BIOMECHANICAL ANALYSIS OF THE "O'NEIL"

Abstract

Paul O'Neil was the first gymnast to perform the "stretched double felge backward to forward swing in hang on the rings" at the World Gymnastic Championships in Brisbane,l994. This skill can be placed in the movement category (Brueggemann, 1994) of (backward) rotations in the vertical plane with a flexible horizontal axis of rotation. The O'Neil is listed in the current FIG code of points as a D-part in the difficulty category. The purpose of this case study is to provide a descriptive kinematic analysis and a description of the technique employed by O'Neil performing the "O'Neil". This dynamic skill is initiated by generating rotational kinetic energy during the downward swing phase from a momentary handstand position. Thus the angular velocity of the body in the sagittal plane is maximized simultaneously with the maximisation of the moment of inertia relative to the body's centre of gravity. The maximum vertical velocity during the downswing phase before the beginning of the O'Neil was -4.2 1 m/s and reached a value of 3.91 m/s 0.24 seconds after the beginning of the up-swing. Ludwig (1992) suggests that the rotation of the trunk around an axis through both shoulder joints becomes the most important determining factor for the swing on the rings. The data revealed, that during the up-swing the hip joint reached its lowest value (flexion) distinctly in advance of the shoulder joints. Once the arm-trunk (shoulder) angle reached its minimum value, the hip joint reached hyper extension throughout the skill. Also, the arms and shoulders remained under the rings, which was consistent with the findings of Nissinen (1983). The CG displacement at the beginning of the skill, the start of the upswing to its highest value was 1.75 m. The analysis of the joint angle movements provides an inside into the mechanism for increasing rotation. The angular velocity over time of the hip angle was -949&g/sec and for the shoulder angle was -670 &g/sec. The p o w d closing ofthe arm-trunk angle is the most important technical component for thesuccessful performance of the O'Neil. The duration of the skill was 1.46 sec from the beginning of the upward swing to the vertical body position at completion of the skill. It seems, that only O'Neil, who has that natural" anthropometric make-up", is able to perform such an exciting, unique, and novel skill.