Técnica intrapulpar

18 female participants were recruited for the current study (age 20.7 +/- 2.4 years, height 1.7 +/- 0.1m, weight 61.5 +/- 8.2 kg). All participants had at least one year of previous experience in competitive soccer and are still currently playing. Competitive soccer was defined as soccer at the level of high school, club, collegiate or Olympic Development Program (ODP). Within this year, participants needed to have played soccer at least two times per week. Any participants who had played over half of their soccer career as a goal keeper were excluded from the study. All participants were healthy with no current complaints of lower extremity injury. Participants who received treatment from a physician or doctor concerning a musculoskeletal injury in the past six months were excluded from the study. Such an injury could affect the ability of the participant to perform the instep soccer kick and possibly alter the mechanics of the previously injured plant limb. Also, any participant with a previously injured ACL was excluded from the study. All participants reported that their right limb was their dominant

kicking limb. This means that the left limb of all the participants in the current study was the dominant plant limb.

2.2 Procedures

A standard full body marker set was applied to each participant in preparation for the motion capture protocol. Lower body markers included a cluster of markers on the right and left lateral side of the thigh, shank and foot, one marker each on the right and left anterior superior iliac spine, posterior superior iliac spine, lateral and medial epicondyle of the knee, and lateral and medial malleoli of the ankle. The upper body markers included one on the left and right medial and lateral wrist, lateral forearm, lateral left and right upper arm, lateral left and right shoulder, clavicle, manubrium, xiphiod process, right scapula, C7, T10, and right and left side of the anterior head and right and left side of the posterior head (Kellis et al., 2004, Besier et al. 2001b).

Participants were then asked to perform a series of calibration trials in order to calculate functional joint centers of the right and left knee and the right and left hip (Schwartz and Rozumalski, 2005). Participants then warmed up on a treadmill for 3 minutes. The treadmill started off at a speed of 1.5 miles/hour and continually increased its speed 1.0 miles/hour every 10 seconds. Participants were allotted several practice trials to warm up and familiarize themselves with kicking a soccer ball in the laboratory. The participants were aligned at a 60˚ angle from the direct approach of the ball and were allowed three preparation steps towards the soccer ball. Each participant performed three instep soccer kicks at a 60˚ angle from the right side of the ball and the left side of the

possible while aiming at a marked target in the shape of an X on the net along the y-axis of the coordinate system. A kick that did not result in full placement of the foot on the force plate was excluded from data analysis.

2.3 Data Analysis

Labeled 3D trajectory and force plate data were imported into Visual 3D (C- Motion, Inc. Germantown, MD) for analysis of the kinematic and kinetic variables. The kinematic and kinetic data were filtered in Visual 3D using a Butterworth low pass filter at a cutoff frequency of 6 Hz for the kinematic data and 40 Hz for the kinetic data (Lin et al., 2009). Custom processing protocols developed in Visual 3D were used to determine AP GRF impulse, knee joint impulse in all three planes, and lateral trunk lean. All variables were calculated between the times of initial plant foot contact (IC) to 50 ms after IC. The force plate data collected during each kicking trial was used to determine IC and the trial was manually cropped to 50 ms thereafter. The average of the net AP GRF impulse, knee joint impulse in all three planes, and lateral trunk lean was calculated over all three trials for the dominant and non-dominant limbs. These average values for each limb were used in the statistical analysis to determine if any significant differences existed between the limbs.

2.4 Statistical Analysis

In order to test for significant differences across the non-dominant and dominant limbs Repeated Measures MANOVA was used with significance set at p < 0.05. A

discriminate analysis was used as a post-hoc test to determine how the individual variables contributed to the difference between limbs.

3. Results

The RM MANOVA revealed a significant multivariate main effect for limb (Wilks’ λ = 0.348, F(5,30) = 11.25, p = 0.000). A discriminant analysis was performed to determine which variables were most responsible for the difference between limbs. This analysis revealed that the net frontal plane knee moment impulse, AP GRF impulse and knee sagittal plane knee moment impulse were the main contributors to the difference between conditions. The structure coefficients for these variables were 0.538, 0.493, and 0.424, respectively.

Table C.1 The Means and Standard Deviation of Each Variable Within the Dominant and Non-Dominant Plant Limb.

Variables DL NDL

AP GRF Impulse (Nms) 4.11 -1.24

Net Sagittal Knee Moment Impulse 0.00 -0.03

Net Frontal Knee Moment Impulse 0.05 0.02

Net Transvers Knee Moment Impulse -0.02 -0.02

Trunk Lean (deg) -2 (3) -4 (3)