Effect of the kinesio taping application method for the activation and strength of gastrocnemius muscles in healthy adults

The objective of this study was to verify the effect of kinesio-taping (KT) application of the origin for muscle insertion (O>I) and insertion for muscle origin (I>O) in healthy participants, through surface electromyography and peak torque of gastrocnemius muscles. A total of 69 participants with an average age of 22.9±5.2 years were evaluated, 41 women with an average age of 22.0±5.1 years, BMI 25.1±4.6 kg/m2, and 28 men with an average age of 22.0±5.1 years, BMI 23.1±3.3 kg/m2, randomized under three conditions: O>I, I>O and no KT (control), repeated three times with five-minute rest between sessions. The peak torque of the gastrocnemius lateral (GML) and medial (GMM) muscles was evaluated at speeds 30o/s 60o/s 120o/s and muscle activity through surface electromyography. Repeated-measurement ANOVA showed effect only on the variable speed (F=767,1; p<0.001) and the variables condition (F=0.010; p=0.990) and interaction (F=0.199; p=0.892) were not significant. In electromyography, Root mean Square (RMS) did not differ in the conditions evaluated, presenting standard behavior without significant differences. The KT application regardless of being O>I or I>O muscular, did not alter the muscle recruitment or contribute to the increase in peak torque performance during the three speeds.


Introduction
The therapeutic elastic bandage technique (BET) consists of an intervention where, a type of elastic and adhesive tape known as Kinesio Taping® (KT) is applied to the skin providing a tension force that is produced by its stretch (Choi & Lee, 2018).With the KT application some results such as: 1-Neuromuscular optimization and coordination, 2-Alignment and reduction of joint instability, 3-Increase of muscle activation and strength, 4-Favor of static and dynamic functionality, are expected (Chang, et al., 2010;Fratocchi, et al., 2013;Simon, et al., 2014;Wong, et al., 2012). However, there is still a lack of consensus on what is expected and observed in this technique.
The KT has been used in the search for improved performance (Huang, et al., 2011), injuries prevention (Chen, et al., 2013), rehabilitation (Rojhani-Shirazi, et al., 2015) and pain relief (Song, et al., 2015). Two theories are used to justify its benefits (Cai, et al., 2016): the first explains the skin 'lifting effect' that is pointed out as a mechanism capable of increasing the blood and lymphatic fluids circulation , the second says that KT is capable of pressing and lengthening the skin surface and thus stimulating cutaneous mechanoreceptors that in turn increase the somatosensory stimuli (Yeung & Yeung, 2016) and, therefore, it is capable of facilitating the muscle contraction and increase strength (Choi & Lee, 2018;Ridding, et al., 2000).
However, its effects remain conflicting in the literature in order to clarify its real benefits. The directions that KT can be applied (origin-insertion or insertion-origin) generate controversy in the literature, some authors report an increase in strength, torque and muscle activation regardless of the direction that KT was applied (Choi & Lee, 2018;Serrão, et al., 2016;Vercelli, et al., 2012). The KT technique efficiency on muscle strength development and activation should be determined by tests that are capable of providing objective measures that are reliable and reproducible. In this case, isokinetic dynamometer and electromyography are effective tests that can evaluate muscle torque and activation respectively.
The objective of this study was to verify the effect of two forms of kinesio-taping application (from muscle origin, to muscle insertion and from muscle insertion, to muscle origin) in healthy participants, on muscle activation, and peak torque of gastrocnemius muscles. It is believed that many controversial results observed in the literature are caused by the diversity of techniques and management during the BET application (origin-insertion or insertion-origin), in addition to the investigation of healthy muscles, necessary to better understand the KT action mechanisms, without suffering changes caused by other mechanisms that may happen in individuals with pathologies. Thus, being able to verify whether the practice of applying BET Research, Society andDevelopment, v. 11, n. 1, e11311124198, 2022 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v11i1.24198 3 is efficient in improving performance in healthy people, as has been observed in the practice of sports and leisure. As a hypothesis of the study, it is believed that the BET (through KT) can contribute with the performance, but the way in which it is applied (from origin to insertion or from insertion to origin) does not interfere with neuromuscular activation and peak torque.

Study Place
The study was carried out in accordance with Resolution 466/12 of the National Health Council and was initiated after

Sample size calculation
The sample size was calculated using the mean values of torque peak strength in the plantar flexion of O>I application condition (84.1 Nm and DP=44.2 N.m) and the I>O condition (mean 67.9 Nm and DP=26.2 N.m) previously collected in a pilot study of a sample containing 8 participants. Considering an alpha of 0.05, a power (1-beta) of 0.80 and an effect size of 0.42, the sample size was estimated at 68 participants, by the GPower program (Faul, et al., 2007).

Participants
For the sample selection, the inclusion criteria adopted were: age group between 18 and 35 years; individuals without lower limb injury (MMII), without gait dysfunction, and who presented a readiness for physical activity verified by the PAR-Q questionnaire. Therefore, in order to promote the sample homogeneity, volunteers presenting degenerative muscle diseases; use of analgesics, anti-inflammatory or muscle relaxants in the last week and history of trauma in the lower limbs were excluded from the study.
Everyone consented to be part of the study and signed the Written Informed Consent Form (FCLE).

Study design
All participants carried out evaluations under all the proposed conditions. The order of application of the conditions was randomized for each individual, through opaque and sealed envelopes that were listed and drawn by a blind evaluator. The Conditions were tested with rest intervals of 5 min.

Procedures
The peak torque of the medial and lateral gastrocnemius muscles of the participants was evaluated using the isokinetic dynamometer, the participants were submitted to three types of evaluation: A -KT application in the direction from muscle insertion to muscle origin, B -KT application in the direction from muscle origin to muscle insertion and C -Control, without KT application. Each evaluation was repeated three times with five-minute rest between sessions. The KT used in the study was TMAX® brand, which was always applied by the same professional qualified for the method application.

KT Application
For the KT application, all the participants were asked to remain in a stretcher in the prone position, with the ankle in neutral position (90º). The KT application was performed using two application models: A -insertion-origin (I>O) and Borigin-insertion (O>I). In the first model (I>O), the tape was laid from the calcaneus tuberosity by means of the tendon calcaneus to lateral and medial epicondyle of the femur. In the second model (O>I) the tape was applied from the popliteal fossa to the calcaneus tuberosity by means of the calcaneus tendon, both models were applied by the Y technique, without the KT tension (Figure 1), the KT application was always performed on the right lower limb, according to the study by Bastos (2014), that found no significant difference when KT is applied to the dominant or non-dominant lower limb. The KT application was always performed by the same skilled professional and 8 years of experience with the technique. Source: Authors.

Muscle Torque Evaluation (isokinetic)
The isokinetic dynamometer brand Biodex System 4® was used to evaluate the immediate effect of isokinetic muscle strength. The equipment provides constant speed and resistance while articulating within a predetermined range, so it can draw a curve that displays muscle torque throughout the test. The torque peak is identified by the highest point of the curve.
Additionally, previous studies attest to the high reliability of the isokinetic dynamometer test and retest (intraclass correlation coefficient, 0.82-0.95) (Feiring, et al., 1990;Sole, et al., 2007). Before starting the tests, the subjects underwent low-intensity warm-up on the stationary bicycle for five minutes (Simão, et al., 2004). The medial and lateral gastrocnemius muscles torque was evaluated in angulations of 30°/s, 60°/s and 120°/s for each of the applied KT interventions (O>I -KT application in the direction origin-insertion, I>O -KT application in the direction from insertion to origin and without KT).
The speeds stipulated for the evaluations in the isokinetic are suggested and described in the Biodex® manual for the plantar flexion and dorsi flexion evaluations, establishing concrete relation with the objective of this study of torque strength A B C Research, Society and Development, v. 11, n. 1, e11311124198, 2022 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v11i1.24198 5 evaluation and was this study is evaluating the gastrocnemius muscle which in turn is a dynamic muscle, working separately, gastrocnemius has a short predominance in the amount of type II fibers, with glycolytic characteristics, that is, they play a greater role of strength than resistance, having thus the capability to develop a greater tension in a short period of time. As a function of its characteristics, the gastrocnemius muscle has been widely investigated because it has ease of application, allow high control of variables, besides showing good metabolic responses (Moret, et al., 2013).
The individuals were positioned sitting on the dynamometer chair brand Biodex® with their back tilted back, the trunk and thighs were fastened by belts and the ankle was fixed in the torque meter. Regarding the dynamometer positioning, the following was adopted: guidance = 90 °, tilt = 0 ° (axis direction), seat orientation: 90 °, trunk tilt with the seat back: 70 °, knee flexion: 30 °, and ankle in neutral position, the axis passing through the body of the talus, fibular malleolus and through or just below the tibial malleolus. Participants in the study were verbally stimulated during the tests to encourage them to use their maximum muscle strength. Muscle torque was measured at angular velocities of 30°/s, 60°/s and 120°/s during the five plantar flexion and dorsiflexion movements. Individuals rested for five minutes after the measurements for a given angular velocity were completed. This rest period was adopted based on the time of adenosine triphosphate (ATP) resynthesis, and the five minutes were considered adequate for the complete recovery of ATP stocks (Baker, et al., 1993). Source: Authors.

Surface electromyography (EMG)
To identify the muscle activity during the 9 evaluations performed with the tests on the Biodex® isokinetic dynamometer, surface electromyography was used (miotool 200/400 of myotec®). Electromyographic signals were collected at a frequency of 2000 Hz. The active bipolar electrodes standard distance of (10mm) were positioned on the belly of the gastrocnemius muscle in the medial and lateral portions, following the muscle fibers direction. Trichotomy and site cleaning were performed with alcohol (70%) to decrease skin impedance. In addition, in order to verify the signal quality of the electrode positioned, the individual was requested to perform the ankle plantar flexion movement. For the maximum pressure in this position, it is necessary to apply the pressure against the forefoot as well as against the calcaneus. The use of electrodes followed the guidelines of the Surface Electromyography for the Non-Invasive Assessment of Muscles (SENIAM). Research, Society andDevelopment, v. 11, n. 1, e11311124198, 2022 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v11i1.24198 6 Electromyographic signals were initially softened with a low pass filter and high pass with a cut-off frequency from 20 to 450 Hz. The signals were normalized by the electromyographic activity peak during the task itself, considering the average of the highest RMS values of each series obtained during the test. After the first and last contraction was withdrawn, an activation percentage average of the 5 intermediate repetitions was performed. For the analyzes, each of the RMS values obtained during the five plantar flexion and dorsiflexion movements and their mean were considered. Thus, activation percentage values were obtained for medial and lateral gastrocnemius muscles during plantar flexion and plantar dorsiflexion movement at different speeds.

Data Analysis
For the statistical analysis, Shapiro Wilk test was initially used to verify the data distribution. Mean and standard deviation were used to describe the numerical data that presented normal distribution, whereas absolute and relative frequency were used to describe categorical data. Comparisons between experimental conditions (O>I origininsertion, I>O insertionorigin and control -without KT) and speeds tested at isokinetic 30º/s, 60º/s, 120º/s, were performed by the ANOVA repeated measures test. To determine the effect of the three conditions studied on muscular electrical activations, considering the differences between genders, mixed ANOVA test was used for repeated measures.
Additionally, 5 activations were selected regarding 5 plantar flexions performed during the isokinetic dynamometer evaluation, and comparisons throughout the activations and between the experimental conditions and the same were analyzed again by mixed ANOVA for repeated measures, with Greenhouse-Geisser correction when necessary. For all analyzes, the significance of p<0.05 was adopted and the statistical program used was SPSS 21.0. Table 1 shows the general characteristic of the sample investigated, from which it is observed that the majority of the 69 volunteers were composed by female participants. There were no differences between age and BMI between genders, but differences between weight and height were found (Table 1). In the isokinetic test evaluation, presented in Table 2, no differences were observed among the experimental conditions (O>I, I>O and control) at the peak torque at the speeds investigated.

Results
The repeated-measured ANOVA analysis showed an effect only on the speed variable (F=767.1; P=<0.001), whereas the condition variable (F=0.010; P=0.990) and interaction (F=0.199; P=0.892) were not significant. The evaluation of muscular electrical activity of GML and GMM muscles during the isokinetic dynamometer test at the three speeds were presented in Table 3. It was observed that the data maintained the same patterns regardless of sex; therefore, the sexes were grouped in table 3 and presented together. There was a significant difference between the conditions only for the medial gastrocnemius muscle evaluated with RMS 120º/s (p=0.047). However, comparisons by pairs showed that there is no significant difference between control vs O>I (p=0.912), control vs I>O (p=0.054) and I>O vs O>I (p=0.427), that is, it was possible to observe that RMS does not differ among the experimental conditions in the muscles investigated. Note: O>I: KT applied in the direction from muscle origin to muscle insertion; I>O: KT applied in the direction from muscle insertion to muscle origin; Control: No KT application. Source: Authors.
In Figure 3, a similar behavior is observed between the tests. Thus, regardless of the tested speed or investigated musculature (medial or lateral gastrocnemius), no differences were observed among the experimental conditions (O>I, I>O and control) and in the interaction among the experimental conditions and the moments (repetitions). Significant differences were found only among the test moments (1,2,3,4,5). Additionally, the effect sizes of the conditions studied varied between 0.002 to 0.058. Research, Society and Development, v. 11, n. 1, e11311124198, 2022 (CC BY 4

Discussion
The objective of the present study was to evaluate the KT effect on peak torque torque strength and neuromuscular activation on medial and lateral gastrocnemius muscles in healthy individuals. And as the main results, our data do not show significant difference, therefore denoting, that application (O>I and I>O) did not show alterations in muscle activity and peak torque in the population and musculature investigated, However, a tendency of variation in the medial gastrocnemius muscle was observed evaluated with RMS 120 º/s in the KT applications.
In addition to these findings, studies evaluating other muscle groups are found in the literature, both investigating the acute effect of KT application, Choi and Lee, (2018) verified that when applied KT to the rectus femoris, vastus medialis and vastus lateralis of quadriceps muscle, there was an increase in muscle torque, regardless of the tape application direction.
Where as Lemos, et al. (2018) in healthy individuals, without any type of dysfunction or injury, does not influence the femoral rectum strength and knee ROM.
The applications directions in facilitation or inhibition, as well as the different amounts of tensions evaluated in this study, did not generate any change in the torque measurements investigated. This pattern remains in different populations studied and different muscle groups (Choi & Lee, 2018;Lemos, et al., 2018).
So far, no studies have been found that investigated muscle strength and activation in lateral and medial gastrocnemius investigating the outcome of the KT use, due to the fact that this muscle exhibits glycolytic characteristics, and predominance of type II fibers, thus developing the capacity to develop great tension in a short period of time (Moret, et al., 2013).
These findings refute the theories of Kase, et al. (2013) about the KT ability to increase the number of motor units during muscle contraction and to produce a greater muscle strength. Additionally, the differences highlighted by the same authors in the form of application (origin>muscular insertion or insertion>muscular origin) and its effects of activation and/or relaxation were also not observed in the analyzes performed.
On the other hand, some studies in the literature have pointed to the KT effects on some variables investigated being dependent on the form of application (Fukui, et al., 2017;Hosseini, et al., 2019). When evaluating these contradictory results, it is possible to note that it may be associated with the muscle group investigated, since these authors evaluated different regions than those adopted in the present study. Fukui, et al., (2017) evaluating the gluteus maximum, demonstrated that the way in which the KT is applied interferes with the muscle strength capacity performed, and when applied from I>O there is an improvement in muscle strength.
There are also controversies in the literature regarding the KT use in upper limbs. Fratocchi, et al. (2013) andKennan, et al., (2017) evaluated peak torque with isokinetic dynamometer in MMSS, the first identified an increase in peak strength of those who used KT, whereas the second did not obtain results indicating an increase in the participants' strength.
One important factor to consider is the tension in tape application, a study carried out on tape property and the tension effect showed that the tension only causes a statistically significant effect when the voltage in the load cell is above 75% stretch, however, this study was carried out by evaluating the tape properties and not the tape application on the human skin, nor by investigating outcomes in humans (Morini Junior, et al., 2020), however no studies have been found that investigated the different tensions and the possible effects of this variable on humans, since there is a very large divergence of materials, therefore, it was opted for not exerting tension in the KT application in the present study..
Another factor relevant to the interpretation of the KT effects is the previous time of the KT application, Soares, et al., (2018) in their study, evaluated the vastus medialis oblique, the vastus lateralis oblique and the vastus lateralis longus muscles.
To perform the isokinetic strength test, a dynamometer was used 60°/s before and 24 hours after the KT application. After the tests, the authors reached the conclusion that the time of 24 hours was not enough to improve peak torque, maximum repetition, fatigue, antagonist/agonist ratio, deceleration time and time to reach torque.
However, Soares, et al., (2018) had already tested several periods after the KT application: 1-before application, 2right after application, 3-after 24 hours, 4-after 48 hours and 5-after 72 hours. Similarly, the technique was not capable of improving isokinetic strength and electromyographic activity of the vastus lateralis muscle (same muscle evaluated by Soares, et al., (2018). Therefore, the authors suggested that KT does not promote immediate and late changes over any of the variables analyzed (Lins, et al., 2016).
In the study by Limmer, et al., (2020) when the acute KT effect was evaluated in climbing athletes, no significant differences were observed in the parameters of peak grip strength, fatigue index, finger waiting time, distance and rise time, or maximum blood lactate values after climbing. The participants' climbing ability with KT did not show any difference in the strength and resistance of the fingers flexor muscles, nor did the performance parameters of the sports climbing such as distance, time and maximum blood lactate values after the ascent.
Another very important issue is the understanding of KT and its mechanism in cases where it changes strength. Some authors hypothesized that KT indirectly could be interfering with neuromuscular activation, but the present study corroborates with Mak, et al., (2019), in which electromyographic activity does not change with KT, even presenting changes in maximum grip strength (wrist flexor muscles). There seems to be a "facilitator" effect of using KT related to some indirect work mechanism capable of inducing force increase in some muscle groups.
And since the KT use does not cause changes in neuromuscular activation, it is refuted that the theories that the placement of the KT application with the objective of inhibiting (insertion-origin) or facilitating (origin-insertion) muscle function does not seem to alter the magnitude of electromyographic activity of the vastus lateralis, vastus medialis and femoral biceps muscles during squat exercise. Additionally, the perceived effort was also not affected regardless of the direction that KT was applied (Serrão, et al., 2016).
Based on the findings of Dos Santos Glória, et al., (2017), that used the evaluations with EMG and isokinetic dynamometer as well as in this research, did not find any significant difference for the activation of the femoral straight muscle and also has no effect on the muscle torque peak, in activity or jumping performance among soccer players.
Despite the evidence observed herein that the KT use does not cause changes in strength and activation, it is essential to consider the population investigated, that are healthy individuals. Some reviews indicate when it comes to individuals who present muscular fatigue or chronic musculoskeletal diseases, the use of KT promotes greater effects compared to other types of treatment (bandages, bands, adhesive plasters and adhesives) for the increase of the lower limbs strength (Mostafavifar, et al., 2013;Mine, et al., 2018;Yam, et al., 2019).
Previously, Williams, et al., (2012) had already developed a systematic review seeking to answer the same questions reported above, analyzing the KT effects on healthy and injured people. Similar to later published studies, the author concluded that KT could have a "small" positive effect on the strength of an injured area, but additional studies would still be necessary to confirm the hypothesis.
Finally, as a practical application, we do not recommend the use of KT for healthy individuals when the goal is activation or relaxation, or improved strength in gastrocnemius.

Final Considerations
The KT tape application on the lateral and medial gastrocnemius muscles regardless of the use or direction of the application (origin > insertion or insertion > origin) did not alter the isokinetic strength or the activation of muscle fibers in healthy adults.
Therefore, it is suggested that in future studies, the tension of KT application is controlled more precisely in a clinical trial with a longer intervention time (in order to verify the chronic effect of the application of the tape), this may come to produce different results.