Biomechanical Principles

What do we use biomechanics for? To improve performance we need to know: How the movement occurs How to make the movement How to control the movement The factors affecting the movement To improve equipment: Shoes Rackets balls

What is a force? A force is a push or pull on an object that: Causes or stops motion e.g. pushing & trapping a hockey ball. Increases or decreases speed e.g. pedalling or breaking on a bike Causes a change in direction e.g. hitting a tennis ball

Force Summation What is it? A combination of forces produced by different parts of the human body. Its purpose is to achieve maximum force/acceleration and apply it to an object or the human body.

Force Summation To gain maximum momentum, the force needs to be generated by: 1.Using as many segments of the body as possible. 2.In the correct sequence, using large muscles first and then the smallest muscles last but fastest. 3.With correct timing 4.Through the greatest range of motion –to allow maximum force to be generated and applied to object

3rd Law - Action - Reaction “ The third law states that for every force there is an equal and opposite force. For example, if you push on the ground, it will push back on you as hard as you are pushing on it. "

What is the Centre of Gravity (COG)? The CG of a body refers to its balance point or that point in which the body would balance without any tendency to rotate. For the latter reason, the CG is that point where all of the weight of the body is concentrated.

Your centre of gravity is your body's point of balance. It's close to your belly button. The lower is your centre of gravity, the more stable you are. When you put your centre of gravity outside your base of support, you can lose your balance. COG is normally based around our navel. Where's yours?

At all times gravity is the main force acting on all parts of the body. The COG depends on the distribution of mass and may not always lie within the body. An imaginary line also exists which passes through the COG vertically and is called the line of gravity

Base of Support The larger the base of support, the greater stability a person has. A person is more stable when standing on two feet than does a person standing on one

BALANCE Balance is a physical ability that may be improved through purposeful practice. There are two types of balance: 1. Static balance, when a person remains over a relatively fixed base and 2. Dynamic balance, when a performer is in motion. Static Dynamic

The principles of stability and balance

Principle One The closer the line of gravity is to the centre of the base of support, the greater the probability of maintaining balance.

Principle Two The broader the base of support, the greater the probability of maintaining balance.

Principle Three The probability of maintaining balance is increased when the COG is lowered in relation to the base of support.

Principle Four The further one body part moves away from the line of gravity, the probability of maintaining balance decreases unless another body part moves to compensate for this

Recap: What is force summation? What are the four components of force summation? (Discuss with your partner for 1 minute) To gain maximum momentum, the force needs to be generated by: 1.Using as many segments of the body as possible. 2.In the correct sequence, using large muscles first and then the smallest muscles last but fastest. 3.With correct timing 4.Through the greatest range of motion –to allow maximum force to be generated and applied to object

Recap: When someone is doing a basketball free throw can you tell me at least two ways of increasing the force applied to the ball? Discuss with your partner for 1 minute

Projectile Motion Projectile motion is a form of motion in which an object or particle is thrown and moves along a curved path.

What is a projectile? As soon as an object is thrown it becomes a projectile. This includes objects such as balls, athletic equipment such as the shot put and the human body (in activities such as jumping)

Once a body leaves the ground it becomes a projectile and comes directly under the influence of TWO forces: Gravity Air resistance

There are 4 key factors that influence the flight of a projectile 1.Angle of release 2.Height of release 3.Speed of release/force applied 4.Spin applied (this also affects flight)

Angle of Release - Different angles of release affect the distance travelled and the height attained by an object - Generally the optimum angle for the furthest distance is 45˚ 90 Degrees 45 Degrees 0 Degrees

Height of Release - The height an object is released will determine the distance an object travels Height of release Distance travelled Ground level

Speed of Release Also refers to the amount of force applied because the greater the force the faster the object will travel Generally the greater the speed, the greater the horizontal distance travelled

Spin When applying force to a projectile below, above or to the side of the COG you will impart spin onto the projectile. This helps the projectile to maintain its course and can cause it to change height or direction. This helps the projectile to maintain its course and can cause it to change height or direction.

Spin continued…. Top Spin – this is where you hit over the ball. Top spin creates a downward force on the ball causing the ball to drop. Clockwise Spin – this is where you hit the ball on the left side of the COG. It causes the ball to swing to the Right.