The human body contains 3 types of muscle tissue: smooth, cardiac and skeletal. Skeletal muscles are responsible for locomotion and other body movements under voluntary control. The body includes more than 600 skeletal muscles of various shapes and sizes. The largest muscles, which often function in groups, perform the most strenuous tasks.
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The gluteus maximus is the biggest muscle in the human body, by volume. The gluteal muscle group -- commonly known as the glutes -- includes 3 muscles located at the back of each hip. The glutes are the major components of each buttock. Gluteus maximus is the largest and most superficial of the gluteal muscle group, which also include gluteus medius and gluteus minimus. Gluteus maximus, along with the other gluteal muscles, serves many important functions. It stabilizes the pelvis and lower back, enabling an upright posture. It also has important roles in hip and thigh movements, and is a key player in powering walking, running and climbing.
Latissimus dorsi is the widest muscle in the human body. The Latin name of the muscle translates as the broadest muscle of the back. Commonly known as the lats, these fan-like muscles originate in the lower and middle back and attach on the inner aspect of the upper arm bone, the humerus. The lats are powerful muscles that enable a range of shoulder movements, working in conjunction with other muscles. They are particularly active in sports that require powerful upper arm movements, such racket sports and swimming. The lats also assist with deep breathing.
Quads and Hamstrings
The muscle groups of the thighs are also among the largest in the human body. The quadriceps femoris, commonly known the quad, is a 4-headed muscle located at the front of the thigh. This large, bulky muscle includes the rectus femoris, vastus lateralis, vastus medialis and vastus interomedialis. The quads power extension of the knee and aid in flexion of the hip. The hamstrings muscle group, located on the back side of the thigh, includes the semimembranosus, semitendinosus and biceps femoris. Broadly considered, the hamstrings oppose the quads, powering knee flexion and hip extension. The hamstrings also aid in rotation of the knee. Any activity involving the upper legs -- even standing still -- requires activation of the quads and hamstrings.
Many other skeletal muscles are contenders for inclusion among the biggest muscles of the human body. For example, the back contains 3 layers of muscles. Large superficial back muscles include the triangular trapezius, which originates from the spinal bones of the chest and neck and attaches to the shoulder blade and clavicle. The deep muscles of the back, also known as the intrinsic back muscles, run the entire length of the spinal column to the base of the skull. These muscles work together to support the spine and enable its movements.
The front of the trunk also includes many large muscles and muscle groups. Some of the largest make up the abdominal wall, including the rectus abdominus and internal and external obliques. In the chest region, the large pectoralis major muscles fan out from the breastbone and inner end of the clavicle and attach to the upper end of the humerus to power several movements at the shoulder.
Reviewed by: Tina M. St. John, M.D.