Participants
Thirty-one healthy adults (19 males and 12 females) age from 21 to 31 years old were recruited in this study. They were completely inactive without habit of regular exercise before the study. Before formal testing, the evaluations of based on the clinical criteria in lower extremities were assessed by well trained physical therapist. Subjects were excluded if they had a history of spinal, hip, knee or foot pathology, any neurological impairment or a history of lower limb fractures. Their average age, body weight and height were 25.3 ± 3.8 years old, 64.1 ± 6.2 kg, and 169.4 ± 7.3 cm, respectively.
Experimental design
Before the data collection, all participants were informed about the study processes and then were asked to sign a consent form approved by the Institutional Review Board of National Cheng Kung University Hospital. All participants executed the vertical jump tests prior to and during the elastic taping. Two tapes, elastic tape A (Kinesio Tex KT-X-050, Tokyo, Japan) and non-elastic tape B (Micropore, 3 M, St. Paul, USA), were applied to the participants, respectively.
For the elastic taping technique, we used a Y shaped Kinesio tape (Kinesio Tex KT-X-050, Tokyo, Japan) for calf muscle taping according to the recommendation of Kase (1980). First, the proximal head of Y shaped Kinesio tape was applied on the surface of calcareous bone on the sole of the foot with the subject in a relaxed prone position. Then, two distal heads of Y shaped Kinesio tape were attached following the soleus muscle and ended on the surfaces of medial and lateral gastrocnemius muscles below the knee joint, respectively (Figure 1-b). The same sized Y shaped Mplacebo Micropore tape was applied over the calf muscle.
Before doing sports activities, warm up procedures are often recommended to promote performance and prevent injury. Easy, gentle movement has been suggested for jumping rather than proprioceptive neuromuscular facilitation or static stretching exercise, both of which could decrease muscle force production [19, 20]. After placement of the electrodes, the subjects walked on a treadmill at 1.34 m/s, the mean fast walking speed of total subjects, for 5 minutes as the warm up period. Before performing the vertical jump, the subjects were instructed in the proper jumping technique. This involved performing a 2-legged upward vertical jump with both feet on the force plate with the subject's maximal effort with the bilateral hands placed on the hips [21]. To reduce training effects, subjects were initially allowed to practice until they were full adapted and familiar with the protocol.
After the brief warm-up and practice, participants performed the vertical jump test in the following sequence: first, the subject performed five trials of a maximal vertical jump as the baseline trials; second, the elastic tapes were applied over the bilateral triceps surae muscles by an experienced physical therapist while subjects were blinded for taping type; third, to let participants obtain full resting and avoid muscle fatigue induced by the previous trials, after a period of 30 minutes with the tape, the another five trials were tested.
Baseline vertical jump performance was assessed on every test session. Upon arriving for a test session, subjects were fitted with EMG surface electrodes. A pretest/posttest repeated measure design was used to understand the effects of Kinesio and Mplacebo taping during the performance of the maximal vertical jump. Every subject applied both A and B tapes. The test sequence of tape A and tape B was randomly processed for each subject to avoid bios. Two taping sessions were performed at an interval of at least 3 days to avoid accumulation of the taping effects.
Data recording
The jump height was measured using a video-based motion analysis system (Motion Analysis Corporation, Santa Rosa CA, USA). Kinematic data was collected using an eight-camera motion analysis system with the sampling rate set at 100 Hz. Reflective marker was placed on the dorsal aspect of the calcaneus bone on the bilateral legs to collect the jump height.
The vertical ground reaction force (VGRF) was measured using a force platform (9281B, Kistler Instrument Corporation, Amherst, NY, USA) at a sampling rate of 1000 Hz. The electromyographic (EMG) activity reflects the signal of active muscle fibers [22]. It was used to record from the medial gastrocnemius (MG), tibialis anterior (TA), and soleus (Sol) muscles using Ag-AgCl electrodes (MA-300 EMG system, Motion Control, USA) at a sampling rate of 1000 Hz during the whole jump task (Figure 1).
Data analysis
In kinematics, the coordinate data were then smoothed with a 2nd order forward and backward Butterworth filter with a cut off frequency of 6 Hz, and the displacement was calculated. The cut off frequency was chosen from the results of the residual analysis performed on the data [23].
The EMG signals were band-pass filtered from 8 to 1000 Hz [4]. The EMG value was collected with the duration from minimal to maximal GRF during lower extremity concentric contraction to push off (Figure 2, red trajectory), then calculated using a moving average window of 31 ms [4]. VGRF data from the force platform were digitally filtered using a bi-directional, low-pass, fourth-order, Butterworth filter, with a cut-off frequency of 7 Hz. Displacement data from the cable-extension transducer were filtered similarly with a cut-off frequency of 7 Hz [4]. Finally, the individual VGRF was normalized by the body weight, as a new parameter (ratio of body weight) to analyze the tapping effect on performance of VGRF (Figure 2, second layer).
Statistical analysis was undertaken using SPSS version 10.0 (SPSS Inc., USA) with significance level defined as p < 0.05 for each test. All data were presented as average ± standard error of the mean (SEM). For the changes in the vertical jump height, vertical ground reaction force and EMG at before and after taping, a repeated measures analyses of variance (ANOVA) was used with time as within-subjects main factor. Pair-t test was used as post-test to compare before and after taping when the main effect of was significant. Also, the effects of dependent variables in different types of taping, the independent t-test was performed to determine the contributions of individual taping effects.