COM, COG, COP Flashcards
What is COM?
The centre of mass (CoM) is the point at which
the mass of the body is evenly distributed in all
directions.
It is the point at which the mass of the system
could be concentrated without affecting the
behaviour of the system.
What is COG?
CoG only denotes the centre of the body in the vertical direction while the CoM accounts for all directions. The CoG is often taken as a point on the ground through which the weight of the CoM acts.
How is COM calculated?
uses moments of individual body segments alongside published data on individual segment masses
Where is COM positioned?
CoM position depends on body shape:
– Horse: Just below line connecting point of
shoulder and point of buttock at around the
13th rib.
– Dog: Mid-chest, behind scapula but varies
with breed.
– Human: when standing in anatomical zero the
CoM is located just below the belly button.
How is COM and position related?
• CoM position can vary hugely with body position. • As it is an ‘imaginary’ point, the CoM can be located outside of the body in some positions.
How do you calculate COM of body segments?
need segment lengths, masses and inertial properties
- Properties of different tissues
- non-uniforms properties
variation with breed, sex and exercise history
altered by muscle contraction
When does COM change?
during movement
How do quadrupeds load?
60% forelimb
40% hindlimb
What is COP?
• The centre of pressure is the point where the individual
pressures exerted on a surface are concentrated.
• Centre of pressure moves throughout a stride and can
be an indicator of posture and balance.
• Asymmetries in CoP can be the causes or result
of injuries.
What is pressure?
force per unit area that an object exerts on surface
pressure accounts for the distribution of force rather than just the absolute force
eg; saddle pressure/ foot pressure
How does swaying effect our COP?
moves around
analyse the COP during quiet standing to give an idea of posture and balance
