Boxer's muscle is a/an?

AIIMS Bhuvneshwar NO- 2018

Applied Anatomy

Easy

Appeared in: AIIMS Bhuvneshwar NO- 2018

Explanation

The serratus anterior is colloquially known as the 'boxer's muscle' or 'swimmer's muscle'.
Its primary function is the protraction of the scapula, which is the forward-reaching or punching motion of the arm.
This muscle is essential for stabilizing the scapula against the thoracic wall, providing a stable base for arm movements.
The image provided correctly illustrates the location of the serratus anterior on the lateral chest wall.

Option A: Brachioradialis is a muscle of the forearm. Its main function is to flex the elbow, particularly when the forearm is in a neutral (thumb-up) position. It does not contribute to the punching motion.
Option C: Biceps brachii is a prominent muscle on the front of the upper arm. It is a powerful flexor of the elbow and a primary supinator of the forearm (turning the palm upwards). It is not the main muscle for the forward thrust of a punch.
Option D: The deltoid muscle forms the rounded contour of the shoulder. It is the prime mover for arm abduction (lifting the arm out to the side). While it is involved in many shoulder movements, it is not the specific muscle responsible for the protraction seen in punching.

Visual 1: Diagram: An illustration showing the action of the serratus anterior in protracting the scapula during a punch.
Visual 2: Clinical Image: A photograph demonstrating 'winging of the scapula' in a patient with long thoracic nerve palsy, highlighting the muscle's stabilizing function.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Anatomy and function of the serratus anterior muscle as background academic context rather than a clinical decision trigger.
Nurses should assess for scapular winging after procedures involving the axilla or chest wall, such as mastectomy or axillary lymph node dissection, as the long thoracic nerve is vulnerable to injury.
The test for serratus anterior function involves having the patient push against a wall with outstretched arms. If the muscle is weak or paralyzed, the medial border of the scapula will lift off the back, creating a 'wing-like' appearance.
What if? If a patient has difficulty lifting their arm above their head (overhead abduction) and shows scapular winging, the issue is likely with the serratus anterior and/or trapezius, not just the deltoid muscle.

How to Approach the Question

This is a factual recall question that tests your knowledge of anatomy and muscle function.
First, identify the key term in the question: 'Boxer's muscle'.
Mentally review the primary action of a boxer's punch, which is a forward thrust of the arm, involving protraction of the shoulder blade (scapula).
Consider the function of each muscle listed in the options.
Serratus anterior is the primary protractor of the scapula, making it the 'boxer's muscle'.
Eliminate the other options based on their main functions: Brachioradialis (elbow flexion), Biceps brachii (elbow flexion and forearm supination), and Deltoid (arm abduction).

Concept Tested & Keywords

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