MOTION ANALYSIS BY DR AJAY KUMAR READER SCHOOL
MOTION ANALYSIS BY DR. AJAY KUMAR READER SCHOOL OF PHYSICAL EDU.
STEPS OF ANALYSIS Name of the skill Brief description of the skill The specific objective of the motor skill Identification of major and secondary categories
STEPS OF ANALYSIS (cont) The objectives of analysis i. e. mechanical, anatomical or both Identification of principles Application of principles in motor skills
Analysis of Walking Name of the skill: Discus Throw
Description of Skill of Discus Throw Discus throw technique has evolved from standing on a sloping platform to a one and three quarter turn that is still the technique used today. Because of its rotational nature, it is often perceived as a complex event.
The truth is that the discus is not that complex and can be understood with a little bit of work to understand the process of discus throw development, as well as the science behind it.
Description of Skill (cont) When discussing discus throw technique it is important to make a clear distinction between two things, technique and style. Some coaches use these terms as if they are the same thing. In reality, they are very different.
Science tells us that technique is the mechanical principles that dictate the movements in an event. Style is the individual athlete and coach's interpretation of that model. In simple terms Physics doesn't change and we do not coach robots! So lets make sure as coaches we are looking at technique not style.
Description of Skill (cont) While competent athletes will focus on the entire throw itself, the phases of the throw are important and need to be looked at. For example, imbalances or position at the back of the circle, could be causing problems of imbalance and poor right leg action at the front of the circle.
No matter which discus throw phase we are in it is important that the coach understands the process of fault and correction, and the biomechanics behind the technical changes made.
Description of Skill (cont) While discus drills are useful in removing technical deficiencies, it is only by understanding the technique of the event, that drills can be applied successfully.
Objective of Motor Skill The objective of discus throw is to achieve maximum linear distance by using a circular momentum produce through an efficient and dynamically balanced movement of the body in side circle.
For achieving this the mechanical principles relating centripetal and centrifugal force, projectile, aerodynamics, and maintaining dynamic balance should be taken care of.
Identification of Categories Primary Category: Giving impetus to external object. Secondary Category: Supported by ground and locomotion on foot.
Objective of Analysis Mechanical Analysis
Identification of Principles In all four throwing events the distance obtained is dependent upon the releasing speed, releasing angle, releasing height and aerodynamics factors. The principles related to these factors are important to understand the mechanical analysis of discus throw.
Application of Mechanical Principles 1. Principles related to maintaining dynamic balance. 2. Principle related to providing maximum releasing speed. 1. Application of force 2. Angular Momentum 3. Lever (Range of Motion)
3. Principles related to maintaining correct releasing angle and aerodynamics. 1. Drag 2. Lift
Application of Mechanical Principles (cont) An efficient throwing technique is one in which the athlete exert the force of his entire body over the greatest range possible (force x distance = work) and therefore for the longest period of time (force x time = impulse)
The force must be exerted against the implement in proper direction as far as practicable in the direction of ultimate throw. (As a general rule, preliminary movement of discus throwing is more in horizontal direction and in delivery more lift than horizontal drive.
These two principles are fundamental to correct preliminary swing in discus throw and it needs fast stretching and powerful recoiling of large muscle group. In particular, by driving the pelvis ahead of the trunk, the good thrower creates torque between hips and shoulder
Application of Mechanical Principles (cont) Summation of force : The various forces of the body should be exerted in definite sequence and proper timing. Turn in the discus throw should be so fast as an athlete can use it for good purpose but never so fast that he is unable to exert full body force in the delivery.
Principles (cont) For maximum speed of release the ground must provide adequate resistance to thrower’s movement and for as long as he is in contact with the implement. Some advance athlete use jump release throwing and it is a matter of research.
Principles (cont) Angle of Release When points of release and point of landing are the same height above the ground (and aerodynamic factors may be ignored ) the optimum angle for the projectile of a missile, regardless of its speed is one i. e. 45 degree.
Principles (cont) However in all four throwing events in athletics the implement is thrown from a point above the ground but the landing is on the ground i. e. below the level of release angle, as well the shape of the implement differ and it may affects the release angle.
Principles (cont) In shot and hammer events (where aerodynamic factors are of no account, due to their shape) the optimum release angle will be near the 45 degree.
Principles (cont) In discus throw by the virtue of their size and shape, aerodynamic forces also influence the flight as they do not follow the simple parabolic curves. In moving through the air a discus pushes the air and perform work. This work needs energy which reduces the speed of discus.
Principles (cont) The air resistance depends upon the shape and size of the discus: – The thinner and sharper it is in front, the smaller is the air resistance. – This can be further reduced if the cross-section narrows gradually i. e. streamline effect. If
If the discus is thrown at an angle the upper side develops irregular air whirls and under side air passes as streamlined. It develops a reduced air pressure on the above side of discus and an increased air pressure on under side of discus.
This air pressure develop a vertical force i. e. lift and a horizontal force i. e. drag on discus. The ratio between lift and drag depends upon the angle of attack.
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