Date of Final Oral Examination (Defense)

8-2011

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Exercise and Sport Studies, Biophysical Studies

Department

Kinesiology

Major Advisor

Eric L. Dugan, Ph.D.

Abstract

INTRODUCTION: Over the past 15 years, participation in women’s soccer has increased drastically and with that comes increased exposure to injury. When athletes perform deceleration tasks, such as planting the limb during a kick, there is an increased risk of anterior cruciate ligament (ACL) injury. Low knee flexion angles at contact, high posterior ground reaction force (GRF), increased lateral trunk lean, high knee abduction angle, and high knee external rotation of the knee have all been identified as potential mechanisms of ACL injury during deceleration tasks. At higher levels of competition, a soccer player becomes more valuable if they are able to produce quality kicks with both of their legs. While there is some evidence that plant limb mechanics differ between the dominant and non-dominant plant limb, there is little known about how these differences in mechanics relate to ACL injury risk through the previous specific variables (Clagg et al., 2009). The purpose of the current study is to determine the differences in the mechanics between the dominant and non-dominant plant limb during instep soccer kicking of competitive female soccer athletes.

METHODS: 18 female participants were recruited for the current study (means and standard deviations were: age 20.7 +/- 2.4 years, height 1.7 +/- 0.1 meters, weight 61.5 +/- 8.2 kg, respectively). Each participant performed three instep soccer kicks at a 60° angle from the right side of the ball and the left side of the ball for a total of six kicks. Three dimensional coordinate locations of a standard full-body marker set were recorded during the kicking trials with a Vicon MX motion capture system (VICON, Denver, CO, USA). Plant foot ground reaction forces were recorded with Kistler force plates. Three dimensional trajectories and force plate data were imported into Visual 3D (C-Motion, Inc.; Germantown, MD) for subsequent analyses of the kinematic and kinetic variables. Custom processing protocols developed in Visual 3D were used to determine posterior GRF, knee joint angles in the sagittal, transverse and frontal planes, and lateral trunk lean. All variables were calculated between initial plant foot contact (IC) and 200 ms after IC.

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.

RESULTS & CONCLUSION: A repeated measures MANOVA was used with significance set at p < 0.05 in order to test for significant differences between the nondominant and dominant limbs. A non-significant multivariate main effect of limb was found (Wilks’ λ = 0.873, F(5,30) = .872, p = 0.511). The current study found insignificant differences between the dominant and non-dominant plant limb with respect to kinematics. Previous research on kinematics during a deceleration task has been inconsistent. The results of the current study are however consistent with previous research by Sigward and Powers (2006a) who found that kinematic differences within a deceleration task were non-significant between genders and also between experienced and novice female soccer players (Sigward and Powers, 2006a). Even with the lack of differences between genders and experienced and novice soccer athletes with respect to kinematics, Sigward and Powers did find significant differences when assessing kinetics. Further research on kinetic differences between the dominant and non-dominant plant limb would be beneficial to ACL injury risk research as it pertains to female soccer athletes. In conclusion, the non-significant differences in the current study and those found in previous studies imply that kinematic differences vary dramatically within each individual athlete, perhaps suggesting that ACL injuries are a result of other types of mechanisms (Sigward and Powers, 2006a).

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