ESSENTIALS: ANATOMY & PHYSIOLOGY

The meaning of the anatomical core has become confused over time. Originally used as a word added to modify the phrase “body temperature," in the 1990s and 2000s, it became associated with lumbar and abdominal exercises designed to address lower back pain. In reality, a far greater number of muscles are part of the core's structure, and these contribute to what we refer to in CrossFit as midline stability.

Ligaments connect bone to bone, and as there are 26 bones in the foot, there are numerous ligaments connecting and crisscrossing the foot’s interior. The foot receives quite a bit of support from the simple interlocking of the tarsal bones via their shape and via the intertarsal ligaments.

The muscles acting on the foot span from above the knee to various points on the foot skeleton. The muscles with proximal attachments at points outside the foot are referred to as extrinsic muscles of the foot. Another set of muscles, the intrinsic muscles of the foot, have both proximal and distal attachments within the foot’s bony architecture, from calcaneus to distal phalanx.

The many ligaments of the ankle complex hold 14 bones in close proximity, including the tibia, fibula, and tarsals.

The anterior and lateral muscles of the ankle equip the joint for various movements and functions, including plantar flexion, dorsiflexion, extension of the toes, and the inversion and eversion of the foot.

The muscles of the ankle, like its skeletal architecture, are essential to function. There are a number of muscles that dorsiflex, plantar flex, evert, and invert the foot at the ankle. Together, these muscles can also act to stabilize the joints they cross during locomotion.

The posterior knee muscles are more numerous and expansive than those in the anterior musculature. Four cross the hip and knee, and two cross the knee and ankle. There are larger, more powerful muscles in this group as well as smaller weaker muscles.

The muscles acting at the knee are generally categorized into two groups: anterior extensors and posterior flexors. The anterior muscles — the vastus medialis, vastus lateralis, vastus intermedius, tensor vastus intermedius, and rectus femoris — are commonly known as the quadriceps.

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The medial hip musculature consists of several muscles whose primary function is to adduct the femur at the hip.

The lateral musculature of the hip is generally considered a driver of hip abduction, with the abductors being moderate- to small-sized muscles that range in position from superficial to deep. These muscles overlap each other as they course along the lateral ilium and over the hip joint to their attachments on the femur and below.

The posterior aspect of the hip includes the extensors, which are large and powerful superficial muscles. It also includes a smaller, deep set of muscles that rotate the femur and maintain the proximity of the femoral head and acetabulum.

The musculature around the hip includes some of the largest and most powerful muscles in the human body. The extension of the hip can move thousands of pounds, propel the body up and over obstacles equal to or greater in height than the body in motion, and move the body at speeds greater than 25 miles per hour. But running, jumping, and lifting are just a few of the hip’s unique abilities.

Movements of the hand are, by nature, complex. Even muscles attaching at the shoulder affect the orientation of the hand in space. If we look specifically at the intrinsic muscles of the hand — i.e., those that have both attachments within the carpals, metacarpals, and phalanges — we find a number of small muscles that control thumb and finger positions.

The wrist includes a complex aggregation of muscles that drive movement about its joints. The posterior muscles of the wrist are generally used for extension but in a few exceptions carry out an additional action. The wrist extensors are found on the posterior arm, opposite the flexors on the anterior side. These muscles can be attached proximally to the humerus, radius, or ulna and distally to the carpals, metacarpals, or phalanges.

The muscular structure of the wrist and hand is quite complex, reflecting the complexity of the tasks they perform.

"Trainers … apply exercises to their clients in order to induce adaptations in structure and function that lead to improved fitness. In order to do this effectively, reliably and safely, the working trainer must understand the structures they are stressing with exercise to produce the functional change that is fitness. This is the primary reason we learn anatomy and physiology."

The muscles on the back of the arm that oppose the roles of the anterior flexors are few in number, including only the triceps brachii and anconeus. These posterior muscles of the elbow are considered elbow extensors, increasing the angle of the humerus and the two bones of the forearm: the radius and ulna.

The elbow musculature is an integral part of an upper axillary system and is capable of both extremely refined and very powerful movement. The anterior muscles of the elbow are considered elbow flexors, reducing the angle of the humerus and the two bones of the forearm, the radius and ulna. If the upper and lower arm are aligned in extension at 180 degrees (straight), flexion will reduce that angle to about 30 degrees. As with other regions, the muscles are arranged in layers: superficial, intermediate, and deep.

Impingement refers to the impeding interaction of hard bony surfaces with softer muscular, connective, and neural tissues, causing pain. The conventional wisdom for the genesis of this syndrome is that the acromion process comes into contact with and impinges upon the tendinous underlying tissues. This is suggested to occur when the arm is lifted, bringing the humeral head and shaft into close proximity with the acromion. The idea is that this movement, when repeated over time, compresses and damages the softer tissues.