Unit 32: Mobility and Exercise P4, P5, M3. P4 - describe how muscle groups work as levers to produce movement around a joint. P5 – describe how proprioception helps to maintain balance posture and movement. M3 – assess how muscle groups maintain posture and produce movement.
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P4 - describe how muscle groups work as levers to produce movement around a joint.
P5 – describe how proprioception helps to maintain balance posture and movement.
M3 – assess how muscle groups maintain posture and produce movement.
P4 - Muscles and bones act together to form levers. Leavers can be classified into one of
three classes, these are known as first class, second class and third-class leavers. All three
classes of leavers are in the body, having a third-class leaver being most common. A leaver is
typically the length of a bone and is known as a “rigid rod” that turns about a pivot, this is
typically a joint. The role of leavers is most common for mechanical advantage; where it is
used so that a small force can move a much greater force.
The difference between each class is the positioning of the load, effort, and fulcrum.
• Load – known as the weight.
• Effort – the force, typically provided by
muscles.
• Fulcrum – this is known as the pivot, this
being a joint.
Figure 1 demonstrates a first-class lever, having figure
2 showing a second-class leaver and figure three
illustrating a third-class leaver. Figure 1: 1st Class Lever
When are leavers used in the body? Examples are
listed below: (Science Learning Hub, 2007)
• When nodding the head up and down – 1st
class
• When standing on tip toe. – 2nd class Figure 2: 2nd Class Lever
• When bending the arm – 3rd class
The following are mechanical aspects of leavers:
• Antagonistic pairs – these are antagonist and agonist muscles working in pairs,
meaning that, as one muscle relaxes, the other contracts. An example of where this
can be located within the human body is in the biceps and triceps, being that, the
biceps contract to lift the arm whilst the
triceps relax.
• Synergist muscles – the role of these muscles
is to help perform / fully perform the same
motion as the agonist muscles. This it to Figure 3: 3rd Class Lever
cancel out the additional movement from the
agonist muscles, to ensure for a force that is
generated to be within the desired level of
motion. Due to this role, it is sometimes given the name of “neutralizer”.
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