Movement Analysis - Levers, Mechanical Advantage And Planes And Axes

Question 1

Fulcrum - effort - resistance

Answer 1

Levers are made up of three parts.
- the fulcrum is the pivot point of a lever - joint
- the effort is the force that is applied to one part of a lever - muscle
- the resistance is at the other end, working against the force of the effort - weight of object or limb

Question 2

First class lever

Answer 2

• fulcrum lies between the effort and the resistance. For example the way the triceps muscle of the arm acts during extension
  ( the only first class lever in the body is elbow extension caused by the triceps )

Question 3

Second class lever

Answer 3

• resistance lies between fulcrum and effort. For example the ankle joint in plantar flexion
  ( only second class lever in the body is at the ankle during plantar flexion )

Question 4

Third class lever

Answer 4

• effort lies between resistance and fulcrum. For example the biceps acting on the elbow joint to move a resistance in the hand

Question 5

Explain mechanical advantage

Answer 5

• Different types of levers have different types of mechanical advantage in how they work. The mechanical advantage of different levers depends on the distance between the effort and the fulcrum when compared to the distance between the resistance and the fulcrum. These distances are known as the effort arm and the resistance arm. Mechanical advantage = effort arm / resistance arm

Question 6

Mechanical advantage of first and third class levers

Answer 6

• First and third class levers have an effort arm that is much shorter than the resistance arm, and therefore the effort arm / the resistance arm is less than one.
• This arrangement of short effort arm and longer resistance arm will help speed up the movement of the resistance and produce a wide range of movement. For example this occurs in the action of the biceps acting on the elbow joint as a third class lever system. During flexion at the elbow, the effort arm is short and the resistance arm is long, allowing the hand to move very quickly and through a large range of movement.

Question 7

Mechanical advantage of second class levers

Answer 7

• Second class levers, such as the ankle joint, are able to overcome a large resistance with an effort that is fairly small in comparison because the resistance arm is sorter than the effort arm. This gives a high value for mechanical advantage, and therefore, the action of the effort can easily move the resistance, which is essentially the weight of the body. So, the mechanical advantages of second class levers systems are that they can ,over heavy weight, and they permit a large force to be applied.

Question 8

Planes

Answer 8

Movements are described as taking place in one of three planes.
- The saggital plane is for forward or backward movement. Imagine slicing through the centre of the body, dividing it into left and right parts.
- the frontal plane is for side to side movements. Imagine slicing through the body from the left side to the right, separating the front and back halves.
- the transverse plane is for rotational or turning movements. Imagine cutting straight through the hips to divide the top of the body from the bottom.

Question 9

Axes

Answer 9

An axes is a straight line that an object rotates or turns around. SomeTimes Fun Starts Too Late
- The transverse axis passes horizontally through the body from left to right. Movements in a saggital plane take place around a transverse axis.
- The saggital axis passes horizontally through the body from back to front. Movements in a frontal plane take place around a saggital axis
- The longitudinal axis passes vertically from the top of the body to the bottom. Movements in a transverse plane take place around a longitudinal axis.