NCEA Level 1 PE Biomechanics Comprehensive Study Guide

Flexion: Bending a joint to decrease the angle between the bones (e.g., bending the elbow).
Extension: Straightening a joint to increase the angle between the bones.
Abduction: Moving a limb away from the midline of the body.
Adduction: Moving a limb toward the midline of the body.
Rotation: A movement where a bone turns on its own axis (e.g., turning the head from side to side).
Circumduction: A circular motion that combines flexion, extension, abduction, and adduction.
Pronation: Rotation of the forearm so that the palm is facing down.
Supination: Rotation of the forearm so that the palm is facing up.
Dorsiflexion: Lifting the foot up toward the shin.
Plantarflexion: Pointing the foot downward.
Inversion: Turning the sole of the foot inward.
Eversion: Turning the sole of the foot outward.
Elevation: Raising a body part (e.g., shrugging shoulders).
Depression: Lowering a body part.
Protraction: Moving a body part forward.
Retraction: Moving a body part backward.

Bone Functions:
- Support: Provides the framework for the body.
- Protection: Shields vital internal organs.
- Movement: Acts as levers for muscles to pull against.
- Mineral Storage: Acts as a reservoir for essential minerals.
- Blood Cell Production: Occurs within the bone marrow.
Major Bone Groups:
- Skull
- Vertebral column
- Rib cage
- Upper limb
- Lower limb
- Pelvis
Muscle Types:
- Skeletal: Voluntary muscles used to move the body.
- Smooth: Involuntary muscles found in internal organs.
- Cardiac: Involuntary muscle found exclusively in the heart.
Attachment and Function:
- Muscles attach to bones via tendons.
- Muscles are only capable of pulling; they cannot push.

Fibrous: Fixed or immovable joints, such as the sutures in the skull.
Cartilaginous: Joints that allow for slight movement, such as the vertebrae in the spine.
Synovial: Joints that allow for free movement and are the most relevant to sports.
Synovial Joint Classification:
- Hinge: Allows movement in one direction (flexion/extension). Examples include the elbow and knee.
- Ball-and-Socket: Allows movement in almost all directions. Examples include the shoulder and hip.
- Pivot: Allows rotation around a single axis. An example is the neck.
- Gliding: Allows sliding movements. Examples include the wrist and ankle.
- Saddle: Allows movement in two directions. An example is the thumb.
- Condyloid: Allows movement in two directions but does not allow rotation. Examples include the wrist and knuckles.

Agonist (Prime Mover): The muscle that is contracting to cause the movement.
Antagonist: The opposing muscle that relaxes and lengthens to allow the movement to take place.
Synergist: A muscle that assists or stabilises the agonist during movement.
Fixator: A muscle that stabilises the joint or bone during movement.
Muscle Pairings by Joint and Movement:
- Elbow Flexion: Agonist is Biceps brachii; Antagonist is Triceps brachii.
- Elbow Extension: Agonist is Triceps brachii; Antagonist is Biceps brachii.
- Knee Flexion: Agonist is Hamstrings; Antagonist is Quadriceps.
- Knee Extension: Agonist is Quadriceps; Antagonist is Hamstrings.
- Ankle Plantarflexion: Agonist is Gastrocnemius/soleus; Antagonist is Tibialis anterior.
- Ankle Dorsiflexion: Agonist is Tibialis anterior; Antagonist is Gastrocnemius/soleus.
- Hip Flexion: Agonist is Iliopsoas; Antagonist is Gluteus maximus.
- Hip Extension: Agonist is Gluteus maximus; Antagonist is Iliopsoas.

Definition: The coordination of body movements in the correct sequence and timing to produce maximum force at the point of release or impact.
Sequential Summation:
- Involves moving body segments from largest to smallest and proximal to distal.
- Segments add momentum in a specific order.
- Example: In a throw, the sequence follows legs → hips → trunk → shoulder → elbow → wrist.
Simultaneous Summation:
- Occurs when all body parts move together at the same time to create one combined force.
- Examples: A rugby scrum push or a weightlifting clean.
Risks of Summation Errors:
- Poor timing or incorrect sequencing results in less generated force.
- Increases the risk of injury to the athlete.

1st Law — Inertia: An object will stay at rest or remain in motion unless an external force acts upon it. (Sport Example: A ball stays still on the grass until it is kicked).
2nd Law — Acceleration: The force an object exerts is equal to its mass multiplied by its acceleration.
- $F = m \times a$
- (Sport Example: A heavier shot put requires more force to achieve the same acceleration as a lighter one).
3rd Law — Action-Reaction: For every action, there is an equal and opposite reaction. (Sport Example: A swimmer pushes the water backward in order to propel their body forward).

Base of Support (BOS): The area under the body including all contact points with the ground. A larger BOS results in more stability.
Centre of Mass (COM): The specific point where the mass of the body is evenly distributed. A lower COM results in more stability.
Line of Gravity: A theoretical vertical line stretching from the COM to the ground. A body is stable when this line falls inside the BOS.
Mass: An object or person with greater mass has greater stability, as they are harder to move.
Friction: Increasing friction between the body and the surface (e.g., using better grip shoes) increases stability.
Stability vs. Mobility Trade-off:
- High Stability: Achieved with a wide base and low COM, but results in less mobility.
- Low Stability: Allows for faster movement but makes it easier for the body to be unbalanced.