Question

how do muscles work ?

Answer 1

Muscles contain special proteins called contractile proteins which contract and relax to cause movement.
Muscles present in our limbs move when we want them to and stop when we so decide.Such muscles are known as voluntary muscles.

Answer 2

the muscles are connected with the bones through rope like tendons and can only be contracted most of the muscles work in pairs so that difference type of movements are possible. such muscle pair is needed for instance , to bend the elbow while one muscle , the biceps , contracts and bends the arm .