Myotomes

Myotomes are distinct functional units of muscles that play a vital role in the human body's motor control system. Derived from the Greek words "myo" meaning muscle and "tome" meaning cutting, myotomes refer to the specific muscles that are innervated by a single spinal nerve root. These nerve roots arise from the spinal cord and extend outward, branching into various peripheral nerves that control specific muscle groups throughout the body.

Each myotome is responsible for the contraction and movement of a particular group of muscles, enabling coordinated motion and precise control over our limbs, trunk, and other body parts. By working together, these myotomes allow us to perform a wide range of activities, including walking, lifting objects, maintaining balance, and engaging in fine motor tasks.

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When we discuss weakness in a muscle or group of muscles.  We should check the spinal segment that they attach to.  Pain/stiffness or any sort of bad input to a segment of the spine will cause reduced neural output to its myotome.  For example, if you have been experiencing patellar pain and your physical therapist has found gluteal muscle weakness as a contributor, it is important to screen L5 and S1 segments for signs of problem to help maximize the muscles input to get the best output.  This is also helpful when looking at tendon problems.

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Here are some useful charts that show what spinal segments feed major muscles in the upper and lower extremities.