Comparison of the Strength and Electromyography of the Evertor Muscles With and Without Toe Flexion in Patients With Chronic Ankle Instability

Factors contributing to chronic ankle instability in parcel delivery workers based on machine learning techniques

BACKGROUND

Ankle injuries in parcel delivery workers (PDWs) are most often caused by trips. Ankle sprains have high recurrence rates and are associated with chronic ankle instability (CAI). This study aimed to develop, determine, and compare the predictive performance of statistical machine learning models to classify PDWs with and without CAI using postural control, ankle range of motion, ankle joint muscle strength, and anatomical deformity variables.

METHODS

244 PDWs who had worked in parcel delivery for more than 6 months were screened for eligibility. Thirteen predictors were included in the study: 12 numeric (age, body mass index, work duration, the number of balance retrials eyes-closed single-limb stance, Y-balance test, ankle dorsiflexion range of motion, lunge angle, strength ratio of the evertor in plantar flexion and neutral position to the invertor, ankle dorsiflexor strength, navicular drop, and resting calcaneal stance position) and one categorical (success of the eyes-closed single-limb stance). Five machine learning algorithms, including LASSO logistic regression, Extreme Gradient boosting machine, support vector machine, Naïve Bayes machine, and random forest-were trained.

RESULTS

The support vector machine and random forest models confirmed good predictive performance in the training and test datasets, respectively, for PDWs. For the Shapley Additive Explanations, among the five machine learning models, the variables entered into three or more models were low ankle dorsiflexion range of motion, low lunge angle, high body mass index, old age, a high number of balance retrials of the eyes-closed single-limb stance, and low strength ratio of the evertor in the neutral position to the invertor.

CONCLUSION

Our approach produced machine learning models to classify PDWs with and without CAI and confirmed good predictive performance in PDWs.

Machine learning for classifying chronic ankle instability based on ankle strength, range of motion, postural control and anatomical deformities in delivery service workers with a history of lateral ankle sprains

OBJECTIVE

Chronic ankle instability (CAI) frequently develops as a result of lateral ankle sprains (LAS) in delivery service workers (DSWs). Identifying risk factors for CAI is crucial for implementing targeted interventions. This study aimed to develop machine learning (ML) models for classifying CAI in DSWs with a history of LAS (DSWsLAS) and to identify key contributory factors.

DESIGN

Exploratory, cross-sectional design.

SETTING

and participants: A total of 121 DSWsLAS were screened for eligibility among 289 DSWs.

METHODS

A total of 121 DSWsLAS were assessed for demographic characteristics, including ankle strength, range of motion, postural control, and anatomical deformities. Seven ML algorithms were trained and tested for classifying CAI. Principal component analysis (PCA) was used for feature extraction, and feature permutation importance (FPI) and Shapley additive explanations (SHAP) were employed to identify influential features.

MAIN OUTCOME MEASURES

Model performances were assessed using area under the curve (AUC). To interpret the classifications, we used FPI and SHAP values.

RESULTS

PCA derived 7 principal components (PCs) accounting for 83.5% of the total variation in the data. The support vector machine (SVM) algorithm achieved the highest classifying performance (AUC = 0.817) among the ML models. FPI and SHAP revealed that PC1, PC2, PC5, and PC7 were the most influential features for classifying CAI in DSWsLAS.

CONCLUSIONS

The SVM algorithm, utilizing PCA-derived factors related to body mass index and ankle muscle strength demonstrated high classifying performance for diagnosis of CAI in DSWsLAS, emphasizing the importance of considering multiple contributory factors in the prevention and management of this condition.

Application of Smart Insoles in Assessing Dynamic Stability in Patients with Chronic Ankle Instability: A Comparative Study

Chronic ankle instability (CAI), due to its chronic nature and biomechanical complexity, is well-suited for continuous monitoring and tele-rehabilitation using wearable sensor technology. This study assessed whether a smart insole system, equipped with 4 force-sensing resistor sensors and an inertial measurement unit, combined with functional tests and biomechanical indices, could distinguish CAI patients from healthy controls. A total of 21 CAI patients (23.8 ± 5.1 years) and 16 controls (22.62 ± 2.60 years) completed a battery of functional performance tests while wearing the smart insole system. The results showed an increased medial-lateral pressure ratio in the CAI during heel raise (p = 0.031, effect size = 0.82) and hop tests, suggesting an everted foot position. Significant deviations in center-of-pressure trajectory during double-leg heel raises (p = 0.005, effect size = 1.10) suggested asymmetric motion coordination, while compensatory fluctuations of the lifted limb during single-leg balance tests (p = 0.011, effect size = 1.03) were greater in CAI patients. These findings facilitated the development of features to characterize CAI-specific movement patterns. Together, this system shows promise as a quantitative assessment tool for CAI, supporting improved treatment outcomes through tele-rehabilitation.

High-Density Surface Electromyography Feedback Enhances Fibularis Longus Recruitment in Chronic Ankle Instability

PURPOSE

This study aimed to determine whether individuals with chronic ankle instability (CAI) can activate the fibularis longus compartments with high-density surface electromyography (HD-sEMG) biofeedback to the same extent as those without CAI, and to analyze the effect of ankle position on compartment activation in individuals with CAI using HD-sEMG feedback.

METHODS

There were 16 volunteers per group (CAI and No-CAI). The sEMG amplitude at each compartment (anterior and posterior) and the barycenter of the spatial sEMG amplitude distribution of the fibularis longus were recorded during eversion in neutral and plantar flexion positions at 30% and 70% of maximum voluntary contraction force, both with and without visual feedback on the spatial sEMG amplitude distribution.

RESULTS

sEMG amplitude of the posterior compartment of the fibularis longus in the CAI group trained with HD-sEMG feedback during eversion at 70% maximum voluntary contraction (in plantar flexion) was significantly higher than without HD-sEMG feedback (95% CI = 3.75-34.50% root mean square) and was similar to the activation of the No-CAI group (95% CI = -14.34% to 34.20% root mean square). Furthermore, individuals with CAI who underwent training with HD-sEMG feedback in plantar flexion exhibited a posterior displacement of the barycenter (95% CI = 0.56-2.84 mm).

CONCLUSIONS

Utilizing HD-sEMG feedback during eversion in plantar flexion position increases activation of the fibularis longus posterior compartment in individuals with CAI to the same extent as healthy people. HD-sEMG-based topographic maps can serve as effective feedback training to restore motor control of the ankle. Long-term efficacy for improving motor function requires investigation through longitudinal studies.

Selective Strength Training Changes the Morphology and Ankle Strength of the Peroneus Longus and the Peroneus Brevis

This study aimed to investigate the 8-week selective training effect of the peroneus longus (PL) and the peroneus brevis (PB) on muscle morphology, echogenicity, and ankle strength and to examine post-intervention detraining effects. Twenty healthy participants without orthopedic disease in the lower extremities were assigned to either the PL intervention group (training consisted of pushing the Thera-Band® out from the ball of the foot to emphasize ankle eversion) or the PB intervention group (training consisted of pulling the Thera-Band® from the base of the fifth metatarsal to enhance ankle valgus and external rotation). Each intervention was performed three times per week for 8 weeks. The cross-sectional area (CSA), thickness, echogenicity, and ankle strength of the PL and the PB were measured before week 1 and after each training session. Detraining effects were evaluated after the 8-week intervention. The results revealed a significant interaction between within-group (week) and between-group (type of intervention) variables on CSA and ankle strength of both the PL and the PB. Over the 8-week training period, the CSA and ankle strength of the PL significantly increased in the PL intervention group, as did the CSA and ankle strength of the PB in the PB intervention group (p < 0.05). The residual effect of muscle hypertrophy was observed during the detraining period. In conclusion, 8-week selective PL and PB training interventions can increase the CSA and ankle strength of these muscles over time. Long-term selective intervention is required to improve peroneus muscle morphology and function, with separate assessments of the CSA and ankle strength of the PL and the PB.

Effects of Peroneus Brevis versus Peroneus Longus Muscle Training on Muscle Function in Chronic Ankle Instability: A Randomized Controlled Trial

Chronic ankle instability (CAI) is a common injury that can occur in daily life or sporting events. Injuries to the anterior talofibular, posterior talofibular, and calcaneofibular ligaments are common, and the core of rehabilitation training involves strengthening the peroneus muscle. Many studies on rehabilitation training have focused on strengthening the peroneus brevis muscle, and few studies have focused on specific training to strengthen the peroneus longus muscle. Therefore, this study aims to investigate changes in the symptoms and functions of patients by applying training to strengthen the peroneus longus and peroneus brevis muscles. Home-based training and mobile monitoring were utilized for 12 weeks, divided into peroneus brevis training (PBT) and peroneus longus training (PLT), in 52 adult males with CAI. Participation was voluntary, with enrollment done through a bulletin board, and intervention training allocation was randomly assigned and conducted in a double-blind manner. This study was registered as a trial protocol (KCT 0008478). Foot and ankle outcome scores (FAOS), isokinetic ankle strength tests, and Y-balance tests were performed before and after the intervention. Both PLT and PBT significantly improved in FAOS, inversion, and eversion at angular velocities of 30°/s and 120°/s and in the anterior and posterolateral directions of the Y-balance test (p < 0.05). Interaction effects by time and group were not significant for the FAOS (p > 0.05). However, PLT improved eversion muscle strength and muscle power to a greater degree, compared with PBT, in the anterior and posterolateral directions of the Y-balance test (p < 0.05). In conclusion, both PLT and PBT were effective for CAI patients; in addition, PLT had greater potential for improving strength and balance.

Individuals with chronic ankle instability show altered regional activation of the peroneus longus muscle during ankle eversion

Individuals with chronic ankle instability (CAI) present muscular weakness and potential changes in the activation of the peroneus longus muscle, which likely explains the high recurrence of ankle sprains in this population. However, there is conflicting evidence regarding the role of the peroneus longus activity in CAI, possibly due to the limited spatial resolution of the surface electromyography (sEMG) methods (i.e., bipolar sEMG). Recent studies employing high-density sEMG (HD-sEMG) have shown that the peroneus longus presents differences in regional activation, however, it is unknown whether this regional activation is maintained under pathological conditions such as CAI. This study aimed to compare the myoelectric activity, using HD-sEMG, of each peroneus longus compartment (anterior and posterior) between individuals with and without CAI. Eighteen healthy individuals (No-CAI group) and 18 individuals with CAI were recruited. In both groups, the center of mass (COM) and the sEMG amplitude at each compartment were recorded during ankle eversion at different force levels. For the posterior compartment, the sEMG amplitude of CAI group was significantly lower than the No-CAI group (mean difference = 5.6% RMS; 95% CI = 3.4-7.6; p = 0.0001). In addition, it was observed a significant main effect for group (F1,32  = 9.608; p = 0.0040) with an anterior displacement of COM for the CAI group. These findings suggest that CAI alters the regional distribution of muscle activity of the peroneus longus during ankle eversion. In practice, altered regional activation may impact strengthening programs, prevention, and rehabilitation of CAI.

Acute Effects of Selective Strength Exercise on the Peroneus Longus and Brevis

The peroneus muscles are muscles that mainly act in ankle eversion and can be divided into PL and PB, which have different but important roles in foot and ankle functions. Therefore, PL and PB dysfunction can lead to foot and ankle issues, making. selective strength exercise necessary. This study aimed to identify the effect of two different exercise techniques on PL and PB morphologies. Two interventions were performed on separate days: the PL intervention, in which a Thera-Band® was placed on the ball of the foot and pushed out from the contact point, and the PB intervention, in which the Thera-Band® was pulled from the base of the fifth metatarsal. Cross-sectional area (CSA) and thickness of the peroneus muscles at 25% (showing the PL morphology) and 75% (showing the PB morphology) proximal to the line connecting the fibular head and lateral malleolus, as well as ankle strength was measured before and immediately after the interventions and at 10, 20, and 30 min later. A repeated-measures two-way analysis of variance was conducted to identify differences in the effects of the interventions on the PL and PB. Main and interaction effects on CSA, thickness, and ankle strength, with a significant increase in CSA and thickness in the proximal 25% in the PL intervention and the distal 75% in the PB intervention immediately after implementation, were observed (p < 0.05). The transient increase in muscle volume due to edema immediately after exercise indicates the acute effect of exercise. The CSA and thickness of the proximal 25% in the PL intervention and the distal 75% in the PB intervention increased immediately after the intervention, indicating that these interventions can be used to selectively exercise the PL and PB.

Morphological and Functional Characteristics of the Peroneus Muscles in Patients with Lateral Ankle Sprain: An Ultrasound-Based Study

Background and Objectives: The effectiveness of multiple ultrasound evaluations of the peroneus muscles morphology, including muscle cross-sectional area (CSA) and connective tissue, after lateral ankle sprain (LAS) is unknown. This study aimed to measure the peroneus muscles after LAS at three points, adding distal 75% to the conventional measurement points, in order to obtain a detailed understanding of the post-injury morphology and to propose a new evaluation index of the peroneus muscles for multiple LAS. Materials and Methods: Participants with and without LAS (LAS and control groups, 16 each) were recruited. The muscle cross-sectional area (CSA) and muscle echogenicity were measured using a B-mode ultrasound system at 25%, 50%, and 75% proximal to the line connecting the fibular head to the lateral malleolus. The ankle evertor strength was measured using a handheld dynamometer. Simultaneously, the peroneus longus (PL) and peroneus brevis (PB) muscle activities were measured using surface electromyography. Measurements for the LAS side, non-LAS side, and control leg were performed separately. Results: The CSA was significantly higher at 75% on the LAS side than on the non-LAS side and in the control leg. Muscle echogenicity of the LAS side at 75% was significantly lower than that of the non-LAS side and the control leg. Muscle activity of the PL was significantly lower and the PB was higher on the LAS side than on the non-LAS side and in the control leg. Conclusions: The PL was less active than the PB, while the PB was found to be overactive, suggesting that PB hypertrophy occurs due to an increase in the percentage of muscle fibers and a decrease in the connective tissue. Therefore, it is necessary to evaluate the condition of the PL and PB separately after LAS.

Tensiomyographic Neuromuscular Response of the Peroneus Longus and Tibialis Anterior with Chronic Ankle Instability

This study aimed to investigate the muscle contractile response of the peroneus longus (PL) and tibialis anterior (TA) in groups with and without chronic ankle instability (CAI) using tensiomyography. Twenty-three adults, 12 with CAI and 11 healthy participants, participated in this study. All subjects underwent a tensiomyographic assessment of the PL and TA to measure delay time, contraction time and maximal displacement. The ankle evertor and invertor normalized peak torques, maximum work done and muscle thickness of the PL and TA were calculated. The delay time and contraction time of the PL in the CAI side were significantly higher than those in the healthy group (p < 0.05); however, no significant difference could be detected in the TA between groups. Furthermore, there was no significant difference in the normalized peak torques, maximum work done and muscle thickness of the PL and TA between groups. The CAI side demonstrated a delayed muscle contractile response of the PL when compared with the healthy group although there was no difference in muscle strength and muscle size. Clinicians should consider the muscle contractile response of the PL for rehabilitation of the ankle evertor with CAI.

Ankle Stability and Movement Coordination Impairments: Lateral Ankle Ligament Sprains Revision 2021

This revised clinical practice guideline (CPG) addresses the distinct but related lower extremity impairments of those with a first-time lateral ankle sprain (LAS) and those with chronic ankle instability (CAI). Depending on many factors, impairments may continue following injury. While most individuals experience resolution of symptoms, complaints of instability may continue and are defined as CAI. The aims of the revision were to provide a concise summary of the contemporary evidence since publication of the original guideline and to develop new recommendations or revise previously published recommendations to support evidence-based practice. J Orthop Sports Phys Ther 2021;51(4):CPG1-CPG80. doi:10.2519/jospt.2021.0302.