Biofeedback + Peroneals: A Game-Changing Duo for Chronic Ankle Instability

Chronic ankle instability (CAI) is one of the most common long-term consequences of a lateral ankle sprain, affecting between 20% and 75% of individuals who sustain this injury.(1) Despite being so common, CAI remains a challenging condition to treat due to a combination of arthrogenic muscle inhibition, delayed neuromuscular responses, and disrupted motor control in the muscles responsible for stabilizing the ankle.(1) 

The peroneal muscles, particularly the peroneus longus, plays a central role in maintaining dynamic lateral ankle stability, controlling foot posture, and responding appropriately during gait, landing, and rapid directional changes.(1,2) Research shows that individuals with CAI demonstrate significant impairments in both the strength and recruitment of these muscles compared to healthy individuals.(1)

Anatomically, the fibularis longus is divided into an anterior and posterior compartment, and each contributes differently depending on the position of the ankle.(2) Notably, the posterior compartment demonstrates lower sEMG amplitude during eversion in people with CAI compared to those without instability, highlighting a specific deficit that can negatively impact stability.(2,3) Because of this, optimizing activation of the fibularis longus—particularly the posterior portion—is essential for restoring normal ankle mechanics. During dynamic tasks such as cutting, landing, or transitioning into a single-leg stance, the peroneal muscles help generate tension and stabilize the ankle through eccentric control.(1,4) When this mechanism is impaired, the ankle is more likely to experience the recurrent “giving way” episodes that define CAI, reinforcing the importance of targeted rehabilitation for this muscle. 

How mTrigger Biofeedback Supports Neuromuscular Training 

Standard strengthening alone often isn’t enough for patients with CAI, because they struggle not just with force production but with timing, recruitment, and neuromuscular strategy.(1) This is where mTrigger sEMG biofeedback becomes especially valuable. mTrigger provides clinicians with a way to retrain the neuromuscular system by converting muscle activity into real-time visual and auditory feedback.(2) This approach helps patients activate the right muscles at the right time, improving both strength and coordination.

Clinical Relevance

Ankle position plays a critical role in how effectively the peroneal muscles activate, making it an essential consideration in rehabilitation programs for chronic ankle instability (CAI).(2) Research shows that combining plantarflexion with eversion requires significantly greater activation of both the peroneus longus and brevis, and this position is particularly effective for targeting the posterior compartment of the fibularis longus—an area commonly underactive in individuals with CAI.(2) Working eversion in plantarflexion also reduces synergistic help from muscles like the tibialis anterior and extensor digitorum longus, forcing the peroneals to assume greater responsibility for generating tension and stability.(2) This makes the plantarflexed-eversion position highly relevant for clinical practice, as it mirrors the demands of functional movements such as landing, cutting, and lateral transitions. In contrast, performing eversion in a neutral ankle position generally results in lower activation levels, particularly in patients with CAI.(2) While not an inappropriate exercise, this suggests that training neutral eversion alone may not be enough when the goal is to re-establish peroneal recruitment and restore meaningful activation patterns. Patients should really be performing both exercises with biofeedback. 

Biofeedback plays an important role in closing the gap by refining motor control and reinforcing the higher activation thresholds necessary for functional strength gains. High-load training further supports this process, as greater external loads naturally require higher fibularis longus activation.(2) Multiple studies emphasize that high-load resistance is essential for restoring full muscle function in CAI.(2) Unfortunately, many traditional ankle rehabilitation programs underload the peroneals relative to the demands of sport, leaving patients underprepared for high-intensity, real-world movements. Incorporating mTrigger biofeedback into progressive resistance training ensures that patients not only lift heavier loads but also activate the correct muscles while doing so, reducing compensatory patterns and improving training efficiency.

Summary 

Training the fibularis longus with precision is essential for restoring stability and performance in individuals with chronic ankle instability (CAI). Research shows that ankle position dramatically influences peroneal activation, with plantarflexion + eversion producing significantly higher engagement of the fibularis longus—especially its posterior fibers—compared to neutral positions.(1,2) Patients with CAI will benefit from high-load training and targeted muscle activation as critical components of rehab. mTrigger sEMG biofeedback enhances this process by improving both muscle activation and neuromuscular timing deficits commonly seen in CAI, such as delayed onset and reduced pre-activation during dynamic tasks.(2)  By understanding the role of the fibularis longus and brevis and using biofeedback to guide positioning and effort, clinicians can deliver more specific, effective, and sport-relevant rehabilitation programs.

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References

1. Donnelly L, Donovan L, Hart JM, Hertel J. Eversion Strength and Surface Electromyography Measures With and Without Chronic Ankle Instability Measured in 2 Positions. Foot Ankle Int. 2017;38(7):769-778. doi:10.1177/1071100717701231
2. Mendez-Rebolledo G, Calatayud J, Martinez-Valdes E. High-Density Surface Electromyography Feedback Enhances Fibularis Longus Recruitment in Chronic Ankle Instability. Med Sci Sports Exerc. 2025;57(1):1-10. doi:10.1249/MSS.0000000000003537
3. Mendez-Rebolledo G, Guzmán-Venegas R, Cruz-Montecinos C, Watanabe K, Calatayud J, Martinez-Valdes E. Individuals with chronic ankle instability show altered regional activation of the peroneus longus muscle during ankle eversion. Scand J Med Sci Sports. 2024;34(1):e14535. doi:10.1111/SMS.14535
4. Labanca L, Mosca M, Ghislieri M, Agostini V, Knaflitz M, Benedetti MG. Muscle activations during functional tasks in individuals with chronic ankle instability: a systematic review of electromyographical studies. Gait Posture. 2021;90:340-373. doi:10.1016/j.gaitpost.2021.09.182