SEHS Movement analysis - Fundamentals of Bio-mechanics:

Center of Mass

A hypothetical point where the entire mass of an object may be assumed to be concentrated to visualize its motion is called the center of mass.

The point at which the mass and weight of a body/object are balanced in all directions

A change in body position during sporting activities can change the position of the centre of mass

The centre of mass remains within the body throughout the movement in sporting activities such as walking, Javelin, Discus, golfing, etc

The centre of mass temporarily lies outside the body in sporting activities such as the Fosbury Flop High jump

Multiple Choice

The diagram shows a gymnast. Which represents the correct location for the centre of mass?

• A

• B

• C

• D

Multiple Choice

The diagram shows a high jumper performing a Fosbury Flop. During which phase is the centre of mass outside the athlete?

• A

• B

• C

• D

Multiple Choice

What happens to the centre of mass when the basketball player prepares to shoot, moving from position A to position B?

• Does not move

• Moves upwards

• Moves downwards

• Moves forwards

Multiple Choice

What is the centre of mass of a body?

• The geometric centre of the body

• The average weight between the appendicular and axial skeletons

• The point equidistant between the navel and the third lumbar vertebrae

• The point at which the mass and weight of a body/object are balanced in all directions

Levers: Is the human body is a machine?

We need to Distinguish between first, second, and third class levers.

Class depends on the position of Pivot/fulcrum, Load and Effort

Normally but not always in sports,

• the pivot is provided by joints;

• Load by the body weight and sporting equipment;

• Effort is provided by muscles

The central component of the three (PLE) determines the class of the lever

Levers

What about the triceps-elbow?

What about the ankle-calf joint?

Multiple Choice

Levers are working throughout the body when a basketball player performs a jump shot. Where is the effort applied in the lower right leg?

• A

• B

• C

• D

Multiple Choice

What is an example of a first-class lever?

• Triceps contracting, moving the elbow

• Biceps contracting, moving the elbow

• Quadriceps contracting, moving the knee

• Hamstrings contracting, moving the knee

Multiple Choice

What is the displacement of an 800 metre runner who runs two laps of a 400 metre running track and finishes at the same point as he started?

• 0 metres

• 200 metres

• 400 metres

• 800 metres

Multiple Choice

The diagram shows elbow extension. Which type of lever is used?

• First

• Second

• Third

• No lever is used during elbow extension

Multiple Choice

Which is an example of a second-class lever?

• The ankle joint during plantar flexion

• The elbow during flexion

• The knee during extension

• The hip during abduction