Date of Award

2010

Degree Type

Thesis

Degree Name

Master of Science

Program

Kinesiology

Supervisor

Dr. Volker Nolte

Second Advisor

Dr. Jim Dickey

Third Advisor

Dr. Horia Hangan

Abstract

In order to be competitive in elite swimming competition, underwater dolphin kick (UDK) is considered an essential skill to master, although swim researchers and coaches claim that the mechanics of UDK are poorly understood and are often overlooked in training. The purpose of this study was to identify kinematic differences in the UDK between experienced swimmers within a broad range of competitive abilities, using a model which more accurately represents UDK trunk undulations than models used in previous kinematic studies. Fifteen competitive male swimmers (22.16 ± 3.48 years) ranging from provincial to international level were recruited from local varsity and club programs. Swimmers were filmed performing three 15m maximum effort trials of UDK. The videos were manually digitized using a 2D twelve point model that identified three points of rotation along the trunk. A correlation analysis with horizontal velocity revealed significant correlations with downkick kick displacement (r=0.642, p=0.010), kick cycle displacement (r=0.561,p=0.029), upkick vertical toe velocity (r=0.643, p=0.010), the ratio of downkick/upkick vertical toe velocity (r=0.742, p=0.002), Strouhal number (r=-0.580, p=0.024), finger-tip amplitude (r=-0.674, p=0.006), and amplitude ratios of fmger/toe (r=-0.666, p=0.007), fmger/shoulder (r=-0.604, p=0.017), fmger/chest (r=-0.691, p=0.004), fmger/hip (r=-0.662, p=0.026), shoulder/hip (r=-0.571, p=0.026), and shoulder/chest (r=-0.723, p=0.002). Vertical toe velocities appear to be important for propulsion, and are likely related to vortex shedding. It appears that symmetry between the downkick and upkick is important for UDK performance, both mechanically and propulsively. Faster UDK swimmers were able to minimize arm and upper body amplitudes better than slower UDK swimmers, which is likely a mechanism for drag reduction. The 2D model used in this study demonstrated the presence of undulations along the trunk; however, did not accurately represent the UDK as bilateral asymmetries were identified which could not be measured. 3D models should be employed in the future to evaluate the importance of bilateral asymmetries during UDK.

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