Q:

What is an antagonistic muscle in the leg?

A:

Quick Answer

According to the BBC, antagonistic muscles are pairs of muscles that work by alternately contracting and relaxing. In the human leg, the quadriceps and hamstrings are one example of antagonistic muscles. As York College explains, skeletal muscles always work in groups and never work in isolation.

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Full Answer

Muscles pull on the bones of the skeletal system to cause the body to move. HowStuffWorks.com explains that antagonistic muscle pairs work by pulling a bone in different directions to produce motion. For example, to pull the foot up towards the buttocks, the hamstring contracts, while the quadriceps relax. When it is time to straighten the leg, the quadriceps contract, while the hamstring relaxes, which straightens the leg.

The University of the Western Cape explains that muscles achieve movement by making bones move as levers. The quadriceps and hamstrings produce a third class lever, just as the biceps and triceps of the arm do; other parts of the body use first and second class levers. For example, the calf muscles, which allow humans to walk, produce a second class lever, where the load lies between the fulcrum and the effort applied. By contrast, the head and neck muscles create a first class lever when they cause the head to nod.

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Related Questions

  • Q:

    How do pairs of skeletal muscles work together?

    A:

    According to the University of the Western Cape, skeletal muscles work in pairs so that they can alternately pull on a bone to achieve movement. In other words, when a human wants to bend his elbow, he must relax his triceps muscle, while contracting his biceps. Such muscle groups are called antagonistic muscles, because they pull in opposite directions.

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  • Q:

    Why must skeletal muscles be arranged in antagonistic pairs?

    A:

    Skeletal muscles must be arranged in antagonistic pairs so that when one muscle moves a joint the other muscle can return the joint to its original resting position. Without an antagonist muscle pairing, there would be no way for the body to return the joint to its original position.

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    What do the leg muscles look like?

    A:

    When viewed anatomically, the leg muscles are seen as overlapping layers of striated muscle fibers that range in color from pale to dark red, depending on myoglobin content. These striated muscle fibers give the leg muscles their stripped appearance.

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    What is in a gluteal muscle diagram?

    A:

    As the Stanford Visible Female explains, a gluteal muscle diagram is a 3D image of the muscles in the buttocks. According to My Weight Lifting, a diagram of the gluteal muscle should include the three gluteal muscles: the gluteus maximus, gluteus medius and the gluteus minimus.

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