Study design
A randomised crossover controlled trial was conducted in the School of Science and Health at Western Sydney University in New South Wales, Australia. Reporting of the study followed the Consolidated Standards of Reporting Trials (CONSORT) guideline extension for crossover trials [27], as well as the recommendations provided by Li, Yu, Hawkins and Dickersin [28]. The study was funded by the School of Science and Health at Western Sydney University.
Ethics and registration
All participants received written and verbal descriptions of the experiment and provided written informed consent prior to testing. The study was conducted in accordance with the Declaration of Helsinki [29] and Australia’s National Statement on Ethical Conduct in Human Research [30]. This study was approved by the Human Research Ethics Committee at Western Sydney University (H10184), and was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12616001506482).
Recruitment and eligibility
Healthy participants aged between 18 and 40 years were eligible for the study. Healthy individuals were recruited to ensure that any changes in athletic performance, strength, or neuromuscular function could be attributed to the colour of the tape applied rather than the provocation of pain or other symptoms. Participants were recruited through flyers and advertisements on social media networks. People were excluded if they experienced pain during data collection or presented with lower limb osteoarthritis or rheumatoid arthritis; low back pain; referred or radicular pain to the lower limb in the previous 12 months; sensory disturbances; a history of ankle or knee instability; a history of osteomyoarticular lesion or surgery in the lower limb over the last 12 months; non-corrected neurological, vestibular, visual or hearing impairments; or allergy to adhesive material. All participants were also safety screened for transcranial magnetic stimulation (TMS) to exclude individuals with contraindications to TMS or a history of stroke, seizure, epilepsy, brain injury, metallic implants, and use of implanted devices [31].
Intervention
All participants were assessed under five experimental conditions, allocated in random order: (1) no kinesiology tape (control), (2) beige-coloured kinesiology tape applied with tension (sham A), (3) beige-coloured kinesiology tape applied with no tension (sham B), (4) red-coloured kinesiology tape applied with tension, and (5) blue-coloured kinesiology tape applied with tension (Team Tape®) (see Fig. 1 and Fig. 2).
Randomisation was concealed using opaque envelopes and conducted by an independent person not involved in data collection. For conditions involving kinesiology tape application (red, blue, or beige), the tape was applied to the rectus femoris, vastus lateralis, and vastus medialis muscles of the dominant lower limb. Longitudinal strips of the tape were applied from proximal to distal with 50% tension in the middle (apart from the no tension condition), and no tension at the end of the strip [17]. This approach has been recommended previously [5, 17]. Kinesiology tape on the rectus femoris muscle was applied from 10 cm below the anterior superior iliac spine to the superior boarder of the patella [17]. Tape applied to the vastus lateralis muscle extended from the greater trochanter to the lateral boarder of the patella, while tape on the vastus medialis muscle extended from the middle third of the vastus medialis muscle to the medial boarder of the patella [17]. When applying the tape, all participants were asked to stand on the non-dominant leg, while flexing the dominant knee at 90 o with support (see Fig. 1). Positioning the knee in flexion and applying the tape from proximal to distal is consistent with previous investigations and is thought to facilitate quadriceps activation [7, 8, 32, 33].
Outcomes
The primary outcome was lower limb functional performance (distance on the single leg hop test) and secondary outcomes included: (1) knee extensor torque (maximal torque produced using an isokinetic dynamometer); and (2) neuromuscular function of the quadriceps muscles (assessed using transcranial magnetic stimulation). Participant characteristics such as age, gender, leg dominance (right or left), leg length (distance from the anterior superior iliac crest to medial malleolus), body mass index (BMI, weight/height2), and participant colour preference were also collected.
Lower limb functional performance
Lower limb functional performance was assessed with the single leg hop test, a reliable measure of the strength and functional stability of the lower limb [17, 34]. After a verbal explanation of the test, participants were asked to hop horizontally as far as possible using only the dominant limb. All participants were asked to perform the test barefoot. Hallux-hallux distance (cm) was recorded using a metric tape, and the greatest distance of three attempts was recorded [17, 34].
Knee extensor torque
Knee extensor torque was obtained using an isokinetic dynamometer. When recording knee extensor torque, subjects were seated with their hips and dominant thigh supported, and the pelvic and thoracic regions secured by a belt. The force pad of the dynamometer was positioned 5 cm above the centre of a line drawn between the distal ends of the medial and lateral malleoli [17]. Isometric knee extensor activity was assessed with the knee flexed at 90o. Standardised verbal encouragement was provided throughout the assessment to all participants. The best of three performances was recorded for each experimental condition.
Neuromuscular function
Following assessment of knee extensor torque, transcranial magnetic stimulation (TMS) was used to explore the corticomotor activity of the quadriceps muscle. Corticomotor activity was used as an index of neuromuscular function [35]. Assessments were performed during active voluntary contraction of the quadriceps. Participants were seated in a chair with their head and arms supported. Resisted knee extension at 10% of the participant’s maximal voluntary contraction (MVC) was performed when recording corticomotor activity [36]. Real-time visual feedback was provided on a computer screen in the form of electromyography recordings. All data was obtained from single-pulse, monophasic stimuli delivered using a figure-of-eight coil connected to a Magstim 200 stimulator (Magstim Co. Ltd., Dyfed, UK). The optimal cortical site for stimulation (‘hotspot’) was determined by identifying the coil position that evoked a maximal peak-to-peak motor evoked potential (MEP) in the rectus femoris muscle [36]. Active motor threshold (aMT) was then determined at the hotspot. The aMT was defined as the minimum TMS intensity required to elicit at least five discernible MEPs in a trail of ten stimuli at 10% MVC of the quadriceps muscle [35,36,37,38,39]. Stimulation intensity for the rest of the testing session was then set at 110% of aMT [37,38,39]. Electromyography recordings were obtained using Ag-AgCl electrodes (Noraxon dual electrodes, product #272S, inter-electrode distance 2.0 cm) positioned over the muscle belly of the rectus femoris, vastus lateralis, and vastus medialis muscles. Twenty peak-to-peak MEP amplitudes were recorded and stored on a computer for offline analysis using Signal software (version 5.08 × 86, Cambridge Electronic Design, Cambridge, UK).
Participant colour preference
After testing, participants were questioned regarding their colour preference when presented with the options of ‘red’, ‘blue’, and ‘no preference’. Colour preference was collected as it is hypothesised to be linked with arousal levels, personality traits, and athletic performance [40,41,42,43].
Data processing and storage
Participants were de-identified using codes generated by the researchers. Assessments and kinesiology tape application were conducted by two registered physiotherapists. To minimise human error, collected data were entered into two separate spreadsheets by two of the researchers. These spreadsheets were then compared, with any discrepancies being investigated and corrected. All hard copies were stored in a locked filing cabinet and digital copies were stored in password-protected computers.
Statistical analysis
Data analyses were performed using SPSS (version 23.0; IBM, New York). Two-way repeated measures analyses of variance (ANOVAs) were performed to analyse hop distance, knee extensor torque, and corticomotor activity with the factors “taping condition” and “colour preference”. Assumptions of normality and sphericity (equal variance) for parametric analyses were assessed using the Shapiro-Wilk test and Mauchly’s test of sphericity, respectively. The Greenhouse-Geisser correction was applied for data sets that violated the assumption of sphericity [44]. To detect a mean difference of 5 cm on the single leg hop test between the red and blue tape conditions (80% power), a total of 32 participants was required [34]. An intention-to-treat principle was used for data analyses, and those analysing the data were blinded to taping conditions and the nature of the study.