Therapeutic Exercises Induce Distinct Regional Activation Patterns of the Fibularis Longus Muscle in People With Chronic Ankle Instability

Abstract

Background:

Chronic ankle instability (CAI) is common in athletic populations and is associated with recurrent sprains and impaired performance. Recent evidence shows that fibularis longus has distinct anterior and posterior regions and that, during isometric eversion, people with CAI display a reduced relative contribution of the posterior region. This muscle is typically trained with band-resisted eversion in supine (BES) and BOSU-based exercises (seated and single-leg eversion, BOSU-Sit and BOSU-SL, respectively), yet it is unknown whether these specific tasks correct or perpetuate regional activation deficits.

Hypothesis:

As exercise demands increased from BES to BOSU-based tasks, fibularis longus activation would be differentially modulated and people with CAI would exhibit a greater anterior shift of the activation barycenter together with a reduced relative contribution of the posterior region, particularly during the BOSU-based tasks.

Study Design:

Descriptive laboratory study.

Level of Evidence:

Level 5.

Methods:

A total of 40 physically active adults (CAI, n = 20; no-CAI, n = 20) performed 3 exercises: BES, BOSU-Sit, and BOSU-SL. High-density surface electromyography recorded fibularis longus activation using a 64-electrode grid. Root mean square was computed for anterior and posterior regions, and the activation barycenter was calculated along the x-axis (anteroposterior) and y-axis (cephalocaudal).

Results:

In CAI, both BOSU exercises shifted the x-axis barycenter anteriorly relative to BES (BOSU-Sit, P = 0.01; BOSU-SL, P = 0.01). BES was the only exercise in which people with CAI exhibited greater posterior-region activation than controls (P = 0.003). In contrast, BOSU-SL produced an anterior-dominant pattern, with greater anterior-region activation than the posterior region (P = 0.04) and lower posterior-region activation than BES (P = 0.008).

Conclusion:

Therapeutic exercises commonly grouped as “fibular strengthening” are not neuromuscularly equivalent. In this acute task comparison, BES was associated with a more posterior barycenter and greater posterior-region activation in CAI, whereas BOSU-based tasks primarily activated the anterior region.

Keywords

chronic ankle instability electromyography fibularis longus rehabilitation therapeutic exercise

Get full access to this article

View all access options for this article.

References

Altun

Dixon

Nunns

Rice

How do neuromuscular characteristics of the peroneal muscles differ in adults with and without chronic ankle instability? A systematic review with meta-analysis. Gait Posture. 2025;117:352-362.

Anguish

Sandrey

MA.

Two 4-week balance-training programs for chronic ankle instability. J Athl Train. 2018;53(7):662-671.

Bakkum

Russell

Adamcryck

Keyes

Gross anatomic evidence of partitioning in the human fibularis longus and brevis muscles. Clin Anat. 1996;9(6):381-385.

Baldim

Miguel

Spinoso

DH.

Electromyographic activity of the ankle and foot during functional exercises and traditional exercises. J Bodyw Mov Ther. 2024;40:862-867.

Barbero

Merletti

Rainoldi

Atlas of Muscle Innervation Zones. Springer Milan; 2012. http://link.springer.com/10.1007/978-88-470-2463-2. Accessed May 18, 2023.

Bellew

Frilot

Busch

Lamothe

Ozane

CJ.

Facilitating activation of the peroneus longus: electromyographic analysis of exercises consistent with biomechanical function. J Strength Cond Res. 2010;24(2):442-446.

Bouillon

Hofener

O’Donnel

Milligan

Obrock

Comparison of muscle activity using unstable devices during a forward lunge. J Sport Rehabil. 2020;29(4):394-399.

Buckley

Borg

GAV

. Borg’s scales in strength training; from theory to practice in young and older adults. Appl Physiol Nutr Metab. 2011;36(5):682-692.

Cain

Ban

Chen

Y-P

Geil

Goerger

Linens

SW.

Four-week ankle-rehabilitation programs in adolescent athletes with chronic ankle instability. J Athl Train. 2020;55(8):801-810.

10.

Cho

B-K

Park

J-K

Choi

S-M

Kang

S-W

SooHoo

NF.

The peroneal strength deficits in patients with chronic ankle instability compared to ankle sprain copers and normal individuals. Foot Ankle Surg. 2019;25(2):231-236.

11.

Cohen

Gallina

Ivanova

Vieira

McAndrew

Garland

SJ.

Regional modulation of the ankle plantarflexor muscles associated with standing external perturbations across different directions. Exp Brain Res. 2020;238:39-50.

12.

Cohen

Vieira

Ivanova

Garland

SJ.

Regional recruitment and differential behavior of motor units during postural control in older adults. J Neurophysiol. 2023;130(5):1321-1333.

13.

Cruz-Montecinos

Sanzana-Cuche

Mendez-Rebolledo

Regional muscle fiber conduction velocity of the fibularis longus in individuals with chronic ankle instability. J Anat. 2025;247(2):375-384.

14.

Doherty

Bleakley

Delahunt

Holden

Treatment and prevention of acute and recurrent ankle sprain: an overview of systematic reviews with meta-analysis. Br J Sports Med. 2017;51(2):113-125.

15.

Drost

Stegeman

Van Engelen

BGM

Zwarts

MJ.

Clinical applications of high-density surface EMG: a systematic review. J Electromyogr Kinesiol. 2006;16(6):586-602.

16.

English

Wolf

Segal

RL.

Compartmentalization of muscles and their motor nuclei: the partitioning hypothesis. Phys Ther. 1993;73(12):857-867.

17.

Feger

Donovan

Hart

Hertel

Lower extremity muscle activation in patients with or without chronic ankle instability during walking. J Athl Train. 2015;50(4):350-357.

18.

Gallina

Disselhorst-Klug

Farina

, et al. Consensus for experimental design in electromyography (CEDE) project: high-density surface electromyography matrix. J Electromyogr Kinesiol. 2022;64:102656.

19.

Gribble

Delahunt

Bleakley

, et al. Selection criteria for patients with chronic ankle instability in controlled research: a position statement of the International Ankle Consortium. J Orthop Sports Phys Ther. 2013;43(8):585-591.

20.

Guo

Cheng

Yang

Huang

Wang

A systematic review and meta-analysis of balance training in patients with chronic ankle instability. Syst Rev. 2024;13:64.

21.

Hall

Docherty

Simon

Kingma

Klossner

JC.

Strength-training protocols to improve deficits in participants with chronic ankle instability: a randomized controlled trial. J Athl Train. 2015;50(1):36-44.

22.

Han

Ricard

MD.

Effects of 4 weeks of elastic-resistance training on ankle-evertor strength and latency. J Sport Rehabil. 2011;20(2):157-173.

23.

Hertel

Corbett

RO.

An updated model of chronic ankle instability. J Athl Train. 2019;54(6):572-588.

24.

Herzog

Kerr

Marshall

Wikstrom

EA.

Epidemiology of ankle sprains and chronic ankle instability. J Athl Train. 2019;54(6):603-610.

25.

Karandikar

Vargas

OOO

. Kinetic chains: a review of the concept and its clinical applications. PM&R. 2011;3(8):739-745.

26.

Kazemi

Javanshir

Saadi

, et al. The effect of additional neuromuscular training on peri-ankle muscle morphology and function in chronic ankle instability subjects: a randomized controlled trial. Sports Health. 2025;17(3):572-584.

27.

Kennedy

Hug

Bilodeau

Sveistrup

Guével

Neuromuscular fatigue induced by alternating isometric contractions of the ankle plantar and dorsiflexors. J Electromyogr Kinesiol. 2011;21(3):471-477.

28.

Koshino

Kobayashi

Effects of conservative interventions on static and dynamic balance in individuals with chronic ankle instability: a systematic review and meta-analysis. Arch Phys Med Rehabil. 2023;104(4):673-685.

29.

Kunugi

Nishikawa

Watanabe

Eversion force control and neural drive to the peroneus muscles in male collegiate soccer athletes with and without perceived ankle instability. JOSPT Open. 2024;2(4):315-321.

30.

Labanca

Mosca

Ghislieri

Agostini

Knaflitz

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.

31.

Méndez

Gatica

Guzmán

Soto

AE.

Evaluation of the neuromuscular compartments in the peroneus longus muscle through electrical stimulation and accelerometry. Braz J Phys Ther. 2013;17(5):427-434.

32.

Mendez Rebolledo

Coronado Gallardo

Suazo Galdames

. Anatomical study of the fibularis longus muscle motor points and electrical stimulation therapy application. Int J Morphol. 2009;27(3):699-703.

33.

Mendez-Rebolledo

Calatayud

Martinez-Valdes

High-Density surface electromyography feedback enhances fibularis longus recruitment in chronic ankle instability. Med Sci Sports Exerc. 2025;57:1-10.

34.

Mendez-Rebolledo

Guzmán-Venegas

Cruz-Montecinos

Watanabe

Calatayud

Martinez-Valdes

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.

35.

Mendez-Rebolledo

Guzmán-Venegas

Orozco-Chavez

Cruz-Montecinos

Watanabe

Martinez-Valdes

Task-related differences in peroneus longus muscle fiber conduction velocity. J Electromyogr Kinesiol. 2023;71:102795.

36.

Mendez-Rebolledo

Guzmán-Venegas

Valencia

Watanabe

Contribution of the peroneus longus neuromuscular compartments to eversion and plantarflexion of the ankle. Plos One. 2021;16(4):e0250159.

37.

Mendez-Rebolledo

Orozco-Chavez

Salazar-Méndez

Morales-Verdugo

Martinez-Valdes

Effect of experimental and clinical pain on the spatial distribution of muscle activity: a systematic review and meta-analysis. Front Hum Neurosci. 2025;19:1603807.

38.

Muñoz-Garcés

Peñailillo

Mendez-Rebolledo

Regional activation of the latissimus dorsi muscle by high-density surface electromyography during isometric shoulder and trunk exercises. Sports Health. Published online December 4, 2025. doi:10:1177/19417381251393643.

39.

Rodrigues

Soares

Tomazini

JE.

The influence of fatigue in evertor muscles during lateral ankle sprain. Foot. 2019;40:98-104.

40.

Sánchez-Barbadora

Alepuz-Moner

Moreno-Segura

Martín-San Agustín

Comparison of lower-leg muscle activation and establishment of muscle activation patterns during single-leg stance under various instability conditions in healthy active subjects: a cross-sectional study. PeerJ. 2025;13:e19461.

41.

Van Melick

Meddeler

Hoogeboom

Nijhuis-van

Der

Sanden

MWG

Van Cingel

REH.

How to determine leg dominance: the agreement between self-reported and observed performance in healthy adults. Plos One. 2017;12:e0189876.

42.

Whittaker

Alenabi

Kim

Dickerson

CR.

Regional electromyography of the infraspinatus and supraspinatus muscles during standing isometric external rotation exercises. Sports Health. 2022;14(5):725-732.

43.

Zhang

Luo

Fei

Xie

Effectiveness of exercise therapy on chronic ankle instability: a meta-analysis. Sci Rep. 2025;15(1):11709.

44.

Zivari

Yousefi

Pezeshk

Caderby

Muscle synergies of the lower extremities during gait initiation in individuals with and without chronic ankle instability. J Foot Ankle Res. 2025;18(3):e70077.