Stability Flashcards
What is the scientific term for centre of gravity?
Centre of mass (CoM)
The centre of mass is the point of concentration of mass in a body.
What does the centre of mass represent?
The point of balance of the body
The centre of mass varies due to the irregular shape and constant movement of the human body.
What factors affect the position of the centre of mass?
Shape of the body
Raising arms can cause the centre of mass to rise to maintain balance.
Define stability in the context of the body.
The ability to resist motion and remain at rest
Stability also includes the ability to return to an original position without damage.
What are the mechanical principles to consider for increasing stability?
Mass of the performer, height of the centre of mass, area of the support base, line of gravity
Each principle affects how well a body can maintain stability.
How does the mass of the performer influence stability?
Greater mass leads to greater inertia and stability
For example, sumo wrestlers have high mass for stability.
What effect does lowering the centre of mass have on stability?
Increases stability
Gymnasts bend at the hips and knees to lower their centre of mass for stable landings.
How does the area of the support base affect stability?
The greater the size of the base of support, the greater the stability
Increasing points of contact or spreading limbs can enhance stability.
What is the line of gravity?
An imaginary line extending vertically from the centre of mass to the floor
A central line of gravity within the base of support increases stability.
True or False: A netball goal shooter has her line of gravity outside her base of support.
False
A goal shooter’s line of gravity falls within her base of support.
What is maximising stability in sports?
Achieving a balanced position with a low centre of mass and a large base of support
Example: A sprinter in blocks has maximum stability.
What happens when a sprinter lifts their hips before a race?
They reduce stability by raising the centre of mass and shifting the line of gravity
This prepares them for movement.
What occurs when a sprinter starts running after the gun is fired?
Instability is maximised to aid performance
The sprinter’s body falls forward, needing to drive one leg forward quickly.
What does toppling mean in the context of a swim start?
Maximising instability to tip forward into the water
The swimmer adjusts their line of action to fall in front of their feet.
How does the line of action of a force affect a jumper at take-off?
Determines whether the jumper rotates in the air
A force acting directly through the CoM results in linear acceleration.
What happens when a force acts eccentrically to the centre of mass?
It initiates angular acceleration and causes rotation
For example, a high jumper turning in the air.
What are two factors that affect the stability of a gymnast holding a headstand?
- Height of centre of mass of the gymnast
- Area of base of support for the headstand
- Position of line of gravity and body mass
How does the musculo-skeletal system assist a tennis player in maintaining stability?
Muscle attachment to bones and formation of joints allows movements into stable positions
How does the neuromuscular system assist a tennis player in maintaining stability?
Recruitment of muscle fibres through isometric muscle contraction helps maintain a stationary position
What can a performer do to best maintain stability?
Lower the height of their centre of mass and increase the area of their base of support
Fill in the blank: The greater the base of support, the _______.
[more stable]
True or False: A higher centre of mass increases stability.
[False]
What is the definition of stability in the context of performance?
The ability to maintain balance/equilibrium
What happens to stability when a performer reduces the height of their centre of mass?
It increases stability
What is the area beneath an object or person that includes every point of contact with the supporting surface called?
Base of support
List factors affecting stability.
- Height of centre of mass
- Area of base of support
- Line of centre of gravity
- Performer’s mass when moving
What effect does a wider base of support have on a performer?
It increases stability
How can a tennis player achieve a stable position as shown in the figure?
By flexing the legs at the knee and hip, and adducting the leg at the hip
What muscle contraction is required to maintain a stable position?
Isometric muscle contraction
What is the relationship between the line of gravity and stability?
The closer the line of gravity is to the base of support, the more stable the performer
How does spatial summation affect a tennis player’s ability to maintain stability?
It varies the amount of force produced by recruiting different motor units
What role do large motor units play in maintaining stability?
They produce the required force to maintain a stationary position
Fill in the blank: A lower centre of mass means _______.
[more stability]
