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Extensor Muscles

What Does Extensor Muscles Mean?

Extensor muscles are a group of muscles that serve the biomechanical function of contracting to straighten the articulating joint (connecting bones) and its corresponding limb, increasing the spatial distance, or angle, until it is parallel with the center of the body. Extension of the joint generally falls within a 0-180 degree range of motion (ROM), but some joints can extend otherwise normal limits, for example, hyperextending the back to stretch lumbar musculature.

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WorkplaceTesting Explains Extensor Muscles

Although every joint has varying degrees of range of motion, extension generally coincides with the anatomical position (zero degrees). Joint elasticity and stability are contingent on the fibrous connective tissue including cartilage, ligaments, tendons, and muscle that permit fluid biomechanical movements. Individuals concurrently engage the use of extensor muscles when lowering the arm from a curled position or during walking/running where hip extensors contract, returning the leg to its normal position as the flexor muscles perform the opposite effect (flexion).

Given the mobile variations of the back, many people capitalize on the use of hyperextension exercises that stretch the lower back extensor muscles, a viable method in preventing detrimental lumbar issues in the future. Conversely, the neck is vulnerable to hyperextension injuries due to forceful impacts, also called whiplash, characterized by rapid hyperextension of the lower cervical vertebrae and subsequent hyperflexion of the upper cervical vertebrae. Commercial vehicle operators who experience whiplash may require rehabilitative treatment that can impose economic setbacks for employers due to productivity loss and workers' compensation claims.

Examples of extensor muscles include the latissimus dorsi, teres major, and triceps brachii of the upper limb and the biceps femoris, gluteus maximus, and quadriceps of the lower limb. Since extensor muscles contribute to the biomechanical performance of regular activities, consistent exercise and stretching serve as the mainstay in preventing debilitating injuries. Substantial ligament or muscle tissue damage may warrant physical therapy or, in some cases, surgery to assist in reaching the optimal range of motion in the affected joint.

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