Health Library

Skeletal muscle

Regular workouts that include resistance training, such as weight lifting, cause the muscle fibers of skeletal muscle to increase in size and improve overall body tone.

Skeletal muscle is a well-organized body tissue, composed in a complex array of smaller and smaller structures. Let’s take a look at a cut-section to see how skeletal muscle is organized.

Each skeletal muscle is composed of many units called muscle fascicles. Notice that the fascicles are bound together by a type of connective tissue, which is called fascia. And from that fascicle, we can pull away smaller organizational units called muscle fibers.

And from that muscle fiber, we can pull away even smaller strands called myofibrils. Here you can see the myofibrils move as the muscle is contracting. It’s the interaction of these myofibrils as they slide and pull along side each other that gives skeletal muscle its functional ability to do work and move things.

Putting it all back together, myofibrils compose muscle fibers, that make-up muscle fascicles, which are grouped together within a skeletal muscle.

Review Date: 10/27/2025  

Reviewed By: Joseph V. Campellone, MD, Department of Neurology, Cooper Medical School at Rowan University, Camden, NJ. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

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