Named Muscles, Movement and Fibre Types

The muscles that move you 💪

Bones cannot move themselves; **muscles** pull on them. Skeletal (voluntary) muscles work across joints to create every movement in sport. This module covers the **named muscles**, how they work in **pairs**, and the **fibre types** that suit different activities.

Named muscles 🏷️

Learn the main muscles by where they are: - **Biceps** (front of upper arm), **triceps** (back of upper arm), **deltoid** (shoulder). - **Pectorals** (chest), **latissimus dorsi** (back), **abdominals** (stomach). - **Quadriceps** (front of thigh), **hamstrings** (back of thigh), **gastrocnemius** (calf), **gluteus maximus** (buttock).

Match each muscle to its location

Straighten the arm

Which muscle contracts to straighten (extend) the elbow?

• Triceps
• Biceps
• Deltoid
• Quadriceps

Antagonistic pairs 🤝

Muscles can only **pull**, not push, so they work in **antagonistic pairs**. As one contracts, its partner relaxes: - The muscle that contracts to cause the movement is the **agonist** (prime mover). - The muscle that relaxes to allow it is the **antagonist**. To bend the elbow, the biceps is the agonist and the triceps is the antagonist.

Who relaxes?

When you bend your elbow, the biceps contracts as the agonist. What is the triceps doing?

• Relaxing, as the antagonist
• Also contracting hard
• It is not involved at all
• Acting as the agonist

Match each muscle to its antagonistic partner

Types of movement 🤸

Joints allow named movements. The main ones: - **Flexion** (decreasing the angle) and **extension** (increasing it). - **Abduction** (away from the body) and **adduction** (back towards it). - **Rotation**, plus **plantar-flexion** (toes down) and **dorsi-flexion** (toes up) at the ankle.

Which are movements?

Select the THREE that are types of body movement at a joint.

• Flexion
• Extension
• Rotation
• Digestion
• Sweating
• Breathing

Point the toes

Pointing your toes downward, like a diver or ballet dancer, is which movement?

• Plantar-flexion
• Dorsi-flexion
• Abduction
• Rotation

Muscle fibre types ⚡

Not all muscle fibres are the same. There are three types: - **Type I** (slow-twitch): contract slowly with low force, but resist fatigue for a long time. Great for **endurance**. - **Type IIa** (fast-twitch): faster and more powerful, with some endurance. Good for **middle-distance**. - **Type IIx** (fast-twitch): fastest and most powerful, but tire quickly. Built for **sprints and power**.

Match each fibre type to its use

Order by power

An interactive activity.

Muscle summary

The biceps and triceps work as an _____ pair; the muscle that contracts to cause a movement is the _____. Pointing the toes down is _____-flexion. A marathon runner relies on slow-twitch Type _____ fibres.