Why does your muscle form a hump when your arm is bent?
Because the tissue is bunched together in a shorter length.
Well there are two muscles which bend the arm: bending your arm from a straight position to a bent position uses the bicep (Latin name - Bicep Brachii) which is on the topside of your upper arm. Bending your arm from a bent position to a straight position uses the tricep (Latin name - Tricep Brachii) which is on the underside of your upper arm. Both muscles work in sinc with each other, so as…
You bent your arm the wrong way and now you are getting severe sharp pains between your bicep and tricep but you can flex your muscles without anyproblem what is wrong with your arm?
Abduction of the arm occurs in three segments, and hence is performed by three different sets of muscles. From 0-15 degrees, the arm is abducted by the Supraspinatus muscle. From 15-90 degrees, the arm is abducted by the Deltoid muscle. From 90-180 degrees, the arm as abducted by the Trapezius muscle with help from the Serratus Anterior muscle.
While one muscle contracts, the other muscle in the pair returns to its original length. The main muscle that bends your upper arm is called the Biceps brachii. The action is called flexion at the elbow. This muscle is on the "front" of the arm. The muscle that acts against this one is called the Triceps brachii. Its' action is extension at the elbow. This muscle is on the "back" of the arm. See the…
The raising of the arm can be divided into three phase. The initial phase is carried out by the supraspinatus muscle. After the arm as been raised to 30 degrees, the deltoid muscle takes over. This muscle performs this action until the horizontal plane. In the last phase, the serratus anterior raises the arm above the horizontal plane. So the answer to your question is the supraspinatus muscle, deltoid muscle, and the serratus anterior muscle.