Kinesio taping (KT) is a technique which uses the application of an elastic adhesive tape on the skin. KT is manufactured with elastic cotton which can be stretched from 120 to 140% its original length. It is used to pressurize the skin to affect the somatosensory system under the areas where the tapes are applied (Kase et al., 2003).
KT has become a widely rehabilitation modality for the prevention and treatment of musculoskeletal disorders (Thelen et al., 2008). This technique has become popular after being widely used by athletes in the 2008 Olympic Games (Williams et al., 2012). It is claimed that KT supports injured muscles and joints and helps to relieve pain by lifting the skin, thus improving blood and lymph flow (Kase et al., 2003). It is also suggested that it brings a small immediate increase in muscle strength (Fratocchi et al., 2013; Hsu et al., 2009) by producing a concentric pull on the muscle fascia which may stimulate increased muscle contraction (Hammer, 2006). Additional hypotheses suggest that it facilitates muscle activity and improves muscle alignment (Hsu et al., 2009), increased range of motion (Hsu et al., 2009; Lewis et al., 2005; Thelen et al., 2008) and improves patellar alignment (Whittingham et al., 2004).
The type of the KT application determines theoretically the neuromuscular effects which are: a) the KT application from the muscle origin to insertion produces a concentric pull on the fascia, facilitating the muscle activation; and b) the KT application from the muscle insertion to origin produces eccentric pull on underlying fascia, inhibiting or decreasing the muscle contraction (Basset et al. 2010; Kase et al., 2003).
Some studies with surface electromyography (EMG) report that KT application may increase muscle activity. Csapo et al. (2012) applied KT (ktape[R], biviax GmbH, Dortmund, Germany) over both heads of gastrocnemius muscle adjusted from muscle origin toward the insertion. They found an increase in EMG activity of gastrocnemius in only one of the five angles of the maximum isometric voluntary contraction (MVIC), though. Huang et al. (2011) found EMG activity of medial gastrocnemius increased in a KT group (Kinesio Tex KTX050, Tokyo, Japan). Tapes were applied from calcaneus bone on the sole of the foot to medial and lateral gastrocnemius muscles below the knee joint. Briem et al. (2011) performed an ankle stability test, in fifty-one healthy male volunteers, where EMG activity of fibularis longus muscle was evaluated in placebo and kinesio tex gold elastic sports tape (Kinesio USA, LLC, Albuquerque, NM) conditions. A non-elastic white bandage was used as placebo. The only variable that showed significant changes was the average EMG activity which was higher in the placebo group when compared to group without any bandage. Hsu et al. (2009) reported that KT application increased EMG activity of lower trapezius muscle during shoulder abduction in amateur baseball players. On the other hand, Voglar and Sarabon (2014) found no differences between kinesio taping (Darco International, Inc., Huntington, USA) and placebo taping conditions in anticipatory postural adaptations. Lins et al. (2013) also found no differences in either EMG or torque peaks. They compared the root mean square (RMS) of muscles vastus lateralis, rectus femoris and vastus medialis during the knee flexion and extension in an isokinetic device at 60[degrees]/s without KT and non-elastic adhesive tape (kinesiotex gold[R]). Only Alexander et al. (2003) used a rigid tape (Endura Fix tape) applied without tension on the trapezius muscle compared to the elastic tape (Endura Sports tape) applied with tension. They found inhibition in EMG activity of lower trapezium.
The most recent systematic reviews have concluded that there is little quality evidence to recommend the usage of KT to prevent or treat musculoskeletal injuries (Morris et al., 2013; Williams et al., 2012); and regarding efficacy of KT applications to promote strength gains has recently been reviewed (Csapo and Alegre, 2015).
Williams et al. (2012) concluded in their meta-analysis that there was no substantial evidence to support the use of KT to enhance muscle activity. Their meta-analysis mentions that only one of the 16 studies analyzed concerning muscle activity has been verified with high methodological quality (controlled experimental study and blinding) and, thus, concluded that the placebo control is necessary for future research.
Only few studies have used some forms of placebo to compare results. Placebo is an inherent procedure with a similar therapeutic application, but without a specific effect (Moerman and Jonas, 2002). Among these studies, the placebo was conducted in different ways: KT transversely to the muscle fiber and without tension (Chang et al., 2010; Simsek et al., 2013; Thelen et al., 2008; Voglar and Sarabon, 2014); non-elastic tape (Briem et al., 2011); or micropore tape 3M[R] (Hsu et al., 2009; Huang et al., 2011). These differences among placebo application in the studies could influence the expected results.
A single article used an analog visual scale (VAS) to check the performance (Cai et al., 2016), but they did not utilize the placebo control. This approach can help to analyze the subjective effect of KT. There are no studies that evaluate the effect of the KT on traditional strength exercises. Strength exercises are used in varied situations such as rehabilitation and performance increasing for sport training which represent most of the KT applications (Hsu et al., 2009; Huang et al., 2011; Thelen et al., 2008), whose effects are relevant in this kind of exercise.
Therefore, the aim of this study was to verify the effect of application of Kinesio Taping Denko[R] (KTD) in three conditions (facilitation, inhibition, and placebo) on EMG activity of mm. quadriceps and hamstrings on facilitating or inhibiting muscle function and on the perceived exertion during barbell back squat exercise. Our hypothesis was that KT application did not modify EMG activity during the strength exercises.
Eighteen male adults (28.0 [+ or -] 6.7 years old; 85.8 [+ or -] 8.2 kg mass; 1.80 [+ or -] 0.07 m tall; 0.97 [+ or -] 0.04 m lower limb lenght) with no history of musculoskeletal disorders in the last six months participated in the study. Subjects had at least one year of experience in strength training and had been performing barbell back squat exercise with 8 repetition maximum (RM) at least once a week in the last six months (ACSM, 2009). Sample size was calculated based on coefficient of variation reported by Linset. al. (2013) and results in a minimum number of 15 subjects. Thus, 18 subjects were recruited to ensure a balanced order of experimental conditions application. The experimental procedure was approved by the research ethics committee of the University of Sao Paulo and all...