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Surface EMG for early detection of muscle inhibition

The treatment of 'muscle inhibition' has become increasingly common for physiotherapists in recent times.

In itself, muscle inhibition is a healthy phenomenon, controlled by the nervous system, which makes it possible to adjust and optimise mobility in the broadest sense. In the field of re-education, this term is becoming more and more common as we talk about cases where there is a dysfunction in the management of these inhibitions. This complex phenomenon is the result of different compensations in the nervous system, whether spinal or central.

In this case, muscle inhibitions refer to a phenomenon in which the motor function of a muscle or muscle group is temporarily reduced or suppressed. These inhibitions can be caused by a variety of factors, including nerve damage, muscle imbalances, inflammatory processes or dysfunction of the central or peripheral nervous system. They can manifest themselves in different ways, such as weakened muscle responses, delays in muscle activation, or even a total inability to activate a given muscle.

Case study: Quadriceps muscle inhibition

Let's take the example of quadriceps muscle inhibition, which is particularly familiar to physiotherapists, especially in patients treated after knee injury and/or surgery. This is often referred to as Arthrogenic Muscle Inhibition (AMI), described as the long-term inability to achieve correct activation of the quadriceps. The most common picture observed is inhibition of the vastus medialis obliquus (VMO), sometimes associated with a secondary extension deficit and reflex contracture of the ischial muscles. These phenomena must be identified as soon as possible, both pre-operatively (to avoid post-operative stiffness) and post-operatively, to limit the long-term effects and optimise rehabilitation. AMI is a major obstacle to rehabilitation because it accentuates amyotrophy, joint instability and pain, and delays or blocks the return to motor skills, despite well-managed rehabilitation.

It is therefore vital to be able to identify, classify and treat AMI in patients following knee injury and/or surgery.


How do you spot an AMI? Surface EMG is an effective and extremely practical tool.

The differential diagnostic of AMI is highlighted using simple steps.

Quadriceps sideration is assessed :

  • By comparing, visually, the quality of contraction of the quadriceps in relation to the contralateral limb,

  • By the patient's inability to move into active recurvatum

  • By a difference in muscle activity detected by surface EMG.

Reflex contraction of the hamstring is assessed visually by placing the patient in a prone position, so that muscle contraction can be easily observed.

In 2022, the Lyon team, led by Dr Bertrand Sonnery-Cottet, published the first 4-grade classification of AMI.

  • Grade 0: Normal VMO contraction.

  • Grade 1: Muscle inhibition of the VMO without knee extension deficit.

  • Grade 2: Muscle inhibition of the VMO associated with a knee extension deficit due to a reflex contracture of the ischial legs.

  • Grade 3: Chronic passive extension deficit due to retraction of the posterior capsule.

This work provides guidance to practitioners in the detection, characterisation and management of AMI.

The contribution of EMG biofeedback to treatment.

Muscle re-training is fundamental.

Once again, surface EMG provides the best possible support for the patient and removes this inhibition more quickly and effectively. The aim is not just to recover muscle strength, but above all to re-establish confidence in the patient's ability to engage the muscle in functional situations, without apprehension.

Recent results have shown how the biofeedback offered with EMG solutions can increase cortical motor excitability, which is reduced in people suffering from ACLR.  Christanell's study showed the benefit of conducting a therapeutic exercise programme guided by EMG biofeedback in patients with CLRA, compared with patients performing the same exercises but without EMG feedback. In addition, EMG biofeedback-guided gait retraining has been successfully tested to achieve more optimal gait biomechanics following ACLR.

How is surface EMG used in practice?

Surface EMG can therefore be used to visualise muscle activation of the vastus medialis during tests and during re-training exercises.

There are several points to bear in mind when setting up the measurement:

  • Place your electrodes correctly.

  • Remember to record MVC (Maximum Value Contraction) measurements so that you can compare the measurements from one day to the next.

Placing the electrodes: SENIAM (Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles) is a concerted European action carried out as part of the European Union's biomedical health and research programme (BIOMED II). This action led to the establishment of global recommendations on the implementation of surface EMG and provides free access to a number of valuable resources. In particular, there are sheets detailing the optimal placement of sensors depending on the muscle being investigated. For the Medial Vastus, the SENIAM recommends placing the electrodes 80% on the line between the anterior superior iliac spine and the joint space in front of the anterior edge of the medial ligament.

Measuring the VCM: for the vastus medialis, the VCM can be measured by performing a leg extension (without hip rotation) under maximum stress, this stress being applied just above the ankle, in the opposite direction to the extension. This is the procedure recommended by the SENIAM. The maximum stress will be applied either manually by the physiotherapist, using an elastic band attached to a fixed point, or via an isokinetic system.

Today, there are several solutions adapted to physiotherapists and practice routines. At Blueback, we offer the EMG-4000, which can be used with the Blueback Physio and allows 2 channels to be measured at the same time, all fully included in the Blueback application.

There are also wireless sensors with ergonomic display and analysis solutions, such as the K-myo, E.M.I.L sensors, the DELSYS solution, the mDurance solution and the MuscleBan.


(1) Hopkins, J. T.; Ingersoll, C. D. Arthrogenic Muscle Inhibition: A Limiting Factor in Joint Rehabilitation. Journal of Sport Rehabilitation 2000, 9 (2), 135–159.

(2) Rice, D. A.; McNair, P. J. Quadriceps Arthrogenic Muscle Inhibition: Neural Mechanisms and Treatment Perspectives. Semin Arthritis Rheum 2010, 40 (3), 250–266.

(3) Sonnery-Cottet, B.; Saithna, A.; Quelard, B.; Daggett, M.; Borade, A.; Ouanezar, H.; Thaunat, M.; Blakeney, W. G. Arthrogenic Muscle Inhibition after ACL Reconstruction: A Scoping Review of the Efficacy of Interventions. Br J Sports Med 2019, 53 (5), 289–298.

(4)Bertrand Sonnery-Cottet; Graeme P. Hopper and Adnan Saithna. Arthrogenic Muscle Inhibition Following Knee Injury or Surgery: Pathophysiology, Classification, and Treatment. Video Journal of Sports Medicine Volume 2, Issue 3, May-June 2022.

(5) Pinto FG et al. Hamstring Contracture After ACL Reconstruction Is Associated With an Increased Risk of Cyclops Syndrome Orthop J Sports Med. 2017 Jan 27;5(1):2325967116684121.  doi: 10.1177/2325967116684121. eCollection 2017 Jan.

(6) Shelbourne KD. Results of Anterior Cruciate Ligament Reconstruction With Patellar Tendon Autografts: Objective Factors Associated With the Development of Osteoarthritis at 20 to 33 Years After Surgery m J Sports Med. 2017 Oct;45(12)155.

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(10) Christanell F, Hoser C, Huber R, Fink C, Luomajoki H. The influence of electromyographic biofeedback therapy on knee extension following anterior cruciate ligament reconstruction: a randomized controlled trial. Sports Med Arthrosc Rehabil Ther Technol. 2012;4(1):41. PubMed ID: 23126601 doi:10.1186/1758-2555-4-41

(11) Luc-Harkey B, Franz JR, Hackney AC, Blackburn JT, Padua DA, Schwartz TA, et al. Immediate biomechanical changes after gait biofeedback in indiiudals with anterior cruciate ligament reconstruction. J Athl Train. 2020;55(10):1106–1115. PubMed ID: 32966563 doi:10. 4085/1062-6050-0372.19 12

(12) Luc-Harkey BA, Franz JR, Blackburn JT, Padua DA, Hackney AC, Pietrosimone B. Real-time biofeedback can increase and decrease vertical ground reaction force, knee flexion excursion, and knee extension moment during walking in individuals with anterior cruciate ligament reconstruction. J Biomech. 2018;76: 94–102. PubMed ID: 29921523 doi:10.1016/j.jbiomech.2018.05.043


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