A study of reproducibility of kinesiology tape applications: review, reliability and validity

Recent years have seen significant developments in bandaging techniques, above all with the appearance of kinesiology tape (KT). These tapes have a plain weave structure and, thanks to their elastane content, allow for longitudinal stretch.

Some authors credit KTs with effects such as the improvement of somatosensory stimulation and an increase in mechanoreceptive and proprioceptive impulses which cause various responses such as the facilitation or inhibition of muscle activation [1‐3]. However, there is insufficient clinical evidence to support these claims [4, 5].

The application of KT has become a popular treatment among athletes, although its real effects are still being investigated [6].

Nevertheless, various authors encourage the use of KT for all athletes as a way to prevent and treat musculoskeletal injuries [7‐10] or control static and dynamic posture [9, 11].

There is no clear consensus regarding the key aspects of KT application methodology, such as the percentage elongation to be used [5]. Notwithstanding Lim’s [5] results regarding percentage elongation, their review suggests that the effect size for pain reduction was lower when the studies applied more tension and left the tape in situ longer.

Consequently, KT applications cannot be reliably reproduced. According to the analysis in published systematic reviews [12‐16], studies into KT present either low or very low methodological quality when assessed using the Grading of Recommendations Assessment, Development and Evaluation system (GRADE) adopted by the Cochrane Collaboration; as a result, there is currently no clinically significant evidence to support the use of KT as a therapeutic tool [17]. GRADE methodology is not a definitive fixed guide but rather provides suggestions regarding how to approach the literature, developing an optimal system of rating quality of evidence and strength of recommendations for clinical practice guidelines [18].

Even though extensive effort has been invested in evaluating the efficacy of KT, there is still a dearth of attempts to collate the findings from individual studies to determine the effects of KT application on pain and disability and, if these effects are found, their magnitude [5].

It is necessary to define standardized methodological criteria so to that effects of KT can be demonstrated. [19, 20].

Specific research studies, such as that by Pamuk and Yucesoy [21] deem the application of KT to be effective. Magnetic resonance (MR) imaging has been used to provide a reliable representation of tissue deformation, including changes in the length of muscle fibers and the direction of this change after the application of KT. The lack of homogeneity in the deformation of muscle fibers produced by KT strain indicates the occurrence of epimuscular myofascial force transmission. Accordingly, changing the level of tension the KT applies to the skin can transmit different levels of force directly to muscle tissues, either to stimulate or inhibit. Pamuk and Yucesoy [21] produced a detailed evaluation of the local tissue deformation occurring acutely under the mechanical load imposed by the application of KT. Their results show local tissue deformations produced by the effects of KT application, confirming that KT also affects non-targeted tissues and sustaining the role of a neuro-mechanical coupling in the entire limb.

Although these studies show that kinesiology tape is effective, the specific action mechanisms of KTs and their real physiological effects remain unknown [19‐21].

As a result, defining the methodological characteristics of the application of kinesiology tape is deemed to be a priority.

As they do not use an agreed methodology, positive results in previous KT studies may be attributed to placebo effects, too [19].

Two studies have been published regarding the mechanical properties of KT [22, 23]. The first, by Fernández Rodríguez et al. [22], included 11 tapes from 4 brands which were analyzed and compared in terms of maximum percentage stretch, maximum force applied before rupture, thickness, density and grammage. The authors postulate that there are differences between the mechanical properties of the various brands and colors of KT but do so without completing a statistical analysis of their results.

The second study, by Matheus et al. [23], found significant differences between 50 specimens of KT (10 samples from 5 different brands or manufacturers), testing the maximum strain, maximum deformation, maximum load, and rigidity using an EMIC universal testing machine (model DL 10.000). They also found significant differences in adherence force when removing KT specimens from a metal plate.

There are no studies into the characteristics of KT, its mechanical properties, maximum adherence force and work done when removing it from skin in dry, wet, or sweaty state (the state of the skin will affect the tape’s adherence) which follow ISO international standard test methods for bandage stretching [24]. Following standard test methodology is necessary to enable KT applications to be reproduced.

The reproducibility of the effect of KTs is crucial in clinical settings. It is possible that the effect the application produces on the tissues may differ depending on the mechanical properties of each tape. Perhaps the absence of any effect from the application of KT reported in previous studies is related to the characteristics of the different KTs and the application time.

Consequently, to repeatedly obtain a certain level of strain there would have to be no variation in the properties of the tape. The reproducibility of the effects of KT has not been studied with sufficient rigor until now.

Our objective was to determine if KTs have different characteristics and mechanical properties in terms of rupture and adherence in dry state, wet state and after being submerged in artificial acid sweat solution. The tapes studied were grouped by color and brand to standardize the KT applications. This analysis will facilitate the reproducibility and standardization of KT application strain through knowledge of the different elongation percentages of each KT, thereby facilitating methodologically correct tape applications to achieve reproducible effects and so determine the limitations of KT.

The objective of this study was to define the characteristics, and mechanical rupture and adherence properties of a wide variety of KT specimens. In this way, we attempt to respond to the need to define standardized and reproducible application criteria so that the effects of KTs can be specified.

In the previous studies we analyzed, the values described for the maximum elongation, expressed as a percentage of the specimen’s initial elongation, ranged from 20 to 40% [20, 29‐31] or 55–60% [32] to 120–140% [1, 33‐37], 140–150% [38] and 250 to 400% [23]. None of the 380 specimens tested reached an elongation of 100% of their initial length (600 mm) before rupture.

The two previous studies [22, 23] found differences between their specimens, and [23] found significant differences between the KT brands tested. This study revealed considerable variation between the different brands and colors of KT in terms of maximum force, tenacity, work, pre-elongation and percentage elongation y grammage (Table 1). Following the standard testing methodology, the grammage of each specimen must be taken and a pre-load must be carried out before each test. The previous study which used a dynamometer [23] does not mention this information and consequently the method used to extract the data remains unknown. This makes it impossible to reproduce the research and could lead to the generation of further conflicting results.

Untanned sheepskin was used to ensure that the adherence test was as reliable as possible and its results were applicable to clinical practice. The maximum adherence force and work done when removing the tape from the skin in dry state was very high, lower when the skin had been submerged in an aqueous solution, and even lower when it had been submerged in an artificial acidic sweat solution (Tables 2 and 3). Study [23] obtained far lower values using a metal plate.

Taking the maximum elongation of 4 KT specimens (Fig. 3) as a reference, they can be seen to be at different deformation points. Tape 4 will generate lower levels of strain because 30% elongation is within the material’s elastic deformation range and its flexibility means it will stretch considerably without limiting body movements. At its maximum elongation (point of rupture) the tape has lower energy absorption potential as it is in the plastic-elastic region of the stress-strain curve, tenacity is lower and, consequently, the work or total area under the curve is very large (Fig. 3). This reasoning can be considered fundamental and demonstrates that the tension produced by different tapes does vary.

We concur with Pamuk and Yucesoy [21] that the application of KT produces effects and that different applications cause different effects, but in order to specify said effects the same mechanical response must be achieved using an optimum, specific and reproducible level of tension. Achieving said mechanical response may require different elongations in different KTs. To this end the characteristics and properties of the KT used must be specified in addition to its maximum adherence force. It is also necessary to know the elongation reference used, the work done when removing the tape from the skin, the skin conditions, and the elongation of the skin to be bandaged to produce the same tension in each patient to produce the same effect (P < .05) without exceeding the elastic elongation of the KT both at the point of application and once the movement to be trialed has been completed.

This would facilitate the objective discovery of the different action mechanisms of KTs which could affect clinical results, as González-Iglesias et al. [39] believe.

In their literature review Morris et al. [14] only included KT studies which used the Kinesio® Tex brand. This exclusivity was to improve the accuracy of their conclusions, as they believed other brands of KT used in clinical practice were different.

It remains to be shown whether the variability in the tension and adherence of KTs changes the effect they produce during their application even when the same application metholodolgy is used for different tapes.

Our results suggest that the basic concepts of KT application are not yet complete and that studies which tried to determine the effects of KT are not reproducible. This may explain the disparity in the results obtained by different studies investigating the effects of KT. According to Lim’s review [5], there are studies that did not report the amount of stress applied while others did not report the length of each tape used in situ.

This study is limited by testing using a uniform strain and a constant velocity. Moreover, there may be a certain degree of variability between the KTs and the different brands due to them coming from different production lots.

The KT specimens studied had the same structure but different chemical compositions, characteristics and mechanical properties.

The different KTs presented different behaviors with regard to rupture and removal when applied to skin in dry state, wet state and after being submerged in artificial acidic sweat solution.

If the elongation limits of each KT are unknown, many of them will produce different levels of strain even though the same elongation is used.

The absence of these data limits the reproducibility and the reliability of clinical studies using KT. Clinical studies should specify the reference used (tape length or tape elongation) to define the percentage elongation employed, something which has not been specified in studies to date.

In order for future clinical studies to be standardized and reproducible, the physiotherapist must achieve the same effect with each KT application, taking into account the reaction of its mechanical rupture and adherence properties, as well as the stretching of the skin to be bandaged.

Depending on the characteristics (body dimensions) and properties (skin elongation) of each subject in the sample, bandages with different elongations must be applied to achieve the same strain in all of them and therefore produce the same effect.

Adapting the analysis offered by MRI, the dynamometer and other devices for the study of KT would facilitate the definition of protocols to carry out highly-important studies to promote understanding of the specific mechanisms of action of KTs, their real physiological effects and the possible clinical and sporting outcomes of their use.