ISM (Industrial, Scientific and Medical) frequencies. These wireless protocols are attractive because they are technologically advanced and use inexpensive, consumer grade, integrated circuits. But while they may work flawlessly under ideal conditions, there are problems when used with EMG systems in an integrated 3D Motion Capture environment. All Wi-Fi wireless protocols features In this example, EMG data from a competing wireless EMG system shows automatic data rate fallback to maintain a data individual data errors caused by a local network using the same Wi-Fi channel. connection at a lower rate during interference or data transmission problems. This behavior helps when downloading movies, or browsing the Internet, but causes subtle problems when EMG data must be transferred in real-time to synchronize with a 3D Motion Capture system. A common problem can be seen in the EMG data displayed above where a section of data has obviously disappeared while other bursts of EMG in the same trace show less obvious signs of interference.

4 New Wi-Fi consumer devices are appearing every day so interference in the Wi-Fi band will only increase in the future. In addition to intermittent data rate changes that may occur due to interference, packet based radio telemetry systems have delays due to the overheads involved in assembling the data into packets and reassembling the data upon reception. These inherent delays can be 50ms (1/20th of a second) or more, the equivalent to several frames of 3D Motion Data. The inability of telemetry systems to produce reliable realtime data results in a loss of synchronization between the EMG data and other data collection systems (3D Motion Capture data and Force Plate data) without postprocessing methods to remove the delay in the EMG data after the data collection has completed. The 2.4GHz Wi-Fi band may contain many different devices and signals. Motion Lab Systems telemetry systems uses a proprietary FSK radio-telemetry method that encrypts the EMG data stream and does not have any of the inherent delays associated with Wi-Fi, ZigBee, Bluetooth and other proprietary packet systems. In addition, Motion Lab Systems telemetry supports up to three separate radiotelemetry receivers, each receiving and verifying the received signal quality, allowing the system to cover much larger areas with greater reliability than is possible with a single receiver. Motion Lab Systems supports a proprietary FSK radio-telemetry method that does not have the inherent delays associated with Wi-Fi, ZigBee, Bluetooth and other proprietary packet systems. This design makes it simple to interface to any motion capture system and guarantees reliable, real-time operation and clean EMG data even in the presence of other Wi-Fi systems. Signal Levels and Gain Controls EMG signal levels can vary from less than one tenth of a millivolt up to several millivolts depending on the degree of activation and physical condition of the muscle (among other factors) so if the EMG is to be analyzed it is vitally important that the EMG signal is accurately recorded. Competing telemetry EMG systems - to ease the design of the system - have a single fixed gain (amplification) setting and do not allow the user to adjust the amplitude of the recorded EMG signal. In order to avoid distorting large EMG signals, these fixed-gain EMG systems set the overall gain to accommodate the largest expected EMG signal which generally provides a good signal for active, healthy subjects; unfortunately this can leave the user unable to detect EMG signals when the muscle activation is low - for example, resting EMG levels in normal subjects or activity in clinical patients with atrophied muscles. Other EMG systems, designed for biofeedback or lowresolution recording and monitoring, may have only two or three EMG gain settings - these systems are generally designed for normal subjects with good muscle tone and large EMG levels. Such systems lack the flexibility needed for clinical and research applications and a limited gain range can compromise the EMG signal-to-noise ratio resulting in thicker (noisy) baselines and occasionally even clipped EMG data with athletes and spastic muscle contractions. Baseline noise - MA300 (upper trace) vs fixed gain system (lower trace).

5 In clinical and research use, the detected EMG levels can vary over a wide range and so to accurately detect EMG activation and activity patterns it is very important to look at a clean, well defined EMG signal. EMG systems with a range of gain settings that cover a wide range of EMG levels allow the user to record and analyze EMG signals with ease - avoiding the problems of trying to examine very small EMG signals (not enough gain) or distorted EMG signals (too much gain). All Motion Lab Systems EMG systems have individual, 10-position gain controls on each EMG channel together with individual overload indicators and calibration features that are not available on EMG systems from other vendors. EMG Bandwidth Many EMG systems compromise on the overall EMG bandwidth, limiting the high frequency EMG signals to no more than Hz (shown in red in the graph below). While this eases the design of the EMG system, it removes any possibility of recording the higher frequency components of the EMG signal for fine-wire or research studies - these low performance systems are simply not capable of recording the full EMG bandwidth. 20Hz-450Hz. -3dB (red) vs. 10Hz-2kHz. -3dB (blue) signal bandwidth. Limiting the high frequency response of the EMG system improves the signal to noise ratio of the system at the expense of rounding the peaks of the detected motor unit action potentials and delaying the initial rise time. This can materially affect the waveform and spectral analysis of the EMG data and produce inaccurate appraisal of muscle fatigue due to the spectral distortion. The frequency response of an EMG system is normally quoted as the lower frequency to upper frequency bandwidth, minus three decibels (-3dB) which means that the amplitude of the EMG signal at the quoted frequency will be 50% of the amplitude of the EMG signal at the middle of the quoted bandwidth. As a result the EMG bandwidth of the 20Hz to 450Hz system shown above is only 30Hz to 350Hz without attenuation. All EMG systems include some EMG signal filtering to limit the signal bandwidth and define a specific system performance for the EMG data. These filters may be simple R-C filters with relatively low performance, or they may be more complex, active filters implemented using integrated circuits. The choice of a suitable filter for EMG data is critical if the data is to be accurately reproduced for analysis - a cheap, low quality filter can introduce significant distortion and delay of the EMG signal and spectrum. These artifacts will usually dramatically increase as the signal filters reduce the EMG signal bandwidth - lower bandwidths increase the EMG signal latency as well as adding additional distortion in the form of significant signal oscillations - called ringing - when the EMG signal changes rapidly. Since the EMG signal is essentially a complex chain of muscle unit action potentials (MUAPs), EMG systems with a poor pulse response and limited bandwidth will usually exhibit significant EMG signal latency and unwanted frequency distortion due to the internal electronic signal processing ringing. This can be illustrated by applying a single EMG level pulse in the millivolt level to the EMG channel and observing the resulting output as shown below.

6 A Motion Lab Systems EMG system with Bessel filters (10-500Hz). A competing EMG system using Chebyshev filters (10-500Hz). In the recordings above, the top trace (green) displays the input signal applied to the EMG system input, while the lower (blue) trace displays the signal output. The Motion Lab Systems EMG system (left) was configured with an EMG bandwidth of 10Hz to 500Hz to match the competing EMG system shown on the right. The difference between the two signals illustrates the relatively low distortion of the Motion Lab Systems EMG filters while significant ringing is added to the signal in the second EMG system. The increased signal delay (2.44ms) in the Motion Lab Systems signal in this test is caused by the reduced EMG bandwidth setting selected for this test to ensure that both systems have an identical bandwidth for this test. All Motion Lab Systems EMG systems can record EMG signals up to a minimum of 1000Hz (MA300-X systems) or 2000Hz (MA400 systems) making them ideal for both research and clinical use where the ability to reproduce the full EMG spectrum without distortion is essential. All Motion Lab Systems EMG systems have sufficient bandwidth to record accurate intramuscular (fine-wire) EMG signals and have the required FDA 510(k) for clinical use on humans. Competing EMG systems often lack the bandwidth for fine wire recordings and lack the clinical approvals for recording EMG data from human beings via indwelling electrodes - a fact they try not to discuss. All Motion Lab Systems EMG systems feature high performance, Bessel filters designed to preserve the wave shape of filtered EMG signals in the passband with minimum ripple distortion while maintaining the full EMG spectrum for both Research and Clinical applications. The Muscle Identification Question Multi-channel EMG systems work in the 3D Motion Capture environment by detecting EMG signals from a number of the subjects muscles and transferring the EMG signals to the 3D Motion Capture system for analysis, together with 3D and force information. It is important that the EMG signal from the muscle is correctly identified to avoid problems at the later stages of the data analysis. Therefore the application of the EMG sensors to the muscles usually includes a check that each of the individual EMG sensors is placed over the correct muscle. Often a manual muscle test is performed to confirm the correct placement prior to the start of data collection. All Motion Lab Systems EMG systems make it easy to confirm that a given muscle is connected to the desired analog channel. If a problem develops during a test, it is usually simple to remove a faulty EMG sensor and replace it with another working unit, connected to the same analog channel. This causes few problems during later data analysis as the muscle signal remains on the original analog channel in all trial recordings.

7 But what happens if the EMG system is using wireless EMG sensors? If a problem develops with a wireless EMG sensor during a test then the wireless sensor must be replaced with a different sensor - if one is available. This new wireless sensor will almost certainly transmit the EMG data on a different telemetry channel to the one used by the original faulty unit. As a result, the muscle signal will appear on two different analog channels at different times during the test - complicating the later data analysis with wireless EMG sensors. Obviously this is a minor problem if you carry spare sensors but since each telemetry transmitter uses a different radio frequency, you must either carry a full set of replacement sensors or stop the test to reprogram a sensor to replace the defective unit Motion Lab Systems use a range of interchangeable EMG preamplifiers that can be connected in seconds so that the end-user has complete confidence in the recorded signal identifications. Hardware versus Software In recent years, mass production of many peripheral components for smart phones, and the increasing availability of smart and connected devices, has reduced the cost of simple wireless telemetry devices, most of which are built from programmable components with their functionality and operating parameters defined by software. Almost all wireless EMG sensors are built using cheap, off the shelf, programable radio chips and processors with the operating parameters defined by software loaded into the sensors during the production process resulting in small portable sensors that can cost less than $40 to build. The entire functionality of these devices is controlled by software which controls the operating parameters, frequencies, sampling rates and data processing and transmission methods. Any bug, no matter how small, in the software that controls these devices can affect the data quality - such bugs can be pervasive yet subtle in their effects and may only occur under very specific conditions or circumstances making it very difficult to verify that they devices always produce accurate and verifiable data when the entire process is control by software that nobody, except the programmer can review. The manufacturers of these software controlled wireless telemetry systems do not provide the end-users with the source code, or even any means of verifying the system performance or the version of the code in each system. All manufacturers have had to release multiple versions of the internal sensor operating code to fix bugs as they are discovered. All Motion Lab Systems EMG systems are hardware systems, designed to function in a specific way, controlled by standard logic circuits that do not have programmable functions. These EMG systems do not contain software and as a result the operation and function of a Motion Lab Systems EMG system can be verified by simply by tracing the signal path through the hardware. This makes reliability and repeatability something that is literally built into a Motion Lab Systems system, guaranteeing that the performance will always be repeatable and reliable - there s never any doubt about the way that a Motion Lab Systems EMG system is operating. Motion Lab Systems EMG systems are hardware systems with functions that are defined by logic circuits operating according to published specifications - the functionality and performance of such a system is never in doubt with hardware LEDs indicating any error conditions. FDA 510(k) When asking an EMG manufacturer about the regulatory status of their equipment it is important to make sure that you ask the right question. Some manufacturers claim to have FDA clearance but the equipment that they sell does not have FDA 510(k) approval to market for clinical use with humans - if in doubt, you should ask the manufacturer to provide a copy of their 510(k) approval letter from the FDA for the equipment that you are purchasing to confirm that the system is designed for medical purposes, not just biofeedback.

8 All Motion Lab Systems EMG systems and the patient connected preamplifiers have received US FDA 510(k) clearance (Sec ) and can be marketed in the USA for use as a diagnostic electromyograph for medical purposes. A diagnostic electromyograph is defined by the FDA as: A diagnostic electromyograph is a device intended for medical purposes, such as to monitor and display the bioelectric signals produced by muscles, to stimulate peripheral nerves, and to monitor and display the electrical activity produced by nerves, for the diagnosis and prognosis of neuromuscular disease. [21CFR ] Many EMG systems that claim to have US FDA 510(k) or claim to be exempt from the FDA 510(k) requirements, usually only have FDA510(k) clearance for use as a biofeedback device (Sec ). These systems can be used for research, biofeedback, and animal studies but should not be used for diagnostic functions on human beings. A biofeedback device is defined by the FDA as: A biofeedback device is an instrument that provides a visual or auditory signal corresponding to the status of one or more of a patient's physiological parameters (e.g., brain alpha wave activity, muscle activity, skin temperature, etc.) so that the patient can control voluntarily these physiological parameters. [21CFR ] When selecting an EMG system you will have to determine if your application for the EMG system, and the data that it generates, is primarily medical or research based. If you are working with human beings in a medical environment then an EMG system with FDA 510(k) under 21CFR is strongly recommended. A Motion Lab Systems EMG system with an FDA 510(k) under 21CFR (clinical use) can be used for both medical and research applications. An EMG system lacking an FDA 510(k) approval, or an FDA 510(k) under 21CFR (biofeedback), is generally not designed for clinical or medical applications with human subjects. Fine-wire use and Patient Safety Motion Lab Systems EMG systems and preamplifiers have passed a review by the FDA to demonstrate that the EMG system and its pre-amplifiers are intrinsically safe - that means that a fault or malfunction either in the EMG system, or in an external device connected to the system, cannot cause injury or harm to the subject attached to the system. This review is part of the process of obtaining FDA 510(k) 21CFR clearance. EMG systems that do not have this level of FDA clearance have not demonstrated that their systems are intrinsically safe and a fault in the operation of the system, a fault in a component within the system, or equipment connected to the system could potentially cause injury to the subject. This clearance is important when the system is used with intramuscular fine-wire electrodes as there is a low impedance electrical connection to the subject with the potential of large fault condition current flows between the EMG sensor and the subjects internal organs regardless of whether the system uses battery and AC line power sources. Mechanical Design and Construction Of the three major components in a 3D Motion Capture environment, the 3D data collection system, the force plates, and the EMG system, only one will come into contact with the subject in a trial - the EMG system. As a result, the construction and workmanship of the EMG system is very important - unlike the other components, the EMG system or sensors carried by the subject will almost certainly be dropped, kicked, knocked off the table and stepped on at some point. Unless the EMG system and associated sensors are well built, or easily repairable, you will need to budget for the repair of damaged components, as well as significant downtime. The modular design of Motion Lab Systems EMG systems makes repairs and upgrades quick and easy. Almost any component in the system can be rapidly replaced to minimize system downtime and the costs of the repair as virtually every part of the system can be interchanged with another system without any configuration or calibration issues.

9 Therefore, when looking at the economics of purchasing an EMG system, ask about service and support costs and the cost of spares and replacement parts. Is the system well made with a metal housing? What will happen when the subject drops the unit, or falls on it? Motion Lab Systems EMG systems meet international standards for Medical Equipment and carry both CE mark for sale in Europe, and the UL mark indicating that a thorough, third-party review of the system design and construction has been performed by Underwriters Laboratories. Motion Lab Systems manufacture the only EMG systems on the market that have met the testing standards to display the UL mark. Both the EMG system and the preamplifiers have separate FDA 510(k) approvals to market for Clinical Use on human beings. Any equipment attached to the subject may be damaged during normal operation. Motion Lab Systems preamplifiers are inexpensive and easily repaired but many wireless EMG sensors can cost more than $1000 each to replace if lost or accidentally damaged during a subject test. Motion Lab Systems EMG Highlights Easy to Install - All Motion Lab Systems EMG systems have individual analog outputs for each EMG channel making them very easy to connect to any Analog Data Collection (ADC) system. All systems include an analog signal cable with BNC connectors or any custom cable configuration. Easy to Use - 10 position gain controls on each EMG channel, together with individual signal level indicators and a built-in calibration test signal make clean, accurate EMG recordings an everyday event. Very Low Signal Delay - Motion Lab Systems EMG systems have a negligible signal delay. It takes less than 2ms for a 1kHz bandwidth EMG signal, detected at the subjects skin surface, to reach the ADC input of the 3D Motion Capture system, guaranteeing that the EMG data is perfectly synchronized with 3D data. Full EMG bandwidth - with an EMG signal bandwidth up to 2kHz, Motion Lab Systems EMG systems reproduce the EMG signal more accurately than competing systems with limited bandwidths. High Quality EMG filters - Motion Lab Systems EMG systems use high quality Bessel-Thompson filters in the EMG channels to ensure clean EMG data with a minimum of signal and spectral distortion. Cabled and Telemetry - It takes seconds to switch between cabled operation or radio-telemetry with no change in the system performance and EMG signal timing. Diversity Telemetry - The Motion Lab Systems radio-telemetry option can support three separate telemetry receivers mounted up to a hundred feet apart to provide reliable radio-telemetry operation in almost any environment and cover large volumes or multiple rooms. Versatile with Low Running Costs - Our EMG sensors are small, reliable and available in a range of different types to suit almost any purpose - they are (unlike wireless EMG sensors) both inexpensive and easy to repair. This keeps the lab running costs low - and allows users to maintain spare EMG sensors in case of accidents. Labs that use the wireless EMG sensors may have to keep an complete set of the radio-telemetry sensors to achieve the same level of support. Flexible - Motion Lab Systems EMG systems offer the convenience of surface EMG preamplifiers, fine-wire needles, and standard Ag/AgCl disposable electrodes as well as foot switches and other devices, and has the performance for both research and clinical studies. Interchangeable - All EMG systems and preamplifiers are fully interchangeable - subject back-packs can be moved from one system to another with any mix of pre-amplifiers or other options as needed.

10 Modular Upgrades - Motion Lab Systems EMG systems are designed to make it easy for users to upgrade from one model to another, adding additional capabilities (e.g. radio-telemetry, additional EMG channels, higher bandwidth, variable high pass and low pass filters etc) as their needs and the demands on the lab change. Meets US and International Standards - with CE, UL, CSA and FCC class B approvals, together with an FDA-510k for Clinical Use (a much stricter standard than the biofeedback 510k applications of competing vendors), our EMG systems are suitable for almost any multi-channel EMG application, whether Clinical, Educational, or Research worldwide. Free Shipping - the quoted price for an EMG system includes packing, shipping and insurance costs so there are no addition or hidden costs when systems are delivered within the USA. EMG systems shipped outside the USA may incur additional customs and importation fees but there will be no transportation charges. 30 day Money Back Guarantee - If your new Motion Lab Systems EMG system does not perform to your satisfaction for any reason then return it to us within 30 days and you will receive a complete refund of the price paid. About Motion Lab Systems Unlike competing EMG manufacturers, Motion Lab Systems started by designing EMG systems for use by Physical Therapists with 3D Motion Capture systems in the pediatric gait lab environment. We realized from the start that without a guarantee of accuracy and precise synchronization of all of the analog data sources the resulting data analysis would be severely compromised. As a result we started by designing EMG systems to be as accurate as possible with a research level performance for high fidelity EMG signals under all conditions. Our systems produce clean, accurate data under any working lab conditions. Early on in the design process, working with children with cerebral palsy, we discovered that accuracy alone was not enough. If EMG was to be widely used then the equipment had to be easy to install, as well as robust, reliable and easy to use - and yet flexible enough that good data could be recorded from a wide range of subjects and muscles without heroic efforts. The result has been a range of EMG systems to cater for many different needs - with some of our original MA-100 EMG systems remaining in use over thirty years later. Customer Support has always been a major factor in the success of Motion Lab Systems - our background in the 3D Motion Capture market convinced us that spending money to design and build reliable EMG systems - and then supporting both the systems and their users, would be beneficial to everyone. Clean, unfiltered radio telemetry EMG data from an MA400 EMG system - 10Hz to 2,000Hz -3dB These experiences, over the years, have made Motion Lab Systems the natural choice when high quality and reliable EMG systems are required for Research, Biomechanics and Gait Analysis.