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#Industry News
The DEEP EMG® method for the evaluation of the transversus abdominis muscle (TrA)
All about the differences between s-EMG and Deep EMG®
As the deepest muscle of the abdominal strap, the transverse abdominis (TrA) is by its anatomical position very difficult to evaluate. The TrA extends from the spine by inserting itself on the 4 and 5 transverse processes of the L4 or L5 vertebrae anteriorly on the iliac crest and along the inguinal canal. You can find all the details of the anatomy of the TrA in our Internal White Paper n°1.
The complexity of the evaluation of this muscle is as important for the patient as for the practitioner. Invisible to the eye and difficult to feel, the physiotherapist's instructions will be essential to help the patient understand and control the solicitation of this muscle, which does not activate on a movement.
Until then, the only techniques used to control the TrA activation during the sessions were palpation, the correct posture of the patient during the exercises performed and ultrasound imaging. We would think that the classical EMG technique would allow this, but it doesn’t. Indeed, this technique is only validated for surface muscles.
Why is the classical EMG not applicable to biofeedback of the transversus abdominis muscle?
Surface electromyography, also known as EMG or s-EMG, is the most commonly used method to measure and monitor the electrical activity of a muscle.
This technique is well known among physiotherapists, who use it for its non-invasive aspect and for its capacity to evaluate the muscle function in motion. It is particularly popular in the care of the most frequent sports pathologies such as anterior cruciate ligament rupture, pubalgia (also called groin pain) or muscle injury. This surface EMG method takes its name from its mode of operation.
The principle is to put the electrodes directly on the patient's skin, as close as possible to the muscle we intend to evaluate, and with a very precise positioning regarding the anatomy of the muscle (motor units, direction of the fibers, and so on...). Thereafter, these electrodes will collect the electrical signal from the targeted muscle. This is why this technique cannot be used to evaluate the muscular activity of the transversus abdominis: electrodes need to be placed as close as possible to the muscle chosen so they can capture principally its signal. However, the TrA is by definition a deep muscle and not a surface muscle. This means that the electrodes cannot be placed that close from this muscle, and as a consequence, they cannot capture exclusively its signal. Indeed, despite its many advantages, EMG remains very sensitive to interferences. And in the case of the transverse muscle, which is located under three other muscle layers, interferences will be considerable. The electrical signal from the TrA will be weakened and impacted by the signals from the various surrounding muscles, and it will have to overcome them in order to reach the electrodes.
Moreover, the electrodes used do not have sufficient resolution to capture this electrical current.
They will only collect a multitude of signals coming from these same surrounding muscles, without being able to affirm that the transverse muscle is part of it, and without being able to differentiate a contraction of the transverse muscle alone, from a co-contraction of the transverse muscle with the oblique, for example.
All these elements are the reason why it is impossible to evaluate the activity of deep muscles: this classical EMG technique is based on the proximity of the electrodes to the targeted muscle and its motor units.
This EMG method is therefore perfect for biofeedback of surface muscles such as the biceps, triceps, deltoids, or surface muscle groups such as the hamstrings or quadriceps. The s-EMG method is also perfect for perineal biofeedback, as the Phenix or the BioStim allow (vaginal probe allows a close contact). However, it cannot be used for the specific detection of a deep muscle such as the transverse.
Blueback found the solution !
To make transverse assessment possible, Blueback decided to twist this EMG technique, and complete it. To do so, Blueback coupled electromyography with a powerful and intelligent signal processing algorithm, and chose to integrate Ultra High Definition Soft Pulse ®️ electrodes.
Unlike the traditional EMG method, Blueback decided to place these flexible conductive polymer electrodes in a location where maximum electrical activity can be monitored : in the triangle between the anterior superior iliac spines and the pubic symphysis.
These sensors, chosen for their high resolution and precision, will allow us to capture this multitude of signals. And among this multitude of signals, it will capture the signal of the transversus abdominis muscle, with the needed sensitivity to be able to process them mathematically in a robust and efficient way. And that's where Blueback's patented technology comes in !
The signal processing algorithm will extract only the information that interests us: whether the deep muscles are contracted or not. In other words, it will apply calculation methods and specific algorithms, in order to detect and individualize the electric signal of the TrA among this multitude of received characteristics (those of the obliques, the large rights of the abdomen). To ensure the reliability of this technique, the French company compared this method to the gold standard of TrA activity assessment, ultrasound measurement. In this context, it was compared to palpation and ultrasound, and demonstrated an average correlation of 97% with ultrasound.
To date, Blueback Physio is the only specific biofeedback of the transverse abdominal muscle activity, in motion and in real time. This new EMG technique named Deep-EMG®, was made possible thanks to the scientific skills of the Blueback teams.
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