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Massage Therapy Licensing Exam (MBLEx) · Kinesiology

Massage Therapy Licensing Exam (MBLEx): Muscles: Attachments and Actions Concepts

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Overview

This chapter is about where muscles attach and what they do when they contract. The MBLEx often asks which muscle performs a movement or which muscle is the opposite of another. Learning the main groups and their actions is more useful than memorizing every small muscle.

Every muscle has at least two attachments. The origin is usually the more fixed end, and the insertion is the end that moves more. When a muscle contracts, it pulls the insertion toward the origin. Knowing these attachments tells you the muscle's action.

Muscles work in teams. The agonist, or prime mover, does the main work. The antagonist does the opposite action and must relax to let the movement happen. Synergists help the agonist, and stabilizers hold nearby bones steady.

Some groups appear on the exam again and again. The rotator cuff has four muscles known as SITS that steady the shoulder. The hamstrings bend the knee and straighten the hip, while the quadriceps straighten the knee. The biceps bend the elbow, and the triceps straighten it.

Key concepts

  • Origin

    The attachment of a muscle that usually stays more still during movement. It is often closer to the center of the body.

    Memory tipOrigin = the anchor that stays put.

  • Insertion

    The attachment of a muscle that usually moves more. A contracting muscle pulls the insertion toward the origin.

    Memory tipInsertion = the end that gets pulled.

  • Agonist and antagonist

    The agonist is the prime mover that does the main action. The antagonist does the opposite action and relaxes so the movement can happen.

    Memory tipBiceps bend the elbow (agonist); triceps must let go (antagonist).

  • Synergist

    A muscle that helps the prime mover do its job, either by adding force or by steadying a joint so the movement is smooth.

    Memory tipSynergist = helper.

  • Rotator cuff (SITS)

    Four muscles that hold the head of the arm bone in the shoulder socket: supraspinatus, infraspinatus, teres minor, and subscapularis.

    Memory tipSITS: Supraspinatus, Infraspinatus, Teres minor, Subscapularis.

  • Hamstrings vs quadriceps

    The hamstrings on the back of the thigh bend the knee and extend the hip. The quadriceps on the front straighten the knee, and one of them also helps flex the hip.

    Memory tipBack of thigh bends the knee; front of thigh straightens it.

Often tested

  • The origin is usually the fixed attachment; the insertion is the moving one.
  • The agonist does the action; the antagonist does the opposite action.
  • The rotator cuff muscles are supraspinatus, infraspinatus, teres minor, and subscapularis.
  • The hamstrings flex the knee and extend the hip.
  • The biceps flex the elbow; the triceps extend it.

Easy to confuse: Origin vs insertion

FeatureOriginInsertion
Movement during contractionUsually stays stillUsually moves
Typical locationCloser to the body's centerFarther from the body's center
Direction of pullInsertion is pulled toward itPulled toward the origin

3 sample questions

Verified practice questions from this unit.

Practice questionReviewedKinesiology › Muscles: Attachments and Actions★★★★★

Question 1. Which muscle group flexes the knee and extends the hip?

  1. ① The hip adductors
  2. ② The quadriceps
  3. ③ The hamstrings
  4. ④ The gluteus medius
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Answer: ③ The hamstrings

Key point: Hamstrings: flex knee, extend hip

The hamstrings run down the back of the thigh and cross both the hip and the knee. They bend (flex) the knee and pull the thigh back (extend the hip).

Wrong choices

  • The gluteus medius: The gluteus medius mainly abducts the hip.
  • The quadriceps: The quadriceps extend the knee.
  • The hip adductors: The adductors pull the thigh toward the midline.
Practice questionReviewedKinesiology › Muscles: Attachments and Actions★★★★★

Question 2. Which of these is one of the four rotator cuff muscles?

  1. ① Deltoid
  2. ② Teres major
  3. ③ Supraspinatus
  4. ④ Pectoralis major
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Answer: ③ Supraspinatus

Key point: Rotator cuff = SITS muscles

The rotator cuff is made of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis (SITS). They hold the head of the arm bone in the shoulder socket.

Wrong choices

  • Pectoralis major: The pectoralis major is a chest muscle.
  • Teres major: Teres major is near the rotator cuff but is not part of it.
  • Deltoid: The deltoid covers the shoulder but is not a rotator cuff muscle.
Practice questionReviewedKinesiology › Muscles: Attachments and Actions★★★★★

Question 3. What is the main action of the biceps brachii at the elbow?

  1. ① Flexion (bending the elbow)
  2. ② Pronation (turning the palm down)
  3. ③ Adduction (moving toward the midline)
  4. ④ Extension (straightening the elbow)
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Answer: ① Flexion (bending the elbow)

Key point: Biceps brachii flexes the elbow

The biceps brachii is on the front of the upper arm. It bends (flexes) the elbow and also turns the palm up.

Wrong choices

  • Adduction (moving toward the midline): The elbow is a hinge joint. It does not adduct.
  • Extension (straightening the elbow): The triceps brachii straightens the elbow.
  • Pronation (turning the palm down): The biceps does the opposite. It turns the palm up (supination).
Practice 5 questions from this unit →