COM and stability

how does height of COM affect stability?

Lower centre of mass, greater stability

how does base of support affect stability?

the wider the base, the greater the stability

what is the line of gravity and how does it effect stability?

• an imaginary line which extends down from the centre of mass to the floor

• keeping line of gravity within the base of support helps maintain stability

what is stability able to withstand?

external forces

what are 4 factors that affect stability?

• mass of the body

• height of centre of mass

• base of support

• line of gravity

how does mass affect stability?

the greater the mass, the greater the inertia, so the more stable it is

explain how high jumpers use COM and stability to their advantage?

• Curved run-up creates angular momentum for rotation.

• At take-off, arms drive upwards to raise the centre of mass (CoM) and increase vertical lift.

• The athlete rotates so their back faces the bar and arches into the Fosbury flop shape.

• This curved body position moves the CoM to below the body, so the CoM can pass at or below the bar while the body clears it.

• This makes the jump more efficient and increases the chance of clearing a greater height.

what is stability?

the ability of a body to resist motion and remain at rest

what is the centre of mass?

the point at which a body is balanced in all directions

what does centre of mass rely on?

• the distribution of the body mass

• can be manipulated to improve performance

what is a sporting example of a footballer using COM for performance?

• footballer will raise hands above head when jumping for header to raise COM to enable them to jump higher and remain in air for longer

example of how starting on blocks to running race using COM and stability to advantage

Crouch position (“on your marks”)

• Large base of support

• Low COM

• Line of gravity within base of support

• Stable position → helps balance/control

Set position

• Hips raised → COM higher

• Base of support effectively smaller

• Line of gravity near/outside front of base

• Unstable position → allows quick acceleration

Drive/run phase

• Line of gravity outside base of support

• COM pushed forwards

• Very unstable → maximises forward acceleration out of blocks