Effect of balance training on ankle function and dynamic balance ability in patients with chronic ankle instability：A systematic review and meta- analysis

doi:10.21203/rs.3.rs-4194078/v1

Conclusion: Balance training benefits ankle function with CAI patients and improve the dynamic balance ability. It is recommended to obtain the best rehabilitation effect by intervening 3 times a week, each intervention time of 20min to 30min, and consecutively intervening for 4 weeks or 6 weeks.

Objective: To investigate and contrast the effects of balance training on ankle function and dynamic balance ability in patients with chronic ankle instability (CAI).

Methods: The PubMed, Embase, Web of Science, Medline, Cochrane were searched up to December 2023. Quality assessment was performed using the Cochrane Collaboration’s risk-of-bias guidelines, and the standardized mean differences (SMD) or mean differences (MD) for each outcome were calculated.

Results: Among 20 eligible studies, including 682 participants were analyzed in this meta-analysis. The results of the meta-analysis showed that balance training was effective in improving ankle function with self-functional scores (SMD =1.02 ; 95% CI,0.61 to 1.43;P < 0.00001; I² = 72%) and variables associated with the ability of dynamic balance such as SEBT-A (MD=5.88; 95% CI, 3.37 to 8.40; P<0.00001; I²= 84%), SEBT-PM (MD=5.47; 95% CI, 3.40 to 7.54; P<0.00001; I² = 61%), and SEBT-PL (MD=6.04; 95% CI, 3.30 to 8.79; P<0.0001; I² = 79%) of CAI patients. Meta-regression showed that the intervention time may be the main reason for heterogeneity (P=0.046) in self-functional scores. In subgroup analyses of self-functional score across intervention types, among the intervention time, more than 20 minutes and less than 30 minutes had the best effect(MD=1.21, 95% CI: 0.96 to 1.46, P<0.00001，I²=55%);among the intervention period, 4 weeks (MD=0.84, 95% CI:0.50 to 1.19, P<0.00001，I²=78%)and 6 weeks (MD=1.21, 95% CI: 0.91 to1.51, P<0.00001，I²=71%) had significant effects; among the intervention frequency, 3 times (MD=1.14, 95% CI:0.89 to 1.38), P<0.00001，I²=57%)had significant effects. Secondly, in subgroup analyses of SEBT across intervention types, a 4-week and 6-week intervention with balance training 3 times a week for 20-30 min is the best combination of interventions to improve SEBT (dynamic balance) in patients with chronic ankle instability.

Conclusion: Balance training benefits ankle function with CAI patients and improve the dynamic balance ability. It is recommended to obtain the best rehabilitation effect by intervening 3 times a week, each intervention time of 20min to 30min, and consecutively intervening for 4 weeks or 6 weeks.

Systematic review registration: http://www.crd.york.ac.uk/PROSPERO/,identifier CRD4202450 2230.

Health sciences/Diseases

Health sciences/Health care/Therapeutics

balance training

chronic ankle instability

meta-analysis

self-functional

SEBT

Lateral ankle sprains (LASs) are the most common musculoskeletal injuries in young and active individuals(Miklovic, Donovan et al. 2018). The incidence rates of LASs are between 75% and 85% in all ankle injuries(Braun 1999) ,meanwhile 40% of the general population experience LASs during their lifetime(Hiller, Nightingale et al. 2012, Shah, Thomas et al. 2016). Despite initial treatment (taping/bracing) and physical rehabilitation for LAS, 30%-40% of LAS patients develop chronic ankle instability (CAI). (Delahunt, Bleakley et al. 2018). CAI is characterized by repeated episodes or sensations of ankle loosening; persistent symptoms such as pain, weakness, or decreased ankle range of motion (ROM), diminished self-reported function, recurrence of ankle sprains more than 1 year after initial injury(Hertel and Corbett 2019). These potential long-term consequences highlight the need for suitable treatments for these conditions.

In current treatment methods, traditional conservative interventions is the most common choice for CAI, such as resistance training, joint mobilization, balance training, soft tissue mobilization, passive calf stretching and orthotics(Kosik, McCann et al. 2017) .Impaired balance ability is one of the main causes of recurrent ankle sprains, postural stability training provides a great boost in the rehabilitation of patients with CAI(Taube, Gruber et al. 2008). Dynamic and unstable balance training have been reported to be an effective modality for improve the symptoms of ankle instability and promote proprioceptive recovery in clinical practice(Yoshida, Kuramochi et al. 2023). A review concluded that balance training effectively reduces the risk of ankle sprain in sports participants (Schiftan, Ross et al. 2015). Previous studies also showed that their self-reported function and neuromuscular control ability were improved both by dynamic balance training and single leg balance training for CAI(Anguish and Sandrey 2018, Minoonejad, Karimizadeh Ardakani et al. 2019). The possible mechanism is that balance training on stable ground may correspond with enhanced static postural control, whereas instability balance training may improve dynamic postural control(Kibele and Behm 2009, Kibele, Classen et al. 2014)

There have been previous systematic reviews and meta-analyses on the impact of balance training on CAI(Mollà-Casanova, Inglés et al. 2021, Wang, Zhang et al. 2021, Jiang, Huang et al. 2022),and the systematic reviews of Mollà-Casanova, Inglés et al. and Jiang, Huang et al have suggested that balance training can significantly improve ankle instability symptoms and dynamic stability while the studies of Wang, Zhang et al was a protocol for a systematic review and meta-analysis. However, in the previous meta-analysis, there was no uniformly recommended exercise prescription (such as exercise frequency and duration of a single exercise), which led to the existing exercise forging can improve the efficiency of exercise, reduce the ineffective exercise, and strengthen the clarity and operability of exercise guidance by refining the exercise dose.Therefore, this article analyzed the adjustment effect of different doses of balanced exercise intervention on chronic ankle instability through a systematic review and meta-analysis, providing a reliable theoretical basis for the scientific formulation of exercise prescriptions for patients with CAI.

The review follows the Cochrane Handbook for the Preferred Reporting Items for Systematic Reviews (PRISMA) statement (Moher, Liberati et al. 2009) and as it was registered( Identifier: CRD42024502230）in the International Prospective Register of Systematic Reviews (PROSPERO).

2.1 Study search and selection

The references on PubMed, Embase, Web of Science, Medline, Cochrane Central Register of Controlled Trials up to December 2023 without any date restrictions were searched. Search terms were: [“chronic ankle instability” OR “function ankle instability”] AND [“balance training ”OR“neuromuscular control training”].The inclusion criteria of this meta-analysis included: (a) the study was conducted on patients diagnosed with CAI, (b) reporting quantitative data related to ankle functional or balance ability such as Foot and Ankle Ability Measure, Star Excursion Balance Test and Cumberland Ankle Instability Tool, (c)interventions were only balance training, such as Progressive Jump Stable Balance (PHSB)training method or the balance training based on the unstable surface or Biomechanical Ankle Platform System (BAPS) plate or swing boards, (d) the control group was non-balance training program, including conventional physical therapy, strength training and so on, and(e) using randomized control trial design. The exclusion criteria of this meta-analysis included: (a)studies excluded patients with CAI’s plus other ankle disorders, (b) the origin of the subject population is repeated, (c) literature other than English, (d) the trial was not conducted with a comparison group, or data on baseline score or end-point outcome were not provided sufficiently, (e) Review articles, case reports, editorials, and conferences were also excluded.

The duplicates article from the search was removed by the EndNote X9 software, and then the titles and abstracts of articles to establish eligibility for inclusion was read independently by two reviewers. Studies that failed to meet the inclusion criteria were not reviewed further. Articles that could not be excluded was searched and the full text was evaluated by two reviewers (FT and SY). The authors were contacted via email when data validation or more information was required. Disagreements or ambiguities were resolved through a third reviewer (PG) discussion.

2.2 Data extraction and quality assessment

The following data were extracted from included studies: first author, year of publication, simple size, age, sex, intervention method, intervention period/time/frequency, outcome measurements, and adverse effect of the study subjects. The quality of the included studies was evaluated using the Cochrane Collaboration’s risk-of-bias guidelines(Higgins, Altman et al. 2011). We will evaluate the risk of bias (low, high and unclear risk) in seven areas, including: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessments, incomplete outcome data, selective reporting, and other biases. The final decisions will be made by a third reviewer (PG) if discrepancies appear.

2.3 Types of outcome measures

The primary outcome parameters was self-functional score of ankle instability,which comprises Cumberland Ankle Instability Tool (CAIT) and Foot and Ankle Ability Measure-Sport (FAAM)-S. Furthermore, the secondary outcome parameter was Star Excursion Balance Test (SEBT), which it mainly reflects the dynamic balance ability of the ankle joint and it consists of a star-shaped offset balancing test in 3 directions: anterior(SEBT-A), posterior medial a(SEBT-PM)nd posterior lateral(SEBT-PL).

2.4 Data synthesis and statistical analysis

All outcome parameters of this studies included in this meta-analysis were continuous variables, and the mean difference (MD) with 95% CI will be used for the continuous variables, and standardized mean difference (SMD) and 95%CI will be used for the continuous variables if the units are different. Data processing was conducted by the RevMan5.3 and Stata14.0 software for this meta-analysis. Stata14.0 software was used to perform Z tests to compare differences in the subgroup’s overall effect sizes based on the intervention period/frequency/time. Heterogeneity test was performed using the Q statistic, and if p < 0.05, and I² ≤ 50%, indicating that the studies are homogeneous, then a fixed‐effect model was used for analysis. If p ≤ 0.05, and I² > 50%, indicating statistically heterogeneity, then a random‐effect model was used for analysis. Subgroup analysis and sensitivity analysis were performed if there was large heterogeneity in the pooled study results. A subgroup analysis according to intervention period/frequency/time was performed. A sensitivity analysis was conducted to prove the reliability of our meta-analysis results by removing each study to evaluate the consistency and quality of the results(Gao, Tang et al. 2021) When there were more than 10 studies with outcome indicators, funnel plots, and Egger asymmetry tests were used to detect publication bias. It was hard to find the cause of asymmetry when there were fewer than ten studies(Sterne, Sutton et al. 2011). Statistically significant differences were set at a = 0.05.

3.1Search results

A total of 672 records were retrieved after initial database search, and 446 records were included in the initial screening after removing duplicates with EndNote. The abstract and text for each study was reviewed by two reviewers based on the inclusion and exclusion criteria. 358 studies were excluded due to review articles, case report, unavailability of full text, and unrelated study design, interventions, and outcome parameters (e.g., protocol studies). Eighty-eight records were included in the full-text screening. After further screening, we find another 68 studies that did not fit the criteria and exclude them. Finally, 20 articles met the criteria and were included in our study, and all studies were published in English(McKeon, Ingersoll et al. 2008, Cloak, Nevill et al. 2010, Schaefer and Sandrey 2012, Hale, Fergus et al. 2014, Cruz-Diaz, Lomas-Vega et al. 2015, Donovan, Hart et al. 2016, Linens, Ross et al. 2016, Cain 2017, Wright, Linens et al. 2017, Deussen and Alfuth 2018, Sierra-Guzmán, Jiménez-Diaz et al. 2018, Ardakani, Wikstrom et al. 2019, Lee, Cho et al. 2019, Minoonejad, Karimizadeh Ardakani et al. 2019, Cain, Ban et al. 2020, Chang, Chen et al. 2021, Kim, Estudillo-Martínez et al. 2021, Shamseddini Sofla, Hadadi et al. 2021). The flowchart is shown as Figure 1.

3.2 Participant characteristics

Twenty studies were included in this meta-analysis including 682 patients with CAI (range of mean age =15～41 years), and the mean age of CAI’s patients in one study(Hale, Fergus et al. 2014)was not reported. The sex of CAI’s patients in the study (Sierra-Guzmán, Jiménez-Diaz et al. 2018, Chang, Chen et al. 2021) were not reported. The Hoehn and Yahr scale ranged from 1 to 5. The adverse effect was not reported in all studies. Specific details regarding participant characteristics are shown in Table 1.

3.3 Methodological quality assessment

The methodological quality of all included studies was evaluated using the Cochrane Collaboration’s techniques for assessing bias risk. In the domain of random sequence generation, all of the included trials described randomized allocation and were evaluated for low-risk. 10 studies (Hale, Fergus et al. 2014, Donovan, Hart et al. 2016, Linens, Ross et al. 2016, Cain 2017, Deussen and Alfuth 2018, Hall, Chomistek et al. 2018, Ardakani, Wikstrom et al. 2019, Lee, Cho et al. 2019, Cain, Ban et al. 2020, Chang, Chen et al. 2021) were classified as having an unclear risk in the field of allocation concealment while one study(McKeon, Ingersoll et al. 2008) were classified as having a high risk. In the domain of blinding of participants and personnel, eight studies (McKeon, Ingersoll et al. 2008, Schaefer and Sandrey 2012, Cain 2017, Anguish and Sandrey 2018, Sierra-Guzmán, Jiménez-Diaz et al. 2018, Minoonejad, Karimizadeh Ardakani et al. 2019, Cain, Ban et al. 2020, Chang, Chen et al. 2021)were assessed as having an unclear risk, while four study(Cloak, Nevill et al. 2010, Donovan, Hart et al. 2016, Hall, Chomistek et al. 2018, Lee, Cho et al. 2019) had a low risk. In their outcome assessment, four studies(Cloak, Nevill et al. 2010, Cruz-Diaz, Lomas-Vega et al. 2015, Cain 2017, Chang, Chen et al. 2021) were deemed as an unclear risk, and the rest were classified as low risk. All studies were reported as low risk in the field of incomplete outcome data. Regarding to selective outcome reporting bias, 8 studies (Hale, Fergus et al. 2014, Cruz-Diaz, Lomas-Vega et al. 2015, Donovan, Hart et al. 2016, Wright, Linens et al. 2017, Hall, Chomistek et al. 2018, Cain, Ban et al. 2020, Kim, Estudillo-Martínez et al. 2021, Shamseddini Sofla, Hadadi et al. 2021) were deemed to be at unclear risk, while three study (McKeon, Ingersoll et al. 2008, Deussen and Alfuth 2018, Minoonejad, Karimizadeh Ardakani et al. 2019)was deemed to be at high risk. Fifteen studies (McKeon, Ingersoll et al. 2008, Cloak, Nevill et al. 2010, Hale, Fergus et al. 2014, Donovan, Hart et al. 2016, Cain 2017, Wright, Linens et al. 2017, Anguish and Sandrey 2018, Deussen and Alfuth 2018, Hall, Chomistek et al. 2018, Sierra-Guzmán, Jiménez-Diaz et al. 2018, Ardakani, Wikstrom et al. 2019, Lee, Cho et al. 2019, Cain, Ban et al. 2020, Chang, Chen et al. 2021, Kim, Estudillo-Martínez et al. 2021)were evaluated as having an unclear risk , and two studies (Schaefer and Sandrey 2012, Linens, Ross et al. 2016)were assessed as having a high risk of other bias. These results are summarized in Figure 2.

3.4Meta-analysis results

3.4.1 Meta-analysis results of balance training on self-functional scores of patients with chronic ankle instability

3.4.1.1 Overall effect sizes of the intervention

A total of 14 article(McKeon, Ingersoll et al. 2008, Schaefer and Sandrey 2012, Hale, Fergus et al. 2014, Cruz-Diaz, Lomas-Vega et al. 2015, Donovan, Hart et al. 2016, Wright, Linens et al. 2017, Anguish and Sandrey 2018, Deussen and Alfuth 2018, Ardakani, Wikstrom et al. 2019, Lee, Cho et al. 2019, Minoonejad, Karimizadeh Ardakani et al. 2019, Cain, Ban et al. 2020, Kim, Estudillo-Martínez et al. 2021) were included in the study of balance training on self-functional scores of patients with chronic ankle instability, including 460 patients with CAI. Test for overall effect using a random effects model showed that balance training had prominent significant effect on the self-functional scores of patients with CAI (SMD = 1.02, 95% CI: 0.61 to 1.43, P<0.00001,I² =72%), as shown in Fig. 3.

3.4.1.2 Results of Meta Regression Analysis and Subgroup Tests

When the heterogeneity I² ≥ 50%, so it is necessary to explore the reasons for the heterogeneity and further subgroup testing by Meta regression(Westmacott, Sanal-Hayes et al. 2022). Three moderating variables were set according to the literature: intervention period, intervention frequency and intervention time. Intervention period was categorized as 4 weeks, 6 weeks, and > 6 weeks; intervention frequency was categorized as 2 times, 3 times, and > 3 times; and intervention time was categorized as >30min,20 min < t ≤ 30 min, and t ≤ 20 min. The result of meta regression analytic showed that the P value of intervention time (P=0.046) was less than 0.05, and the P values of intervention period (P=0.347) and intervention frequency (P=0.305) were greater than 0.05, as shown in Table 3. Thus, the intervention time indicator may be the main reason for heterogeneity.

The result of subgroup analysis revealed that among the intervention time, interventions of More than 20 minutes and less than 30 minutes had the best effect(MD=1.21, 95% CI: 0.96 to 1.46, P<0.00001，I²=55%), in addition, the p-value for the more than 30 minutes subgroup, despite its significance, was not supported by sufficient research evidence as it included only 2 articles ;among the intervention period, 4 weeks (MD=0.84, 95% CI:0.50 to 1.19, P<0.00001，I²=78%)and 6 weeks (MD=1.21, 95% CI: 0.91 to1.51, P<0.00001，I²=71%) had significant effects; among the intervention frequency, 2 times (MD=1.34, 95% CI:0.74 to 1.93, P=0.01，I²=22%) and 3 times (MD=1.14, 95% CI:0.89 to 1.38), P<0.00001，I²=57%)had significant effects, however, in the subgroup of 2 interventions times, there was also a lack of evidence for the significance of the findings, as only 3 studies were included in the literature .Therefore 3 times having the best effect; and as shown in Table 4. In summary, interventions of 4 weeks and 6 weeks, interventions of 3 times per week, and intervention time of 20 to 30 minutes were the most effective ways to improve the functional health of patients with chronic ankle instability, as shown in Table 3.

3.4.1.3 Results of sensitivity analysis

The heterogeneity of the article I²was 76% (Figure 3), so it is necessary to explore whether one study will have a greater impact on the whole study by eliminating the study one by one. through the sensitivity analysis, the exclusion of a study has little effect on the overall heterogeneity, indicating that the results of meta-analysis are stable and reliable, see Figure 4

3.4.1.4 Results of the literature publication bias test

The funnel plot and Egger's method test were used to test the publication bias of the self-functional score in the study. The results of the Egger's method test shown that the P-value of the self-functional score (P=0.261) is greater than 0.05, as shown in Table 5, and the left and right distributions of the funnel plot are more balanced, as shown in Fig. 5, which indicates that there is no obvious publication bias in the literature included in the self-functional score, the results of the included literature are stable.

3.4.2 Results of Meta-analysis of Balance Training on Dynamic Balance Ability

3.4.2.1 Results of the overall effect size test of the SEBT

SEBT is an evaluation method to detect the dynamic stability of the affected ankle joint, which consists of the evaluation of the distance of maximal extension in three directions: anterolateral (SEBT-A), posterolateral (SEBT-PL) and posteromedial (SEBT-PM). A total of 13 articles were included in the study of balance training on SEBT with CAI patients. The heterogeneity test (I² = 84%, 61% and 79%，P <0.00001) showed a high degree of heterogeneity, so a random effects model were used for testing of overall effect. The overall effect found that the balance training had significant improving effect on SEBT-A (MD=5.88; 95% CI, 3.37 to 8.40; P<0.00001; Figure 6), SEBT-PM (MD=5.47; 95% CI, 3.40 to 7.54; P<0.00001; Figure 7), SEBT-PL (MD=6.04; 95% CI, 3.30 to 8.79; P<0.0001; Figure 8) compared with the control group. The above data suggest that balance training can improve the dynamic balance ability of with CAI patients.

3.4.2.2 Subgroup test results of SEBT

Subgroup analyses results of the effects of the SEBT on the three directions are shown in Table 5. In terms of intervention time, interventions of less than 20 min had an improvement in the SEBT-A(MD=3.91, 95% CI:1.48 to 6.33, P=0.002，I²=42%) and SEBT-PM (MD=4.42, 95% CI:1.29 to 7.55, P=0.003，I²=41%) but not in the SEBT-PL, and interventions of 20-30 min had an improvement and a large effect size in all SEBT directions[SEBT-A(MD=6.71, 95% CI:2.75 to 10.66, P=0.0009，I²=91%);SEBT-PM(MD=5.18, 95% CI:2.27 to 8.18, P=0.0007，I²=69%);SEBT-PL(MD=8.68, 95%CI:4.32 to 13.04, P<0.0001,I²=86%)]; In terms of the intervention period, the 4-week and 6-week intervention showed significant improvements in all SEBT directions [4-week:SEBT-A(MD=4.90, 95% CI:3.10 to 6.70, P<0.00001,I²=64%); SEBT-PM(MD=3.82, 95%CI:0.93 to 6.70, P=0.009,I²=25%); SEBT-PL(MD=4.40, 95% CI:0.72 to 8.08, P=0.02,I²=39%)]; [6-week:SEBT-A(MD=5.65, 95% CI:4.57 to 6.72, P<0.0001，I²=91%); SEBT-PM(MD=5.61, 95% CI:2.54 to 8.67, P=0.0003,I²=75%);SEBT-PL(MD=7.04, 95% CI:2.84 to 11.24, P=0.001,I²=90%)]and large effects in the SEBT-PM and SEBT-PL. Regarding the frequency of interventions, there were significant improvement on all SEBT directions by the 2 and 3 interventions per week[2-times:SEBT-A(MD=6.53, 95% CI:1.73 to 11.33,P=0.008,I²=71%);SEBT-PM(MD=5.28 95% CI:2.68 to 7.87, P<0.0001,I²=64%);SEBT-PL(MD=5.04, 95% CI:1.28 to 8.80, P=0.009,I²=0%)];[3-times:SEBT-A(MD=5.73, 95% CI:2.76 to 8.70, P=0.0002,I²=86%);SEBT-PM(MD=3.82, 95% CI:0.93 to 6.70, P=0.009，I²=25%);SEBT-PL(MD=6.96, 95% CI:3.53 to 10.38, P<0.0001,I²=83%)]. In conclusion, a 4-week and 6-week intervention with balance training two and three times a week for 20-30 min is the best combination of interventions to improve SEBT (dynamic balance) in patients with chronic ankle instability.

3.4.2.3 Results of sensitivity analysis of SEBT

Since the heterogeneity of the combined effect sizes of SEBT-A, SEBT-PM, and SEBT-PL were all greater than 50%,so sensitivity analyses were performed , see Fig. 9-11, the results showed that the exclusion of one study had little effect on the overall heterogeneity of the above indicators, which indicating that the results of the meta-analysis were stable and reliable.

3.4.2.4 Results of the literature publication bias test

Funnel plots and Egger asymmetry tests were performed for testing the publication bias on SEBT parameters (SEBT-A, SEBT-PM, SEBT-PL). The results of the Egger's method test indicated that SEBT-PM (P=0.104) and SEBT-PL(P=0.108) were greater than 0.05 while the P-value of SEBT-A(P=0.032) less than 0.05, as shown in Table 6, and the left and right distributions of the funnel plot of SEBT-PM and SEBT-PL parameters are more balanced, as shown in Fig. 12-14. The above results indicate that SEBT-A has some publication bias whereas SEBT-PM and SEBT-PL do not, and therefore the results for SEBT-PM and SEBT-PL from the included literature are stable.

To our knowledge, this is the first meta-analysis to analyze the effectiveness of different doses of balanced exercise intervention on chronic ankle instability. In this meta-analysis, we reviewed 20 articles, including 682 patients with CAI. Our results found that balance training improved ankle function by self-functional score.

Self-functional score, which included two scales, CAIT and FAAM-Sport, which were mainly related to the assessment of the patients' main perception of ankle pain, usual activities, stairs, sharp turns, jumping, and one-legged standing, and recovery time, as well as describing the patient's feelings to assess the changes in the functioning of the calf and foot and ankle muscles. Self-functional score is reliable and valid scales that correlate the degree of motor function and quality of life with rehabilitation outcomes parameter in patients with CAI. Previous studies have shown that clinical evaluation of the rehabilitation of chronic ankle instability by means of the CAIT Scale(Hiller, Refshauge et al. 2006) and the FAAM Scale (Martin, Irrgang et al. 2005)has been shown to have high test efficacy. Therefore the self-functional score was included as one of the key outcome measures in our review. Several clinical reports have shown that balance training effectively treats patients with CAI(McKeon, Ingersoll et al. 2008, Cruz-Diaz, Lomas-Vega et al. 2015, Youssef, Abdelmohsen et al. 2018, Burcal, Sandrey et al. 2019). Relevant systematic review of studies also suggests that the addition of balance training to exercise can be effective in preventing recurrent ankle sprains, improving balance stability, and improving ankle function symptoms by improving self-functional score(Loudon, Santos et al. 2008). Our findings showed that balance training improved the self-functional score by an average of 1.02 points. The magnitude of the effect for self-functional scores found in our study is larger than previous reviews (WANG Yuetong 2024),which reported improvements of 0.82 points. This difference may be due to methodological differences and the previous study include several studies which published in Chinese. On the other hand, in subgroup analyses of intervention types, interventions of 4 weeks and 6 weeks, interventions of 3 times per week, and intervention time of more than 20 min were the most effective ways to improve the self-functional score of patients with chronic ankle instability. The possible mechanisms of CAI patients by different intervention type is that ankle rehabilitation training to ensure the muscles are in a high state of excitement, because balance training requires fine neuromuscular control and recruit more muscles to participate in the movement, but also exercises need to reach a certain amount of exercise in order to effectively stimulate the ankle muscle function, When the body exercises for too short a period of time, it leads to insufficient activation time for the muscles and the brain's nervous system, while too long a period of time can also lead to nerve and muscle fatigue , at this time the efficiency of the exercise will be reduced. Therefor our study showed that a balance training program of 20 minutes to 30 minutes 2-3 times per week for 4 weeks-6 weeks is an ideal regimen for the recovery of ankle function.

Furthermore, in terms of proprioceptive deficits, the main reason for chronic ankle instability symptoms is that patients with chronic ankle instability suffer from impaired nerve information afferent, reduced muscle sensitivity, and a sense of powerlessness and loss of control due to diminished proprioception and prolonged peroneal reaction time, which often results in a weakened ability of the ankle joint to perceive changes in the outside world, and can cause injury when an excessive external force is accidentally exerted. As we known, although the rest, ice, compression and elevation of the affected limb can effectively relieve pain and promote the recovery of some structural functions after acute ankle joint injuries, the lack of proprioception can only be effectively improved through balance training. Balance training enhances the patient's overall ability of balance, as well as promoting both proprioception and muscle strength(Schaefer and Sandrey 2012). Clark et al found that after a balance board training intervention in CAI patients, activation times of the peroneus longus and peroneus brevis muscles during the inversion interference state were reduced in both groups(CLARK V M 2010). The same similar results were confirmed in a study by Ardakani et al., 2019, who found that after 6 weeks of jumping dynamic balance training, pre-activation and reactive activation were significantly increased and the duration of activation in lower limb muscles was significantly shorter in CAI patients (Ardakani, Wikstrom et al. 2019). In a study by Rozzi et al , subjects with self-reported impairments showed a substantial increase in single-leg stance stability after 4 weeks of balance board training, suggesting that balance training is an effective means of improving postural stability of the ankle joint (Rozzi, Lephart et al. 1999).In summary, it was found that balance training is an important part of exercise rehabilitation for chronic ankle instability, and that the choice of exercise program is key to improving the efficiency of the exercise, and the article can provide strong evidence to support balance training programs.

The SEBT is a reliable dynamic balance evaluation method incorporating anterolateral (SEBT-A), posterolateral (SEBT-PL) and posteromedial (SEBT-PM). It has significant correlation with lower limb postural control and dynamic balance ability with high testing efficiency. In our study of meta-analysis, balance training was found to improve dynamic stability in SEBT-A, SEBT-PM and SEBT-PL.

As far as we know, action and control in human locomotion are dependent on the sensorimotor system, and when the ankle joint is damaged the sensitivity of the musculoskeletal receptors decreases, resulting in impaired afferent information pathways, prolonged peroneal reaction time, and reduced neuromuscular conduction velocity(YIN Yan 2018) , and since the control of postural stability is affected by afferent information from vision, vestibular sensation, positional sense, and proprioception, postural control deficits are most likely secondary to the combination of impaired neuromuscular control and proprioceptive impairments in combination. Studies have shown that balance training using either stable or unstable surfaces can improve SEBT scores in patients with chronic ankle instability(Linens, Ross et al. 2016, Youssef, Abdelmohsen et al. 2018). Moreover, One study analyzed moderate effect size evidence to support the improvement of dynamic postural stability through balance training and neuromuscular control in patients with CAI(O'Driscoll and Delahunt 2011) . Balance training improves postural control deficits and enhances neuromuscular control thereby improving dynamic stability. In subgroup analyses of this study, a 4-week and 6-week intervention with balance training three times a week for 20-30 min is the best combination of interventions to improve all SEBT (dynamic balance)-directions in patients with chronic ankle instability.

Although we conducted a thorough and comprehensive analysis of this meta-analysis study, it still has some limitations. First, several studies showed only randomized trials but no specific methods of random sequence generation, RCTs of allocation concealment, or blinding of outcome assessment. Many of the included RCTs were generally of low methodological quality and may have a high risk of bias; Second the diversity of the protocols used in each study may have led to variability in the results, such as the balance training program included single-leg balance training, unstable balance training and other balance interventions. Although our results demonstrate the effect of balance training on patients with CAI, the few studies and the heterogeneity of stimulation protocols should be considered when interpreting the results. Finally, the study included different load parameters and self-assessment scales for the interventions, which may have biased the results.

In the future, we should focus on different forms of balance training such as dynamic and static balance training to determine the optimal stimulation regimen on CAI patients, including stimulation intensity, duration, and sites.

In summary, the current of systematic review and meta-analysis provided evidence that balance training benefits ankle function with CAI patients and improve the dynamic balance ability. It is recommended to obtain the best rehabilitation effect by intervening 3 times a week, each intervention time of 20min to 30min, and consecutively intervening for 4 weeks or 6 weeks.

Data availability statement

This article is a systematic review and meta-analysis and the original contributions presented in this study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

Author contributions

FT and PG did the study conception, design, data collection, statistics, and writing.,SY, XL, XD, and did the data collection and participated in writing. All authors read and approved the final version of the manuscript.

Funding

This study was supported by the Youth Project of Hunan Provincial Natural Foundation (2021JJ40383), Hunan Provincial Social Science Achievement Review Committee Subjects (XSP2023JYZ036), and Educational Science Planning Project of Jiangsu Province (C/2023/01/61).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Table 1 Basic characteristics of the included studies

Author (Years)	Simple Size(E/C,n)	Age(E/C,year)	Sex (M/F)	Intervention method	Intervention period/time/ frequency	Outcome	adverse effect
Anguish 2018	9/9	18.33± 1.87/ 18.44± 1.87	2/16	E: Progressive dynamic balance training: Jump on one leg from different distances to a stable, 9-marked grid in 4 different difficulty levels，Jump to a stable, open and closed eye jump on a dangerous plane C: Maintain daily routines	4Weeks/5Times,15min	SEBT-A, SEBT-PM, SEBT-PL, FAAM-S	NR
Ardakani 2019	14/14	22.78±3.09/22.57±2.76	28/	E: Different forms of jump stability training, complete 80 landings in the first week, then increase 20 times per week (150 times in the sixth week), the movement requires increasing difficulty C: Maintain daily routines	6 weeks /3 times, 30 min	CAIT	NR
Cain 2020	10/11	age range from 15 to18	12/9	E: Balance training using resistance bands and BAPS boards C: No intervention	3 times a week for 4 weeks, 15min	CAIT, SEBT-A, SEBT-PM, SEBT-PL	NR
Cain2017	11/11	16.45± 0.93/ 16.55± 1.29	11/11	E: Five sets of 40 s clockwise and counterclockwise rotations (10 s intervals) were completed on a Biomechanical Ankle Platform System (BAPS) plate. 5 sets of 40 s of clockwise and counterclockwise rotation (1 change of direction every 10 s) with 1 min rest in between; difficulty level (1 change in direction every 10 s), the difficulty level of the exercises was increased from 1-5. C: No intervention	3 times a week for 4 weeks,10-15min	SEBT-A, SEBT-PM, SEBT-PL,	NR
Chang 2021	21/21/21	20.31±1.28/20.43±1.25 /21.23±1.47	NR	E1: performed the exercises while standing on the vibration platform, which operated at a frequency and amplitude of 5 Hz and 3 mm, respectively E2: performed the exercises on the balance ball C: continue their normal daily activity and avoid exercise	3 times per week for 6 weeks, 30min	SEBT-A, SEBT-PM, SEBT-PL	NR
Cloak2010	11/22	19± 0.8/ 19± 1.3	33/0	E: Using the swing board and vibrating ball, complete the actions of single leg standing, single leg heel raising, single foot stepping, single leg straight leg hard pulling, etc.The difficulty increases with the weeks C: Maintain daily routines	6 weeks /2 times, 15 min	SEBT-A, SEBT-PM, SEBT-PL	NR
Cruz-Diaz D2015	35/35	31.89±10.52/ 28.83±7.91	35/35	E: Add balance training on the basis of strength training, use BUSO ball, foam roller and other tools to stand on one leg, jump on one leg, one leg standing throwing and catching exercises C: Conventional strength training	6 weeks /3 times, 20-25 min	CAIT , SEBT-A, SEBT-PM, SEBT-PL	NR
Deussen 2018	6/14	30.0±6.83/29.833±8.18/26.67±6.22	6/14	E: Standing on one and two legs on different unstable devices. The number of practice sets increases over time C: Maintain daily physical activity	6 weeks /2 times, 20-30 min	CAIT	NR
Donovan2016	13/13	21.31± 3.35/ 21.46± 2.88	7/19	E: Ankle-destabilization devices C: Lower limb strength training	60 min, 3 days/week for 4 weeks	FAAM-ADL， FAAM-S	NR
Hale 2014	12/9	Not report	8/26	E: a unilateral balance training program: Single-legged stance, Wobble board, Steamboats, ball catch, Toe touch downs, Hop ups and downs, etc C: continue their normal activities	twice weekly for 4 weeks, 30 min	SEBT-A, SEBT-PM, SEBT-PL, FAAM-S	NR
Hall2018	26/13	23.5±6.5/24.8±9.0	21/18	E: Dynamic balance training: including jumping to stability, jumping to stability and stretching, jumping to stability box, standing on one leg with eyes open and eyes closed，Stand on one leg for 5 moves and include 7 difficulty levels C: Keep up a routine activities	6 weeks /3 times, 20 min	FAAM-S	NR
Kim 2021	25/24	29.76±10.009/29.67±9.407	25/24	E: The mixed balance training of single leg standing, single leg standing throwing and catching, single leg hard pulling, single leg jumping to stability, etc., has different difficulty progress C: Keep up a routine activities	6 weeks /3 times, 20 min	CAIT , SEBT-A, SEBT-PM, SEBT-PL	NR
Lee 2019	15/15	21.53±2.47/22.00±2.70	15/15	E: Perform instability training on the stability trainer C: Receive routine physiotherapy	8 weeks/3times， 20-25 min	CAIT	NR
Linens 2016	17/17	22.94± 2.77/ 23.18± 3.64	6/28	E: Balance training using swing boards C: maintain daily physical activity levels	4 weeks/3times，15 min	SEBT-A, SEBT-PM, SEBT-PL	NR
McKeon 2008	16/15	22.2±4.5/19.5± 1.2	12/19	E: Dynamic balance training: including jumping to stability, jumping to stability and stretching, jumping to stability box, standing on one leg with eyes open and eyes closed Stand on one leg for 5 moves , include 7 difficulty levels C: Keep up a routine activities	4 weeks/3times，20 min	SEBT-A, SEBT-PM, SEBT-PL, FAAM-S	NR
Minoonejad 2019	14/14	22.78±3.09/22.57±2.76	28/0	E: Complete the jump training combination on different planes, the first week needs to complete 80 landings, and the subsequent week increases by 20; intergroup interval 30 s, different exercises interval 1 min C: Keep up a routine activities	6 weeks /3 times, 15-20 min in the first week, 30-40 min in the second week	CAIT	NR
Schaefer2012	13/11	18.4±5.9/17.1±0.3	16/8	E：consisted of 4 exercises for single-limb hops to stabilization, 5-repetition hop to stabilization and reach, unanticipated hop to stabilization, and single-limb-stance activities with 7 levels of difficulty. C: Conventional physical therapy	8 weeks/2times，45 min	SEBT-A, SEBT-PM, SEBT-PL , FAAM-S，	NR
Shamseddini Sofla 2021	12/12/10	40.58±8.76/35.83±12.08/38.40±10.49	13/21	E1: received the vertical type WBV machine, The progressive program consisted of increasing duration and frequency of vibration E2: received WBV with the same parameter and duration as the E1 group while they wore the shoe with an unstable surface. C:Receive routine physiotherapy	4 weeks/3times，30 min	SEBT-A, SEBT-PM, SEBT-PL	NR
Sierra-Guzmán 2018	17/17/17	22.4±2.6/23.6± 3.4	NR	E1：Training with BUSO ball, the training plan consists of 3 series of 4 45 s exercises, with 45 s intervals; Increase the difficulty of the exercise after 3 weeks E2: trained on an Excel Pro vibration platform C: Maintain physical activity	6 weeks/3times，15 min	SEBT-A, SEBT-PM, SEBT-PL	NR
Wright 2017	20/20	22.60± 5.89/ 21.45± 3.24	11/29	E: Balance swing board training: 5 sets of 40 s clockwise and counterclockwise rotation (alternating directions every 10 s), 60 s interval for each set. The swing level increased with the intervention progress from 1 to 5. C: The ankle joint resistance training was performed with elastic bands in 4 directions for 3 sets of 10 repetitions. The strength of elastic band increased with the progress of intervention	4weeks/3times，5 min	CAIT	NR

Note: E=experimental group; C= control group; FAAM-S= Foot and Ankle Ability Measure-Sport; SEBT= Star Excursion Balance Test; A=Anterior; PM= Posterior Medial; PL= Posterior Lateral; CAIT= Cumberland Ankle Instability Tool，NR= not reported

Table 2 Meta-regression analysis results of different covariates on self-functional score of chronic ankle instability patients

Regulatory variables	β Regression coefficient	standard error	t	P>\|t\|	95%CI
intervention time	0.8471	0.3763	2.25	0.046	0.1876
intervention period	0.3184	0.3251	0.98	0.347	-0.3900
intervention Frequency	-0.5649	0.5226	-1.08	0.305	-1.7294

Table 3 Result of subgroup analysis on different covariates on self-functional score of patients with CAI

Regulatory variables	subgroup	Number of effectors	SMD(95%CI)	P	I²
intervention time	t<20min	3	0.35(-0.12,0.82)	0.15	85%
	20min<t≤30min	9	1.21(0.96,1.46)	<0.00001	55%
	>30min	2	1.76(1.09,2.43)	<0.00001	0%
intervention period	4 weeks	6	0.84(0.50,1.19)	<0.00001	78%
	6 weeks	6	1.21(0.91,1.51)	<0.00001	71%
	>6weeks	2	1.33(0.92,1.93)	<0.0001	53%
intervention Frequency	2	3	1.34(0.74,1.93)	0.01	22%
	3	10	1.14(0.89,1.38)	<0.00001	57%
	>3	1	-1.39(-2.44，-0.33)	0.01	Not useful

Table 5 Meta-analysis of Egger test result of self-functional score

Std_Eff	Coef.	Std.Err	t	P	95%CI
slope	2.367	1.083	2.19	0.049	0.008
bias	-3.16	2.676	-1.18	0.261	-8.989

Table 5 Result of subgroup analysis on SEBT of patients with CAI

Regulatory variables	subgroup	Number of effectors	SEBT-A MD(95%CI)	SEBT-PM MD(95%CI)	SEBT-PL MD(95%CI)
intervention time	t<20min	7	3.91(1.48,6.33)*	6.14(2.12,10.17)*	3.29(-0.68,7.27)
	20min<t≤30min	8	6.71(2.75,10.66)*	5.18(2.17,8.18)*	8.68(4.32,13.04)*
	>30min	1	12.80(6.74,18.86)	10.20(1.16,19.24)	7.20(-2.03,16.43)
intervention period	4 weeks	8	4.90(3.10,6.70)*	3.82(0.93,6.70)*	4.40(0.72,8.08)*
	6 weeks	7	5.65(4.57,6.72)*	5.61(2.54,8.67)*	7.20(-2.03,16.43)*
	>6weeks	1	12.80(6.74,18.86)	10.20(1.16,19.24)	10.20(1.16,19.24)
intervention Frequency	2	3	6.53(1.73,11.33)*	5.59(0.41,10.77)*	5.04(1.28,8.80)*
	3	12	5.73(2.76,8.70)*	5.28(2.68,7.87)*	6.96(3.53,10.38)*
	>3	1	4.49 (0.01，8.97)	2.14 (-2.79,7.07)	-1.30 (-6.06，3.46)

Table 6 Meta-analysis of Egger test result of SEBT parameter

variables	Std_Eff	Coef.	Std.Err	t	P	95%CI
SEBT-A	slope	-1.148	0.834	-1.38	0.190	-2.936
	bias	5.271	2.210	2.39	0.032	0.531
SEBT-PM	slope	2.088	0.813	2.57	0.022	0.344
	bias	-3.853	2.214	-1.74	0.104	-8.602
SEBT-PL	slope	3.117	1.356	2.30	0.037	0.210
	bias	-6.161	3.592	-1.71	0.108	-13.866

No competing interests reported.

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Effect of balance training on ankle function and dynamic balance ability in patients with chronic ankle instability：A systematic review and meta- analysis

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