Question

Why do most skeletal muscles work in pairs?

Answer 1

One tightens and the other relaxes to make the bones move.

Step-by-step explanation:
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Answer 2

Because Skeletal muscles can only contract and shorten, not extend

Most skeletal muscles are attached to the bones by bundles of collagen fibers called Tendons.

When one muscle set flexes (pulling a bone in one direction) , the other set will relax and control its speed