Is Kinesio Taping Effective for Sport Performance and Ankle Function of Athletes with Chronic Ankle Instability (CAI)? A Systematic Review and Meta-Analysis

Background and Objectives: Ankle injuries are the most common type of injury in healthy active individuals. If not treated properly, recurrent sprains can lead to a condition of chronic ankle instability (CAI). The aim of the present review is to evaluate the effects of Kinesio Taping (or KT) on sports performances and ankle functions in athletes with CAI. Materials and Methods: This systematic review with meta-analysis was carried out following the criteria of the Prisma Statement system (registered on Open Science Framework, number: 10.17605/OSF.IO/D8QN5). For the selection of the studies, PubMed, Scopus and Web of Science were used as databases in which the following string was used: (“kinesiology tape” OR “tape” OR “taping” OR “elastic taping” OR “kinesio taping” OR “neuro taping”) AND (unstable OR instability) AND (ankle OR (ankle OR “ankle sprain” OR “injured ankle” OR “ankle injury”)). The Downs and Black Scale was used for the quality analysis. The outcomes considered were gait functions, ROM, muscle activation, postural sway, dynamic balance, lateral landing from a monopodalic drop and agility. Effect sizes (ESs) were synthesised as standardized mean differences between the control and intervention groups. Calculation of the 95% confidence interval (CI) for each ES was conducted according to Hedges and Olkin. Results: In total, 1448 articles were identified and 8 studies were included, with a total of 270 athletes. The application of the tape had a significant effect size on gait functions, ROM, muscle activation and postural sway. Conclusions: The meta-analysis showed a significant improvement in gait functions (step velocity, step and stride length and reduction in the base of support in dynamics), reduction in the joint ROM in inversion and eversion, decrease in the muscle activation of the long peroneus and decrease in the postural sway in movement in the mid-lateral direction. It is possible to conclude that KT provides a moderate stabilising effect on the ankles of the athletes of most popular contact sports with CAI.


Introduction
Ankle injuries are the most common injury in healthy active individuals [1][2][3], affecting women more frequently than men (13.6 vs. 6.94 per 1000 exposures), children more frequently than adolescents (2.85 vs. 1.94 per 1000 exposures) and adolescents more frequently than adults (1.94 vs. 0.72 per 1000 exposures) [4]. These high incidence rates show that these injuries can cause high costs for health care systems; Gribble et al. showed that ankle injuries cost USD 6.2 billion in high school athletes in the US and EUR 208 million in the Netherlands annually [5,6].

Data Sources and Search Strategy
Findings of the present systematic review and meta-analysis are reported according to the "Preferred Reporting Items for Systematic Reviews and Meta-Analysis" (PRISMA) guidelines [41]. The study protocol has been registered within the Open Science Framework depository (Identifier code: DOI:10.17605/OSF.IO/D8QN5).
A search string related to KT was devised based on three major components: kinesiology taping, ankle and instability. For each component, an exhaustive list of keywords and relevant synonyms were generated, using proper Boolean connectors. The following string was used: ("kinesiology tape" OR "tape" OR "taping" OR "elastic taping" OR "kinesio taping" OR "kinesiotape" OR "neuro taping") AND (unstable OR instability) AND (ankle OR (ankle OR "ankle sprain" OR "injured ankle" OR "ankle injury")).
The existing literature was systematically searched from 2010 to December 2021 using the databases PubMed/MEDLINE20, ISI/Web of Science (WoS) and Scopus. A language filter was also applied, searching in English only.

Inclusion Criteria
Only articles written in English and designed as original studies were included. Only randomised clinical trials (either cross-sectional or cross-over), cohort studies, case-control studies and case series were selected that met the following criteria: the participants were adults, both females and males, with a diagnosis of chronic ankle instability (CAI); the participants were athletes; there was at least one intervention group; there was at least one group who had KT applied to their ankle; at least one ankle function was analysed in the groups.

Exclusion Criteria
All studies that included non-athletic patients or those who underwent ankle surgery or had an ankle fracture of at least 6 months were excluded. Non-English-language articles, review articles, meta-analyses, editorials, letters, comments, conference abstracts or case reports, duplicate or non-full-text articles were also excluded.

Screening
This systematic procedure, according to PRISMA guidelines, consists of identification, screening, assessment and inclusion of those studies and the relative patients included that were suitable for the review aims [41]. Hence, the screening was carried out by reading first the abstracts of all of the articles found. If the abstracts met the inclusion criteria, the full-text manuscript was retrieved and assessed. A cross-reference search of the selected articles was also performed to obtain other relevant articles for the study.
After this initial process, the selected articles and references were reviewed and assessed independently by two reviewers (GDR and MT), and all queries were discussed and resolved by the supervisory team (CB and PN) during regular meetings. If there was disagreement among the investigators regarding the inclusion or exclusion criteria, the senior investigator (PR) made the final decision. The level of agreement was high, with kappa statistics ≥ 0.80 [42,43].

Data Collection
Finally, data extraction was completed by an independent assessor (NLB). The studies that were selected as includible were ordered in an Excel file in which the data extraction was completed independently. Data were extracted for the various studies, (authors, publication date, study design, level of evidence, outcome measurements) and for the patients included: numbers, sex, age, type of sport.

Quality Appraisal
The quality analysis was carried out using the Downs and Black Scale [44], attributing to each item 1 point if the study fully complied with the criteria and if not, 0 points. The only exception was made for item 5 of the scale where 1 point was awarded even if the criteria was not fully met or was partially met, and 2 points instead if the criteria was fully met. The average value was calculated among the total scores to define the average quality of the articles included in the systematic review and meta-analysis.

Meta-Analysis
Effect sizes (ESs) were synthesised as standardized mean differences between the control and intervention groups, correcting for the small sample size when necessary (Hedges' g). Calculation of the 95% confidence interval (CI) for each ES was conducted according to Hedges and Olkin (1985) [45]. For studies with a pre-and post-design, overall ES was computed both sensu Morris (2002) and sensu Klauer (2001) [46]. While the latter computes the overall ES simply subtracting the pre-ES from the post-ES, Morris (2002) weighs the pre-post mean differences using the pooled pre-test standard deviation [46]. Using Cohen's rule of thumb, the magnitude and meaning of the computed ES was interpreted as follows: small = 0.20, moderate = 0.50 and large ≥ 0.80 [47]. Fixed-effect models were applied when heterogeneity among studies was not significant according to the I2 statistics; otherwise, a mixed-effect model was applied. All statistical analyses were conducted by means of the commercial software "Statistical Package for Social Sciences" (SPSS version 28.00, IBM Corporation, Armonk, NY, USA). Graphs were generated by means of the commercial software MedCalc ® version 20.011 (MedCalc Software Ltd., Ostend, Belgium).

Search Yield
The literature search yielded a pool of 1448 items: 1123 from Scopus, 200 from ISI/Web of Science and 125 from PubMed, as shown pictorially in Figure 1. Included studies are reported in Table 1.

Study Characteristics
A total of 270 athletes were included in the review: 171 were male (63.33%) and 99 female (36.66%). The sports of the various groups of athletes were football, basketball, volleyball, baseball and badminton, and college athletes were also present (81 in total). More details of study characteristics are reported in Table 1.

Outcome Measurements
The outcome measurements included were as follows: gait functions including stride velocity, step length, stride length and Heel-Heel (H-H) distance of base of support, measured by the GAITRite Portable Walkaway SystemC; agility through different tests, such as the Illinois Test, 5-0-5, Shuttle Test, Compass Drill Test, T-Agility Test and Figure of 8; dynamic balance by the SEBT and the Y Balance Test; joint ROM; electromyographic muscle activation; lateral landing from a monopodalic drop with the Kistler Force Plate. All of the outcome measurements mentioned above are reported in Table 2 with the tests used to assess them.

Quality Assessment
For the quality appraisal, the Downs and Black scale was used; the studies achieved an average score of 19.25/28, with values ranging from 16 to 22. All items are shown in Table 3. Table 3. Quality Assessment with Downs and Black Scale. 1.

Meta-Analysis
The effect of KT on dynamic balance was expressed in terms of SEBT. Pooled ES was 0.20 for SEBT (ranging from 0.08 for SEBT-AL to 0.29 for SEBT-L), indicating no significant impact of KT on dynamic balance. Significant large effects could be found for the following: lateral landing in loading time with an ES of 0.717 and a p-value of 0.050; gait functions with ES ranging from 1.92 for H-H base support to 2.28 for stride and a p-value of 0.000; ROM, only in ankle inversion-eversion angle peak, with an ES of 0.52 and a p-value of 0.048; sway parameters, with a relevant ES for sway velocity in medio-lateral direction, with a p-value of 1.25; ES for average muscle activity, peroneus longus contraction, with an ES of 0.55 and a p-value of 0.042. Further details are reported in Table 4.

Discussion
CAI is a frequent complication of ankle sprains that may be associated with long-term consequences in athletes. Although taping is a common intervention that is widely used by clinicians and athletic trainers for the treatment of sports injuries and various neuromusculoskeletal disorders, no studies have evaluated its effectiveness specifically for sports performance and ankle function in athletes affected by chronic ankle instability. This is the first systematic review and meta-analysis to investigate only the effect of KT on the sports performances and ankle functions of athletes with CAI. In all of the studies included, KT was analysed as the only treatment implemented on athletes, without concomitant physiotherapy or other types of exercises, so that the potential improvement parameters registered were exclusively attributed to KT. Nevertheless, the recent literature supports a multifactorial approach as the most effective on CAI using multiple interventions such as KT associated with specific proprioceptive exercises [56].
Among the most popular contact sports (football, basketball, volleyball, baseball), the ankle is the joint district most prone to injury [1][2][3]. Without recovering sufficient stability of the ankle, athletes can suffer multiple sprains and relapses during sports seasons, potentially reaching a condition of chronic instability [57][58][59][60].
Many articles have been published in the literature about the application of KT in athletes [2,18,19], most of them concerning the upper limb and generally the shoulder complex. In contrast, the available articles about KT and CAI have been very limited and quite recent [48]. This can be explained by the increasing use of KT in recent years and the large interest in evaluating its real effectiveness, even though it is an elastic bandaging technique that was proposed in the early seventies.
Among the eight articles included in this review, the sports performance and ankle functions that could be meta-analysed were (1) gait functions, (2) joint ROM, (3) muscle activation, (4) sway parameters, (5) dynamic balance, (6) lateral landing from a monopodalic drop and (7) agility. The main finding of this review, as reported in Table 4, is that KT had a significant impact only on the following outcomes: (1) gait functions, as reported by Kim et al. [48], who included gait velocity, step length, stride length and Heel-Heel

Gait Functions
In patients with CAI, the entire gait cycle can be altered by an increase in ankle inversion, which can cause both a shorter step length and an increase in the base of support and a reduction in gait speed [61,62]. In our review, the gait functions on which the tape had the greatest impact were the increase in step length and stride length with a relative ES of 2.27 and 2.28, respectively, an increase in speed, with an ES of 1.98 and the reduction in H-H base distance, with an ES of 1.92.
The increase in stride velocity, expressed in m/s, corresponds to a greater looseness during the phases of gait, which, associated with a smaller width of the base of support in dynamics, indicates a greater sense of stability of the athlete during movement [63][64][65][66]. A wider base of support in dynamics usually allows lowering the centre of mass (COM), increasing the body's stability [67,68].
In the 22 athletes included in the study, the width of the base of support decreased because taping seems to have provided greater stabilisation during walking. The main problem with the study by Kim et al. [48] is the wide range of the confidence interval (95% C.I.) of the gait functions, with values between 1.21 and 3.33; these can be justified by the low number of athletes included in the study, i.e., a very limited sample size, although the methodology of the study was of good quality (21/28).

Ankle Joint ROM
Ankle joint motion has also been found to influence the lower extremity landing pattern in people with CAI [69]. It has been repeatedly confirmed to have a great influence on bilateral postural stability [69,70]. For joint ROM, the only parameter in which taping had a significant impact was in the post-tape reduction in inversion-eversion ankle range, as shown by Sarvestan et al. [55], with an ES of 0.52 and a p-value of 0.05, while no substantial change was found in all other joint parameters of the ankle, knee and hip. During the agility tests evaluated by Sarvestan et al. in a previously included study [52], the change in grades in dorsi-plantar flexion during movement was assessed. The results were not included in the meta-analysis because they were not comparable, although Sarverstan et al. reported an improvement in ankle sagittal ROM during linear sprinting. An increase in ankle ROM could reduce the vertical ground reaction forces and the impact on the entire lower limb [30,71].
Sarvestan et al. measured the peak joint movement in dorsiflexion and plantar flexion in the sagittal plane and in inversion-eversion in the frontal pllane [55]. It was shown that, after the use of the tape, the joint peak in the frontal plane decreased drastically, limiting excessive rotation of the calcaneus and consequently reducing the oscillations in inversion and eversion during walking, favouring greater stability. Similar results regarding gait functions were also found by Kim et al. [48].
Inversion-eversion tilt is a movement that, both in a mechanical and perceptive sense, reduces the feeling of ankle stability [72]. According to Smith et al. [72], application of the tape decreased the sensation of instability in inversion-eversion, suggesting an effect that contributes to preventing recurrent ankle sprains.

Muscle Contraction
In the literature, the possible action of KT in improving muscle contraction is much debated. Some authors speculate that cutaneous stimulation of the tape may induce a greater sensitisation of type 2 mechanoreceptors and improve the recruitment of motor units [73,74]. Other possible explanations may be related to a concentric traction that the tape exerts on the fascia, which may improve muscle contraction by shortening the distance between the origin and insertion of the muscle [75][76][77].
In contrast, Sarvestan et al. [55] analysed whether the tape could modify muscle contractions using an electromyographic examination, and an opposite effect was found after application of the KT on the lateral leg muscles. The only muscle among those considered on which the KT had a considerable impact was the peroneus longus with an ES of 0.55 and a p-value of 0.05. In the leg with the KT applied, there was a strong decrease in muscle activation justified by a supporting action that the tape provided when applied laterally along the ankle, partially reducing activity of the eversion muscles, especially the peroneus longus. However, this element has both a positive aspect in a phase in which the athlete is looking for an external element of support that allows him to have a more stable ankle during sport performance, but can also have a negative effect on active stabilisation from lateral muscles, which risk being partially lacking and inhibited with the tape on, as demonstrated in Sarvestan et al. [55].

Postural Sway during Movement
Athletes with CAI often do not have instant and corrective ankle reactions when they make contact with the ground. A lack of corrections during movements greatly accentuate body postural sway [72]. Some studies conclude that postural sway depends on a loss of balance, which is an important indicator of possible falls during dynamic performances and in pre-fatigue conditions [78][79][80].
Sarvestan et al. [55] showed that in the mid-lateral direction, KT significantly reduced sway speed and reduced peak acceleration with an ES of 1.25 and a p-value of 0.03. In contrast, there were no significant changes in speed and sway area in the anterior-posterior direction. Many studies in the literature have confirmed the effectiveness of KT in improving postural sway parameters, both in relation to speed and sway area, especially in mid-lateral directions [81,82]. Reducing sway velocity in the mid-lateral direction suggests better control in prone-supination movement, corresponding to greater overall stability [82].

Dynamic Balance
The meta-analysis for dynamic balance was carried out on the studies of Souza et al. and Gehrke et al. [50,51], which had in common the use of the SEBT test. Data relating to dynamic balance of Alawna et al. [53], in which the Y Balance Test was used, were not meta-analysed, as they were not comparable. Table 4 shows that the ES did not reveal a statistically significant impact, with p-values between 0.26 and 0.75. However, both studies only evaluated 34 athletes in total. In the general population with CAI, Hadadi et al. [83] showed that KT had a significant effect on both static and dynamic balance. Other researchers, however, found no improvement in dynamic balance after the application of KT [84,85].

Lateral Landing from Monopodalic Drop
Lateral landing is very difficult, having an impact on the entire lower limb due to the dissipation of energy that is required [86]. For this reason, an alteration in the motor patterns or in the joints involved, such as CAI, can adversely affect the ability to land, even more so if the landing is performed after a monopodalic drop, which is a more challenging function [87,88].
In this review, lateral landing from a monopodalic drop was only assessed by Lin et al. [54] who considered ground reaction forces, loading rate and loading time. The p-values of the loading rate and the loading time were between 0.15 and 0.63. Therefore, it was not possible to define a significant impact of the KT on these functions. For the ground reaction forces, although the p-values were <0.05 and therefore statistically significant, they had an overall ES-including both the measurements before and after the application of the tape-that did not show a real effectiveness in improving the performance of lateral landing from a monopodalic drop. The values on the CoP (centre of pressure) were not considered for the purposes of the meta-analysis because they did not include interquartile ranges, only median values.
In another study [71], Lin et al. also concluded that KT was not sufficient to improve both frontal and sagittal postural control during landing, while Mason-Mackay et al. [89] added that KT must be combined with specific training to improve landing techniques and strategies.

Agility
Agility is an athletic condition that is essential in sports such as those included in this review (football, basketball, volleyball, baseball). This skill allows players to make heterogeneous movements in rapid succession, such as changing direction, turning quickly and cutting, all activities that have a significant impact on the ankle [49,51].
In our analysis, agility was assessed by Sarvestan et al. [49] and Gehrke et al. [51]

Time of Application
In all of the included studies, only Sarvestan et al. [55] reported the time of application of the KT before tests and measurements were carried out. They waited 25 min between application of the tape and the start of the tests.
Some authors have found a positive effect of KT to increase balance and proprioception in patients with CAI between 48 and 72 h [90]. Assessing the effectiveness of KT in the tests seen in this review with a longer application time could be an important aspect to evaluate in future studies.

Limitations and Strengths
There are several limitations in this review. First, since the studies included in the meta-analysis did not evaluate identical outcome variables, there is potential for bias in the validity of our results. However, if multiple data not representing the same outcome of one study were included in the meta-analysis, the weight of that study would increase in proportion. As a result, the total effect would not deviate towards the study with more outcome data. Second, there is no specific technique for KT application: it usually varies according to the symptoms of the patient, the therapist's experience and intended purpose. This heterogeneity, such as different tensions of the tape or applying KT in different directions and shapes, may have caused inconsistent results and led to non-significant total effects. Furthermore, the taping technique seems to have been kept consistent across the participants in the different studies during activity; however, it was not possible to know how long the taping was kept on during sports performances and the time from taping and injury; this may be affected by variation in the injury mechanisms of the sports. Therefore, it remains to be investigated whether a different taping technique could achieve a better outcome for a specific sport or injury. Finally, KT is not typically used as a single treatment tool but is combined with other treatments such as physical therapy and exercise therapy, aspects influencing the final outcomes that were not possible to evaluate separately.
Our literature review also has strengths. First, it is the first meta-analysis of randomised controlled trials (7/8) that focuses specifically on the effectiveness of KT. In all studies, except in Sarvestan et al. [55], participants were randomised, which guarantees a more accurate methodology. The eight studies included reported a high level of quality and scientific evidence: an average score of 19.25/28, according to the Downs and Black Scale, and a level of evidence between I and II (three studies I; four level II). Second, the studies included in this review were published recently and very close to each other (from 2017 to 2020), including different sports population groups to guide clinical judgements. Hence, our meta-analysis represents a synthesis of the most current knowledge on this subject in the literature since the seventies. Third, even though this study included ankle function and athletes' functional performance testing as outcomes to provide more evidence for clinical practice, it was designed with a different approach with respect to previous meta-analyses that reported non-significant results for the effectiveness of KT.
Finally, since the sports performances and ankle functions analysed among the included studies were heterogeneous, several independent meta-analyses were carried out, stratifying the outcomes according to subgroups to avoid comparing outcomes considering different parameters. There may be disparate ankle functions and performances that require very specific skills and ad hoc evaluation tests, especially when comparing different sports and related parameters. Through the meta-analysis of each outcome, it was possible to evaluate the efficacy of KT for every single item, avoiding overall conclusions that did not give significance to single parameters for which KT was effective, without omitting any of them. This should be considered as a strength of our study since it ensures the quality, consistency and generalisability of our findings. Furthermore, seven out of eight studies had a sample size of fewer than 35 athletes, which would have increased the risk of bias in a large-scale comparative analysis with heterogeneous data.
Certainly, future studies maintaining the same level of quality of those included in this review but increasing the number of participants and standardized outcome measurements are required to better clarify the role of KT in CAI. In addition, further investigation is necessary to define the influence of psychological aspects on the athletes' performances during KT application [9][10][11]71]. It is possible that individuals with CAI perceive their ankle to be more stable and have more confidence in their ankle and their ability to perform challenging tasks because of factors such as increased mechanical stability or a placebo effect of the tape [91][92][93]. Although not sufficient, there is considerable evidence in the current literature for the psychological effects of taping.

Conclusions
The present systematic review and meta-analysis shows that KT, used on athletes with CAI (playing football, basketball, volleyball, baseball and badminton), is effective only on some of the performances and ankle functions analysed. It was not possible to define the precise time of the application of KT to the ankle joint of the athletes included to see the benefit in performing sports. However, the meta-analysis showed a significant improvement particularly on the following: gait functions (step velocity, step and stride length and reduction in the base of support in dynamics); reduction in the joint ROM in inversion-eversion; decrease in the muscle activation of the long peroneus; decrease in the postural sway in movement in the mid-lateral direction.
In contrast, other aspects such as dynamic balance, lateral landing from a monopodalic jump and agility tests did not improve significantly by applying KT to the ankle joint.
Finally, as the improvement achieved by some of the parameters analysed reflects an increased stabilisation of the ankle joint of these athletes during sports performance, it is possible to conclude that KT has a moderate stabilising effect on the ankles of the athletes of the most popular contact sports with CAI.