For reference, 180 deg indicated full knee extension and normal standing position, respectively. The ankle in a neutral position was equal to 90 deg (angles 0�C90 deg indicated dorsiflexion selleck bio and angles 90�C180 deg indicated plantarflexion). The raw EMG data were low-pass filtered at 500 Hz and high-pass filtered at 10 Hz to eliminate movement artefacts, using a Butterworth fourth-order zero-lag filter. The onset/offset time selected from starting knee extension of the swinging leg to impact the ball. After removing the signal offset, the root mean square (RMS) was estimated from raw EMG signal data using a smoothing window. In each kick, we examined the (1) maximum RMS of RF, VM and VL muscles, (2) maximum knee angular velocity (KAV), (3) maximum ankle angular velocity (AAV), (4) maximum foot velocity (FV) and (4) maximum ball velocity (BV).
Foot velocity (Vfoot) was estimated as the velocity of the center of mass of the foot, which was calculated in each frame based on ankle and toe marker data. The mechanics of collision between the foot and ball were analyzed as suggested by Lees and Nolan (1998). Particularly, the resultant ball velocity (Vball) was calculated from V foot as follows: vball = 1.23 �� vfoot + 2.72 The Pre-stretching and Post-stretching values for each protocol were averaged across days and therefore for each participant there were four values: pre- and post- static stretching and pre- and post-dynamic stretching ones. Subsequently, in each variable, the percentage differences between pre- and post- stretching protocol were calculated and compared between protocols.
Statistical Analysis A one-way analysis of variance was used to compare relative changes in each dependent variable between static and dynamic stretching. The level of significance was set at p �� 0.05. When justified, paired sample t-tests were performed to confirm significant changes within each condition. Effect sizes (ES) were calculated and are also reported. The power was �� 0.94 and the test�Cretest reliability values for the testing order of tests ICCRs (intraclass correlation reliability) were �� 0.97. Results An example of EMG raw data of RF, VL, and VM activity after different acute stretching methods is illustrated in Figure 2. The descriptive results of raw EMG and KAV data are presented in Table 2 while mean group values are presented in Figure 3.
The ANOVA showed a statistically significant higher increase in RF EMG (Figure 3) after dynamic stretching (37.50% �� 9.37%) versus a non-significant (?8.33% �� 3.89%) decrease after static stretching (p = 0.015) (ES �� AV-951 0.94). Similarly, VL EMG increased after dynamic stretching (20% �� 10.21%) but it decreased (?6.60% �� 8.77%) after static stretching (p = 0.004) (ES �� 0.98). There was also a statistically significant increase in VM EMG after dynamic stretching (12.00% �� 6.29%) as opposed to a decrease (?12.00% �� 5.