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Clinical Evaluation

The most common mechanism for sustaining a pectoralis muscle injury is from weight-lifting or athletics. Wolfe et al.It described the transition period from eccentric loading to concentric loading (bench press position) as the most stressful to the inferior muscle fibers of the pectoralis muscle. The patient typically presents after sudden onset of pain in the […]

Capsulolabral Repair with Suture Anchors

For capsulolabral repair with suture anchors, the 30 degree arthroscope should be placed in the posterior viewing portal. It also can be placed in the anterosuperior portal (“bird’s eye” portal) to view the anterior labrum. Working instruments can be then placed in the anteroinferior portal. In some instances, it is helpful to use a 70 […]

Common Sport Injuries

An overuse injury results from excessive wear and tear on the body, particularly on areas and muscles subjected to repeated activity such as ankle, knee, shoulder and elbow joints.

The most common high impact sport that leads to injury is running. We see more runners than any other recreational athletes in our clinics, followed by […]

Length–Tension Relationship

Experiments studying the relationship between muscle length and the tension produced at a fixed length during passive stretch and active isometric contraction have demonstrated that force generation depends on the length of the muscle.

The passive curve was determined by measuring the tension in muscle at a series of different lengths. The increasing tension with […]

Biomechanics of Skeletal Muscle

Fiber Types and Muscle Adaptability

As mentioned, muscle fibers vary in type and can be differentiated by their histological, biochemical, and physiologic properties. Muscle fiber types can be divided into at least three separate entities based on these criteria. Each motor unit possesses fibers that are all of a similar fiber type, but some overlap […]

Sarcoplasmic Reticulum

Activation of skeletal muscle contraction is triggered through the release of calcium ions from a system of membranous sacs within the cell known as the sarcoplasmic reticulum (SR). Release of calcium from the SR is accomplished through rapid propagation of the muscle action potential throughout the muscle fiber via a complex system of membranes.

The […]

Motor Unit

Muscle fibers are arranged into discrete entities known as motor units. The muscle fiber motor unit is the most basic neuromuscular contractile unit, and it is composed of a single α-motor neuron and all the muscle fibers that it innervates. A single motor neuron can innervate as few as 10, or as many as several […]

Skeletal Muscle Cytology

Each muscle fiber is surrounded by its plasma membrane, or sarcolemma. Within this sarcolemma lie quiescent satellite cells that are essential for the repair of muscle after injury.

Following muscle injury, inflammatory substances are thought to stimulate these satellite cells to undergo proliferation and differentiation into new muscle fibers.

Fibers are further divided into smaller […]

Structure And Architecture Of Skeletal Muscle


Understanding the structure and architecture of skeletal muscle begins at the level of the muscle cell, or fiber, itself. Muscle fibers are multinucleated cells with a cylindrical shape, and they have diameters ranging between 10 to 100 µm. Fibers range a few millimeters to several centimeters in length. This wide variation in muscle fiber […]

Skeletal Muscle and Tendon

Key Points

Skeletal muscle has a complex organization of nerves, blood vessels, and connective tissue matrix that protects against injury and organizes individual cellular elements into functional contractile units of muscle. Muscle fibers range a few millimeters to several centimeters in length. Fibers are arranged into larger units known as fascicles. Perimysium, a connective tissue […]