The human body’s musculature allows for a vast range of movements. Among these, some muscles stand out due to their size and influence. When considering the upper body, the question of which muscle holds the title for being the largest is common, and the answer can be nuanced.
The Latissimus Dorsi
The Latissimus Dorsi, commonly known as the “lats,” is widely recognized as the largest muscle in the upper body. This broad, flat muscle spans a significant portion of the back, contributing to a distinctive V-shaped torso when well-developed. Its expansive coverage makes it the widest muscle in the human body.
The lats are part of the superficial layer of extrinsic back muscles, which primarily govern the movement of the humerus (upper arm bone) and scapula (shoulder blade). Its size and flat, fan-like shape allow it to cover almost all other back muscles in the posterior trunk, except for the trapezius. This makes it a powerful and influential muscle for overall upper body function and strength.
Location and Role
The Latissimus Dorsi muscle has extensive attachment points, contributing to its widespread influence on movement. It originates from the lower six thoracic vertebrae, lumbar vertebrae, sacrum, posterior iliac crest (hip bone), and lower three to four ribs. From these broad origins, its fibers converge and twist, extending upwards towards the armpit before inserting onto the intertubercular groove of the humerus (upper arm bone).
This muscle performs several actions at the shoulder joint, including adduction (bringing the arm towards the midline of the body), extension (moving the arm backward), and internal rotation (turning the arm inward). The Latissimus Dorsi is particularly active in pulling movements, such as chin-ups, pull-ups, rowing, and climbing. It also plays a role in forceful exhalation.
Understanding Muscle Size
The term “biggest” when referring to muscles can be interpreted in various ways, often leading to confusion. Muscle size can be assessed by factors such as surface area, length, or volume. While the gluteus maximus (buttock muscle) is generally considered the largest muscle in the entire human body by volume, the Latissimus Dorsi holds the title for the upper body primarily due to its expansive surface area.
The Latissimus Dorsi’s wide, flat, and triangular shape allows it to cover a significant portion of the back, making it the widest muscle in the body. Other prominent upper body muscles, such as the pectoralis major (chest muscle) and trapezius (upper back and neck muscle), are also substantial in size. However, the Latissimus Dorsi’s anatomical structure, spanning from the lower back to the upper arm, solidifies its position as the largest in the upper body based on its broad coverage.