Tuesday, February 1, 2011

Learn to Ollie

What I wrote this evening for a course in Biomechanics. Ahh man it's gettin' nerdy in here and stuff!

Snowboarding involves many technical movements but none share the same fundamental importance such as that of the ollie. Ollie is the term used to describe the jumping motion that a snowboarder uses to leave the ground. Advanced snowboarders combine spins and grabs to the ollie to create different maneuvers during the period of time when he/she is not touching the ground.

The technique involved in the ollie is fundamentally the same for every individual. The ollie requires understanding of the laws of motion and force. One's technique can be improved through analysis of applicable principles of motion and force.

Principles of Motion
Principle-Direction of the counterforce. The counterforce is directly opposite and equal to the applied force.

Application. When one pushes against the surface of the Earth, the Earth pushes back with equal and opposite force. So, when one flexes ones hips and knees, lowering oneself into a crouched position, and then extends his/her knees and hips creating a downward force onto the surface of the Earth which in turn creates an equal and opposite force on one's center of mass in the opposite direction. This allows one to overcome the force of gravity and leave the surface for a period of time.

However, the ollie requires a bit more technical movement in order to utilize the elastic force of the snowboard attached to one's feet (see Temporarily stored counterforce). In order to do this one must first lead the extension of the knees and hips with his/her front leg followed a fraction of a second later by his/her back foot. This creates a flexing motion of snowboard.

Principle-Continuity of motion. When performing activities in which two or more consecutive motions contribute toward movement in the same direction, the performer should not pause between motions.

Application- Since one must lead the ollie with one's front leg followed by one's back foot it is important that these movements have a fluid and successive motion. That is to say that one must fully extend his/her front knee and hip followed immediately by the extension of his/her back knee and hip. If one pauses between the extension of the front leg and the back leg then one would essentially be overcoming the force of gravity twice thus achieving much less than the height that one could potentially reached.

Principle-Temporarily stored counterforce. If a surface, implement , or object used in a performance has elasticity, then an applied force produces bend or compression, which represents stored energy.

Application. Snowboards are manufactured of material that when flexed stores elastic potential energy that creates momentum in the direction opposite to that of the applied force. In this case ones can create elastic potential energy by leading the ollie with his/her front foot, followed by his/her back foot in order to flex the snowboard momentarily creating a stored elastic potential. This potential will help the snowboarder to overcome the force of gravity enabling he/she to leave the ground for a period of time.

Principles of Force
Principle-Total Force- The total force is the sum of velocities of all contributing movements, if performed with continuity and proper timing.

Application. The upward velocities created by both the legs and the force stored by the elastic energy stored in the snowboard can be summed in order to determine the total upward force created by a snowboarder. If there is a lack of continuity then the force will be significantly reduced.

Principle-Duration of force application. If a constant force is applied to a body, the body develops greater acceleration as the distance over which the force is applied increases.

Application- The force of one's legs can be applied to the surface of the Earth for a longer period of time, and consequently distance, if one crouches deeper (flexion of knees and hips, allowing one to become closer to the surface of the Earth). If one crouches deeper his/her legs will apply a force on the surface of the Earth for a longer distance. Since the surface of the Earth exerts an equal but opposite amount of force on a person the result is a larger upward velocity of a snowboarder.

The analysis of mechanics of snowboarding is very dynamic and involves much more detailed descriptions that what is provided in this analysis. The mechanics described in this analysis are meant to aid one in preventing errors while attempting to ollie on a snowboard. Major topics were identified and continuity was emphasized.

To achieve the maximum period of time when one is not touching the surface of the Earth one must complete a deep crouch, extend one's front leg, and extend one's back leg. One must complete these motions with continuity in order to utilize the stored potential of a snowboard.

One wishing to improve the height, thus the period of time in which one is not touching the surface of the Earth, should be given time to practice technique and should participate in leg strengthening exercises, primarily exercises the muscles responsible for leg extension.

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