Biomechanical Principles

Overview NEWTONS THREE LAWS FORCE SUMMATION STABILITY AND BALANCE Inertia Force Action and reaction FORCE SUMMATION Generating momentum Stretching muscles Sequencing Timing Full range of motion STABILITY AND BALANCE Line of Gravity (LOG) Centre of Gravity (COG) Base of Support (BOS) LEVERS First Class Second Class Third Class PROJECTILE MOTION Height of Release Angle of Release Speed of Release Spin

Newton’s First Law of Motion INERTIA “An object at rest tends to remain at rest unless acted upon by some external force. {inertia}” Having a great deal of inertia is an advantage when bulk is important. It can be a disadvantage Require a lot of force to get moving, decrease agility. If inertia is the objects resistance to movement which barbell has the greatest inertia?

Newton’s Second Law of Motion FORCE “When a force acts upon a mass, the result is acceleration of that mass.” Force = mass x acceleration F= ma 1. The greater the force, the greater the acceleration. 2. The smaller the mass, the greater the acceleration when a constant force is applied. 3. The mass will accelerate in the direction the force is applied. Applying the rule to a soft ball throw: The more force you apply through your muscles when pitching the softball the further the softball will go

Newton’s Third Law of Motion Action and Reaction “For every action, there is an equal and opposite reaction.” When we apply a force to something, this is known as action force. The object we apply a force to, applies a force back, a reaction force. These two forces always work in pairs. When a ball is bounced it bounces back in a direction opposite to which it is dropped.

STABILITY AND BALANCE There are three aspects that help us to maintain stability and balance CENTRE OF GRAVITY LINE OF GRAVITY BASE OF SUPPORT

CENTRE OF GRAVITY Centre of Gravity (COG) is defined as the centre of weight distribution in the body When we are standing COG is around our belly button COG moves depending on how our bodies are positioned

LINE OF GRAVITY Line of Gravity (LOG) is an imaginary line that runs through the centre of gravity to the base of support

BASE OF SUPPORT Base of Support (BOS) is defined as how the person is standing If their feet are wide apart they have a large BOS which means they have better stability If their feet are close together they have a small BOS which means they are less stable If a person wants to produce speed which BOS would be better and why??

BOS, COG, LOG

PROJECTILE MOTION A projectile is an object that is moving in the air. Factors that effect projectile motion: Gravity Air resistance Speed of Release Angle of Release Height of Release Spin

SPEED, HEIGHT AND ANGLE OF RELEASE The speed, height and angle of release of a projectile have important implications for the projectiles flight path and distance Speed of release is largely determined by muscle force and leverage of the body Angle of release is the angle (measured from the horizontal) that a projectile is released from. Activities requiring large angle of release usually projected from ground level. e.g. golf Activities requiring small angle of release usually have a larger height of release (above ground level) e.g. diving or throwing a cricket ball.

PROJECTILE MOTION AND DISTANCE When projecting for maximal distance apply the following: The greater the speed of release, the more distance is covered The greater the height of release, the more distance is covered. Optimal angle of release is around 45o.

HORIZONTAL AND VERTICAL RELEASE Almost all projectile sports require both horizontal and vertical velocity, the amount of each is dependant on the desired outcome and the nature of the sport. You need enough horizontal velocity to ensure that the projectile travels in the desired direction You need enough vertical velocity to ensure that the projectile covers the desired distance through the air

ANGLE OF RELEASE Projectiles require different angles of release depending on the sport. The optimal angle of release is 45 degrees VERTICAL ANGLE OF RELEEASE HORIZONTAL ANGLE OF RELEASE

HEIGHT OF RELEASE Increasing the height of release increases the horizontal distance covered Which sports would this be important in?? Achieving maximum height of release usually involves creating long levers by straightening body segments involved in releasing the projectile.

Height of release of a projectile affects the speed and angle of a projectile

SPIN A spinning object will follow a different path as a non spinning object spin gives projectiles stability in the air. Spin determines how an object will rebound after landing/or be manipulated to travel a certain path.

FORCE SUMMATION Force Summation is the amount of force produced by the body’s muscles to produce a force There are five aspects that determine the accuracy of force summation Segments Stretching out Timing Sequencing Full range of motion

BODY SEGMENTS We should use as many body segments as possible to generate as much force as we can so that the projectile’s horizontal and/or vertical distance increases To maximise the muscular force that each muscle group associated with each segment can generate Which body segments are used to execute the hockey flick? Legs, hips, shoulder, elbow , wrist

STRETCHING OUT MUSLCES Before we begin the sequence of movements, such as the throwing action, we should stretch muscles out to their optimal length. It allows the muscles to be contracted with optimum force For example: Softball throw Large step forward Extension of shoulder and arm behind

SEQUENCING Generally we use larger muscle groups first and then the smaller muscle groups This creates more force and generates more movement on the projectile – WHY?? JUMPING FOR HEIGHT With straight legs hands on hips With straight legs arms swinging Bend legs, straighten legs, arms swinging

TIMING OF BODY SEGMENTS We need to use the right muscle groups at the right time to so the movement is not uncoordinated We use larger muscle groups first and then smaller muscle groups

FULL RANGE OF MOTION To give maximum momentum in throwing, kicking and striking we need to move the body segments through the greatest range of motion. The greater the range of motion the greater the horizontal and vertical distance covered ACTIVITIES: Ball pass from ground, knees, and feet with minimal to full range of motion. Record distances…..What happened and why??

LEVERS There are three classes of levers First Class , Second Class, Third Class First-class Lever Eg see-saw, crow bar, rowing Second-class Lever Opening a door, wheelbarrow Third-class Lever Bicep curl

THIRD CLASS LEVER This is the main lever humans use TERMINOLOGY: FULCRUM = Also known as pivot point. FORCE = The direction you are pulling or pushing the load LOAD = The weight that you are pushing or pulling against

LEVERS AND PERFORMANCE Levers (arm or leg) can be lengthened or shortened to created speed and force Shortening the lever (by bending the joint) allows lever to generate force and more speed Then the lever can be lengthen (by straightening the joint) to maximise speed at the end of the lever. How does this work with the softball pitch??

Maximising force and speed in a rugby kick Back-swing Kicking leg is bent, creating a short lever to swing towards the ball with force and speed Forward swing Kicking leg straightens, creating a long lever, allowing the ball to be kicked with more speed Follow-through Leg follows through, to improve accuracy and allow the leg to slow down safely.