Major Muscles of the Body Cheat Sheet

A printable reference covering anterior muscles, posterior muscles, muscle actions, and key anatomy terms for grades 7-12.

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This cheat sheet covers the major muscles of the human body, including key muscles on the front and back of the body. Students need it to connect muscle names with locations, actions, and everyday movements. It is useful for anatomy, health science, physical education, and introductory medical science study. The focus is on clear labels, simple functions, and the most commonly tested muscle groups.

Key Facts

The deltoid abducts the arm at the shoulder, which means it helps lift the arm away from the side of the body.
The biceps brachii flexes the elbow, so it helps bend the arm and bring the forearm toward the upper arm.
The triceps brachii extends the elbow, so it straightens the arm after bending.
The pectoralis major flexes, adducts, and medially rotates the arm at the shoulder.
The rectus abdominis flexes the trunk, which helps bend the body forward at the waist.
The quadriceps femoris extends the knee, making it important for standing, walking, running, and jumping.
The hamstrings flex the knee and extend the hip, helping pull the lower leg backward and move the thigh behind the body.
The gastrocnemius plantar flexes the foot, which means it helps point the toes downward during walking, running, and jumping.

Vocabulary

Anterior: Anterior means toward the front of the body.
Posterior: Posterior means toward the back of the body.
Flexion: Flexion is a movement that decreases the angle at a joint, such as bending the elbow.
Extension: Extension is a movement that increases the angle at a joint, such as straightening the knee.
Agonist: An agonist is the main muscle responsible for producing a specific movement.
Antagonist: An antagonist is a muscle that opposes or slows the action of another muscle.

Common Mistakes to Avoid

Confusing anterior and posterior muscles is wrong because anterior muscles are on the front of the body, while posterior muscles are on the back.
Mixing up biceps and triceps is wrong because the biceps brachii bends the elbow, while the triceps brachii straightens it.
Calling the quadriceps one single muscle is incomplete because the quadriceps femoris is a group of four muscles on the front of the thigh.
Assuming every muscle only has one action is wrong because many muscles act at more than one joint or help with more than one movement.
Using everyday location words instead of anatomical terms can cause confusion because medical science uses precise terms like anterior, posterior, medial, and lateral.

Practice Questions

1 Which major muscle extends the knee during a squat, and what muscle group helps flex the knee?
2 A student bends their elbow from 180 degrees to 60 degrees. Which muscle is the main mover, and what movement is occurring?
3 A runner pushes off the ground by pointing the toes downward. Which calf muscle is strongly involved, and what is the movement called?
4 Explain why the biceps brachii and triceps brachii are considered an antagonistic pair at the elbow.

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