Abstract
Kinesiology tape (KNT) is commonly used for injury prevention and as part of rehabilitation to treat muscle and joint pain. KNT is purported to increase local blood flow by lifting the skin and reducing local pressure. Whether or not skin blood flow is increased by KNT is not presently known. We carried out 2 experiments to elucidate the effects of KNT on skin blood flow. Protocol 1: KNT was applied to the skin at 0%, 25%, 50%, and 100% relative tension. Red cell flux, an index of skin blood flow, was measured by laser Doppler flowmetry (LDF) at each site and at a no-tape control site. There was an overall effect of tape on cutaneous vascular conductance (CVC: LDF/MAP) (KNT: 0.12 (95% confidence interval: 0.10, 0.14), control 0.08 (0.07, 0.10) flux•mmHg−1; p<0.01), but no effect of tension (all p>0.05). Subjects kept KNT on for 3 days then returned for follow-up testing. CVC was not changed after 3 days of KNT application (p=0.07). Protocol 2: KNT was applied to the skin with and without convolutions. There was an overall effect of tape on CVC (KNT: 0.30 (0.21, 0.39), control 0.15 (0.09, 0.21) flux•mmHg−1; p=0.03), but no difference between KNT applied with or without convolutions (all p>0.05). These data suggest that KNT modestly increases microvascular blood flow, regardless of tension or presence of convolutions.
Keywords: skin blood flow, kinesiology tape, kinesiotape
PURPOSE
In recent years, kinesiology taping has emerged as a common therapy to treat musculoskeletal injuries1. Application of kinesiology tape (KNT) is purported to have numerous beneficial effects including: neuromuscular re-education, reduction of inflammation, delayed muscle fatigue, and injury prevention2. KNT is also purported to improve blood and lymphatic circulation by lifting the skin, reducing pressure and increasing interstitial space, thus facilitating improved flow2. When applied with this intention, it is usually the practitioner’s goal to reduce swelling or edema. Therefore, validating whether or not KNT increases blood flow is important for determining its therapeutic efficacy.
Few studies have examined the effects of KNT on blood flow and lymphatic drainage. A randomized control trial by Tsai and colleagues compared KNT plus decongestive lymphatic treatment to standard compression plus decongestive lymphatic treatment in the care of breast-cancer-related lymphedema. No difference was found in measures of lymphedema between KNT and standard compression, indicating that KNT was no more or less effective in eliciting lymphatic drainage3. Woodward and colleagues found that KNT did not alter skin blood flow on the forearm of young soccer players, however the authors only evaluated KNT applied with one technique (10% stretch)4. Miller and colleagues examined the effects of KNT compared to standard athletic tape on skin blood flow pre- and post-upper body exercise and found that there was no difference between the tape treatments and that changes in skin blood flow were likely exercise-mediated5. While these studies suggest that KNT may not alter lymph or blood flow, the effect of KNT application on skin blood flow requires further elucidation.
Numerous techniques for KNT application are also purported to alter KNT function. Specifically, tape tension and the presence or absence of convolutions, are thought to be vital to the efficacy of KNT. Convolutions are created when KNT is applied over a stretched muscle and the muscle is returned to resting position. A few studies have investigated the importance of KNT applied with convolutions. Parreira and colleagues found that convolutions in KNT neither improved nor impaired the analgesic effect of KNT on low back pain6, while Vercilli and colleagues found that KNT-induced changes in hematoma color were not affected by convolutions7. Similarly, the few studies examining the clinical importance of KNT tension are limited in scope and examination of underlying mechanism. Bravi and colleagues found that KNT improved sensorimotor coordination regardless of application tension, noting that there was no difference in performance when KNT was applied at either 25% or 50% relative tension8. In a systematic review, Lim & Tay found that the effect size for KNT-mediated pain reduction was reduced when KNT was applied at higher tensions9. The importance of KNT tension or convolutions in facilitating skin blood flow has yet to be determined.
It is unknown if KNT increases blood flow and if certain application techniques are required to elicit changes in blood flow. The purpose of these studies were to (1) determine the effect of KNT on skin blood flow, and (2) to determine how convolutions, tension, and time alter the effects of KNT of skin blood flow. We hypothesized that KNT would increase skin blood flow, with the effects most apparent when applied at 25% relative tension and with convolutions, and that the effects of KNT would persist 3 days post-application.
METHODS
This study was approved by the institutional review board at The Pennsylvania State University and complied with the declaration of Helsinki. Subjects provided written and verbal informed consent prior to participation in the study. Subjects were young, healthy adults, non-smokers, and free of chronic disease. Women were not pregnant or breastfeeding. All protocols took place in a thermoneutral room with subjects in a semi-supine position. Subjects refrained from strenuous exercise and from consuming caffeine or alcohol for 12 hours before the study. In all protocols, blood pressure was measured via brachial auscultation in five-minute increments throughout the protocol (Cardiocap/5, General Electric, Fairfield, CT). TheraBand® Kinesiology Tape (Performance Health, Akron OH) was used for all protocols.
Protocol 1. Tape Tension
The goal of this protocol was to determine the effects of relative KNT tension on skin blood flow. Four strips of KNT were prepared for each study. KNT was cut into 16 cm lengths and rounded at the corners to promote adhesion, and a small (0.5 cm diameter) hole was cut in the middle of the tape to measure skin blood flow. The four strips of KNT were applied to the skin above the rectus femoris on both legs (2 strips per leg, knee in a fully extended position) separated by approximately 3 cm. Kinesiology tape was randomly applied at 0%, 25%, 50%, and 100% relative tension (0% equals resting length, 100% equals length of maximum stretch) using the stretch indicators on the tape. To apply the tape, the researcher held the most proximal and distal cm of tape to keep it free of tension. The proximal end of the tape was anchored on the skin without tension. The tape was then stretched to the appropriate tension and applied to the skin, and the distal end was anchored to the skin without tension. The researcher then rubbed the tape to improve adhesion. Relative tension was verified by measuring tape length post-application.
Local heating units were placed in the hole in the middle of each strip of KNT. A local heating unit was also placed on the skin in a tape-free area of the leg to serve as control. Laser Doppler flowmeter probes (Moor Instruments, Axminster, UK) were placed into each local heater to measure red cell flux, a relative measure of skin blood flow. Local heaters were left off so that local skin temperature could fluctuate. After stable measures of red cell flux were obtained (approximately 20 min), local heaters were set to 33°C to control local skin temperature. Red cell flux was measured until a new stable baseline was obtained (approximately 20 min).
Local heaters and laser Doppler flowmeters were then removed. Subjects kept the KNT on and went about their normal activities for three days. After three days, subjects returned to the lab and underwent the identical protocol to determine the time-dependent effects of KNT on skin blood flow.
Protocol 2. Convolutions
The goal of this protocol was to determine if convolutions in KNT alter skin blood flow. Two 16 cm strips of KNT were prepared as described in protocol 1. One strip of KNT was stretched to 25% relative tension and applied over the rectus femoris with the leg in a fully extended position. The second strip of KNT was stretched to 25% relative tension and applied over the rectus femoris of the opposite leg with the knee joint flexed to 90°. After KNT application, the knee was fully extended to cause convolutions in the KNT. A local heater was placed in the hole in the middle of each strip of KNT, and on a tape-free area of skin to serve as control; local heaters were set to 33°C. Laser Doppler flowmeters were placed in each local heater to measure red cell flux. Red cell flux was measured for approximately 20 minutes.
Data analysis
Data were collected at 40 Hz with a Windaq data acquisition system (DataQ Instruments, Akron, OH) and stored offline for later analysis. Red cell flux was normalized to cutaneous vascular conductance (CVC: flux•mean arterial pressure−1). Data were analyzed with Prism 7.01 software (GraphPad Software, La Jolla, CA). In protocol 1, a 2-way ANOVA was used to detect tension-time interactions. In protocol 2, a 1-way ANOVA was used to detect differences in tape application technique. Tukey’s multiple comparisons tests were conducted where appropriate. Significance was set a priori at α=0.05. Effect size (ES, Cohen’s d), is reported for mean differences. Interpretation of ES follows the convention of Cohen: 0.2, 0.5, 0.8 correspond to ES of “small”, “medium”, and “large”, respectively10.
RESULTS
Subject characteristics are presented in Table 1. Subjects were young, healthy, and free of overt cardiovascular disease risk factors.
Table 1.
Subject Characteristics
| Sex (M,F) | Age (y) | BMI (kg•m−2) | |
|---|---|---|---|
| Protocol 1 | 4,6 | 22 ± 1 | 22.5 ± 0.7 |
| Protocol 2 | 8, 4 | 23 ± 1 | 22.5 ± 0.7 |
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Data are mean ± SE.
Protocol 1: Tape Tension
CVC measured immediately post-KNT application is depicted in Figure 1. There were no differences in CVC between control and KNT applied at any tension, either with the local heaters turned off (Figure 1A) or set to 33°C (Figure 1B) (all p>0.05).
Figure 1.
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The change in CVC after 3 days of wearing KNT is depicted in Figure 2. CVC did not significantly change at the control site or with any KNT tension either with local heaters turned off (Figure 2A) or set to 33°C (Figure 2B) (all p>0.05).
Figure 2.
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Since there were no differences in CVC with KNT tension, protocol 1 data from the KNT sites were pooled together and compared to the protocol 1 control site. With local heaters turned off (Figure 3A), CVC was significantly higher with KNT compared to control (KNT: 0.12 (95% confidence interval: 0.10, 0.14), Control: 0.08 (0.07, 0.10) flux•mmHg−1; p=0.004) and the ES was large (0.80). When local heaters were set to 33°C (Figure 3B), there was no difference between KNT and control (KNT: 0.17 (0.13, 0.21), Control: 0.13 (0.10, 0.17) flux•mmHg−1; p=0.09). There was no difference in ΔCVC between control and KNT when all KNT sites were pooled either with local heaters turned off (KNT: 0.04 (0.00, 0.09), Control: 0.02 (−0.01, 0.04) flux•mmHg−1; p=0.58), or set to 33°C (KNT: 0.07 (−0.03, 0.06), Control: 0.02 (−0.02, 0.16) flux•mmHg−1; p=0.53) (data not shown).
Figure 3.
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Protocol 2: Convolutions
CVC data for KNT applied with and without convolutions is presented in Figure 4A. There were no differences in CVC between control and KNT with convolutions or without convolutions (all p>0.05). Since there were no differences between the KNT sites, KNT data from protocol 2 were pooled and compared to protocol 2 control (Figure 4B). CVC was greater with KNT compared to control (KNT: 0.30 (0.21, 0.39), Control: 0.15 (0.09, 0.21) flux•mmHg−1; p=0.03) and the ES was medium (0.52).
Figure 4.
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DISCUSSION
The main findings from this study were that (1) KNT modestly increased skin blood flow, and (2) convolutions, time, or tension did not significantly alter the effect of KNT on skin blood flow Combined, these findings suggest that the application of KNT modestly increased skin blood flow, regardless of the specific manner in which it was applied.
This is one of the first studies to empirically demonstrate that KNT can increase skin blood flow. We consistently found in protocols 1 and 2 that skin blood flow was higher with KNT compared to control. However, the increase in blood flow was modest, and whether this small rise in skin blood flow produces therapeutic benefits remains to be elucidated.
Similar to other investigations on the influence of KNT tension or convolution6,8, we found that neither tension, nor convolutions of KNT altered skin blood flow. Cumulatively, our data and others suggest that the vasoactive and analgesic properties of KNT are inherent to KNT application and not due to a specific method of application. We also failed to observe a time effect, as skin blood flow measures made immediately post-application were no different from measures taken 3 days post-application. The lack of intermediate measures means that we cannot rule out changes in skin blood flow occurring over shorter (i.e. hours) time periods; however, this possibility is unlikely as skin blood flow changes to most stimuli occur on the order of minutes11,12.
Limitations
The main limitation of this study was that we could not measure skin blood flow through intact KNT. Small holes had to be cut in the tape to allow placement of laser Doppler flowmeters. However, these holes were small and surrounded closely by tape on all sides, so any effect of KNT on skin blood flow should still have been apparent. This study was conducted entirely in young, healthy participants. We cannot directly extrapolate these data to other populations, such as older adults, who exhibit attenuations in skin blood flow.
CONCLUSION
We found that KNT modestly increased skin blood flow. However, this effect appears to be an intrinsic property of the tape being applied to the skin, and not affected by the method of application (i.e. convolutions or tension). This suggests that KNT has some efficacy in locally increasing skin blood flow. When combined with menthol, skin blood flow underneath the KNT induced a robust increase for a short period of time.
CLINICAL RELEVANCE
KNT is a commonly used product with numerous purported benefits. Though augmentation of skin blood flow is often reported as a benefit of KNT, limited scientific data exists to support this claim. We found that KNT modestly increases skin blood flow, suggesting some validity to this claim; however, the clinical importance of this minor increase is unknown and likely minimal.
Footnotes
Conflicts of Interest: Lacy M. Alexander is a member of the Performance Health Scientific Advisory board
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