Centre of Mass and Stability
Centre of mass and stability are key concepts in IB Sports, Exercise and Health Science (SEHS) that explain why some positions are more balanced than others and how athletes control their bodies during movement. These ideas are essential for analysing performance, balance, and injury risk across a wide range of sports.
Understanding centre of mass helps explain how athletes maintain control while accelerating, decelerating, or changing direction.
What Is Centre of Mass?
The centre of mass is the point at which the mass of the body is evenly distributed in all directions. In humans, the centre of mass changes depending on body position and movement.
Key points include:
- It is not fixed in one location
- It moves as body position changes
- It is influenced by limb position
In IB SEHS, students should understand that centre of mass is a theoretical point used to analyse balance and movement.
Base of Support and Stability
Stability depends on the relationship between the centre of mass and the base of support. The base of support is the area beneath an athlete that provides support, usually the points of contact with the ground.
Stability increases when:
- The base of support is wider
- The centre of mass is lower
- The centre of mass remains within the base of support
Athletes adjust these factors to maintain balance during both static and dynamic movements.
Centre of Mass in Sporting Movements
In sport, athletes often deliberately manipulate their centre of mass to improve performance.
Examples include:
- Lowering the centre of mass when defending in team sports
- Leaning forward during sprint acceleration
- Widening stance for balance in weightlifting
These adjustments improve stability and control under external forces such as contact or rapid movement.
Stability and Performance
Greater stability allows athletes to:
- Apply force more effectively
- Resist external forces
- Maintain control during complex movements
However, maximum stability is not always desirable. In activities requiring speed and agility, athletes may sacrifice some stability to increase movement freedom and acceleration.
In IB SEHS, recognising this trade-off is important for high-mark answers.
Centre of Mass and Injury Risk
Poor control of centre of mass can increase injury risk. If the centre of mass moves outside the base of support unexpectedly, balance is lost, increasing the likelihood of falls or joint stress.
Understanding centre of mass helps explain:
- Falls and collisions
- Loss of balance during fatigue
- Importance of technique and posture
Exam Relevance for IB SEHS
Centre of mass questions often require applied explanations. High-mark answers clearly describe how centre of mass and base of support affect stability and apply these ideas to sporting contexts.
Avoid stating definitions without linking them to balance or performance.
RevisionDojo Call to Action
If centre of mass and stability feel abstract or difficult to apply, RevisionDojo helps IB SEHS students master biomechanics with clear explanations and exam-style practice. It is the most effective way to turn theory into exam-ready understanding.
Frequently Asked Questions (FAQs)
What is centre of mass in IB SEHS?
The centre of mass is the point where the body’s mass is evenly distributed and is used to analyse balance and movement.
How does base of support affect stability?
A wider base of support increases stability by providing a larger area for the centre of mass to remain within.
How is centre of mass tested in IB SEHS exams?
Students are often asked to apply centre of mass and stability concepts to sporting movements, balance situations, or injury scenarios.
