SEHS Topic B.1 + B.2.1

Anatomical position

The standard reference position: standing upright, feet together, arms by sides, palms facing forward.

Why is anatomical position used?

It provides a consistent reference for describing movement and body position.

Sagittal plane

Divides the body into left and right halves.

Frontal plane

Divides the body into front and back halves.

Transverse plane

Divides the body into upper and lower halves.

Movement in the sagittal plane

Flexion and extension.

Movement in the frontal plane

Abduction and adduction.

Movement in the transverse plane

Rotation.

Sagittal axis

Runs from front to back; movement occurs in the frontal plane.

Frontal axis

Runs from side to side; movement occurs in the sagittal plane.

Vertical axis

Runs from top to bottom; movement occurs in the transverse plane.

Flexion

Decreasing the angle at a joint.

Extension

Increasing the angle at a joint.

Abduction

Movement away from the midline of the body.

Adduction

Movement towards the midline of the body.

Rotation

Turning a bone around its long axis.

Circumduction

Circular movement combining flexion, extension, abduction, and adduction.

Pronation

Rotation of the forearm so the palm faces down.

Supination

Rotation of the forearm so the palm faces up.

Dorsiflexion

Movement of the foot upwards towards the shin.

Plantarflexion

Pointing the foot downwards.

Ligament

Connects bone to bone and stabilises joints.

Tendon

Connects muscle to bone and transmits force.

Cartilage

Reduces friction and absorbs shock at joints.

Meniscus

Fibrocartilage in the knee that improves stability and shock absorption.

Bursa

Small fluid-filled sac that reduces friction between tissues.

Synovial fluid

Lubricates the joint and reduces friction.

Synovial membrane

Produces synovial fluid.

Joint capsule

Surrounds and protects a synovial joint.

Fibrous joint

A joint with little or no movement.

Cartilaginous joint

A joint with slight movement.

Synovial joint

A freely movable joint with a joint capsule and synovial fluid.

Hinge joint

Allows flexion and extension.

Ball-and-socket joint

Allows movement in all directions and rotation.

Pivot joint

Allows rotation around a central axis.

Saddle joint

Allows movement in two planes with greater range than a condyloid joint.

Condyloid joint

Allows flexion, extension, abduction, and adduction.

Gliding joint

Allows bones to slide over each other.

Example of a hinge joint

Elbow or knee.

Example of a ball-and-socket joint

Shoulder or hip.

Example of a pivot joint

Atlas and axis in the neck.

Example of a saddle joint

Thumb joint.

Example of a condyloid joint

Wrist.

Example of a gliding joint

Carpals in the wrist or tarsals in the ankle.

Agonist

The prime mover responsible for a movement.

Antagonist

The muscle that opposes the agonist.

Synergist

A muscle that assists the agonist.

Fixator

A muscle that stabilises a joint or body part.

Concentric contraction

Muscle shortens while producing force.

Eccentric contraction

Muscle lengthens while producing force.

Isometric contraction

Muscle produces force without changing length.

Isokinetic contraction

Muscle contracts at a constant speed, usually with specialised equipment.

Biceps brachii in elbow flexion

Agonist.

Triceps brachii in elbow flexion

Antagonist.

Fulcrum

The pivot point of a lever.

Effort

The force applied to a lever.

Load / resistance

The force being moved or overcome.

First class lever

Fulcrum is in the middle.

Second class lever

Load is in the middle.

Third class lever

Effort is in the middle.

Example of a first class lever in the body

Neck extension.

Example of a second class lever in the body

Standing on tiptoes.

Example of a third class lever in the body

Bicep curl.

Mechanical advantage

The ratio of effort arm length to resistance arm length.

Mechanical advantage greater than 1

Force advantage.

Mechanical advantage less than 1

Speed and range-of-motion advantage.

Why are most human levers third class?

They favour speed and range of motion, which is useful for sport movement.

Newton’s First Law

A body remains at rest or in constant motion unless acted on by an external force.

Inertia

The tendency of an object to resist changes in its motion.

Newton’s Second Law

Force equals mass times acceleration.

Newton’s Third Law

For every action there is an equal and opposite reaction.

F = ma

The greater the force, the greater the acceleration for a given mass.

Action-reaction forces

When one body exerts a force on another, the other exerts an equal and opposite force back.

Ground reaction force

The force exerted by the ground back onto the body after force is applied downward.

Friction

A force that opposes relative motion between surfaces in contact.

Useful friction

Friction that helps performance, such as grip and traction.

Harmful friction

Friction that reduces efficiency and increases wear.

Examples of useful friction

Sprinting, cutting, gripping a ball, climbing.

Momentum

Mass times velocity.

Momentum formula

p = mv.

Impulse

Force applied over time that changes momentum.

Impulse formula

Impulse = force × time.

Relationship between impulse and momentum change

Impulse equals change in momentum.

Why increase contact time in sport?

It can reduce peak force and help control movement.

Work

Work is done when a force moves an object through a distance.

Power

Power is the rate of doing work.

Why is power important in sport?

It shows how quickly force can be applied and work can be done.

Elastic collision

A collision where both momentum and kinetic energy are conserved.

Inelastic collision

A collision where momentum is conserved but kinetic energy is not fully conserved.

Collision

Involves two bodies exerting forces on each other for a short time.

Projectile motion

Movement of an object after release, influenced mainly by gravity.

Horizontal component of projectile motion

Constant velocity if air resistance is ignored.

Vertical component of projectile motion

Accelerated downward by gravity.

Angle of release

Affects the balance between horizontal and vertical displacement.

Velocity of release

Affects how far or high a projectile travels.

Height of release

Affects the time the projectile stays in the air.

How does friction help running?

It improves traction and prevents slipping.

How does friction help changing direction?

It allows force to be transferred into the ground efficiently.

How does friction hinder movement?

It can resist motion and reduce efficiency.

What do tendons do in movement?

Transmit force from muscle to bone.