Movement studies 2011

University of Hertfordshire - MS 2011/12 Adapted from 2010 slides produced by PR

Define CoG, LoG, BoS and equilibrium and explain how they interrelate

Briefly discuss the implications of CoG, LoG and BoS to human postures and movement

Describe the forces that act on the body

Describe the three orders of levers and how they can be demonstrated within the body

University of Hertfordshire - MS 2011/12

Explain mechanical advantage and benefit to physiotherapists

Explain Newton’s Laws of motion

Analyse movement in relation to Newton’s Laws of motion

University of Hertfordshire - MS 2011/12

Muscles contracting (force) to over come the weight of a limb (load) for movement to occur at a joint (axis)

University of Hertfordshire - MS 2011/12

Where is the axis of movement?

What is force M? What is force W & F?

University of Hertfordshire - MS 2011/12

Where is the axis of movement?

What is force M?

What is force W?

University of Hertfordshire - MS 2011/12

M

W

What do the Internal forces acting on the body consist of ?

What forces will work externally on the body?

University of Hertfordshire - MS 2011/12

When representing a force diagrammatically we use arrows

Longer the arrow the greater the magnitude of the force

The direction the arrow points is the direction of the force

The other end of the arrow is the point of application of the force

University of Hertfordshire - MS 2011/12

There is usually a combination of forces acting on the body – so how can we determine which way movement will occur?

Look at the following examples and determine which way the movement will occur

University of Hertfordshire - MS 2011/12

The deltoid muscle has fibres which run in three directions, what will the resultant movement of the arm be when all of the portions of the deltoid muscle work together?

University of Hertfordshire - MS 2011/12

Resolve these forces. Which way will both

examples move?

University of Hertfordshire - MS 2011/12

University of Hertfordshire - MS 2011/12

Much of the time the internal forces working within the body (e.g. muscles) are working on a lever (e.g. long bones).

When considering levers the moment of force is an important factor

This is the rotary effect that occurs due to there being a fulcrum (fixed point) around which the movement occurs.

University of Hertfordshire - MS 2011/12

University of Hertfordshire - MS 2011/12

FORCE

LOAD

m

m = MOMENT ARM

University of Hertfordshire - MS 2011/12

1st order

2nd order

3rd order

The length of the lever arm between the fulcrum and force (force arm) determines mechanical disadvantage

Hold a weight. Abduct your arm with your elbow in full extension and then in 90° flexion.

Which movement is easier? Why?

How could you make performing elbow flexion more difficult?

University of Hertfordshire - MS 2011/12

Imagine you are testing a patient’s strength in their Quads by manually resisting knee extension.

How can you use mechanical advantage to your favour?

How could you make an exercise for the Quads harder?

University of Hertfordshire - MS 2011/12

University of Hertfordshire - MS 2011/12

Adopt each of the following positions and rank them from most to least stable Standing, sitting, kneeling, lying

Can you account for/justify this ranking?

Can you modify each of these positions to make them more or less stable? Justify your answers.

The point about which the weight of all the body segments is evenly distributed

In the anatomical position it is anterior to S2

The Line of Gravity (LoG)is a vertical line through the CoG

University of Hertfordshire - MS 2011/12

Surface area of the part that is involved in supporting the object

Consider walking aids!

Think about the relationship between the line of gravity and the base of support

Which factors influence the stability of a body?

University of Hertfordshire - MS 2011/12

The surface area & stability of the BoS

The location of the LoG within the BoS

The height of the CoG above the BoS

The mass of the body

University of Hertfordshire - MS 2011/12

22

All stand with legs slightly apart, get a partner to your left to move & push you from behind (carefully)

What happens?Why?

Now repeat in step stance (one leg in front and sideways of other)

What happens?Why?

Look back over the learning outcomes for this session and the associated study required.

Make sure you are happy that they have been met and understand the concepts introduced and discussed

University of Hertfordshire - MS 2011/12

ANY QUESTIONS ??

Thank you for listening & participating

University of Hertfordshire MS - 2011/12