Angular Motion.

Angular Motion

A Presentation By Jack Clayton

Center of mass.

The bodys center of mass is determined by the point in which their mass is evenly distributed in all directions.

The centeral mass of an object is the point which effectively represents the whole object.

By changing their center of mass, an athlete is able to do many things that can aid their performance. For example, a footballer taking a free kick will run at the ball and put their weight over the ball if they want the ball to stay low and be more accurate. Or they can position their body behind the ball, causing the ball to generate lift and the ball will get more hight and dip down with the right technique.

Levers.

Levers can be used so that a small force can move a much bigger force.

Bones act as lever arms. Joints act as pivots/fulcrums. Muscles provide the effort forces to move loads.

1st class levers. This type of lever has the fulcrum between the force and the load.

2nd class levers. This type of lever has the load between the effort and the fulcrum.

3rd class levers. This type of lever has the effort in the middle between the fulcrum and the load.

Torque.

Torque is the rotational equivalent of linear force.

Just as force is what causes an object to accelerate in linear kinematics, torque is what causes an object to acquire angular acceleration. Torque is classified as a vector quantity.

Athletes are able to generate torque by rotating along their horizontal axis. This is what causes the shift from linear motion to angular. Torque is generated when the athlete rotates their torso in one direction. But the amount of torque can be doubled be twisting the oposite direction before the inisation of the spin. By rotating the opposite way first, the distance their torso has to travel is doubled, meaning they are able to generate double the torque then before. This amount of torque will allow the athlete to spin faster, allowing for more rotations to be completed which in certain sports, could be the difference btween a gold and a silver medal at competition.

Axes of rotation.

Similar to the three planes of motion, there are three axes of rotation: the anterior-posterior axis, the mediolateral axis, and the longitudinal axis.

Imagine a pin that inserts through a joint from front to back, effectively pinning down the joint to limit its potential freedom of motion. For example, you can think of a pin entering through the front of the hip joint and exiting out the back. Because of the pin’s position, the only movement allowed about this axis is lateral movement.

Mediolateral means that we take our imaginary pin and insert it from a lateral, or side approach. As in the earlier elbow example, the axis projects from the medial side of the joint and extends out the lateral side. The position of the pin allows only flexion and extension in the sagittal plane about this axis.

If we insert our pin through the joint from top to bottom, it will allow movement in transverse plane only. Imagine a long pin entering the top of the cervical spine and exiting out the lumbar spine. The pin would effectively prevent the spine from bending forward, backward, or side-to-side, but it would allow the spine to twist along a transverse plane.