The wrist extensors are a group of nine individual muscles on the back of the forearm that act on the wrist and fingers. Collectively, their primary function is wrist extension, though they also help carry out other movements of the wrist and fingers. The individual wrist extensor muscles are as follows: Extensor carpi radialis longus … Read more
The posterior deltoid (L. posterior, behind ; deltoides, triangular) refers to the rear head of the three-headed deltoid muscle. It acts on the shoulder joint and is the prime mover in shoulder horizontal abduction. Located on the back of the shoulder – medial to the lateral deltoid and lateral to the middle trapezius – the posterior … Read more
The internal oblique (L. internus, internal ; obliquus, oblique.) is a flat sheet of muscle on either the side of the lower torso. It gets its name from being beneath the external oblique and having an oblique fiber direction relative to the midline. The most prominent actions of the internal oblique are spinal lateral flexion and spinal rotation. Notably, … Read more
The erector spinae (erigere, to erect ; spina, spine.) consists of three long, thin muscle groups running vertically up each side of the vertebral column: the iliocostalis, longissimus and spinalis. These muscles act on different segments of the vertebral column (i.e. lumbar, thoracic, cervical). Collectively, they are the prime movers in spinal extension and spinal … Read more
The hip adductors refers to a group of five muscles that make up the bulk of the inner thigh mass. The primary function of this group is, surprise, hip adduction! The better known of the hip adductors are the adductor brevis, longus and magnus (L. ad, to ; ducere, to lead ; brevis, short ; longus, long … Read more
The external oblique (L. externus, external ; obliquus, oblique.) is a broad, flat sheet of muscle on either side of the abs. It is named after its location (external to the internal oblique) and its fiber direction (oblique relative to the midline of the body). It is the prime mover in spinal rotation, and it … Read more
As is made explicit by its Latin translation, the quadriceps femoris (L. quattuor, four ; caput, head ; femoris, femur.) literally means the four-headed muscle of the femur, or thigh. The four heads of the quadriceps femoris – or simply the quadriceps – include the following: rectus femoris, vastus lateralis, vastus intermedius and vastus medialis. The primary … Read more
The pectoralis major (L. pectus, chest ; major, larger.) is a large, fan-shaped chest muscle. It acts on the shoulder and (indirectly on) the scapula, with its most prominent role being the prime mover in shoulder horizontal adduction. The pec major is the largest and most superficial of the anterior axioappendicular muscles, lying superficial to the entire pectoralis minor … Read more
Literally meaning the three-headed muscle of the arm, the triceps brachii (L. tres, three ; caput, head ; brachium, arm.) consists of a long, lateral and medial head. It is primarily responsible for elbow extension. Known commonly as just the triceps, it is twice as big as its counterpart, the biceps brachii, and thus accounts for … Read more
The transversus abdominis (L. transversus, crosswise [trans, across ; vertere, to turn] ; abdo, to hide.) is a flat layer of muscle in the abdomen, whose fibers run transverse relative to the midline of the body. It is responsible for compressing the abdominal wall, helping to support and protect the internal organs, and assist in … Read more